Oddball engines and prototypes

[malcy25]

I would have gone VW myself, probably all the same shit with a diferent badge anyway

Aye! And yep all variations of the same flavour!

[J.A.W.]

Enough with the junk posts..

Check this machine out.. Napier Sabre - scroll down to the final Mk VII, rated at 3,500hp @ 3,850rpm for take off.. ( on +20lbs boost/321lbs BMEP)

http://www.wwiiaircraftperformance.o...pier_Sabre.pdf

[WilDun]

This is an attempt by a optimistic modeller a few years ago at making a smooth running model engine. It would appear that the crankcases have been glued together with JB Weld or similar and the gears up front are running dry or maybe with a little grease!! - at around 12000 revs!!?
Then the inlet port timing (on the hollow crankshaft) would have to be changed on one of the engines as well because of the backward rotation.
It was a good thought though and probably by someone who wasn't an engineer but game to give it a try anyway! - it would be interesting to know just how well it did work, but we'll probably never know.

- what's the betting it didn't work?

[ken seeber]

Willy,
I agree the connection doesn't look strong at all. He could have easily added more bracing to beef it up. As to lubrication of the gears, I guess a small bleed from the fuel tank, given that the fuel is very high in oil content, might suffice. Or even a separate oil tank. Would be messy though.
This reminded me of a dragster in the US, many, many, many years ago where a guy made a W16 by joining two V8s and using the exposed ring gears to couple the cranks.

[husaberg]

Willy,
I agree the connection doesn't look strong at all. He could have easily added more bracing to beef it up. As to lubrication of the gears, I guess a small bleed from the fuel tank, given that the fuel is very high in oil content, might suffice. Or even a separate oil tank. Would be messy though.
This reminded me of a dragster in the US, many, many, many years ago where a guy made a W16 by joining two V8s and using the exposed ring gears to couple the cranks.

A bit of felt soaked in oil?

[WilDun]

Not 100% sure that exposed gearing is a good idea, but I would at like to see the shaft tunnels connected (up close to the gears) with a piece of ally plate (at least) to keep the clearance right. JB Weld is good I'm told, but not necessarily that good!
The crankshaft inlet timing I think might well be a real problem, - there wouldn't be much of a problem with vibration, unless the JB Weld let loose!
Apart from all that, it was probably done by an inventive teenage kid in America, (a Flettner in the making) and a very brave effort I think.

[J.A.W.]

Riedel had some interesting designs, even if some mills do look a bit lawn mower-ish..

http://www.odd-bike.com/2014/05/imme...of-design.html

[ken seeber]

I'm for it, let's give it another go. I think everyone who was into this thread understands where it went wrong and therefore how to keep it right.

Just for something different and not Ryger, I have posted some pics of a DI system that was mfg by Piaggio, under a system patented by a Dr Marco Nuti, also with Piaggio. The application was for a 50 ccc scooter. I think the system was called FAST, but could be wrong.

It was a hybrid 2 fluid system in that the air and fuel was delivered to the cylinder via a small inverted compressor directly mounted on the head. This was cyclically fed with a metered dose of fuel via a low pressure electronic EFI style injector. The unthrottled compressor was clearly mechanically coupled direct to the crank via a toothed belt. Unlike the Orbital system, which uses a solenoid injector to control the DI injector timing and duration, the timing and duration were fixed. I don't believe it was a great commercial success though.

I thought (and still do) that the basic system would be excellent for competition applications and, being an electronic dummy, also thought that a carburetted version would be the go. Drag out the old gear and take some pics. What I did was to also mount a small model aircraft engine to the head of an ARC kart engine (made in both air and water cooled versions) that was an Australian made kart engine, based very closely on the Yamaha KT100S engine and designed to compete with it. The compressor transfer passages were blocked off and the inlet was achieved by using the exhaust port. The valving was of a simple disc type, although in hindsight a good HC trap. No speed limitation issues, the fog coming out at up to 10k was impressive. The thought was that if it was throttled, ie the mixture was controlled with a carb, some form of favourable load increasing advancing timing could be achieved. Advantages would have been no high fuel pressures required, no fuel mixing (although it would have required a metered oil system (Autolube style) for the crankcase inlet) and fundamentally lower fuel consumption and unburnt HC emissions. Bit rough, this was over 15 years ago. In answer to the question did it work, yes it did. Only on an inertia dyno though, started, idled, free revved a bit, but never on a kart. Lost interest as the Australian karting controlling body, showing its usual level of initiative as being equivalent to that of a pregnant cockroach, just figured too hard as the rules disallowed any form of fuel injection.

