Has anyone ever attempted to build a "split single engine" using the same principle as employed in a Daimler Puch 250cc SGS twin motorcycle engine?

[Kasey]

Has anyone ever attempted to build a "split single engine" using the same principle as employed in a Daimler Puch 250cc SGS twin motorcycle engine?

 

[the engineer]

Has anyone ever attempted to build a "split single engine" using the same principle as employed in a Daimler Puch 250cc SGS twin motorcycle engine?

model engineer had plans for one you may be able to search back issues on line

 

[Kasey]

model engineer had plans for one you may be able to search back issues on line

THANKS, I'LL TRY TO FIND IT. At present I'm making a mock-up of a flat four of 340ccs based on a Victa twin 170cc mower, boxer engine, using its crankshaft and pistons x 4, via my 3D printer making the plastic cylinders, heads, double con rods etc. It's slow work but interesting. If it turns out ok, I'll get the thing cast in aluminium for a running engine.

 

[the engineer]

THANKS, I'LL TRY TO FIND IT. At present I'm making a mock-up of a flat four of 340ccs based on a Victa twin 170cc mower, boxer engine, using its crankshaft and pistons x 4, via my 3D printer making the plastic cylinders, heads, double con rods etc. It's slow work but interesting. If it turns out ok, I'll get the thing cast in aluminium for a running engine.

as you are talking to a small engine tech this is getting very interesting indeed

 

[the engineer]

these are a couple of briggs and tecumseh engines i have built thought you might like to see

 

[Kasey]

these are a couple of briggs and tecumseh engines i have built thought you might like to see

They look good and must have been quite a challenge if based on a single cylinder engine for each one.

If I could get a crankshaft from a B & S flat twin I'd maybe use it instead as 340cc may be too much for the 170 Victa twin crank. I've also made a matchbox sized, 4 chambered oiler on my 3D printer which now runs off C/C compression on one of my Victa twin mowers and feeds oil directly in after the venturi and on to both big ends first.. I'm still testing it for reliability as it must never fail. Ultimately I'd like to build a two stroke using the Puch principle with 4 stroke splash lubrication with a timed, vane, pulse type supercharger running timed, at about 1/2 to 1/4 crankshaft speed to keep it cooler and needing minimum lubrication itself. Maybe with 2 ,3, or 4 special graphile/carbon vanes could be used in the design, to pump in 340ccs each time. ie.170 plus 170 to both sides as it is a simultaneous firing engine as in an original Victa 170cc twin engine. That way I can bypass the crankcase altogether and leave it semi-sealed and no oil mix in the petrol ever needed.

 

[the engineer]

i well remember those victa twins while working in nsw tried to keep my eye out for any over here but none seem to come up
those roller cranks on the victa are pretty tough and will take some punishing
looking forward to what you come up

 

[nx06563]

Did you ever find the plans for the split single. I have researched them quite a bit but have never found plans for one.
I am in the process of designing a single 2 cycle just to better understand the functioning of the ports better but my goal has been to build a "twingle".

 

[the engineer]

this is the one i remember by re mitchell

 

[Kasey]

Did you ever find the plans for the split single. I have researched them quite a bit but have never found plans for one.
I am in the process of designing a single 2 cycle just to better understand the functioning of the ports better but my goal has been to build a "twingle".

Not yet but....The porting here can be rather interesting as the overlap between the 2 pistons at BDC allows for them to be open longer and still open even when the exhaust port has become fully closed. Thus it means almost 100% of the incoming charge cannot get anywhere near it in exhaust cylinder. That and the con rod angles at ignition are what give this type of engine tremendous torque compared to standard practice at ignition, which has only a few degrees of leverage on the crank.

 

[Steamchick]

A most interesting engine... THANKS!
K

 

[KenC]

Some years ago a split-single spark ignition engine came to me for restoration, and I seem to remember it had been featured in some magazine like Model Engineer maybe around 1945. At the owner's request I did not attempt to run it once restored and I think it ended up in the collection of the late Miguel Rancougne. It was quite well made and an interesting engine. Pictures are attached.
Ken Croft in SW France

 

[Kasey]

Thanks for this info. Double big ends make that bit easier. I've had to use a piggy back system for one, as there's no room to double them up like that. I wonder how many revs/min. it could do?

 

[davidyat]

I do remember as a child, in the 1950's my Dad had traded something for a Puch. I remember Him telling me it had 2 pistons and 1 rod with a common combustion chamber. Here is something off the net:

View attachment 119291
Grasshopper

 

[davidyat]

 

[Kasey]

Thanks for that. I believe it was fitted to German TWN and possibly Victoria motorcycles. It had some of it's porting advantages but maybe not the one of improved torque at low revs.

 

[GrahamJTaylor49]

If any of you "Engineers" want to see some very interesting engines try L.J.K. Setright's book "Some Unusual Engines",
It lists all kinds of curious engines from split singles to free piston engines as well as oddities like the Cross and Aspin
rotary valve gear. Well worth a look at. Published by Mechanical Engineering Publications Ltd, for the Institution of Mechanical Engineers.
Have fun.

 

[davidyat]

Want an unusual project? Try this one. Honda in the 80's made Formula 1 and Motorcycle racing engines with OVAL pistons! Here is a Vimeo video of what they looked like.

Grasshopper

 

[Kasey]

Not yet but....The porting here can be rather interesting as the overlap between the 2 pistons at BDC allows for them to be open longer and still open even when the exhaust port has become fully closed. Thus it means almost 100% of the incoming charge cannot get anywhere near it in exhaust cylinder. That and the con rod angles at ignition are what give this type of engine tremendous torque compared to standard practice at ignition, which has only a few degrees of leverage on the crank.

Want an unusual project? Try this one. Honda in the 80's made Formula 1 and Motorcycle racing engines with OVAL pistons! Here is a Vimeo video of what they looked like.

Grasshopper

That concept from Honda encourages me a bit, as I have 2 sets of 2 pistons firing together as a simultaneous 4 instead of just a twin. Just hope the big ends can ultimately take the increased load at higher revs.

 

[Peter Twissell]

It's not uncommon to find 4 cylinder race engines set up to fire two cylinders simultaneously.
The Honda NR engine was intended to pack more valves (and twin plugs) into each head.