OK I decided to dedicate a new page to the engine and the things I am going through to improve its performance. The first few posts are just about things not set right etc etc, but later on I will go into more detailed tricky stuff 🙂
After the first fast taxi yesterday, we decided that the mixture control valve needs to be adjusted. It doesn’t do anything and engine is running rich all the time.
So yes took it home yesterday.
Just finished with it. Took it apart, checked the fuel mixture valve needle, and had to unscrew it, extend it by about 4mm. No wonder it didn’t do anything. now in the lean position, it touches the valve seat. Apparently you lean off an engine to stop it, so I assume that means no fuel, so it needs to touch the valve seat.
Luckily the gasket in between the two halves was still intact, so I used it again, with some new gasket cement. I like the smell of that stuff 🙂
Thursday I might install the carburetor back on the engine and run it for an hour or so, and play with the mixture control, so I can lean off the engine and get it running like a ………. Don’t know the word 🙂 (dream maybe)
And yes today I installed the carburetor again onto the engine.
Yes it looks to work just fine!!!!
There is one interesting initially a bit confusing feature though.
During the throttle range from 0% to 80% or so, you need to adjust the mixture control, like you would expect. More air, more fuel.
But at the highest throttle setting, the carburetor opens a second channel, see diagram below, and suddenly leaning of the mixture hardly does a thing. Like its not killing the engine, but you still hear it revving up a bit from 1500 to 1600rpm.
The acceleration pump is controlled by the throttle, and when the throttle is open very quick, extra fuel is “pumped” into the main discharge nozzle and into the air stream.
But when just opening the throttle slowly or at any speed really, the pump piston with the two pins on top (see diagram) gets pushed down, opening a hole you can’t see on this diagram, allowing extra fuel into the main discharge nozzle.
So yes, the initially confusing behavior is correct. But because I still need to lean of the mixture all the way to 0%, maybe I need to get a smaller jet, the left one.
Now reading the carburetor findings from Wed 9 Jul 2014, I noticed that the fuel pump jet is already smaller then what’s on the id plate on the carburetor. I wonder if the previous owner has been “playing” with this to get full throttle mixture rating correct.
From what I see here it looks like that jet is still a bit to big.
I will have to talk to some people about this !!!!
BUT LOOKING GOOD NOW.
So after my initial engine testing, I started taxing the Bleriot. Went up and down the taxiway twice. All went really well. Could steer really well !!!!
When I came back I did another engine test, and it still goes to 1600rpm. Total engine time was 0.9 hour.
Because I am running the engine a lot leaner then before, the spark plugs aren’t “flooding” anymore, and because of that the engine runs on all 5 cylinders now.
SO READY FOR THE NEXT FAST TAXI AND HOPEFULLY FLIGHT 🙂
Today we did a compression test to see if there is something wrong, as we still don’t get enough power, see last high speed taxi on 29 Dec 2015.
So we found that all 5 cylinders were good really, the differential pressure was better then 70 / 80 psi.
But after talking about the problems and “going backwards and forward” as we didn’t understand the low power, we started looking at the valve tappet clearance, as that’s quite big, and I did set that at .035″ as stated in the manual, but !!!!
I didn’t see the last sentence in that chapter that said, to set the clearance of all valves at .015″
Turns out the .035″ was just an intermediate value, and they all need to be a lot smaller; .015″
So I am quietly positive that this will give us a lot more power.
Currently the exhaust valve closes to fast, so not all exhaust gasses have been driven out,
and the mixture inlet opens to late so it doesn’t get enough air/fuel mixture. Surely this will result in less power.
So in the next few days hopefully good news !!!! 🙂
Last Sunday I changed the clearance on all valve tappets to .015″ as they were set wrong, ooops !!!
Today I tried running the engine but died after 1/2 second every time.
Came back today did another check on fuel level in carb, check a little nut on priming valve and tried starting again.
THIS TIME it started perfect as it has the last we while. Turns out that the mixture control push cable was screwed into the carb at a different position, so the mixture had to be pushed further forward. I fixed that now.
When running at full power, I get now more then 1700 rpm, so that sounds promising.
Pat from Rangiora Aircraft Engineering was there as well and checked the speed with his optical tacho, and his was indicating the same as mine so good as well !
He thought the engine sounded really nice
Also checked the mixture at different speeds and apart from full throttle, all other throttle settings, the mixture lever is in the same position for the correct mixture setting, as it should be.
At full throttle where the mixture is slightly rich, I suppose the mixture lever needs to stay where it is, but I do still notice that when the mixture is leaned off, it goes faster again.
So all looking good, and waiting for calmer weather and my test pilot.
Today we had another fast taxi and managed to get of the ground for the first time WOOOHOOOOOOO !!!! 🙂
But and there is one big thing, stopping us from flying higher at the moment.
There is still not enough power !!!
Every time its a little thing here and a little thing there to improve on, so what’s next.
One of the things Warren and I quickly tried, was making a plenum chamber hanging underneath the carburetor. There is a lot of pulsating air going past the carburetor. We were thinking that that could influence its performance.
Warren had seen it in the past.
But no, that’s not it.
This plenum chamber smooths and equalizes the air going into the carburetor.
Below you see the tin with holes hanging under the carb 🙂
When I set the tappet clearance to the right settings last time, where the exhaust valve closing time is used as a reference, I noticed that the exhaust is opening very early.
I know that the exhaust opens before the piston get to the BDC (Bottom Dead Center) but this one starts opening before the piston is even half way down.
So Warren and I decided to “dive” into this and see what can be done about it. Next weekend I am going to plot the valve position of both valves against the crankshaft position.
To give you another look at the internals of the engine, here are two important pictures…….
Left: 3 cam lobe’s, and the interesting thing is that all 3 are used to open both exhaust and inlet valves.
Right: the 10 valve lifters for the 5 inlet and 5 exhaust valves
Now if you look careful, well its not to hard to see, there is a different spacing between the valve lifters. The pair for each cylinder have a bigger spacing. The bottom 2 that you see here are for cylinder #1. The angle between them is about 40.3 deg I think, just measuring from the screen. I measured all 5 and then averaged it.
Now as you can see in the photo with the 3 cam lubes, the cam “shaft” is geared down. It needs to make 1 revolution for every 6 crank shaft revolutions, that way every 2 revolutions of the crank shaft, one lube goes past the inlet and exhaust valve once.
Now I think this is how this works….. If the cam shaft would go at normal speed, and there was only one lube on it, the 40.3 deg I measured is the real LSA (Lobe Separation Angle). But in this case here, the lube is moving 3 times slower, so the 40.3 deg is not 40.3, but really 40.3 * 6 = 241.8 deg.
According to Warren that is on the high side, and less deg would easily improve the performance.
Now to make the angle smaller may look a hard to achieve, but Warren had this idea. All we need to do is move the rollers a few mm towards each other. We can make 10 new steel pins see photo to the right and drill the roller pin a few mm off center.
Another way to change the timing is to use the original steel pin with roller, and make a new brass guide, with the hole off center or even on an angle.
This last option is something I have seen done on other Velie engines today, So that looks very promising, and also something others have done/tried.
OK this is all talk for now. First I am going to map the valve movement against the crank shaft angle and talk with a CAM specialist here in town, see what he says about decreasing the LSA, or just the whole job of increasing the power output 🙂
Today did a whole lot of measurements, close to 400, measuring the position of the exhaust and inlet valve against the crank shaft angle.
