VW Engines

[eglijim]

That was the direction of my thoughts especially after photos were posted here of some pictures of squish head undersides.

Seem to have a reply from Greg which has not appeared on the thread suggesting that the impulse does not retard the timing, merely spins up the mag for an initial pulse. Can assure you that the Scintilla mag with an impulse coupling does retard the first spark . The impulse spring operated by gravity via a catch to "wind up" and de-activated by a bob weight system as the engine spins up. At hand cranking speed the spark is retarded til after tdc as the wound up spring is not released to spin up the mag til this point. We (legally) ran the motorglider with a heavily modified 1500cc magnesium VW engine with only one mag . If things went south , find a suitable field !.

 

[greg brillus]

Grobb 109 motorglider............? We use to fly in these regularly..........These had VW engine with three position prop, Fine, course, and feather. Lots of fun.............We use to buzz the campers on the top of Mt warning, scared the life out of them...............

 

[oexing]

Actually these VW engines were heavily modified for aviation by the Limbach company. So no way to add a second mag there, Scintilla standard I believe. Last Saturday we helped handpropping this ultralight biplane, no electricity at all. Problem was auto fuel that leaves some sticky gunk when dried after half a year in the Stromberg carb. The owner was used to this extended handpropping in spring, seemed to be normal - to him. In the end I talked him into getting a spray can of ether that did the trick easily. But still today I can feel all muscles in my right arm.
Thanks, Eglijim, your info on the "snapper" device seems logical, have never seen it in daylight but you hear the clicks when turning over the prop. Now have a quick look, the mod will delete soon . . .

Vic

 

[eglijim]

Actually these VW engines were heavily modified for aviation by the Limbach company. So no way to add a second mag there, Scintilla standard I believe. Last Saturday we helped handpropping this ultralight biplane, no electricity at all. Problem was auto fuel that leaves some sticky gunk when dried after half a year in the Stromberg carb. The owner was used to this extended handpropping in spring, seemed to be normal - to him. In the end I talked him into getting a spray can of ether that did the trick easily. But still today I can feel all muscles in my right arm.
Thanks, Eglijim, your info on the "snapper" device seems logical, have never seen it in daylight but you hear the clicks when turning over the prop. Now have a quick look, the mod will delete soon . . .

Vic
View attachment 21419

The motor in our Falke was the Stamo (1500cc) version with no form of generator or electric start, very light as based in the small early VW (Magnesium) crankcases. Searing 42 HP (claimed) and a fixed prop. Have often wondered why impulse units were not used on many old vehicles with mags, would have greatly eased and made safer using the hand crank or kickstart on anything temperamental to start.

 

[oexing]

VW beetle engine cases were all magnesium right to the end I believe. The type in my photo has 2 l big bore cylinders, about 65 hp and no electrics, just the one Scintilla mag.
I guess no impulse device was invented much before WW 2 in aviation or elsewhere. At that time rotating magnets made from modern material could be had with dramatically higher voltage as I see from a late 30ties military Bosch 6 cylinder mag with automatic advance and retard, 15 mm, more than half inch, sparks when spun by fingers. So starting was easier now , no real need for the impulse effect. In aero engines you have twofold needs for that: Higher voltage because of low propping revs plus the retard effect when timing is otherwise fixed at 23 degrees BTDC - to avoid heavy kickback while propping.
In cars and bikes you will find variable ignition timing, either manual or automatic, anyway, so no impulse device here, higher speeds while starting too.
Unfortunately the miserable spinning coil plus slip ring magneto survived with Lucas and BTH into the sixties, an anachronism as Magenti Marelli had a great rotating magnet plus automatic advance and retard from early fifties in Guzzi singles etc. , that type was very rare with Lucas or Bosch, no external magneto was found on German post war motorcycles anymore. BMW had a great mag ignition till end of sixties with rotating magnet and lost spark twin plug coil inside the engine case. I wonder if you could do a twin coil lost spark magneto on a V-twin to save a distributor - that is in effect the segmented slip ring with the spinning coil type.

Vic

 

[oexing]

Yes, there are some , but pretty rare ? What is your rating on these, great I guess ?

Vic

 

[eglijim]

Not

VW beetle engine cases were all magnesium right to the end I believe. The type in my photo has 2 l big bore cylinders, about 65 hp and no electrics, just the one Scintilla mag.
I guess no impulse device was invented much before WW 2 in aviation or elsewhere. At that time rotating magnets made from modern material could be had with dramatically higher voltage as I see from a late 30ties military Bosch 6 cylinder mag with automatic advance and retard, 15 mm, more than half inch, sparks when spun by fingers. So starting was easier now , no real need for the impulse effect. In aero engines you have twofold needs for that: Higher voltage because of low propping revs plus the retard effect when timing is otherwise fixed at 23 degrees BTDC - to avoid heavy kickback while propping.
In cars and bikes you will find variable ignition timing, either manual or automatic, anyway, so no impulse device here, higher speeds while starting too.
Unfortunately the miserable spinning coil plus slip ring magneto survived with Lucas and BTH into the sixties, an anachronism as Magenti Marelli had a great rotating magnet plus automatic advance and retard from early fifties in Guzzi singles etc. , that type was very rare with Lucas or Bosch, no external magneto was found on German post war motorcycles anymore. BMW had a great mag ignition till end of sixties with rotating magnet and lost spark twin plug coil inside the engine case. I wonder if you could do a twin coil lost spark magneto on a V-twin to save a distributor - that is in effect the segmented slip ring with the spinning coil type.

Vic

Not an issue for me now as we have sold the aircraft but for those who are not aware,of the regulations surrounding aircraft, you are not permitted to alter very much without going through significant paperwork.

 

[bmetcalf]

Yes, there are some , but pretty rare ? What is your rating on these, great I guess ?

Vic

Hah, it was one of those almost finished projects that got sold on when the kids arrived.

 

[eglijim]

Hah, it was one of those almost finished projects that got sold on when the kids arrived.

Kids, another idea that seemed great in the heat of the moment !.

 

[eglijim]

Actually these VW engines were heavily modified for aviation by the Limbach company. So no way to add a second mag there, Scintilla standard I believe. Last Saturday we helped handpropping this ultralight biplane, no electricity at all. Problem was auto fuel that leaves some sticky gunk when dried after half a year in the Stromberg carb. The owner was used to this extended handpropping in spring, seemed to be normal - to him. In the end I talked him into getting a spray can of ether that did the trick easily. But still today I can feel all muscles in my right arm.
Thanks, Eglijim, your info on the "snapper" device seems logical, have never seen it in daylight but you hear the clicks when turning over the prop. Now have a quick look, the mod will delete soon . . .

Vic
View attachment 21419

Have always enjoyed flying slowly and savouring the moment when not in any rush to go somewhere in particular, but preferably not backwards into a headwind. Vivid memories on really windy days of flying backwards in a glider while still attached to the winch cable(we all took turns winching so knew what to expect if the pilot did not drop the cable at the top) in an attempt to gain more height before releasing.