Flywheel Drive VW

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

DaveK

Well-Known Member
Joined
Apr 21, 2007
Messages
382
Location
Northern California
Does anyone have experience with the flywheel drive VW conversions? Great Planes has a kit to put a prop extension on the flywheel side of the engine which would put it on the larger bearing on that side. Is anybody using this, does it work out?
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,667
Location
Corona CA
From what I know of VW's you should machine a bigger thrust face onto the crank to take care to the reversed thrust loading on the crank. Maybe it is not even necessary, but it is certainly desirable.
Other than that It seems a perfectly reasonable way to drive the prop.
 

Turd Ferguson

Well-Known Member
HBA Supporter
Joined
Mar 13, 2008
Messages
5,883
Location
Upper midwest in a house
Steve Wittman ran his Formula V racer, the V-Witt off the flywheel end of the engine with a long prop extension. The plans for his engine are out there.
 

Pops

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 1, 2013
Messages
10,145
Location
USA.
When VW engines were first used in aircraft in the 50's, the prop on the flywheel end was the normal way.
I have been making my own flywheel drive parts ( Bob Hoover's drawing), but I haven't decided on what to do about the ignition yet. I do not want an electrical system, so I want to use a mag, but I will not use a Zertex ? Mag that goes into distributor hole. Friend of mine had one on his 1/2 VW and it didn't last 100 hrs. No one is making a Slick or Bendix Mag drive for the pulley end, so I have been doing some drawing. When I get it to what I want, where its as simple and easy to make as possible, I'll get one of my machinist friends to make it up for me. I can do it, but he can do a much better job than I can.
Dan
 

Pops

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 1, 2013
Messages
10,145
Location
USA.
From what I know of VW's you should machine a bigger thrust face onto the crank to take care to the reversed thrust loading on the crank. Maybe it is not even necessary, but it is certainly desirable.
Other than that It seems a perfectly reasonable way to drive the prop.
Correct. Also the main #1 bearing with the thrust face will have to have the oil flutes on the other side and the end play shims with have to have the I.D. opened up a little for the radius on the crank.
Dan
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
7,144
Location
US
I do not want an electrical system, so I want to use a mag, but I will not use a Zertex ? Mag that goes into distributor hole. Friend of mine had one on his 1/2 VW and it didn't last 100 hrs. No one is making a Slick or Bendix Mag drive for the pulley end, so I have been doing some drawing.
Dan,
The "magnatrons" used on the Aerovee are very reliable and inexpensive if built up from parts (Briggs and Stratton parts, I believe). Not very cheap if bought pre-made. When the magnet on the flywheel speeds through the magnetron coil, a spark ensues. The down-side from your perspective is that hand-propping won't provide the necessary speed/spark. Anyway, something to think about--maybe cheaper than a magneto even with adding a starter, alternator, and small battery. As a bonus, you could stay inside to start your airplane with a push of a button (none of us are getting any younger :)). Okay, I know it goes against the spirit of your project.

Added:
Didn't I see somewhere that a guy had rigged up a way to start his plane using a cordless drill or cordless driver from inside the cockpit? It was one of the WW-1 replica planes, I don't remember what type of engine, but it had a sprag clutch and a linkage to a 3/8" square male fitting in the cockpit, a gear engaged the flywheel just like a starter does. Attach the cordless drill, let it twist against a plate nearby, pull the trigger until the motor starts. This might be a way to get enough RPMs to fire the magnatrons without the cost, weight, and bother of an airplane electrical system. Safer than hand-propping, too.
 
Last edited:

Pops

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 1, 2013
Messages
10,145
Location
USA.
Dan,
The "magnatrons" used on the Aerovee are very reliable and inexpensive if built up from parts (Briggs and Stratton parts, I believe). Not very cheap if bought pre-made. When the magnet on the flywheel speeds through the magnetron coil, a spark ensues. The down-side from your perspective is that hand-propping won't provide the necessary speed/spark. Anyway, something to think about--maybe cheaper than a magneto even with adding a starter, alternator, and small battery. As a bonus, you could stay inside to start your airplane with a push of a button (none of us are getting any younger :)). Okay, I know it goes against the spirit of your project.

Added:
Didn't I see somewhere that a guy had rigged up a way to start his plane using a cordless drill or cordless driver from inside the cockpit? It was one of the WW-1 replica planes, I don't remember what type of engine, but it had a sprag clutch and a linkage to a 3/8" square male fitting in the cockpit, a gear engaged the flywheel just like a starter does. Attach the cordless drill, let it twist against a plate nearby, pull the trigger until the motor starts. This might be a way to get enough RPMs to fire the magnatrons without the cost, weight, and bother of an airplane electrical system. Safer than hand-propping, too.

Hand propping is no big deal, being doing that for ( I'll never tell), can't get any easier than a VW engine. I know all about the Aerovee system and that is one of the reasons among others why I would never buy an Aerovee engine. When you add all the weight for a starter and alt and battery,etc on the VW engine, you defeat the purpose of using the engine, might as well use a Cont. One of the reasons I get the performance out of my aircraft with the VW engine is I am striving to save every ounce that I can. Unlike most of the pilots today, I don't want all of the bells and whistles. IF I wanted a starter and no electrical system, I would build my own McDowell recoil starter system like on the Cont A-65's in the Aeronca Chief. Even that is adding weight that I don't need or want. Dan
 

Vigilant1

Well-Known Member
Lifetime Supporter
Joined
Jan 24, 2011
Messages
7,144
Location
US
When you add all the weight for a starter and alt and battery,etc on the VW engine, you defeat the purpose of using the engine, might as well use a Cont.
That's surely a valid approach. But some folks live under a Mode C veil, or need/want to fly at night, can't hand-prop any type of engine, etc. I'd hate for these people to write-off VW power just because they need to have an electrical system. Hundreds of VW powered airplanes are out there with alternators, starters, and batteries, and they are flying just fine. Sure, any plane would fly better if it weighed less, but we all have things we want our airplane to do: there are a lot of Part 103 pilots who probably consider your nice, simple, fun little plane to be way too heavy and complex.
 