So will start entering all the data in a spread sheet, and do some graph magic…
Above you see the overlap measured at a 6 thou opening. It measures about 30 deg, where as normally its about 60 deg. So it looks like the exhaust can indeed be delayed quite a bit….
Lets wait for the comments from the CAM specialist and then decide how we are going to make adjustments 🙂
And if you are interested here is the spreadsheet with all the measurements and graphs :xxxxx
Today Warren and I went to visit a CAM expert company in town, Kelford CAMS. They look like a very knowledgeable company. Been talking with Phil, and we decided to look into two things.
They are going to look at re-grinding the CAM, to make the 3 lobes the same shape as they are slightly different at the moment, and also the are going to make them narrower, as they are to wide ” the valve is open to long”.
We, Warren and I, are going to move the timing of the two valves, the LSA closer together.
All of this will as a result theoretically produce more power. So very exciting times !!!! 🙂
Tonight I did another set of measurements on the CAM basically, checking how the 3 lobs interact with all 10 valves.
Also here is the spread sheet: xxxxx
Some bad things there:
A big LSA (Lobe Separation Angle).
There is something not right about the exhaust of cylinder #1. Its exhaust valve open time is longer then the inlet valve open time. They should be equal.
Also look at the time the exhaust valve opens before the piston gets to the BDC (Bottom Dead Center), that’s massive!!
That last one is the thing that’s going to make the biggest improvement in power output of this engine, I would say !!! 🙂
After a bit of a break because my parents have been here on holiday,
FULL STEAM AHEAD again !! 🙂
Because the idea is to change the valve timing a bit and because there is something not right at the length the exhaust valve for the #1 cylinder is open, I have done another set of measurements for the #2 cylinder valves this time.
Below is the valve open timing shown at 6 thou:
And the valve position:
Just checked the time these two valves are open and they are identical. For the mixture valve its 274 deg and for the exhaust valve its 280 deg, so that’s good. The reason I am saying this is that when I did the measurements on the #1 valves, the exhaust valve was open longer then the inlet (mixture) valve. So when I open up the engine sometime soon, that will be one thing I want to have a look at. We ( Warren and I ) expect that the cam-roller for that valve is bigger then the other ones, but will see.
I also did a measurement to see when the 5 pistons reach the TDC position (Top Dead Center)
The reason I did these measurements (see results below) is this:
In a radial engine with one master rod to the #1 piston and 4 connecting rods (con rod) connecting the 4 pistons with the master rod, the #1 piston will make a nice movement, but the other 4 won’t be ideal, and will have a timing that slightly of the theoretical one of 72 deg between each piston.
Now one of the thoughts Warren had was to give each piston its own triggered timing pulse to optimize the ignition, but I don’t think that’s necessary now.
Very low error, so I am not going top worry about the ignition timing !!
BUT THIS IS INTERESTING:
While I was doing my measurements, a guy walked in and started asking questions. He wanted lots of figures, angles etc etc. I noticed straight away he knew what he was talking about.
This is Wayne Lindebaum, he has a hangar next to me with the opening the other way, maybe that’s why I never met him…..
Wayne has a business there, and one of the things is engines. Has been doing it “all his life”.
The valve timing instructions in my manual say to set the EVC (Exhaust Valve Close) time to the TDC (Top Dead Center), this is with a tappet clearance of 35 thou.
Now if you look in all the literature you can find on engines, you see that the EVC is past the TDC, and that the IVO (Inlet Valve Open) is before the TDC. Wayne called this the valve rocking point, where exhaust is closing and inlet is opening.
Wayne tells me to change the cam timing so that the exhaust closes later. Make it symmetrical around the TDC.
This means that the EVO (Exhaust Valve Open) will be later, which is what I want, and also the IVC (Inlet Valve Close) will be later, so that more fuel can be drawn into the cylinder.
I compared the TDC of all 5 pistons (see 5 measurements just above) with the IVO and EVC times I have measured earlier.
On average the CAM needs to be moved by 25 deg, to delay the valve movements. This is what I always wanted !!! 🙂
By doing this I should get what you see below. Yes I think it looks good.
Oh yes the other thing Wayne was saying is that the LSA (Lobe Separation Angle) that’s currently about 120 deg and maybe needs to be reduced a bit, possibly to 105 deg, is not changing that much. Moving the cam to make the valves rock around the TDC is going to double the power !!!
Today I have been modifying the cam timing, to make them symmetrical.
And guess what it seems to work.
Below is the “vernier adjustment” I think Wayne called it. by taking the 4 bolts out and re positioning it in the next 4 holes, there is a fractional angle change. And because the cam shaft is geared, rotating this ring once around , you have a whole new set of options, but all slightly shifted again.
But the most interesting thing is, when I was talking with Wayne again, and showed him the brass plate at the front of the engine:
Last weekend I finally found what problems I have been having.
Initially I did set up the valve timing according to the manual. and yes the engine ran quite nicely. But when it came to test runs and flying, it barely came of the ground. So we started looking into the problem.
I did find that I had my tappet clearance set wrong, I blame the manual for not being clear and myself for never worked on engines before. I got a bit more power, just enough for getting of the ground. But I need a lot more.
So Warren and I and later Wayne, started looking into the valve timing. And after I did a whole lot of measurements, mainly valve position against crank shaft position, with detailed position of the #1 and #2 cylinder valves, and just opening times for all other valves, I found:
- The exhaust valves open very early, and as a consequence close early, and the same for mixture open and close times.
- The time #1 exhaust valve is open is a lot longer then all the other ones, and the should be the same, so something is wrong with that one.
So I started changing the cam timing to get valve open and close times that make more sense. Its then when “the coin dropped“. The initial valve timing setting was wrong because the #1 exhaust valve has a timing problem. We expect a bigger cam roller for that one.
When increasing the tappet clearance on the #2 and #5 exhaust, after all had been set to reasonable timings, the exhaust valve closed at the time described in the manual, at TDC (top dead center).
Great, so the manual has been correct all the time. Its just the wrong #1 exhaust valve timing that changed everything.
So currently taking more of on the back of the engine to investigate this silly exhaust valve!!!!!
Yes yesterday I took one more “layer” of the back of the engine. Had to use a hoist as the 4 mounting points, the engine is hanging on, stopped me from removing this back. So Pat had one that I could borrow, very nice. On the second photo here you can see that the back is about to pop of, but it was the red shock absorbents and the steel housings that stopped me. With the engine 1″ or so of the mounting studs, I could get the back of, and placed the engine back on the engine frame, so I don’t need the hoist anymore. Will need it though later on to assemble that back .
Today I had a really good look at 4 of the 10 cam rollers, and they are all exactly 1″ in diameter. I was expecting that the #1 exhaust valve cam roller would be bigger, but it wasn’t.
That’s good in a way. That means its all as it should, just doesn’t explain why this #1 exhaust valve was open longer then all the others.
I am seriously starting to think that its all to do with the tappet clearance settings. If that one valve had a clearance less the what it should have been it would have started opening sooner and closing later. Maybe that’s all it is !!!!!!!!