[Lightbulb]

There was a guy who made a scale model with a 7 cylinder radial engine. The engine was made from 7 cox engine, 0.049 I think, with a slot car gear pinion running to a brass looking ring gear. The brass ring gear had the teeth on the inside.It seemed to run ok, but only ran for like 1 min or so. As it had 7 little fuel tanks etc. I asked him how he tuned it, he said he ran each engine on the bench with the same prop and fuel, and tuned each to be running 2 clicks richer than peak power. He put a spot of glue onto each needles so they could not loose their tune. It really sounded quite noisy and rattly.
Neil

[WilDun]

a system patented by a Dr Marco Nuti, also with Piaggio.

It was a hybrid 2 fluid system in that the air and fuel was delivered to the cylinder via a small inverted compressor directly mounted on the head. This was cyclically fed with a metered dose of fuel via a low pressure electronic EFI style injector.

What I did was to also mount a small model aircraft engine to the head of an ARC kart engine
No speed limitation issues, the fog coming out at up to 10k was impressive.
In answer to the question did it work, yes it did. just figured too hard as the rules disallowed any form of fuel injection.

Thanks Ken,
That was a good idea, I tried to explain that one a while back but couldn't find much on the net at all and was beginning to think I might have been dreaming!

I also thought about using a model aircraft engine, but in a different way, ie with the simple model aircraft ignition lighting up a rich mixture and delivering it into the cylinder already on fire and meeting fresh air from the normal transfers which was already compressed and raring to go! Probably wouldn't have worked unless the small engine was using alcohol fuel and glowplug.
Only difference here is that I only dreamed about doing that whereas you gave it a go!

Flettner also said that he had considered a small Wankel engine instead (but maybe as a valve only).

Sometimes competition breeds new designs, but often competition rules also stymie development in the wider scene. eg in Moto GP, insisting on four strokes only and even worse in Moto 2, insisting on Honda four strokes only!

Ok Ken thanks for getting this thing on the road again.

[WilDun]

There was a guy who made a scale model with a 7 cylinder radial engine. The engine was made from 7 cox engine, 0.049 I think, with a slot car gear pinion running to a brass looking ring gear.
Neil

I guess it really wasn't really AN engine, just a COLONY of engines, - I have three of those little Cox engines, noisy little buggers they are and don't have near as good torque as some of the little 'diesels' of comparable size - would be even more difficult with diesels, ie also having to set the compression ratio on each cylinder!!
Never mind, its good to see people attempting things (like the contra rotating engines a few posts ago).

[wobbly]

Sorry guys I had no idea this thread existed, but I do have a couple of things to add re 90* firing configurations.
I first got onto the parallel twin at 90 crankpin phasing when reading about experiments done on Pommie shitboxes that traditionally
have 0-360 cranks.
A couple of analysis were done by those with some knowledge on the subject and it started out that 72* phasing was suggested as being the best
overall compromise of primary and rocking couple generation.
A later analysis suggested the it was better at 90* with one piston stopped at TDC the other at max velocity around 1/2 stroke.
In any case the engines built for speedway sidecars were way smoother then the original 0/360 so the whole thing seemed a win win.
I did an analysis of the forces in the 180* Yamaha RZ 350 and concluded that the reduction in rocking couple was considerable and thus it was worth a shot
to rephase a crank and try it.

Using an Ignitech the ignition issue is non existent, simply using 2 lobes at 90* with a, close by , extra lobe to denote cylinder 1 for the ECU - and deleting waste spark.

Short story is that despite the big reduction in rocking couple, the added ccomplication of decreasing the 100% primary cancellation of the 180 configuration produced hideous
tingling vibes, due to a force vector I hadnt considered - that of the resultant vector force created when both pistons are at 1/2 stroke.
Thus no matter what primary balance factor was tried from 35 to 75 % it simply moved this hideous vibe maxima rpm around.

And this result was obviously thought about at KTM when designing the parallel twin 250 engine into its successful GP configuration, they added a balance shaft with a lobe
that nullified this 45* resultant vector, as well as increasing the system inertia to tame the mid ranges excessively rapid BHP rise delta that shredded tires and high-sided riders.

Going to the even fire TZ750, we have 3 scenarios.
First two as is used in normal 4T cranks.They have 1,2,4,3 or 1,3 ,4,2 firing (note this is firing order, not crank pin orientation, as a 4T always has pairs rising and falling together ).
But in both cases cylinder 1 and 4 will be at 180* - giving a huge rocking couple across the full width of the engine.
And the two inner cylinders will be at 90/270 or 270/90, both of which generate a smaller rocking couple at 90* to that of the outer pair.
Then we have the special case of 1,2,3,4 and when used in a 2T this will result in a pair of the same resultant vector force mentioned above, they will be at 180* and centered on
the cyinder pairs on each side of the engine.
This is alot further apart than what we see in a 180* twin, so I would expect that rocking couple to be alot worse than the normal 180* case.
Thus again a balance shaft is needed to control the couple from violently shaking the frame and the riders components.

