Right, before we go any further, I will never be doing such a thing as the old twin bike engine thing, but bear with me anyway.

Lots of discussion of such things recently and it always boils down to the transfer box costing a fortune.

So, I'm sort of thinking there must be a cheaper way of doing it.

Have a look at this idea. Proportionally, it's a bit out, but the layout is essentially right. It's really three shafts linked by a chain. Two of the shafts are input, one is output.
We would be talking about commonly available shafts, probably RWD gearbox tailshafts.
Internal sprockets would be bike front sprockets probably and the chain would be bike as well.

The case would be fashioned from 10mm thick aluminium plate cut and drilled suitably accurately.

Err, that's about it.

Discuss.

[Edited on 16/9/07 by zilspeed]
Rescued attachment xfer box.JPG

Need an idler gear between two inputs or you rip all teeth off as soon as second engine started Maybe another depending on required diff rotational, compared to engine rotation.

Simple design though!

Edit: Oops just read it Hadn't noticed the chain bit!!

ATB

Simon

[Edited on 16/9/07 by Simon]

i would have thought, for 2 reasons, and over and under arrangment would be good.

1) it would have to be really wide for 2 engines to sit side by side
2) the chain on the middle gear would only be on 2 or 3 teeth at a time.

don't know, just a though. i think fitment and space would be the thing here



xfer

The over and under arrangment is fine apart from all of the shafts needing to rotate in the same directions, which your arrangement does not allow.

It would however be relatively simple to have adjustable idlers on the outside providing tensioning on the chain runs between the sprockets.

i put the second engine over the other side to allow for it turning the opposite way, and allow both engines enough space

It wouldnt allow the engines to load share.

The only place Ive seen this kinda thing done (2 sources into 1 output) is with an epicyclic torque summer.

Having said that, there is a school of helicopter design called "Split torque". That is bascially what you're describing.

I think it could work, but if one engine goes sick, the other engine will see lots of load, as its then the only one doing any work, AND driving a sick 2nd engine too.

Also, dont use just one chain, as the middle sprocket is only in contact with precious few teeth, and would probably slip. Have 2 sprockets on the middle shaft, with a sepaerate chain for both the other engine and the drive.

Ed.

Hi
Why not make it even simpler.
Remove the top Spocket !
As they are all connected why not have one input straight through.

Martin

I think you may have a point

ATB

Simon

If you can mount the engine back to back the idea of using one input shaft can do and is the smallest.

but if you can't or don't want to mount the engines like that and they need to bee in the same arrangement as the Zcars tigers had you might want to do this

it remains to be seen if the direction of rotation is OK in this way,

I wouldn't use chains or anything just a few 1:1 (4th) gears from a strong gearbox
in an enclosed box filled with transmission oil. I understand the MT75 has strong gears, you need 2 firts motion shaft gears and one from the second. make up axles that sit on bearings and have shaft flanges on one end,
it's a load of work but it shouldn't be to hard to make something like that if you know someone with a good lathe. The box itself could be made from steel plate or CNCd from solid alloy. oilseals for the flanges should also be availeble in every size you want so


twin engined coupler box

grtz Thomas

[Edited on 17/9/07 by thomas4age]

I proposed one such idea a littrle while back.

The arrangement I had in mind is to do away with the bike engine gearboxes but to mate the two crankshafts of counbter-rotating engines together with gears or chains.

One of the engines drives a smaller gear that then turns a larger central gear to give a drive ratio of 1:2 so is of suitable rpm for a car gearbox.


gear surround

I have 2 hayabusas sitting in my garage right now alongside a BMW e30 LSD diff and some big ass chains/sprockets. All for the dual busa Bala that my friend Rob is building. This is how we are going to arrange the driveline.



Chain Drive for dual BEC sketc

That's a really wide setup though. Not suitable for a locost-type vehicle at all. How did they squeeze it in the Tiger Z100?

quote:

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Originally posted by akumabito
That's a really wide setup though. Not suitable for a locost-type vehicle at all. How did they squeeze it in the Tiger Z100?

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isn't the length of chain on the left hand engine going to cause problems wearing out with it being so short & on the right hand being so long & lacking tension?

(i'm just remembering comments NS Dev has made about expected chain life on his grass track racer)

MikeR has hit the nail on the head!!!

None of the chain transfer boxes will work with any level of power, let alone a pair of busas.

The short chains are too short, and they overheat in minutes or less, seize their rollers and explode in a shower of bits.

I have seen it happen a fair few times on autograss cars.

Chain length is critical, take a look in an online chain catalogue and see what centre to centre distances are recommended!!!

I have broken all the rules, but I will be using 3/4" pitch 630 drag race chain rated to over 500hp, one per engine, and I expect to spend a fair bit on replacing them, but then my races are only 5 minutes long!