Had another discussion with Warren about an idea I had:
In stead of setting the timing using the tappet clearance procedure etc etc, which is very error prone due to the shape of the CAM lobe as its done on the very gentle beginning of the slope of the lobe, I decided to set the timing using the “top” of the lobe. That way I don’t need to worry about tappet clearance at all. All I need to know is the angle distance between the top of the exhaust and the top position of the mixture valve, and position that symmetrical around the TDC. I looked up my measurements and the spacing between exhaust fully open and mixture fully open is exactly 240 degrees.
So all I need to do is set the CAM so that the exhaust valve “peeks” at 120 deg before TDC and the mixture valve peeks 120 deg after TDC
This new procedure popped into my head when I had another good look at the CAM. Here you can also see that the valve is only a short time at the top, so that’s perfect for using as a reference:
You can also see in this image below what I am trying to achieve:
To have the two valve movements overlap at the TDC (at about 40 deg in the image below), I will have to position the mixture valve top time at the TDC + 120 deg, or the exhaust valve top time at the TDC – 120 deg.
So today I want back to Rangiora and assembled the CAM back onto the back of the engine.
Also spoke with Wayne, as he was very interested to see the inside of the engine. He also agrees with me that setting the CAM timing this way is so much better !!!!
So I am a happy man 🙂
In the next few engine visits I will set the CAM timing and set all 10 individual valve tappet clearances so that all valves open and close at the same time……
Today I started with the “final” settings of the engine valve timing.
After I had taken the CAM of last weekend, I have now installed it back again, I was hoping that the timing was still right.
And yes after all the work I have done a week or so ago, it looked perfect.
The timing for the #1 cylinder is very symmetrical:
I should make a picture of this so its easier to understand
So in the next few days or weeks, I will set the tappets for the other valves, and check the timing….
After my solo flight today !!!!!!!! I continued setting valves.
All these measurements are relative to each piston TDC (top dead center) time
This is what I have so far:
Very happy with this so far, looking good. Next time I will do the last two valves.
All I am doing really is setting the tappet clearance, and the checking what the valves do as the cam timing was set at the beginning when I did valves for cylinder #1. Everything else should be correct, and it looks like they all are !! 🙂
As symmetrical as possible, looking good I think.
All angles measured relative to the TDC of each piston.
The goal was to have all valves fully open at -120deg (exh) and +120deg (mix), because the seoaration between exh fully open and mix fully open is 240deg. All symmetrical.
I set the CAM timing using the valve positions of the #1 cylinder.
That’s looking very good, if you keep in mind that the remaining pistons (#2 – 5) are driven my the master rod, and the valves of these remaining cylinders are all driven by the common CAM. Proves that the TDC separation of all 5 pistons is close enogh to 360/5 = 72 deg….
I think I am happy with these figures.
Next is putting the back of the engine back on, oil pump, oil hoses and magneto’s…..
Can’t wait to see the result 🙂
A bit more work today 🙂
Mounted the back of the engine and the oil pumps. So only things left are connecting the oil hoses to the two pumps and the magneto’s ….. Ooh and also asked Wayne today for a scoop he has that hopefully fits my carburetor. Will have a look what it is when he finds it. Hopefully it has a filter in it as well.
Yes after work and before our “Rudder and Stick group” meeting I connected up all the oil hoses again. 6 Of them:
For the scavenger and pressure pump, 2 hoses each. A drain hose into the sump and a oil pressure gauge hose.
Also connected the fuel line. Next time the magneto’s and the timing of them and then its done 🙂
Today I was going to put the magneto’s on the engine and try to run the engine… BUT
I realized I forgot to put two “oil catchers” in the back of the engine. You see them here (in an old photo) on the two magneto drive shafts. Two disks with a flange folded outward.
Have to remove he oil hoses again, remove the oil pumps and remove the back 🙁
Spent most of the day on the engine.
Silly me, I noticed last Saturday that I forgot two disks that suppose to go “inside”. They are just where the shafts driving the magneto’s come out at the back. Took me three hours to fix that, so not to bad.
After that it was time for the magneto’s, and setting the timing for them.
I was getting nervous as the big moment came closer. Has all this work, investigating how the timing works, changing the timing to what we think is “perfect” worked?
The engine started as usual with one swing. I hopped in and waited for it to warm up a bit and slowly opened up the throttle. All looked good. Then after a few minutes I opened up the throttle and YES making about 200 rpm more.
This increase in engine speed equates to a theoretical power increase of :
( 1900rpm / 1700rpm ) ** 3 = 1.40 = 40%
That should be enough to fly !! 🙂
So I emailed my test pilot Evan the news. Now its waiting for a nice weekend. Not coming weekend, its going to be wet and strong winds……
All my plane friends were happy for me. I am cautiously happy, wanting to see it fly first before I celebrate.
After Saturdays first real flight, today I am starting the next step, finding more power!
After talking with Wayne, we decided to first have a play with the tapped clearance for the inlet valves. He thinks that by increasing the clearance, resulting in the inlet closing earlier, the compression will go up as less mixture is possibly pushed out while the piston is already going up.
So I set all mixture valve clearances to .035″. Also I had to reset the exhaust valve clearances again to .015″ as most of them were a bit more then the .015″ after the nice big run on Saturday.
Just made some adjustments to the inlet valve tappet clearance. Going to start the engine and see if that made any difference. I was preparing myself for a difficult start, as it didn’t start easily last Saturday when we had the nice frost.
But no, it started straight away 🙂
I don’t like the oil pressure readings when its cold. The oil must be so thick that it has problems going through the narrow passages. Very high, so I basically very slowly ramp up the revs of the engine. When the engine gets warmer, it drops more and more.
OK back to engine performance. NO the valve timing change hasn’t done anything. Still a static engine speed of 1900 rpm.
So next time I will increase the exhaust tappet clearance to 0.35″ and set the inlet clearance back to .015″, see what that does.
Today I started my search for more power after the first successful flight last week.
After talking with Wayne from Rangiora Light Aviation who has his hangar next to mine, I changed my mind about what’s next 🙂
I am just going to list the points of action, and will elaborate a bit more in the coming days 🙂
- Advance the timing about 10 degrees so that the mixture valve closes earlier. Although I am not so convinced now, after I had another look at the timing diagrams I made earlier of the valve position in relation of the crank shaft. I want to have another good look at them, and show Wayne.
- Run engine with 92 octane petrol instead of 100 octane. Also advance to ignition timing from 30 to 25 deg.
- Create more compression by removing 1 mm of material of the bottom of the cylinder, resulting in a smaller combustion chamber.
Below is a timing diagram I created to show you what I think needs to be done on top of what Wayne said yesterday (close the mixture valve a bit earlier).
- In this diagram the engine rotates anti-clockwise.
- Ignition (yellow) is 30 deg BTDC (Before Top Dead Centre) the gray line.
- Then the power cycle starts (left half of diagram) and here, still a bit early, the exhaust valve (blue) starts opening.
- During the exhaust cycle (right half) exhaust is pushed out, and when the piston is almost at the TDC (Top dead Centre), the mixture valve (red) starts opening.
- Then in the intake cycle (left half), the exhaust valve (blue) closes, and the whole cylinder is loaded with new mixture.
- In the compression cycle (right half), the mixture valve (red) closes to late, resulting in the cylinder spitting out mixture back into the carburetor.
