The journey of the propeller….
At the time I started looking around for propellers here in New Zealand, I posted a message to my “plane friends” on http://groups.yahoo.com/group/airdrome_builders/ about my engine and how well it was going. I wasn’t asking about propellers, but, Guess what; one of my “plane friends”, also very interested in my project, contacted me and told me about Chad Wille (he LOVES his propellers).
Chad is a propeller manufacturer from “St. Croix Propellers” in Iowa in the US.
He flies a Bleriot that he built himself.
He also owns a Velie engine, like the one I am restoring.
And he has been building propellers for 40 years.
So “he is the ideal combination” !!!
Below is Chad with his Bleriot and a beautiful propeller:
In the weeks following my first contacts with Chad, I learned a lot about propellers.
His Bleriot here has a 1910 fan type Anzani which has 210 cubic inches. My Velie has 250 cubic inches so my prop will be similar.
- He has lots of knowledge of the Velie so that is useful….. Learned a few things about the problems he had with his carburetor. The primer draws raw fuel directly out of the float chamber and will cause a lot of troubles with the mixture and will run rough if there is not a good seal when it’s closed.
- Also the carburetor, would need a simple “scoop”, catching the air.
- And there is a heat exchanger just above the carburetor that needs exhaust gasses, tapped of from one of the exhausts, to preheat the air fuel mixture, but more importantly heat up the carburetor, to stop ice from forming inside.
- And finally, the magneto, might need some work on the coil and the capacitor (condensor) that’s integrated in the coil. The coil could be corroded and would fail to fire.
I asked Chad some questions about the power rating of the Velie, after my plane certifying man here in New Zealand asked me about it:
Gert, People that are not familiar with antique airplanes often think horsepower ratings matter. It doesn’t. Cubic inch displacement and prop diameter matter and these are unrelated to horsepower. A modern high rpm 90 hp engine won’t fly my Waco 10 at all, but it flies beautifully with a Curtiss OX-5 90 hp engine and a 100″ diameter prop.
Specifically to you, the Velie has 250 cubic inches and is extremely powerful, bears no relationship to say, a Continental 65 hp, it’s much more power. It’s a good choice for a Bleriot. The Rotec radial, which I have flown on a Bleriot, is too much, feels like too much, and changes the characteristics of the Bleriot as to lose all it’s charm. It’s a classic case of a slow antique being pulled by too much thrust. It makes for a lousy flying experience. The Velie is a very good choice. I would have used my Velie had I not had a Gnome rotary from the start.
Beyond that, the less power you use on a Bleriot the better and more authentically it flies. And since it is a good design by pioneer standards, it flies well regardless. Chad
After a lot of thoughts and talking with a local propeller, I decided to ask Chad for a quote:
Gert, I’d be happy to build you an 84″ diameter prop in the wide blade chord style for your Velie Bleriot. Delivery about 8-10 weeks.
I asked Chad more questions about propeller design and the relation with the engine and the Bleriot:
People misunderstand the relationship between a propeller design and engine rpm. It is only partly true, and only with clean modern airframes, that an engine should turn it’s maximum rated rpm in full throttle level flight (see below 1). For a fixed pitch prop this means it will run 2-400 rpm less during takeoff and climb when slow airspeed doesn’t allow the prop to unload. The misunderstanding comes from the idea that lack of maximum rpm is “throwing away performance” or that somehow the prop design is “wrong” is false. In the case of very high drag antique airframes this “maximum rpm” concept is even more utterly false.
Performance of propellers on antique airplanes is largely self governing. If the prop rpm is faster it means the primary load, the diameter is less. Lack of diameter is a critical failing in antique prop design because diameter is leverage and leverage is the most important aspect of good design for high drag antiques. If the prop rpm is lower it means that leverage is greater, an ideal situation for high drag airframes. These two scenarios happen to balance themselves perfectly, rpm vs diameter. They do not take into account other important factors such as planform, pitch, blade chord, airfoil and thickness however, and those become real issues of design for best performance. They are commonly referred to collectively as “the black art” of prop design. And I’m not going to go into detail about those here, except to say that they become the cumulative smaller issues that go into making a propeller great compared to having a so-so prop or worse, a club. The club will also fly the airplane by the way, but never well. For antique airplanes and engines, engine maximum rpm or engine over-speed is a critical loss of performance, while engine under-speed, low rpm, is not only acceptable but often results in a much better propeller/airframe/engine combination, provided that other factors (cumulative smaller issues as above) are not in error to begin with.