The problem that Radical had with their early endurance racers was chain life, which is why Quaife designed and built their transfer box for the SR3

PS not sure what running the chain in oil will do. It will certainly extend its life.


PPS, with ref to the original point, the best way to do what you are looking at is to use silent chain (borg warner silent chain). This runs at very high speeds and has not rollers, but does need to run in oil. It can however run on very short length runs. Take a look at the chain transfer units in range rover and sierra XR4x4 transfer boxes for inspiration.

Me and a mate built a similar box to ehat you are talking about, out of a length of heavy wall steel box section with bearing bosses welded on and bored through, then with a silent chain drive inside, this was to drive the 2 rear diffs of a 6wd, 6 wheel steer, 6 wheel independent suspension off roader that we built.

It will go to pieces in no time in that set-up, which will slam the parts in the other working engine, thus costing you 2 engines because of one chain failure.... not good.

the tigerz100 (rwd) had a sort of transferbox like in my picture if I'm not mistaking,

chain issues are the reason that TAD MK etc etc went north south on the installs and fitted the engine to the diff with only a rubber vibration damper in between. + much cleaner install1

you could do that with 2 engines but it should be gears in the coupler box. you could even decide to run 5 gears and have a center take of, to get spacing between engines a little better.

grtz Thomas

I think maybe I have hijacked the thread a bit, but I do appreciate the advice from people that have been there - seen that.

How about this one?



Idea 2 chain/direct drive bec

hey steve,

Maybe when you have the room to build the above mentioned set-up, you could also build it like this,


twin engine coupler box idea 2

maybe if you weld up a diff in the right manner (or not at all) you could get away with this, otherwise 3 gears need to made and a box to carry them.

grtz thomas (chain hater)

quote:

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Originally posted by thomas4age
hey steve,

Maybe when you have the room to build the above mentioned set-up, you could also build it like this,

grtz thomas (chain hater)

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Hey steve,

well then, you know you can!

was just thinking a bit more, a normal diff would give an extra ratio which you probably don't want, but 3 spider gears or 3 input gears could do the trick, seems to me the helical form is OK on ford live axle ones....

getting the backlash right and the paly inbetween the gears, is the biggest problem I think which good machining can fix for a large amount.

grtz Thomas

ps: if you get the pistons in the right place before putting the axles in position you could even play around with the soundtrack of the engines hahahaha!

quote:

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Originally posted by NS Dev
a 6wd, 6 wheel steer, 6 wheel independent suspension off roader that we built.

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I do realize I hijacked this thread and for that I apologize, but the deed is done, so I might as well continue...



How about this layout? It's an inline 8



Description

Connect the engines at the cranks. This would on the surface appear to be a really good idea. The exact details on how this would be accomplished are a bit murky though. Some hellacious adapter.

But this solves some real problems in previous ideas.

The rear differential now mounts in standard BEC middy fashion in a carrier with sealed outer bearings.

Now the left side engine can have it's transmission guts removed for further weight reduction. The engines are timed together and can be controlled with one ECU. There is only one gearbox, preventing the possibility of a mis-shift in one box grenading the second transmission.

If a stronger chain is required, two chains could be duplexed side-by-side from engine to diff.

Comments?

quote:

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O
But this solves some real problems in previous ideas.

Comments?

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Crank on the second engine will snap

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MikeRJ - 25/9/07 at 07:41 AM

quote:

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Originally posted by britishtrident

quote:

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But this solves some real problems in previous ideas.

Comments?

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Crank on the second engine will snap

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That's a bit unfair BT, there's a good chance that the clutch or gearbox in the second unit will expire before the crank snaps

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02GF74 - 25/9/07 at 09:20 AM

that second crank won't be happy for sure.

the more pistons you have on a crank, the bigger the torque will be so the second crank, clinder 1 will see the torqye from the previous engine, at cylinder 4 it will see 2x torque it was designed for.

I've read somewhere that cranks do get beefier towards the flywheel end to account for this - think rover v8 is one but not sure.

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smart51 - 25/9/07 at 10:21 AM

Why not ditch the diff all together and have each engine drive just 1 wheel?

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sgraber - 25/9/07 at 01:41 PM

I do understand what you are saying about the crank breaking, et all. We will scrap that idea for now.

quote:

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Originally posted by smart51
Why not ditch the diff all together and have each engine drive just 1 wheel?

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That's a real smart thought there. I had that one drawn up early on, but didn't think it would fly. But since everything else has failure written all over it, why not?

Direct drive each wheel. When one wheel loses traction, the other continues to receive power. Isn't that like driving them with an LSD diff? If both engines had traction control via ecu then you could get a lot of power down that way.

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Dangle_kt - 25/9/07 at 02:53 PM

quote:

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Originally posted by sgraber
I do understand what you are saying about the crank breaking, et all. We will scrap that idea for now.

quote:

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Originally posted by smart51
Why not ditch the diff all together and have each engine drive just 1 wheel?