I really have the feeling that the overlap at the TDC is sort of right:
- IVO: inlet valve opens 10 – 20 deg BTDC
- EVC: exhaust valve closes 10 – 15 deg ATDC
- IVC: inlet valve should close 30 – 40 deg ABDC
- EVO: exhaust valve should open 30 – 50 deg BBDC
Wayne said, to “close the mixture valve a bit earlier” and I agree with that. But that means that the exhaust valve is going to open to early in the power cycle, back to were I started .
- The LSA (Lobe Separation Angle) on this engine is to big, can be improved by moving the CAM rollers closer together. This will delay the opening of the exhaust valve, and close the mixture valve earlier.
- The valve open time is to long, can be reduced by making the CAM lobe narrower.
A lot of work, but that is going to give me improvements, definitely.
Lets get more opinions………
Today spoken with Wayne, and looked at an engine CAM with the following spec:
IVO: inlet valve opens 31 deg BTDC
EVC: exhaust valve closes 25 deg ATDC
IVC: inlet valve should close 59 deg ABDC
EVO: exhaust valve should open 65 deg BBDC
These valves have a duration of 270 deg, which is the same as mine. Its that the Lobe Separation Angle for my engine is 17 deg more.
So yes, this CAM is sort of similar to mine but with a bit smaller LSA.
We spoke about the next steps…..
What I am going to do is this:
- Move the CAM timing a little so that the IVO is slightly bigger then the EVC. So basically rotate the valve timing in yesterdays’s picture clockwise. But only a little. Probably one step in the timing gear in the back of the engine. This is close to perfect, without having to modifying anything. Currently the exhaust valve is fully open at 119 deg BTDC, and the mixture valve is fully open at 122 deg ATDC. So move that looking at yesterdays picture a bit clock wise, so taht the mixture closes a bit earlier.
- The second thing we are going to concentrate on is compression. If more compression can be gained, that will produce more power. This is a very low compression engine, basically on purpose as the fuels available at the time had a low octane content. Making the compression higher would make the engine ping. But with “better” fuels these days (higher octane), the compression can be increased, and will result in more power. We are going to try and find pistons that fit my engine and have a dome on top, a raised round top, protruding into the combustion chamber, giving us more compression and as a result creating more power.
- Also Wayne thinks the tappet clearance needs to be set to 20 for the mixture valve, and 25 for the exhaust valve.
These three steps are the last things possible we think without making modifications (that’s if swapping pistons is not seen as modifying) to increase the power output for my engine…..
So fingers crossed 🙂
Made a graph with the piston movement.
That is sort of interesting and relevant when looking at the valve timing as the piston is not moving up and down in the same way the shaft of the crankshaft moves.
Length of (master) conrod = 197 mm
Crank shaft movement (stroke) = 95 mm
Spend a few hours adjusting the CAM to change the valve timing to find that it hasn’t changed at all 🙁
Will have a think in the next few days, and do it again……..
OK, so yesterday I tried adjusting the CAM timing.
The thing in the middle is the vernier used for adjusting the CAM timing. Its called “gear timing flange” in the Velie Installation and Maintenance manual. This gear is running at 1/6th of the crank shaft.
By removing the 4 bolts, moving the front disk a bit and screwing the bolts into the next hole, the whole timing is moved by about 10 deg or that’s what I thought.
That was a bit to much, so I thought if I hold the front disk and rotate the prop one hole turn then I might be able to get smaller steps. But it looks like its exactly the same 🙁 or that’s what it looked like.
So how does the CAM vernier work:
The front disk driving the CAM has 16 holes with thread in it. This is 22.5 deg per hole.
The disk behind, is driven by the crank shaft has 20 holes with thread. This is 18 deg per hole.
So by removing the bolts, moving the crank shaft a little, and putting the bolts back in the next lot of 4 holes, the CAM timing is shifted a bit. In fact it’s a step of 4.5 deg (22.5 – 18 deg). This is less then what I had seen yesterday, but oh well….
Another thing that can be done is when the bolts are out, is holding the front disk with the 16 holes, and spin the prop one full revolution. This will move the CAM and the disk with the 20 holes, 60 deg (360 deg / 6) as the CAM moves 6 times slower then the crank shaft. The 60 deg is 3 times a 18 deg step plus 6 deg. In combination with the 4.5 deg from the paragraph above, this gives a 1.5 deg minimal step!!! So in total there are 240 possible positions for the CAM for one complete full 4 cycle of the engine.
So I am thinking that what I have now is maybe 1.5 deg different from before and that’s why I don’t, or hardly see the difference !!!!
While looking at YouTube videos, I found this video. Its about getting more power out of an formula F1 engine. These engines are relatively small, but by using high precision components, in this case cylinders and pistons, they produce a lot more power. Only because of the better fit of the piston, and the use of better piston rings.
Something to think about !!
What I am thinking is, if we try to get more compression using new pistons (with a dome shape head) and modern rings, that might give more power as well just because we will lose less pressure because of the better fit 🙂
Forget what I said about the vernier running at 1/6 of the crank shaft. It’s the CAM drum that’s running at 1/6 of the crank shaft.
The vernier for adjusting the CAM timing is running at 1/2 of the crank shaft!
This means that when the 4 bolts are out and moving the prop one revolution as I described here, is not changing anything, as the number of holes in the vernier is a multiple of 2. So every vernier step of 4.5 deg is all you get, no steps in between by turning the prop one revolution.
Now this makes sense, as I have just adjusted the timing, by about 4 degrees, so that’s good.
Next time when I am back I will start assembling the back of the engine again, and see what difference it had made.
Plus will try different fuels as well. Now running 100 octane, but I will try and see what happens with 95 and 91 octane.
Possibilities, of power output with higher compression ratio:
Was just looking at the website of the “Verner Motor”. They have three radial engines; 3, 5 and 7 cylinder. An interesting thing is that the 5 and 7 cylinder engines run at similar rpm and have a similar engine volume as my Velie:
Scarlett 5SI: 3615 cc, 78 BHP (57 kW) @ 1900 RPM
Scarlett 7Hi: 4466 cc, 97 BHP (71 kW) @ 2000 RPM
The average of these two, looking at he displacement is about 4000 cc (my Velie) with the same rpm as my Velie, would give about 87 HP. All of this with a compression ratio of 1 : 7.3
Oh and these engines run on 95 octane fuel !
So all I am saying is if we can increase my compression ratio from currently 1 : 5.4 to somewhere higher then 1 : 7 , we should get quite a bit more power !!! 🙂
So yes Wayne, believing more and more in what you have been telling me 👍👍👍
Just starting to think about what’s needed to get the compression ratio up, towards what I saw with the Verner radial engines.
In a piston engine, it is the ratio between the volume of the cylinder and combustion chamber when the piston is at the BDC of its stroke, and the volume of the combustion chamber when the piston is at the TDC of its stroke. The compression ratio for the Velie is 1 : 5.4
Now below I am going to calculate how much smaller the combustion chamber needs to get, by razing the piston head, to get a 1 : 7 compression ratio.