Pops

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 1, 2013
Messages
10,145
Location
USA.
That's surely a valid approach. But some folks live under a Mode C veil, or need/want to fly at night, can't hand-prop any type of engine, etc. I'd hate for these people to write-off VW power just because they need to have an electrical system. Hundreds of VW powered airplanes are out there with alternators, starters, and batteries, and they are flying just fine. Sure, any plane would fly better if it weighed less, but we all have things we want our airplane to do: there are a lot of Part 103 pilots who probably consider your nice, simple, fun little plane to be way too heavy and complex.
So they have their choice. Everything is a trade-off or compromise. I'll go light and good performance for a VW. I didn't say that if you want to fly with a VW engine you have to go without an electrical system and all the weight. Take your choice and pay the price. Flying fine and good performance is relative . I like a high power to weight ratio and in the area and at fields I fly from, and the type of flying that I do, its a lot safer. My little VW powered airplane has been on a paved airport 2 times in 7 years, so I do a lot of off runway flying. ( that is why I have "Farm Use Only" on the side of the door) :) I choose what fits my mission, other people are free to chose what meets their mission while using a VW engine.
Dan
 

revkev6

Well-Known Member
Joined
Mar 9, 2010
Messages
425
Location
massachusetts
When VW engines were first used in aircraft in the 50's, the prop on the flywheel end was the normal way.
I have been making my own flywheel drive parts ( Bob Hoover's drawing), but I haven't decided on what to do about the ignition yet. I do not want an electrical system, so I want to use a mag, but I will not use a Zertex ? Mag that goes into distributor hole. Friend of mine had one on his 1/2 VW and it didn't last 100 hrs. No one is making a Slick or Bendix Mag drive for the pulley end, so I have been doing some drawing. When I get it to what I want, where its as simple and easy to make as possible, I'll get one of my machinist friends to make it up for me. I can do it, but he can do a much better job than I can.
Dan
sounds like you mean a vertex magneto?? can't you buy a complete slick aircraft magneto from aircraft spruce for cheaper anyway??
 

Pops

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 1, 2013
Messages
10,145
Location
USA.
sounds like you mean a vertex magneto?? can't you buy a complete slick aircraft magneto from aircraft spruce for cheaper anyway??
Yes, that's it, a Vertex mag.
Wish someone would market a pulley end drive for a Slick or Bendix mag for the VW. That would save me the trouble of building my own. If I remember correcty, it would take the same mag from a Lyc- 235. Rotation and starting lag would work. Could be wrong, I looked it up a few years ago but I have sleep since then. :)
Dan
 

revkev6

Well-Known Member
Joined
Mar 9, 2010
Messages
425
Location
massachusetts
I think the point was the Slick or Bendix is you have to invent your way on a flywheel drive engine. No bolt on available.
gotcha, just looked it up, for some reason I thought they mounted to the camshaft...

Pops, do you know what failed in the vertex?? those are internal coil magnetos... could the coil have overheated??

Mallory used to make one with an external coil. it is also shorter than the vertex because of this. all of these units are made for racing applications so they may be too "hot" for long term use. I wonder if one could be rebuilt to a lower output to increase longevity. there are many reputable magneto shops across the country.
 

revkev6

Well-Known Member
Joined
Mar 9, 2010
Messages
425
Location
massachusetts
I had an idea since my last post, knowing that some vw engines were used in industrial applications I figured it would be a good bet that somewhere along the way they were fitted with a magneto... and it appears they were. scintilla magnetos were used... these are the base for which the vertex magneto is built. I would think it would be worth a look to what the difference between the two magnetos is?? with the scintilla being a generator magneto I'm sure it would be more oriented to the type of service required in an aircraft??
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
16,131
Location
Memphis, TN
All those old industrial ones are very similar to pre WW11 airplane mags. I had to think about the vertex problem for a while; the problem comes in gear, shaft, and bearing quality and the thrust of the cam on the gear. Running an engine not the way it was designed can nullify any of those things even though it worked ok in the original application. Homebuilt engines need homebuilt solutions and sometimes the only person that can figure it out is you, and not off the shelf.
 

revkev6

Well-Known Member
Joined
Mar 9, 2010
Messages
425
Location
massachusetts
All those old industrial ones are very similar to pre WW11 airplane mags. I had to think about the vertex problem for a while; the problem comes in gear, shaft, and bearing quality and the thrust of the cam on the gear. Running an engine not the way it was designed can nullify any of those things even though it worked ok in the original application. Homebuilt engines need homebuilt solutions and sometimes the only person that can figure it out is you, and not off the shelf.
the old industrial mags are scintilla/bosch which are the same as a vertex. the industrial engine was designed to run a magneto off the same distributor/cam gear so I don't see a problem there. he stated a failure with the magneto, not the drive which is internal.

$_57.jpg
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
16,131
Location
Memphis, TN
There is a thrust component to the cam and it can tear up the drive system. It can be fixed but if you are not planning for it and just bolting stuff on, it might break. That is a "New" style mag ;) the one on my 1966 Lincoln welder, which is no new design, is an airplane mag derivative. The old-timer on the field wanted it for parts.
 
Top