another poor man's car engine conversion

Yesterday I was talking to a friend who plans to power his single-seat
slow flyer with an engine from a Citroen Visa. I suppose this engine (a
linear descendant from the famous Citroen 2CV) is not well known in the
US, it is an air-cooled 2-cylinder boxer, in this particular application
it would produce some 45 HP.

My friend absolotely wants it in the plane as it is in the car, i.e.
with the clutch side rearward (the plane is a traditional "puller"), and
wants to take power from the clutch side. His idea is to have a belt
reduction "behind" the engine, then a transmission axle above the engine
to drive the prop. Now I'm sceptical 'cause I heard all kind of bad
things about transmission axles driving propellers, vibration not the
least. But he answers the axle needn't be long, as the engine is only a
2-cylinder.

Any thoughts / ideas / comments / experiences?
TIA,

On Feb 14, 6:38*am, jan olieslagers
wrote:
Yesterday I was talking to a friend who plans to power his single-seat
slow flyer with an engine from a Citroen Visa. I suppose this engine (a
linear descendant from the famous Citroen 2CV) is not well known in the
US, it is an air-cooled 2-cylinder boxer, in this particular application
it would produce some 45 HP.

My friend absolotely wants it in the plane as it is in the car, i.e.
with the clutch side rearward (the plane is a traditional "puller"), and
wants to take power from the clutch side. His idea is to have a belt
reduction "behind" the engine, then a transmission axle above the engine
to drive the prop. Now I'm sceptical 'cause I heard all kind of bad
things about transmission axles driving propellers, vibration not the
least. But he answers the axle needn't be long, as the engine is only a
2-cylinder.

Any thoughts / ideas / comments / experiences?
TIA,

Not a bad concept. I've spent some time thinking about the same
layout with larger engines. It has several advantages and a few
disadvantages.

Some advantages are that it moves the weight of the PSRU to the rear
of the engine and raises the propeller hub for better prop ground
clearance. It puts the radiator at the front of the engine with the
water pump mounted fan right behind it.

I think the key is that the shaft has to be thin and flexible to get
its resonance well below that of any other part of the drive train.
Going the other way to make a very stiff shaft raises its natural
resonance frequency so it's likely to match some other component
resulting in destructive resonance.

bildan wrote:
On Feb 14, 6:38 am, jan olieslagers
wrote:
My friend absolotely wants it in the plane as it is in the car, i.e.
with the clutch side rearward (the plane is a traditional "puller"), and
wants to take power from the clutch side. His idea is to have a belt
reduction "behind" the engine, then a transmission axle above the engine
to drive the prop.

I think the key is that the shaft has to be thin and flexible to get
its resonance well below that of any other part of the drive train.
Going the other way to make a very stiff shaft raises its natural
resonance frequency so it's likely to match some other component
resulting in destructive resonance.

You should model that sometime...

Charles

On 14 Feb, 14:26, bildan wrote:
On Feb 14, 6:38*am, jan olieslagers
wrote:





Yesterday I was talking to a friend who plans to power his single-seat
slow flyer with an engine from a Citroen Visa. I suppose this engine (a
linear descendant from the famous Citroen 2CV) is not well known in the
US, it is an air-cooled 2-cylinder boxer, in this particular application
it would produce some 45 HP.

My friend absolotely wants it in the plane as it is in the car, i.e.
with the clutch side rearward (the plane is a traditional "puller"), and
wants to take power from the clutch side. His idea is to have a belt
reduction "behind" the engine, then a transmission axle above the engine
to drive the prop. Now I'm sceptical 'cause I heard all kind of bad
things about transmission axles driving propellers, vibration not the
least. But he answers the axle needn't be long, as the engine is only a
2-cylinder.

Any thoughts / ideas / comments / experiences?
TIA,

Not a bad concept. *I've spent some time thinking about the same
layout with larger engines. *It has several advantages and a few
disadvantages.

Some advantages are that it moves the weight of the PSRU to the rear
of the engine and raises the propeller hub for better prop ground
clearance. *It puts the radiator at the front of the engine with the
water pump mounted fan right behind it.

I think the key is that the shaft has to be thin and flexible to get
its resonance well below that of any other part of the drive train.
Going the other way to make a very stiff shaft raises its natural
resonance frequency so it's likely to match some other component
resulting in destructive resonance.

You might like this.
http://ibis.experimentals.de/downloa...lvibration.pdf

jan olieslagers schrieb:
Yesterday I was talking to a friend who plans to power his single-seat
slow flyer with an engine from a Citroen Visa. I suppose this engine (a
linear descendant from the famous Citroen 2CV) is not well known in the
US, it is an air-cooled 2-cylinder boxer, in this particular application
it would produce some 45 HP.

In Germany we have some microlights on this engine.

http://www.ulf-2.de/

Under "Bilder" on the left you will see details of the engine.

