- Joined
- Jan 12, 2017
- Messages
- 570
HBAers,
Here's a note I just sent to a guy on the bkflier group on io (forum dedicated to builders and fans of Bruce King's BK-1.3), who has ordered a flywheel forward VW kit from GPAS and is wondering about using Leburg electric ignition. I thought the discussion might interest some of you here, and perhaps you have other ways of making this combination work. Love to hear feedback.
Joachim,
Glad to hear you were able to connect with Art at Great Plains and I hope he comes through with your order. Please keep us posted.
As for my own engine build, I have not gotten very far and do not have any pictures to show you.
As I see it, the challenge with using the Leburg ignition system on a flywheel-forward VW is figuring out where to put the magnets and the sensors.
With the prop on the pulley end, Leburg supplies a timing disc to hold the magnets which is designed to be clamped between the prop and the drive hub, with the sensors mounted to the case. Leburg recommends using a Honda alternator (CBR600F rotor) directly mounted to the back of the crank.
Flywheel-forward we have the flexplate/starter ring and the bell housing up front. Where would the magnets and sensors go within that setup? The obvious choice would be to mount them at the pulley end in back, but then you probably couldn’t use a crank-mounted alternator. I assume the powerful magnets in the rotor would interfere with the timing signals. By the way, Bob Hoover is the one who developed the concept of mounting a motorcycle alternator (Bob insisted the right term was dyno) directly to the crank, intended specifically for flywheel-forward aero VWs. He shared the idea with Steve Bennett at Great Plains, and your kit might include it. But I don’t see how it’s compatible with the Leburg system. (Please let me know if you see a way to make it work!).
My thought is to mount an aluminum VW crank pulley on the pulley end (funny enough!) and to mount the Leburg magnets on it. The pulley could then belt-drive an alternator mounted on top of the case. “Pops” on the Homebuilt Airplanes forum recommended a 12V 20Amp alternator designed for Deere tractors. I sourced mine from www.rareelectrical.com.
However, on reflection, I admit that the prospect of building a mount to attach a starter to the bell housing (per Bruce King’s concept) and another mount to attach an alternator to the top of the pulley end of the case, and getting starter and alternator to work probably, worries me (inexperienced in such things as I am).
One great advantage of the Leburg ignition system is that it makes hand propping much easier and safer. If I decide I can live without a starter, I might do away with the flex plate/starter ring, mount the Leburg timing disc instead, attach the sensors to the interior of the bell housing, and use the direct-drive alternator/dyno on the back (pulley end of the crank).
Even simpler would be to skip not only the starter but also an alternator. Might sound crazy to rely on electronic ignition without power generation and this would certainly not be a good idea for a cross-country flier, but I never expect to fly more than 1 1/2 hrs at a time, and dual ignition with two batteries ought to be safe. I would, of course, need to pay attention to properly charging the batteries before each flight.
Curious to hear your thoughts.
Best,
Mike
Here's a note I just sent to a guy on the bkflier group on io (forum dedicated to builders and fans of Bruce King's BK-1.3), who has ordered a flywheel forward VW kit from GPAS and is wondering about using Leburg electric ignition. I thought the discussion might interest some of you here, and perhaps you have other ways of making this combination work. Love to hear feedback.
Joachim,
Glad to hear you were able to connect with Art at Great Plains and I hope he comes through with your order. Please keep us posted.
As for my own engine build, I have not gotten very far and do not have any pictures to show you.
As I see it, the challenge with using the Leburg ignition system on a flywheel-forward VW is figuring out where to put the magnets and the sensors.
With the prop on the pulley end, Leburg supplies a timing disc to hold the magnets which is designed to be clamped between the prop and the drive hub, with the sensors mounted to the case. Leburg recommends using a Honda alternator (CBR600F rotor) directly mounted to the back of the crank.
Flywheel-forward we have the flexplate/starter ring and the bell housing up front. Where would the magnets and sensors go within that setup? The obvious choice would be to mount them at the pulley end in back, but then you probably couldn’t use a crank-mounted alternator. I assume the powerful magnets in the rotor would interfere with the timing signals. By the way, Bob Hoover is the one who developed the concept of mounting a motorcycle alternator (Bob insisted the right term was dyno) directly to the crank, intended specifically for flywheel-forward aero VWs. He shared the idea with Steve Bennett at Great Plains, and your kit might include it. But I don’t see how it’s compatible with the Leburg system. (Please let me know if you see a way to make it work!).
My thought is to mount an aluminum VW crank pulley on the pulley end (funny enough!) and to mount the Leburg magnets on it. The pulley could then belt-drive an alternator mounted on top of the case. “Pops” on the Homebuilt Airplanes forum recommended a 12V 20Amp alternator designed for Deere tractors. I sourced mine from www.rareelectrical.com.
However, on reflection, I admit that the prospect of building a mount to attach a starter to the bell housing (per Bruce King’s concept) and another mount to attach an alternator to the top of the pulley end of the case, and getting starter and alternator to work probably, worries me (inexperienced in such things as I am).
One great advantage of the Leburg ignition system is that it makes hand propping much easier and safer. If I decide I can live without a starter, I might do away with the flex plate/starter ring, mount the Leburg timing disc instead, attach the sensors to the interior of the bell housing, and use the direct-drive alternator/dyno on the back (pulley end of the crank).
Even simpler would be to skip not only the starter but also an alternator. Might sound crazy to rely on electronic ignition without power generation and this would certainly not be a good idea for a cross-country flier, but I never expect to fly more than 1 1/2 hrs at a time, and dual ignition with two batteries ought to be safe. I would, of course, need to pay attention to properly charging the batteries before each flight.
Curious to hear your thoughts.
Best,
Mike
