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YEH BABY THEY FIT

CraigJ - 27/6/09 at 01:39 PM

This car is going to kill me lol

Aiming for 500kgs or under as well.

Mark Allanson - 27/6/09 at 01:41 PM

One for each rear wheel!

locoboy - 27/6/09 at 02:01 PM

How are you planning on combining their oomph and getting the to run in union so to speak?

Looks crazy

CraigJ - 27/6/09 at 02:03 PM

like this

http://www.mkengineering.co.uk/apps/photos/photo?photoid=10993799

locoboy - 27/6/09 at 02:59 PM

i see how it works now but is there a diff in any of that?

Also how can you get the engines to run at exactly that same rate so that one is not carying the other if you know what i mean?

M$RK_VXRD - 27/6/09 at 03:12 PM

the stronger engine will pull the other along i asked martin the same question when i seen the twin engined kitty

stevebubs - 27/6/09 at 04:04 PM

quote:
Originally posted by locoboy
i see how it works now but is there a diff in any of that?

Also how can you get the engines to run at exactly that same rate so that one is not carying the other if you know what i mean?

Yep - diff is in a carrier below the shaft driven directly by the engines..the 3rd chain (middle one) puts the power from the engines through the diff.

[Edited on 27/6/09 by stevebubs]

Guinness - 27/6/09 at 04:18 PM

Nice one! Straight eight!

Same technique as Russ used on the Furore? His seemed to go well!

Mike

speedyxjs - 27/6/09 at 04:32 PM

Nice one

CraigJ - 27/6/09 at 05:00 PM

Cheers for the comments guys.

It will take time to get it all running together but i have no deadline so i will just keep at it till it goes right.

locoboy - 27/6/09 at 05:31 PM

Surely there should be some kind of diff bit in the shaft connected directly to the engines to allow the engines to work at different speeds. They are not going to be exactly in tune so you will not be maximising your output from both engines as one will inevitably be dragging the other alone and wasting BHP in doing so................

Or have i still not got it!

suparuss - 27/6/09 at 06:08 PM

quote:
Originally posted by locoboy
Surely there should be some kind of diff bit in the shaft connected directly to the engines to allow the engines to work at different speeds. They are not going to be exactly in tune so you will not be maximising your output from both engines as one will inevitably be dragging the other alone and wasting BHP in doing so................

Or have i still not got it!

thats initialy what i thought but when i thought about it- what you are saying is correct if it was just a matter of engine speed, as in one engine keeping up with the other. but i think it is all to do with torque rather that speed. like a beefcake and a skinny guy both pushing the same car, the little guy will be helping a bit even if hes half as strong.

very nice project by the way. being nuts is what we like on here!

locoboy - 27/6/09 at 07:22 PM

Yes but if you have 2 beefcakes, one who cant be arsed and the other one is in the zone.
Whilst the one who cant really be arsed will be helping a bit he is not working to his full potential so you dont gain double the output.

Or a better example is Sir Chris Hoy and me on a tandem, i would help a bit but it wouldnt be the same as haveing 2 x Chris Hoy's pedaling in unison would it.

I know it will be like poo off astick with 2 engines in it but i cant help thinking there is going to be a lot of lost power.

What would be the outcome if one of the engines went down or began struggling could the other one damage it by 'forcing' it along?

JoelP - 27/6/09 at 07:34 PM

I think its not an issue myself. One engine, when revving under load, will raise its revs (ie accelerate the car) at a certain rate. The other engine will definately assist even if it was underpowered, because to actually be a hinderance it would have to raise its own revs slower than the engine that is pulling hard. This is never going to happen because in this situation the engine is doing no work so the revs would rise at the same rate as it would if it were in neutral - ie fast.

Or another way, it will always be able to add something even if completely strangled.

Please say if that doesnt make sense because i know another way to explain it.

JoelP - 27/6/09 at 07:35 PM

more simply maybe, if you engaged both engines and accelerated, dipping the clutch on just one would cause the revs in that engine to shoot up faster than the engine that is under load - proving that it was producing more power than it was using in being turned.

zilspeed - 27/6/09 at 08:31 PM

quote:
Originally posted by Guinness
Nice one! Straight eight!

Same technique as Russ used on the Furore? His seemed to go well!

Mike

As I understand it, it's not the same technique.
The picture shown is how I would do it myself - summing the drives via a jackshaft.

But I believe that the furore has an engine driving each wheel which I must say I'm not quite so sure about.

Sven - 28/6/09 at 12:18 AM

isn't it about load? Meaning, if one engine is putting out more power then there's less load on the other and the latter can spin up quicker until it puts it's power to the jack shaft?

The ideal would be two perfectly matched engines, but I would assume that's almost impossible. This, at least, gives the combined power of both even if one is slightly down on the other?