KH

On Feb 14, 6:38*am, jan olieslagers
wrote:
.. But he answers the axle needn't be long, as the engine is only a
2-cylinder.

Any thoughts / ideas / comments / experiences?
TIA,

The "shortness" may not preclude harmonic vibration. Each situation
is unique.
I've never had any hands on with a @CV motor but from what I see he

http://www.youtube.com/watch?v=7mvTWiF6KFM

It looks to me like it would be much easier to put the belt drive and
prop on the flywheel end. Far fewer things to move and/or
modify..........

For some other interesting insights into the Citroen motor for those
like me that don't have a physical one in front of them to examine,
take a look starting at 1:50.

http://www.youtube.com/watch?v=2QTTAzJbL3w

Are there sources for these motors, and/or parts, in the states?
===============================
Leon McAtee

On Feb 14, 8:41*am, Charles Vincent wrote:
bildan wrote:
On Feb 14, 6:38 am, jan olieslagers
wrote:
My friend absolotely wants it in the plane as it is in the car, i.e.
with the clutch side rearward (the plane is a traditional "puller"), and
wants to take power from the clutch side. His idea is to have a belt
reduction "behind" the engine, then a transmission axle above the engine
to drive the prop.
I think the key is that the shaft has to be thin and flexible to get
its resonance well below that of any other part of the drive train.
Going the other way to make a very stiff shaft raises its natural
resonance frequency so it's likely to match some other component
resulting in destructive resonance.

You should model that sometime...

Charles

It's been done many times - and examples built. If the propeller/
shaft resonance is well below the lowest fundamental frequency of the
engine/PSRU, you're probably OK. If it's above the lowest fundamental
frequency, you're probably not OK.

The neat thing is that the most successful solution is also likely to
be the lightest.

As an example, look at the ridiculously skinny half shafts on the rear
of a Honda CRV.

I ran the models several times on a V8 with a simple flex-plate PTO on
the flywheel housing driving an overhead shaft via a cog belt. It
didn't look as if there would be any problems at all if the propeller
shaft was thin enough.

The V8 sat low in the nose, water pump forward with the radiator in
front of that just like in a car. The prop shaft went forward over
the engine. It would fit perfectly in a 3/4 scale P-40 or a Piper
Pawnee glider tug.

On Feb 14, 9:07*am, Karl-Heinz Künzel
wrote:

Under "Bilder" on the left you will see details of the engine.

KH
-----------------------------------------------------------------------------
Note the excellent method used for belt tensioning.

-R.S.Hoover

jan olieslagers wrote:
Yesterday I was talking to a friend who plans to power his single-seat
slow flyer with an engine from a Citroen Visa. I suppose this engine (a
linear descendant from the famous Citroen 2CV) is not well known in the
US, it is an air-cooled 2-cylinder boxer, in this particular application
it would produce some 45 HP.

My friend absolotely wants it in the plane as it is in the car, i.e.
with the clutch side rearward (the plane is a traditional "puller"), and
wants to take power from the clutch side. His idea is to have a belt
reduction "behind" the engine, then a transmission axle above the engine
to drive the prop. Now I'm sceptical 'cause I heard all kind of bad
things about transmission axles driving propellers, vibration not the
least. But he answers the axle needn't be long, as the engine is only a
2-cylinder.

Any thoughts / ideas / comments / experiences?
TIA,

A two cylinder air cooled 45HP engine implies heat rejection of some
portion of 70%/30% of 45HP/2, or a fraction of about 53 HP X 746 watts
from EACH cylinder.
39 kilowatts is serious heating, even if the biggest part departs via
the exhaust pipe. One reason why people pay attention to fins and ducts
- or even more, to water-cooling such engines.

BrianW

bod43 wrote:

You might like this.
http://ibis.experimentals.de/downloa...lvibration.pdf

That URL would do well to be presented to any engine developer.
Moreover, it's not only engines with jack shafts or quill shafts
that are affected. I read a comparable piece that was - perhaps
still is - available on the net about the historical development
of some Pratt & Whitney engines.
The P&W work also mentioned pendulum crankshaft dampers, one
of the methods not mentioned in bod43's reference.

The automobile clutch friction plate torsion springs mentioned
in the URL aboveremind me of a feature of the first motorbike
I owned; a 1936 BSA 250 CC side valve model with girder forks
and unsprung rear end.
The drive side of the crank was splined. Over the splines,
a chainwheel was free to rotate, but outboard of its hub
was a wavy edged cylinder. On this a splined drive hub with a
complementary wavy cylinder was fitted, and a stiff spring
pressed the driven hub to the chain wheel via those wavy edges.
If the crank wished to move, while the chainwheel stayed fixed,
the driven hub would slide outwards against spring force.
This provided a soft drive characteristic always useful in a
single cylinder engine.

Brian W