Cylinder bore = 4 1/8 ”
Piston stroke = 3 3/4 ”
Displacement of one piston = Pi * (2 1/16)**2 * (3 3/4) = 50.115 “cube
compression ratio = (piston displacement + combustion chamber) / combustion chamber
compression ratio = (piston displacement / combustion chamber) + 1
compression ratio – 1 = piston displacement / combustion chamber
combustion chamber = piston displacement / (compression ratio – 1)
So for the 1 : 5.4 ratio, the combustion chamber is 50.115 / 4.4 = 11.39 “cube
And for the 1 : 7 ratio, the combustion chamber is 50.115 / 6 = 8.35 “cube
So yes as expected, the combustion chamber needs to be reduced in size. About 3.04 “cube smaller.
If I was just going to extend the top of the piston, that would be equivalent to:
piston head = 3.04 / (Pi * (2 1/16)**2) = 0.227” = 5.7mm
So that’s not to bad really. Just need to make sure the new piston head is not touching the spark plugs, and I don’t think the valves are going to be in the way, as they will be almost closed when the piston is at TDC.
Looking promising 🙂
Well after my perfect lesson today, started working on the engine. All I had to do was putting the magneto’s back and run the engine, first on the avgas 100 octane that’s in the tank and then on 91 octane car petrol.
Wasn’t that straight forward, 2 things slowed me down so I finished a bit late…..
Putting the magneto’s back, means I had to put the couplings on the back of the engine that the mag’s connect to. These use a spline I think you call them, not sure. A little piece of steel going into a slot on each end. Anyway, took me a long time to get them on, but got there in the end.
Put the magneto’s on set the ignition timing to 30deg BTDC, and tested the mag that’s driven from battery. When turning the engine around, with the front spark plugs out, you can nicely hear the spark, Cylinder #1, #3, #5, #2, #4…….. So yes all good and at the right time.
Next I reset the tappet clearances to what Wayne told me: .020″ for mixture and .025″ for exhaust valves.
OK time for starting:
Put my two steel pins into the ground to hold the tail down. Nice bright yellow big chocks in front of the wheels. Priming with the throttle closed, primer valve open and ignition off. Swing the prop which makes the carburetor drip lots of fuel, until the prop is in the right position to start.
Throttle set, mixture half, priming off, both mags on, power switch on, climb out of the cockpit and swing the prop.
Started straight away, but also stopped less then a second later. Tried this a few times, half a dozen times, but no luck.
Now I had this before. That time it was the mixture control cable that wasn’t set right after taking off the carburetor. And I was just not giving it enough mixture (fuel) and that’s why it didn’t want to go, this is a few months ago. But I checked the mixture lever, and it was fully open and still not starting.
So I tried it a few more times. Wayne just came back from some flying with his plane, when he asked me if I need help. “Yes please” I said so I started explaining, and while I was, I realized that the mixture valve needle must be blocked or dirty, everything else worked just fine. I noticed that I hadn’t closed the fuel valve on the fuel tank the last time when we flew the Bleriot.
Wayne climbed under the fuselage, behind the main landing gear, and I went through my starting procedure, and at the moment the engine sprong alive, he blocked the air intake of the carburetor, causing a lot of suction, enough to clear the fuel passage !!!!!! Yes it started 🙂
Warmed up the engine and after a few minutes went to full throttle. After the tiny bit of CAM timing adjustment, there was no change in engine refs, still just under 1900 rpm.
So next I drained the 100 octane fuel from the tank, and filled it up with 91 octane. You only need high octane fuel for high compression engines, and this one is so low in compression (1 : 5.4) that it should be able to run on 91 octane car fuel, the lowest you can easily get here. There is probably lower octane stuff but not to worried right now. Lower octane fuel burns faster, so I was expecting some change in the engine rpm, but no, no change. I did notice that I had the run with a richer mixture setting, but yes still the same old just under 1900 rpm.
This time I closed the fuel valve on the fuel tank, and let the engine run the carburetor empty, which takes a few minutes, and is also sugested in the manual to make the engine nicely cool down, but maybe also to empty the carburetor so it stays clean!!!!!!
To be on the safe side, next time I am going to use Wayne’s exhaust analyser, to be sure the carburetor is set right, but that’s for next time.
Then we start working on different pistons to increase the compression. That will surely increase the power !!!!!!!!
I was talking with Evan, my test pilot yesterday, and what he is saying makes sense. Currently my engine is running at the required speed of 1900 rpm static and 2000 rpm in flight, so that’s good. Problem is that there isn’t enough thrust to fly. Have a look below at the propeller on the 1928 plane powered by a Velie like mine. I know the plane is very different, but the prop is like every modern prop, pointy. Mine is like the early ones, were they were initially copying the boat propellers. So maybe I do need to make changes. The problem of my propeller is that the “chord” of my prop is so big that it is “using” a lot of power, wasting power.
1928 Monocoupe 113 – N7808
Location: Pioneers of Flight
Production of the Monocoupe was sporadic until 1928 when the company became associated with W. L. Velie, a former car manufacturer. Velie brought the Monocoupe a reliable source of small engines. The 113 was manufactured by Mono Aircraft Corporation, which was a subsidiary of Allied Aviation Industries.
The Monocoupe was powered by a 65 hp Velie radial engine. The fuselage framework was built of welded steel tubing, which was faired to shape with formers and fairing strips, and then was covered with fabric. The cabin roof had a large skylight for vision overhead. The wings were built of solid spruce spars and spruce and basswood ribs which were also fabric covered.
The Monocoupe 113 was reasonably stable and quite easy to fly. By 1929, approximately ten percent of all licensed US aircraft were Monocoupes. The Monocoupe accumulated a good safety record and promoted longevity. Through the late 1930s it was not uncommon to see scores of Monocoupes flying all over the countryside.
The exceptional performance and sharp maneuverability of the 113 drew the Monocoupe to air races and other events where its pilot could show it off. During the 1929 air race season, many Monocoupes were the headliners. The 113 was also used in the primary phases of flight instruction by flying schools.
EAA’s Monocoupe was the first of the famous Monocoupe line, which was among the earliest cabin monoplanes. The airplane was meticulously restored and flown to the EAA Museum under its own power. At that time, it was one of the last flyable 113s in existence. The Monocoupe 113 is an example of the type of airplane that dominated the light plane scene for several years. In 1968, John Hatz loaned the Monocoupe to the EAA Museum. The airplane was put on permanent display in 1977.
Got to the airport early to measure the exhaust emissions. Wayne has got an analyzer that shows you how good the combustion is really: lean – correct – rich.
A bit on this in Wikipedia : https://en.wikipedia.org/wiki/Air%E2%80%93fuel_ratio
But just one step back. Last time, last week when I had the engine running, I saw issues. Engine had problems running. It ran for a short time with the fuel that was “primed” into the carburetor. Here I was thinking something was wrong. Maybe the 91 octane that I am using now, or the last cam timing change….
It turns out that the engine wasn’t happy because it didn’t get enough fuel !!!
After the valve timing change, it’s sucking in more air during the intake cycle, which is what we wanted, but I never thought it would make such a difference. With the exhaust analyzer, we can now see that the engine is just running to lean at full throttle. In the end the only way to start it was by opening the priming valve a bit for a while, giving it extra fuel until it ran OK.
And I also noticed the oil heating up faster, plus I could feel warm air coming from the cylinders while the engine was running. All of that indicates that the engine is running lean.
So Wayne and I started talking about fixing this. checking the main metering jet, just making sure it was clean etc and maybe looking into a bigger jet.