Alan B - 28/6/09 at 03:32 AM

Why is this problem fundamentally any different to tuning just one engine?...all the pistons are connected by the crank and have to run together at the same speed but some will be driving the crank with more force than others?...effectively this just makes a kind of straight 8 engine (as somebody said earlier)

Alan

zilspeed - 28/6/09 at 06:30 AM

quote:
Originally posted by Alan B
Why is this problem fundamentally any different to tuning just one engine?...all the pistons are connected by the crank and have to run together at the same speed but some will be driving the crank with more force than others?...effectively this just makes a kind of straight 8 engine (as somebody said earlier)

Alan

Totally agree.

Do a compression test and you'll find a variance across the cylinders.
The crankshaft doesn't twist like a barley sugar, it just gets on with it.

As long as you don't exceed the safe rev limits, it's possible to run the two engines / one jackshaft setup in different gears and it still works.
I'm not recommending it, but it still works.
It's like a tug of war onto the jackshaft, some of the guys pulling the rope are different strength, but as long as they're all pulling the rope the efforts are summed at the end of the rope.

I understand that grasstrackers have been doing it for years.
(Jackshafts, not tug of war.)

Tralfaz - 28/6/09 at 12:48 PM

What happens in the event of some sort of shift failure on only one engine?

CraigJ - 28/6/09 at 02:21 PM

quote:
Originally posted by Tralfaz
What happens in the event of some sort of shift failure on only one engine?

Swap the engine for another.

Tralfaz - 28/6/09 at 04:46 PM

quote:
Originally posted by CraigJ

quote:
Originally posted by Tralfaz
What happens in the event of some sort of shift failure on only one engine?

Swap the engine for another.

Ok.

Perhaps I was unclear?

What would the implication/result be of an upshift failure on only one engine while accelerating full out?

One engine shifts to fourth, the other misses, ends up in neutral or stays in third. Say to a linkage problem, or other.

Disaster?

Honestly just curious of the possible result.

T

JoelP - 28/6/09 at 06:34 PM

quote:
Originally posted by Tralfaz

quote:
Originally posted by CraigJ

quote:
Originally posted by Tralfaz
What happens in the event of some sort of shift failure on only one engine?

Swap the engine for another.

Ok.

Perhaps I was unclear?

What would the implication/result be of an upshift failure on only one engine while accelerating full out?

One engine shifts to fourth, the other misses, ends up in neutral or stays in third. Say to a linkage problem, or other.

Disaster?

Honestly just curious of the possible result.

T

I think craig jumped a step in the logic, rather than missing what you meant. The engine would get lunched through over-revving, and then it would get swapped for another. I believe he is using very cheap old engines.

andyd - 29/6/09 at 09:33 AM

That's how Tiff Needel lunched the 0-60 record holder car isn't it? Was it a Tiger or something?

It has (had?) two gear shifters side by side and he missed one of them... result was one shifted up and the other over revved and went pop. Rod through the block if I recall.

Oops.

iank - 29/6/09 at 09:49 AM

quote:
Originally posted by andyd
That's how Tiff Needel lunched the 0-60 record holder car isn't it? Was it a Tiger or something?

It has (had?) two gear shifters side by side and he missed one of them... result was one shifted up and the other over revved and went pop. Rod through the block if I recall.

Oops.

Why wouldn't you lock the shifters together to avoid that. Wouldn't help if a control cable snapped on one engine, but would prevent human error.

andkilde - 1/7/09 at 11:03 AM

You could probably hook up some form of rev-limiter ignition kill/retard device so it worked on both engines. ie, one engine over-revs, then both hit ignition cut simultaneously.

Heck, with a bit of thought you might even be able to run them off a single ECU as an eight cylinder -- though I'm not sure to what benefit.

Cool car BTW

t

CraigJ - 1/7/09 at 05:03 PM

One shifter and 2 cables will be used with the option to un-hook the cable at the engine. also a rev limiter will be fitted for safety.

chrisg - 6/7/09 at 11:28 AM

It's Official Craig me owd fruit - you're mental

Don't forget where I live when comes to a test drive!

Cheers

Chris

JoelP - 6/7/09 at 11:43 AM

I think the best approach is to have the limiter working on both, and to have one gear lever that changes both but a smaller lever somewhere that just changes the one engine, to be used to put them back into the same gear if they end up out.

kb58 - 7/7/09 at 01:44 PM

Separate rev limiters won't help. Imagine driving down the road and accidently putting your car in first gear. The rev-limiter will shut off fuel and/or spark, but the road speed of the car back-drives the engine to about 23,000 rpm. No hope to save it when that happens.

MikeR - 7/7/09 at 04:29 PM

you need a clutch that will automatically engage to protect the engine and hope the gearbox doesn't go bang.

(or better still a clutch on the jack shaft)