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That's a real smart thought there. I had that one drawn up early on, but didn't think it would fly. But since everything else has failure written all over it, why not?

Direct drive each wheel. When one wheel loses traction, the other continues to receive power. Isn't that like driving them with an LSD diff? If both engines had traction control via ecu then you could get a lot of power down that way.

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What would happen if one of the engines wasn't running right?? crab situation? I guess it would show up in excessive tyre wear...

(they are all questions, not statements - I'm just an interested party, with questions to bring to the table rather than answers!)

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thomas4age - 26/9/07 at 08:50 AM

Don't bother about doint that.

Just a very different thought if you have that sort of room so stuff with engines and the lot, why not stuff an extra diff up front and run a prop to it

twin engines
4 wheel drive
no drive connection between engines
seperate ECU's
just a gear linkage to hook up, do air shift and have it on the button.

the possibility of shutting one engine down by putting it in neutral.

should be by far the easiest sollution,
Zcars did it Ultima did it with the twin busa turbo GTR.........

easy to maintain No chains stock parts

ps the coupler box design I put up is used extensivly in tractor pulling so should be quite strong if you do it right.

the engine joining at the cranck can be done but will break, seen that on twin subbaru boxers, flat 8 flatplane without turbo's, went bang in half an hour

grtz Thomas

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Peteff - 26/9/07 at 10:08 AM

With an engine driving each wheel it would work in a straight line but when you corner there will be no differential action unless you slow down the engine driving the inside wheel. It would be more like driving with a spool or a locked differential.

[Edited on 26/9/07 by Peteff]

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Minicooper - 26/9/07 at 10:20 AM

Twin engines one driving each wheel no differential appears to work for this guy

http://furorecars.co.uk/pics.php

Cheers
David

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smart51 - 26/9/07 at 10:46 AM

quote:

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Originally posted by Peteff
With an engine driving each wheel it would work in a straight line but when you corner there will be no differential action unless you slow down the engine driving the inside wheel. It would be more like driving with a spool or a locked differential.

[Edited on 26/9/07 by Peteff]

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If you go in to a corner the inside wheel will slow and the outside wheel speed up taking the engines with them. Remember that the engine speed is not goverend by the throttle or fuel as such but is held down by the resistance of the vehicle.

You would have as much differential action as you'd need.

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Minicooper - 26/9/07 at 10:53 AM

Years ago there was a twin engined wolfrace wheels demo vehicle, it had two rover v8 engines to two complete differentials, one open dif and one lsd diff

This is the only thing I can find

http://www.supercarworld.com/cgi-bin/prototypes.cgi?startfrom=61&sortby=atoz

Cheers
David

[Edited on 26/9/07 by Minicooper]

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NS Dev - 26/9/07 at 12:14 PM

quote:

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Originally posted by thomas4age

should be by far the easiest sollution,
Zcars did it Ultima did it with the twin busa turbo GTR.........

easy to maintain No chains stock parts

ps the coupler box design I put up is used extensivly in tractor pulling so should be quite strong if you do it right.



grtz Thomas

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Ultima DID NOT build the twin engine car. It was built by Z Cars, and was not great as far as I know.

I know cars with individual drives have been done, and I know that they can be made to go very quick in a straight line, but I have yet to see one that handles!!

For this very reason autograss cars were banned many years ago from having seperate drives from seperate engines to seperate wheels.............at some point the drive has to be coupled.

PS yep the spider box coupling you talk about has been used in tractor pulling for years and has proved reliable transmitting over 5000hp and 7000lbft of torque in that application!!!

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thomas4age - 27/9/07 at 02:34 PM

You're right about the ultima, reading it i remember knowing that,
the car is with it's owner in spain now iirc

Grtz Thomas

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ChrisGamlin - 27/9/07 at 04:52 PM

quote:

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Originally posted by smart51
Remember that the engine speed is not goverend by the throttle or fuel as such but is held down by the resistance of the vehicle.

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Agreed but that resisting force has to come from somewhere and its that force that will cause problems IMHO.

Im thinking this through a bit as I type but to better explain my thinking, imagine a triangle with a pivot in the middle, something like this

Image deleted by owner

A and B are two equal forces (equivalent to the engine forces), the blue blob is the pivot.

If you apply a vertically downward force at C (as if you were turning the front of the triangle to go around a corner), unless A suddenly increases it's force (which it doesn't) C is having to apply a force to overcome B to make the triangle turn.

In the real world this force is in addition to the forces the front wheels are subjected to anyway due to the car's mass wanting to carry on going straight ahead. What this will mean is that for any given corner, you've got less front end grip available (compared to a car with an open diff) to generate cornering force because some of it is already used up fighting the force from the inner rear wheel.

I.E. it will comparatively understeer like a pig and not be able to generate as much cornering speed!

I think

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