Somehow we started talking about different carburetors. Then suddenly he mentions a SU carburetor he has in a draw somewhere. A very simple constant velocity side draft carburetor. It’s constant velocity as the venturi size is adjusted as the air demand changes. More air bigger venturi. Resulting in a constant velocity of the air flow. As the piston moves up creating a bigger venturi, a fuel valve needle moves up with it, allowing more fuel. With the right needle shape this results in a constant fuel / air mix ratio.
Also when flying higher or with a low air pressure, no adjustments need to be made, as its adjusted automatically.
Have a read here: https://en.wikipedia.org/wiki/SU_Carburettor#Operating_principle
And a little video explaining how the SU carburetor works (just the throttle and the fuel valve):
So yes Wayne is going to make a tube with flanges to make it fit to my engine and just see how it performs. He is adamant it is going to work well. It’s for engines up to 80 Hp so that’s the right size for me. It’s a lot simpler in operation. I like that !!
With my current carburetor, there are 3 controls, throttle, mixture and priming valve.
This one only has 2. Throttle and mixture. But the mixture is just for an adjustment during the start were you can make it a bit richer, almost like a choke, but it works different. With my old one you had to adjust the mixture to make the engine run right, depending on altitude and the conditions on the day I suppose. But this one adjusts the fuel flow by itself, by measuring the air flow and adjusting accordingly. Very clever.
Below you can see the engine side of the carb with the butterfly valve.
And here you see the piston that moves up when more air is sucked into the engine. Attached to the piston, a needle valve, so when moving up, the needle goes up and more fuel is sprayed into the venturi.
So yes after it is attached to the engine, we need to modify the control cables from 3 to 2 (one becomes redundant), and likely re position them a bit, and reconnect the fuel line.
Can’t wait!!!! 🙂
So happy with Wayne’s support ! If you need anything done related to planes, talk with him !! http://www.lightaviation.co.nz/
Spend most of the day today installing my “new” carburetor An “SU” for people that know about them 🙂
Two weeks ago Wayne with my help welded the pipe between the engine and the carburetor, and last weekend we modified it a bit to make it fit just perfect.
So today I bolted it to the bottom of the engine, connected the two controls, one for the throttle and one for the mixture control. This last one is only used for starting, to make the mixture richer.
After 4 hour, I rolled the Bleriot outside, pinned it down put the chocks in front of the mail landing gear and primed it. Maybe my first start is always failing because it scares me a little, but every other start, and I did half a dozen were all perfect. Almost like it starts even easier now.
Within no time I had people gathering around me, basically because it sounds so nice. They were all wondering were that nice sound came from 🙂 🙂
Turns out that with the new carb, the mixture is a lot better and more even and all cylinders fire, just nicely, where as in the past you could almost hear some miss fire….
Still working on the fine tuning of the mixture, to get that right, and hopefully that will give me the result we have been hoping for, more power. At least now I feel the carburetor is more reliable as its so simple, so that is a great step forward !! 🙂
Below a few seconds of one of the starts, still running at idle speed. VERY NICE. Yes an old fashioned black and white video 🙂
After work I went to the airport to run the engine and try to set the mixture.
The engine started so easy !!! Great 🙂
After a idling for a five minutes, I started playing with the little pin that pushes up the piston for setting the idle speed mixture. If the engine slows down, the mixture is to lean, so you need to make it richer, with a little screw. If it speeds up it is to rich, so you need to lean it off.
In my case it was running to lean, so I started making it richer and richer, until I couldn’t go any further. Even at the highest setting it was still running to lean. So that’s the first finding……
Then at higher revs, while in the cockpit, you can make the mixture richer with the second control. For all speeds but hardly noticeable for the max speed, the engine was going faster when making the mixture richer……
So my conclusion is that I need a different “needle” that releases more fuel for all speeds. Going to see the guy tomorrow, and get one 🙂
Wayne told me to go and get Plasticine 🙂
Cutting it up, like cheese, and sliding it into the cylinder through the spark plug hole, smallest hole, see photo right).
I did cut up just a bit more than what would fit in the combustion chamber.
I fitted the spark plugs , and started compressing the cut up Plasticine, by pulling the propeller around. When it was almost at the TDC position, I couldn’t get any further, so that was good. I took one spark plug out and pulled the prop until the piston reached TDC.
This is the only bit of Plasticine that came out. Pretty good estimation !! 🙂
And on the right you can see what came out of the cylinder. Perfect !!!!
Now what ????
In this post , I calculated how much the combustion chamber needs to reduce in size. From 11.39 “cube to 8.35 “cube so that’s 3.04″cube.
With a cylinder bore = 4 1/8 ” that means the piston needs to go up by 3.04 / (Pi * (2 1/16)**2) = 0.22″ = 5.7mm.
I spoke with an engine guy today who is dealing with the same company in the States, Wayne told me about for making my new pistons. The only valuable information I got out of him was that need to make sure the valves and the spark plugs aren’t going to be interfering with this extra height (pretty obvious), so possibly need to create some voids for that, to keep the same clearance !!!
Don’t know how I am going to do that yet….. But I will find something I suppose, just have to. And then pass on that information to a company who makes the pistons !!!
Next day, this is Sunday morning when I woke up, I realized how easy it was going to be. This what I will be doing:
With the same Plasticine, I will make a 5.7mm disk. The amount that the combustion chamber needs to reduce by.
Then I cut (on an angle) two bits exactly where the valves are, starting at 0 mm thickness on the outside edge, sloping up at the same angle how the valves are positioned.
Do something similar for the two spark plugs.
Then all material I have cut of, will have to be placed somewhere where its not interfering with valves or spark plugs, and all in a way so its nicely flowing. So when its finished it might look like this:
Been to see Richard today. He has been making and designing pistons for over 30 years. These days he designs the pistons and then orders them from a US company.
Richard was very impressed with the homework I have done. He’s the right guy to help me with this job, pretty sure about that.
One of the things I am doing now is checking the figures I have stated before. Like the volume of the combustion chamber.
Using the Compression ratio, Stroke and Bore sizes, I calculated that the combustion chamber would be 11.39″cube = 186.6 cc. Using a bowl with water I measured the volume of the combustion chamber. Turns out the volume of the combustion chamber is about 200 cc = 12.2″ cube. Bigger then expected. Does that mean the compression is lower as well. And what about the power output. That would be lower !!!
To be sure I want to measure the real Bore and Stroke sizes as well. Are they really 4 1/8″ and 3 3/4″ ?? OK just measured them and yes they are.
With these Bore and Stroke figures, the compression ratio I really have is 1 : 5.1 not the 1 : 5:4 I was expecting and the power output wouldn’t be 65 hp but a lot lower !
The other bit of information is that my Velie engine doesn’t have the original cylinders and cylinder heads. I have a cylinder with integrated head from a LeBlond engine, possibly a “LeBlond 70-5DE”, but I am not sure. That engine looks to have the same bore and stroke dimensions. Going by its name it would be rated at 70 hp, but who knows. There is hardly any information I can find on the internet…. I am thinking that the pistons used on that engine wouldn’t have had flat tops but a dome. They couldn’t have produced 70 hp with my pistons !!
I just need to go by what I have and do my calculations and measurements !
All very promising 🙂
More soon !!
Last night I made some Plaster of Paris, pored it in a plastic container and put my Plasticine “combustion chamber” in, upside down.