Lastly, some people may also not have the understanding, and maybe don’t have the experience. They insist on seeing a particular rpm number on their tachometer. They may (wrongly) believe that the perfect accuracy of a given rpm number is very important. It is not at all important if other factors are in error. In general it is correct on a clean modern airframe, but not on a very high drag antique airframes.
(1) Correct rpm is no indicator of correct prop design. Only that the overall load matches the engine.
I got some good references from other people in the US about Chad, so yes I got more and more confident he was the one that was going to make my propeller.
Today I accepted his quote, and ordered the propeller, made from Mahogany !!!
Next I started working on transferring money to his bank account, not that simple, but managed to get it done on the 13th of Nov !!!!
Got an email today from Chad that the prop will be ready in 12 days !!!!!!!
But because it’s winter there, it will take a bit longer to dry 🙁
But YES, its getting close to ready, I am expecting that it will be shipped in the second week of Feb.
Just spoke with Chad about box sizes and weight etc etc for transporting quotes. He is doing the final touch on the prop now. He is putting fiber glass on the tips I think he said….. before varnishing it, not sure now !
But yes all very exciting, that means the prop is REALLY there now 🙂
Can’t wait to open the box when it gets here !!!!!!!!!
Talking with transport company, trying to ship the propeller to New Zealand 🙂
YES got the email from Chad that it’s picked up and on its way to NZ !!!!!!!
It’s almost here. At customs in Auckland, 1000 miles from here 🙁
And yes it did arrive. Will pick it up after work from the airport here 🙂 Photos tonight !!!!!!!!!!
WOW, VERY IMPRESSED WITH IT. EVERY TIME I LOOK AT IT I FEEL HAPPY !!!!!!
Made the right choice to have the prop made by Chad 🙂
Today only had a little bit of time to work on my project, dropping of my parents at the airport going back home to The Netherlands, and a birthday party of my 2 year old grandson Levi 🙂
Any way, I found that my new beautiful prop is a little thinner as the original. This means that the 6 bolts going through the prop are a little to long.
Getting advice from Chad at the moment if I can drill the holes a little bigger, from 7/16 to 1/2″. The holes in the prop hub flanges are 1/2″, but the original bolts are 7/16″ except for where they go through the hub.
Yes, it’s possible to drill the hole up to 1/2″. Might do that as some holes don’t line up perfectly with the holes in the propeller hub. Chad said he would use new 7/16″ bolts and some washers in the flange of the hub to fill up the void, but as the holes don’t line up, its better I think to go up one size.
Today I stared placing 32 little magnets in 8 groups of 4 to the back of the propeller. Warren is making a little sensor to pick up these 4 “pulses” per revolution, so my tacho shows the exact engine speed 🙂
More in the next few days…
Got the sensor back that Warren made for me. He has his own business and makes current sensors with hall sensors, so the perfect man to make me a sensor to pick up the magnetic poles on the back of the propeller !
Below two pictures of the sensor, apart from the heat resistant sheeting around the cable, nothing else to see really 🙂
After I installed it I checked if it worked by connecting the supply wire’s to my car battery, parked right in front of the prop and used a volt meter to measure the sensor output.
Perfect, per revolution 4 times a 5V pulse, evenly spread over the revolution, as you would expect with the magnets as shown above.
So soon, I hope, connect the wires to the tacho and run the engine ……………..
Made a ring of steel sheeting today, got some cutoffs from work, to form the top of the 8 magnet poles.
Cut 8 bits the right length, and pored some epoxy over the magnets before the steel bits went on.
Then I removed the bits of match sticks, finished filling it up with the epoxy. Looking really good now. Ready to start on the sensor !!!