But the rocking couple in a 180 twin can also be efficiently nullified by frequency specific rubber absorption mounting - as a young Furisawa did in the RZ350 to great effect.
So my take on using this firing order in a TZ750 is that it would result in a ball buzzing monster, unless a balance shaft was fitted ( possibly adapt the jackshaft ) or the whole frame was rebuilt to use
rubber mounts and torque control arms to resist chain pull forces.
Not worth the drama imho.

[husaberg]

Sorry guys I had no idea this thread existed, but I do have a couple of things to add re 90* firing configurations.
I first got onto the parallel twin at 90 crankpin phasing when reading about experiments done on Pommie shitboxes that traditionally
have 0-360 cranks.
A couple of analysis were done by those with some knowledge on the subject and it started out that 72* phasing was suggested as being the best
overall compromise of primary and rocking couple generation.
A later analysis suggested the it was better at 90* with one piston stopped at TDC the other at max velocity around 1/2 stroke.
In any case the engines built for speedway sidecars were way smoother then the original 0/360 so the whole thing seemed a win win.
I did an analysis of the forces in the 180* Yamaha RZ 350 and concluded that the reduction in rocking couple was considerable and thus it was worth a shot
to rephase a crank and try it.

Using an Ignitech the ignition issue is non existent, simply using 2 lobes at 90* with a, close by , extra lobe to denote cylinder 1 for the ECU - and deleting waste spark.

Short story is that despite the big reduction in rocking couple, the added ccomplication of decreasing the 100% primary cancellation of the 180 configuration produced hideous
tingling vibes, due to a force vector I hadnt considered - that of the resultant vector force created when both pistons are at 1/2 stroke.
Thus no matter what primary balance factor was tried from 35 to 75 % it simply moved this hideous vibe maxima rpm around.

And this result was obviously thought about at KTM when designing the parallel twin 250 engine into its successful GP configuration, they added a balance shaft with a lobe
that nullified this 45* resultant vector, as well as increasing the system inertia to tame the mid ranges excessively rapid BHP rise delta that shredded tires and high-sided riders.

Going to the even fire TZ750, we have 3 scenarios.
First two as is used in normal 4T cranks.They have 1,2,4,3 or 1,3 ,4,2 firing (note this is firing order, not crank pin orientation, as a 4T always has pairs rising and falling together ).
But in both cases cylinder 1 and 4 will be at 180* - giving a huge rocking couple across the full width of the engine.
And the two inner cylinders will be at 90/270 or 270/90, both of which generate a smaller rocking couple at 90* to that of the outer pair.
Then we have the special case of 1,2,3,4 and when used in a 2T this will result in a pair of the same resultant vector force mentioned above, they will be at 180* and centered on
the cyinder pairs on each side of the engine.
This is alot further apart than what we see in a 180* twin, so I would expect that rocking couple to be alot worse than that case.
Thus again a balance shaft is needed to control the couple from violently shaking the frame and the riders components.

But the rocking couple in a 180 twin can also be efficiently nullified by frequency specific rubber absorption mounting - as a young Furisawa did in the RZ350 to great effect.
So my take on using this firing order in a TZ750 is that it would result in a ball buzzing monster, unless a balance shaft was fitted ( possibly adapt the jackshaft ) or the whole frame was rebuilt to use
rubber mounts and torque control arms to resist chain pull forces.
Not worth the drama imho.

Thank's Wob I must say I was rather surprised when I figured out the NSR500 screamer was actually a 180 degree two up two down configuration. I always assumed it was a 90 degree set up like almost all the early NSR500s Until I looked into it. the Big bang close firing interval had the Balance shaft (as it really needed it) but they left it on when they went back to the 180 crank as Doohan said it steered better.
\pretty sure at some stage they reversed the crank rotation but I can't remember when. Of course none of these problems exist in the TZ750.

[wobbly]

Yea, the TZ750 spins "backwards " due to the clutch jackshaft driven from the centre.

[husaberg]

Yea, the TZ750 spins "backwards " due to the clutch jackshaft driven from the centre.

Which in itself would be costing them a fair bit of HP but unavoidable without a major redesign in order to keep the motor slim , compromises. Life is full of them.