This is what I got this morning 🙂
What I plan on doing , is glue a flat piece of something to it, covering the face where the piston would sit in TDC position.
Then I can pour water in through the “spark plug” hole and measure exactly how big it is. It should work as long as the seal I intend to glue on it is in the same position as the top of the piston.
“a few days later”
Yes, have measured the combustion chamber volume. Its even bigger, its 204 cc ( = 12.45″ cube )
This gives me a compression ratio of (50.115 / 12.45) + 1 = 5.0 . Very low, almost unheard of !!!
Resulting in a lot less power then expected with the original compression ratio of 5.4
After Wayne showed me an example of how more hp is created with a higher compression ratio, I found this explanation by David Vizard, where he compares two engines with extreme different compression ratios:
For a moment, let’s imagine that both the 15:1 and the 2:1 cylinders start off at TDC with 1,000 psi. As the piston of each cylinder moves down the bore, the drop in pressure follows a distinctly different line. The 15:1 cylinder drops pressure much faster than its 2:1 counterpart because of its more rapid change in volume. It only has to go down the bore a short way for the original volume to have doubled, whereas the 2:1 cylinder must travel almost half way down the bore to double its original volume. At the bottom of the stroke the 15:1 cylinder has dropped down to about 25 psi above atmospheric whereas the 2:1 cylinder is still at some 260 psi. In simple terms, the high-compression cylinder, when the exhaust valve opens at BDC, is only dumping 2.5 percent of its original pressure whereas the 2:1 cylinder is dumping 26 percent.
Very interesting !!
Went to a engine re conditioner company today, a place were Wayne used to work. Yes looks like its happening. Honing, basically machining/scraping/sanding the inside of the cylinder so that its as new, ready for my new pistons. Need to remove the remaining 4 pistons from the engine in the next few days !
Took the last two cylinders of today. Wow, never realized, but yes in a radial, after stopping the engine all the oil drips down to sit in the sump and inside the two bottom pistons on either side of the sump.
But anyway, I will be dropping of the remaining 4 cylinders at an engine conditioning workshop “Motor Reconditioners” here in Christchurch today so they can be honed, so yes progress made towards “as new” cylinders and NEW pistons 🙂
And yes, glad a have a good oil drip tray !!! Thanks Sam 🙂
😊 Picked up the honed cylinders today from “Motor Reconditioners” here in Christchurch NZ !
You can feel that the wear is gone ! And looking at picture below you can see the typical honed surface almost like rough sandpaper style grooves, circling around the inside of the cylinder. Sort of looks bad in this picture, but its good !!!
Went to Richard, the piston man from “Proturn Engineering” straight afterwards, so he could measure them and finalize the design. Hope to hear from him tomorrow or the next day !!!! so I can see what they look like (on the computer screen) before they are ordered in the States !
Been to see Richard again today, and yes the design of the new piston is ready. This should give me a compression ratio of 7:1 just a nice step up from what I have now, but still a modest ratio. Two computer model images to give you an idea what they look like. You can see the extra dome on top of the “current flat top” and the clearance for the two spark plugs, and for the two valves (mixture and exhaust) 🙂
😊 Yes the piston’s are on their way to Christchurch !
Not long now !!!
I have the new piston’s now, nice and shiny. First job is to file the rings so the gab is about 0.02″ That might be a big job, 15 rings to do. Checking to see if they fit while I go.
Not a lot else to say, just nice and interesting.
Above you see two angled surfaces to keep the clearance for the valves, and the round cutouts, for the spark plugs and a channel to create a flame front that go’s on an angle creating a flame front that swirls, better combustion !
Wow been putting the Oil and Compression rings in the pistons. Learned a few things here:
The compression rings, the two solid ones:
- are ease, strong enough.
BUT the oil ring is very fragile:
- You need to make sure you warm it up, I used a bowl with hot tap water.
- Squeezing the rings, by pulling the ends together or apart for putting them on the piston. If you just squeeze them together for checking the gab with 2 fingers, they snap… 🙁 Had that happen 3 times until I realized what was happening !!
Started putting the cylinders back on the crank case, the main engine body. After the top one, Cylinder #1 was on, I noticed that one of the bottom conrods was “stuck” inside. So off the cylinder went again. wiggled the mast conrod a bit and out it came 🙂
Anyway, I have 4 cylinders on now (only 3 shown below) , one more to go , then the exhaust !!
So almost there !!!!!!!
Wayne came just when I was leaving. He was really interested in what it looked like, and how it performed. So we put two spark plugs in cylinder #1, and pulled the prop around. He was happy ! 😊
Yesterday and today been working on the engine after work, and finished everything I think:
- All cylinders installed
- Ring exhaust is on
- Tightened the top of the carburetor
- Wire locked the oil drain valve
- Filled up the oil tank
- Installed the valve push rods, and
- Greased the valve rockers
I think I am ready to run the engine, sometime soon.
Oh yes, a photo here looking straight into the spark plug hole. What you see there (yes really) is the flame front slot that’s cut in the top of the piston. In exactly the right position !
Going to try it without adjusting the ignition timing initially, and see how it goes. But I am expecting to get some issues with back firing, a bit scared about that……
Today I had a lot of help from Wayne, setting up the mixture with my SU carburetor. He knows engines !!! 😊
And guess what, with the slightly higher compression, I get about 2100 rpm, that’s 100 higher.
But I do notice that the engine is getting hotter quicker. Can’t be running full power for 5 min on the ground but that’s ok. When flying it will get enough cooling 😊
So now it’s s matter of editing for a good day and try it out !!!!!
Today, Rutger and I spend about 4 hrs getting the Bleriot ready for the show. All went well !
Luckily we have this massive hangar to do it in. Very wet outside !!! But It looks like the weather is going to be on our side by the time the show starts !!! 🙂
Also, I am getting the feeling that I might have to start looking for a different propeller to get more performance, but will see later. Hopefully we find another thing we can tweak a bit, to squeeze a bit more power out of the Velie 🙂
So yes today I have been talking with a lot of people about my propeller. And the consensus is that I might need a bigger pitch, basically grabbing more air, as the engine itself is powerful enough to pull that through the air.
Would love to just try a prop, any prop, that fits my hub, and see what the difference is. But that hub is the big problem. This hub, mounted on the crank shaft, holding the prop is an old American style one. I would be lucky if I find one.
The bolt pattern is 4 5/8″ (117.475mm) diameter, 6 bolts. That gives you 2 5/16″ (58.7375mm) spacing between bolts!
Just in case someone is reading this: If you have one, let me know. Oh and yes it is a clockwise (from the cockpit) rotating prop !
I did get the name of a guy here in NZ who has been making lots of old style props for famous people, with tons of knowledge, so might start talking with him. He is Jeff Fox, lives on the North Island, around Auckland I think….
Today I mounted the valve rocker covers, forgot yesterday…
Had help from Nigel Sheppard today. He also helped me last time (2 years ago) machining a bit of Alu for my stick.
This time we were talking about the air inlet of my SU carburetor. Currently there is nothing mounted to it.
So air basically goes from the big wide world, past these sharp edges into the carburetor. This creates lots of turbulence, and doesn’t help good carburation (mixing fuel and air).