Sun 29 Nov 2015:
Spend 3 hours today connecting up the tacho. Time goes so fast when you are having fun…
The plan was to just connect it and run the engine, plus also add the leather covered back on to the seat.
But didn’t go that fast. Soldering the cable to the 3 individual cables going to the tacho gauge had to be done in open air and took ages, but I got there. Oh yes, there is no power in the hangar, so had to push the plane to another one that had power…
Then I had to take one wing of to get access to the gauge.
Luckily every time I needed help, someone happened to walk past and wanted to look at the plane, so that was lucky as they helped me removing the wing and putting it back on 🙂
So next time when I am back, will run up the engine and see how it goes. Hopefully that will be this Wednesday night after work !!!
Yes ran up the engine today. Was very windy today so decided to face it out of the wind, with the chocks and 2 pegs into the ground holding down the fuselage.
Getting good at starting this engine, always goes, after a few tries so that’s good 🙂
Now back to the Tacho:
The tacho works now so very happy about it, still want to check it against a external speed sensor, something optical, but yes pleased. The not so good thing is that it possibly doesn’t go as fast as was hoping. It was doing 1500 rpm which according to the manual of the engine equates to about 45 hp. Maximum speed is suppose to be 2000 rpm. I am sure, and always thought that the engine is limited by something. It doesn’t produce any more power from 40% throttle too 100%. Maybe its the carburetor… So soon I will need to start getting some experts in I think, to see what they think.
I also know that, when on the ground, the prop won’t go at the full speed, it will go faster when flying, but I somehow don’t think that’s 1/4 extra….. To be continued.
But happy with the tacho working 🙂
A few hours later:
Still thinking about that carburetor….
The engine runs OK at low rev’s, but at higher rev’s is limited by something. Also the mixture control is not behaving, basically closed mixture, it should slow the engine down, or at least do something, so that’s wrong.
But I have had problems with the priming valve in the past. What if it’s not leaking anymore at low rev’s, but at higher rev’s were the engine is trying to suck more air, its possible that some fuel is starting to come through this priming valve. When I open the priming valve just a little bit while its running, the engine dies straight away, so just a little bit of extra fuel will surly stop it from going to max rev’s. I know that my carburetor is an earlier model and that later models had the priming valve modified because of these or similar issues……
THAT’S my thought at the moment…..
Maybe I should go to a new simple carb that doesn’t have these issues.
Sun 13 Dec 2015:
GREAT NEWS (4 years and 3 days since the day we decided to start building the Bleriot…)
Yesterday I suddenly remembered some answers I got from Chad, my propeller man (see Mon 4 Nov 2013 above) in the early stages when I was discussing a propeller for my Bleriot in relation to the propeller speed. Have a read (4 Nov 2013 above here on this page) if you are interested. But this is basically what what he said:
The diameter is critical in antique prop design because diameter is leverage and leverage is the most important aspect of good design for high drag antiques. If the prop rpm is lower it means that leverage is greater, an ideal situation for high drag airframes.
And an earlier comment from him:
Gert, People that are not familiar with antique airplanes often think horsepower ratings matter. It doesn’t. Cubic inch displacement and prop diameter matter and these are unrelated to horsepower.
So yesterday I told him about my suspicions of the carburetor and my findings with the propeller speed of about 1500 rpm.
Chad came back to me this morning;
He thinks the 1500rpm is a bit low, but only marginal. He designed it to go about 1575 to 1675rpm. Also he doubts that I am having primer valve leaks, as that would effect the engine speed. Also and I knew this, when flying, it will speed up a little bit more.
He really thinks that the prop is still developing the necessary torque to fly well.
Now I didn’t tell him this, but the first time I saw the tacho speed, the engine went up to about 1600rpm, which is exactly what he designed it for !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 🙂 🙂 🙂
So I guess we need to try and fly this machine 🙂
I will tell my test pilot.
Sat 20 Feb 2016:
Hmm, just found this interesting website: http://www.woodenpropeller.com/Normale.html
There you see what prop is used on the Bleriot with a 25hp Anzani. It has the same diameter as mine and the same pitch !!!
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….