connecting 2 two stroke engines

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dan

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See in theory a flat plane crank goin all the way accross would work but then the forces pushing on the crank would bend it like this in the middle ) and then it would snap

how so does a single cylinder do this??
 

freakboy

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It doesnt have the load of 4 or 8 pistons on it. and a single cyl crank is much shorter then a v8 one would have so it can take the forces of one without breaking it.
 

dan

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It doesnt have the load of 4 or 8 pistons on it. and a single cyl crank is much shorter then a v8 one would have so it can take the forces of one without breaking it.

aww my bad i thought we were talking about a twin cylinder again :oops:
 

freakboy

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Ok well i could see on a twin cylinder working like that being able to do that, but i think it would be much smoother without much vibration and that crap if they were 180 off.
 

anderkart

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How about the old Harley V-twin design:
(both rods share the same crank journal)

A piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
A piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
And the cycle continues.

(and yes, the girls tell me they do vibrate quite nicely)
 

honda02

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what about something like this? The cranks could both be fitted with a perpindicular rod, (timed appropriately) to rotate a central gear, and the gear (above, its an R/c car diff.) coud be supported by a bearing cassette on either side. Just throwing out ideas.
 

Rotore

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How about the old Harley V-twin design:
(both rods share the same crank journal)

A piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
A piston fires.
The next piston fires at 315 degrees.
There is a 405-degree gap.
And the cycle continues.

(and yes, the girls tell me they do vibrate quite nicely)

That's how the Kohler is setup both rods are on the same journal a bit more difficult to think about but at works quiet nicely
 

VoodooChild

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You talking about those 2/4 Zenoah's hooked up as one?

Just figured out what Zenoah's are, and no I'm not talking about any r/c engines. They looked like 2 and 4, 50cc two strokes tied together, on a regular 70's moped frame. Also the pictures looked old school.

Also i agree with the statements about why no 2 cylinder engines are used these days with the same piston timing. I wonder what the power results would be with 2 lawn boy's connected at the crank and running same timing and 180* apart timing, and then also compare to two separate engines. My gut says the two separate engines would eat up more power with 2 different centrifugal clutches, anyone have any proof as to the power loss through a centrifugal clutch? . I have access to many of those V engines, and i'd like to give it a shot, but i have to finish up many many other projects first.
 

VoodooChild

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Really...?
Check this out
See specs for firing order.
There are many, many others.
This as well: paragraph 5

Yes i'm sure theres a few, but as for the first one thats from a different country so makes sence why i havn't heard of it, but would be interested in the benefits its provides. As for the ducati engine, those types of engines were mentioned earlier, and stated that if you were to downsize that to a 2 stroke engine, you would have a 2 cylinder with an alternating firing sequence. And did you read the 7th paragraph down stating

"The Desmosedici power-unit, designed to tolerate the greater stress generated by simultaneous combustion, is therefore a unique engine with a further advantage: it allows two different versions to be tested. As well as the Twinpulse, we will also be testing a layout with a traditional firing order, which will have a slightly higher power output, but probably to the detriment of traction. Track testing and rider feeling will decide which layout will be used for racing."

But thats in a 1000cc motogp bike, and the only reason there considering using the twin pulse engine (which is not even for sure yet) would be because of traction issues, not for its power.

I'm still interested in advantages/disadvantages to this type of set up, and even more interested why your dual engine auto sync's to that set up.

Back onto topic: Has anyone found a web sight with any info on those mopeds, there was 3 pics or so just on one websight. Makes me think more than a few people have done that sort of thing.
 

brendonv

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Here's a victa kart with twin victas with the cranks welded together.


I think welding the cranks together would be worse. For one, if u weld them then the temper out of the crank would screw up. Two, while welding it, its likely the crank will bend slightly and then u got urself a bent crank. If u make up an adapter like someone said b4 (highly recommended)(think it was kenny) to screw the two cranks together then that would work but why bother? Just have the two engines on separate drive trains. Too many things can go wrong if u start joining two engines together. U wont really get any IF ANY power gain by having them joined together. The only up side with joining them is that u can time em 180 out but i doubt that will have any noticeable difference. Maybe like 0.5km/h top speed difference and like 0.2 seconds acceleration difference.

To put it simply, its just not worth the trouble.
 

freakboy

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Yeah just remember brendonv is backwards cause he lives in austrailia and there upside down all the time.
 

freakboy

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I wasnt sayin your cookie now was i? only certain aussies have gone coo koo because of bein upside down.
 
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