So he was going to make a trumpet, or a bell curved piece of steel. Wasn’t going to be easy. He remembered that Wayne (I think his name was) from the Car Museum, next to the Aviation Heritage Centre used the same carburetor in his Jaguars, and might have something I could use.
So of I went to see him, and there he was talking with two other guys, we recognized me, and said, Oooo there’s the Bleriot man !! 🙂
Anyway, yes he had one I could have !!!!!!!!! Great 🙂
So went back to Nigel, who welded a mounting plate to it !!
Its on the carburetor now, looks great.
Might build a air box around it, with an air inlet facing forward later, to improve it even more.
At least this will improve the air flow a little. All little bits help !!!!
Next to me in the big BP hangar, is a really nice little by-plane made by Louis McNair, his dad Robert and grand-dad Wallace:
What I want to talk about is what Wallace had to say !! 🙂
He has lot of knowledge of engines, so started talking about the optimum valve timing etc. Straight away we were checking mine 🙂
Exhaust closing about 20 or 30 deg past TDC, and mixture opening about 5 to 10 deg before TDC. Yes he was happy with that.
Talked about a few more things, and then the discussion switched to the exhaust collector ring.
What I have is basically a collector, picking up all the exhaust and spitting it out down below. All nice, BUT
The big problem engine people have is that when the piston get’s to TDC position (Top Dead Centre), the exhaust valve is still closing and the mixture is already opening (see above)
When a piston is in this position, and another cylinder is just pushing all the exhaust gas out, into the exhaust collector, you have the situation where “foreign” exhaust gas is entering another cylinder that is just about to start sucking up a fresh amount of mixture (Air and Fuel).
This action basically stops the mixture from entering its cylinder for a while, and even worse, this exhaust gas will stop it from burning properly I think….
So basically you need to make sure that each cylinder has a long enough exhaust pipe, to contain 2 exhaust cycles I think (calculated using volume, and speed, and …..) before they can be combined into one big exhaust pipe.
This of cause is very impractical, so on old engines you often see stubs on each cylinder. No common collector, just a short bit of pipe, and off it goes into the air.
Now to prove that my engine has the same problem, I made this Excel spreadsheet showing the exhaust and air intakes of all 5 cylinders. And yes theoretically I have this same problem. Not to bad for some of the cylinders because sometimes the distance from the exhausting cylinder to the cylinder getting mixture and the distance to the collector outlet make it unlikely that exhaust gas will go the wrong way. but there are definitely situations where it will go wrong:
You can see that at the TDC of every piston movement/ position, were the mixture valve is opening and the exhaust is still closing, another exhaust valve has already opened (exhaust valve is open before, during and a bit after the rising curve and the mixture is open just before, during and a bit after the falling curve).
And because that exhaust valve is opening early, the exhaust gas is already flowing out of that valve and into the collector ring.
So for every cylinder where a mixture valve is opening, another cylinder is already exhausting gas.
Not every combination will cause a problem as the opening exhaust valve could be on the other side of the collector ring somewhere.
Below is a list of cylinders with opening mixture vales and exhaust valves blowing exhaust gas into them:
So maybe not such a problem having an exhaust ring but worth to try without the whole ring collector.
Just a comment on the Velie that was on the Bleriot picture I send to Jack in the US, that one had stubs !!!! See below 🙂
You can clearly see one stub on the left, in the shade two on the top right side by side for the top cylinder and the one to the right. And then there will be two at the bottom, but I can’t see them !! 🙂
I always thought that was, because it was cheaper and easier that way, but maybe there was more to it !!
I keep on changing the reason why we think the engine is not performing anymore. This is after I put the new pistons in a couple of months ago…..
Today Rutger (my son) and I went back to the hangar after we dropped of the Bleriot on its trailer from the Omaka CF2017 trip just over a week ago.
We assembled the plane again. I took the opportunity to put some new foam in the gab between the root of the wing and the fuselage, and this time I used a electric bread knife to cut of the excess material. That looks 100% better then what I did last time (this was quite a few months ago) .
One thing I noticed immediately when I was pulling the Bleriot of the trailer is that it was dripping a lot of oil from one of the exhaust outlet’s. Something I have never seen before. I didn’t understand and stopped thinking about it as I was busy putting the plane together.
UNTIL, I was finished and was about to leave, when Wayne arrived at his hangar. He said he had been thinking about my engine, as you do when things aren’t right 🙂
He recons one of my piston rings is broken.
That’s when it clicked inside my head:
- My previous thought about having problems with my exhaust didn’t make sense for one reason: “How is it possible that the engine was deteriorating over the days during the show”.
- The oil was dripping from the exhaust right next to the cylinder #4 that had the really dirty spark plugs (note that cylinder #4 is at the bottom of the engine, so after stopping, it fills up with oil dripping down inside the engine)
- Wayne did notice a few weeks back, that one cylinder did have less compression then the other ones. Probably this one.
- I might not have been able to see the oil dripping out as this will only happen if the exhaust valve is open, and that depends on the prop position Not sure if it is but will check that next time.
So yes, I have one spare set of rings, so the next time I am going to the airport, I will start taking of that one cylinder, and hope that it has a broken piston ring. Hopefully it hasn’t damaged the inside of the cylinder. Wayne recons it should be OK, I mean, no damage…. Hope he is right.
I wonder if that ring, if it is broken, did break while running or maybe it got damaged at the time I put it in. Who knows.
TO BE CONTINUED….
After talking with Wayne last week, we decided that something was wrong with cylinder #4. We thought that a ring was probably broken but…
This is what I found. No broken ring ! 😊 But there was something else Wayne noticed. Above you see the new piston left and old one right.
The oil ring normally is a split ring with holes behind it. This is good for normal engines with the cylinders pointing up (normal in cars). But with engines with opposing cylinders and radial engines you need more oil “catching” as there is more oil splashing around. With my old piston (right) this is done with a big grove under the oil ring, and lots of holes. When the engine is running, the oil on the cylinder wall gets scraped off and “drips” back into the piston and then gets thrown back inside the engine.
With my new piston’s that extra oil catching mechanism is not there.
This means that
- There is oil getting into the combustion chamber, and that’s not helping the combustion.
- The film of oil prevents the rings from bedding in, as there isn’t good contact. This means the rings won’t seal as well as they could.
- Plus I also might have gabs in my rings that are possibly a little too wide.
So I am going to make a little modification to my two bottom cylinders, #3 and #4.
And re-check the ring gabs 🙂
Went to see Richard today who designed my pistons. Showed him what the problem was that I am having at the moment, and he agreed to cut a new slot into the piston with drain holes, just under the oil ring, to get rid of oil that splashes onto the inside of the cylinder, especially the #3 and #4 cylinders as they are pointing down.
So that’s great news. The bad thing is that it means I need to pull the remaining 4 cylinders off as well…..
Today I took the 4 remaining cylinders of again, so I can get the piston’s out. I left all pistons inside the cylinder so it’s easier to get them home, but the piston in the top cylinder, #1 piston slipped past the bottom ring. I couldn’t get it back in easily so pulled it out completely.
To my surprise I did find oil on top of piston #1. Wow so hard to believe.
With the new oil grove that Richard is going to add to my pistons, all that oil will be scraped of the cylinder and thrown back into the engine.
So even the top cylinder that I thought would be running OK, should run better without that oil in there. CAN ONLY GET BETTER !! 🙂