14 replies to this topic

[isjakar]

Newbie to posting, so please advise whether this should be in the bike engine section.
Am weighing the pros and cons of shaft and chain drive from front to rear. Shaft is the safe, but heavy choice.
For a lighter alternative, check out Denis Palatovs fantastic site/blog, dpcars.net . My question is, does anyone know of Minis with front to rear chain drive? Other cars? Pros and cons from real-world experience?

[mini-geek]

Just to be clear, is that a long chain front to back? if so I think you would find the chain will stretch too much too soon.

[Wil_h]

Really interesting website, cheers.

I can't see any details on it how the drive is connected from box to axle though. I have before seen a race car with long chains from the drive shafts to the hubs as the rear axle was way behind the transversly mounted engine.

But to run a chain front to rear seems a bit too far to me. If that is what you mean?

[isjakar]

Really interesting website, cheers.

I can't see any details on it how the drive is connected from box to axle though. I have before seen a race car with long chains from the drive shafts to the hubs as the rear axle was way behind the transversly mounted engine.

But to run a chain front to rear seems a bit too far to me. If that is what you mean?

Precisely. A Mini has a 2meter wheelbase, and Palatov pinned this as the basis for his revelatory dp1 because he knows his Minis - and they work. If you spend a few hours on his site you will see how the chain drive has gone through permutations. His cars have two chains, one short, the other long, to drive both axles. Drag racing bikes also have very long chains.
In industry long chain drives are standard solutions.
Ideally the engine drive take-off should be in the middle, giving only 1 meter to go to either end, slack taken by delrin guides. No problem. This would rather painfully clash with my or my passengers bum, as my Mini is, and shall remain, a 4 seater. Therefore the 170 hp engine must reside in the little round nose.
The question therefore is whether a 2 meter long chain drive must for practical reasons of resonance, flutter and stretch, be split into two with a double sprocket in the middle. Top speed of car does not need to be higher than 130-140 kph, but it is required to hurry well up from standstill.
I am sufficiently familiar with the basics and on-paper pros/cons, but am after real-life experiences.
Having seen (videos of) FWD 10in BECs tyre torching and lurching about I see front engine, 4wd as a more practical proposition for getting around in a civilized but rapid fashion. Fantasizing about ImprEVOgrale vanquishing in a toddler-tyred antique.
Yes, I have seen the Subaru/Suzuki 4wd projects. Good, very good, but I look for different cups of tea.

[Wil_h]

I guess you're on you own on this one. The only cars I've seen with such a setup were radio controlled.

[Ipod]

Be like a whip when it fails..... sod standing near it...or the fuel lines....eeeeeep

[shed]

gonna point out the obvious and ask why a chain and not propshaft and use a sierra diff? (for example)

[rusty789]

Am weighing the pros and cons of shaft and chain drive from front to rear. Shaft is the safe, but heavy choice.

gonna point out the obvious and ask why a chain and not propshaft and use a sierra diff? (for example)

I guess weight is the issue..

[shed]

DOH! specsavers for someone

[Dan]

Surely once you get to a certain length, a chain is heavier than a shaft. Every link in a chain has to be the same strength obviously, you can't lighten it really. Long chains that can cope with this kind of power are heavy. A prop shaft however is a hollow steel tube with heavier ends. As a chain gets longer, its mass per unit length remains the same while the average mass per unit length of a shaft will reduce as it gets longer.

[dhende84]

And of course you can always use a carbon prop!
Seen a chain go on a bike engined formula student car and even with the mandatory chain guard it left a mess.

[isjakar]

gonna point out the obvious and ask why a chain and not propshaft and use a sierra diff? (for example)

The answer is weight. A sprocket/closed diff is lighter than shaft/90° gear drive. The cons are well known, especially in motorbikes, where chains rule over shaft drives 99 to 1 in spite of their negative aspects.
Why not the obvious Sierra diff etc like all the others? Partly because it's obvious and all the others have done it - and it's heavy.
Partly because of the engine, its shape and orientation being most open to this configuration - and it's light.
Belt drive is another possibility, it rules in the hippopotamus class of motorbiking f.ex. and is lighter, cleaner and requires less maintenance than chains. More bulky, though.
Remember when everybody told you a bike engine can't be used in a car? Not so long ago, eh?

[Dan]

No but still quite correct, unless the car happens to be particularly lightweight such as a Mini or a Caterham. A bike engine would loose the fight with a Land Rover for example.

You say the shape of the engine suggests chain drive, but surely the drive will come from one end of the engine which will be offset by some distance from the centre of the car. I assume this will then become a single seater because the chain will be running through the cabin in the middle of one of the front seats.

Belt drive is another possibility, it rules in the hippopotamus class of motorbiking f.ex. and is lighter, cleaner and requires less maintenance than chains. More bulky, though.

Belts absorb more power too, accelerating either a chain or a belt continuously uses more energy than turning a shaft but of the two a belt is worse. Having said that, this may be another point where the extreme length of this chain alters things.

[isjakar]

Surely once you get to a certain length, a chain is heavier than a shaft. Every link in a chain has to be the same strength obviously, you can't lighten it really. Long chains that can cope with this kind of power are heavy. A prop shaft however is a hollow steel tube with heavier ends. As a chain gets longer, its mass per unit length remains the same while the average mass per unit length of a shaft will reduce as it gets longer.

Thanks, good point. Rule of diminishing returns, surely. The two heavy gearboxes (differential units with ring gear and pinion in a sturdy case to keep them together) at the ends (my application is 4x4) can be served with relatively light rotating shafts up to a length of close to 2 metres.
Flailing chains are uncomfortable companions, sure, more so even than a runaway propshaft. Yet bikemakers put them millimeters away from their customers' valuable feet. Millions of them.
Have you seen those drag bikes with a rear arm the length of the driver? 1000 horses into a marshmallow slick. Only needs to last a few seconds though!

[isjakar]

No but still quite correct, unless the car happens to be particularly lightweight such as a Mini or a Caterham. A bike engine would loose the fight with a Land Rover for example.

You say the shape of the engine suggests chain drive, but surely the drive will come from one end of the engine which will be offset by some distance from the centre of the car. I assume this will then become a single seater because the chain will be running through the cabin in the middle of one of the front seats.

Belt drive is another possibility, it rules in the hippopotamus class of motorbiking f.ex. and is lighter, cleaner and requires less maintenance than chains. More bulky, though.

Belts absorb more power too, accelerating either a chain or a belt continuously uses more energy than turning a shaft but of the two a belt is worse. Having said that, this may be another point where the extreme length of this chain alters things.

Good point, but the car is a 1972 Mini, the drive goes down the centre in a tunnel whether by shaft, chain or belt), and it seats 4. Power is not a problem, turning it into useful propulsion through two patches of front 165-10s is! Therefore this quest for the ideal transmission method to the remaining wheels. Engineering is the art of compromise, and here, weight is accentuated in the weighing up of factors. The quest is to get close to the lowest weight of any 4-seat 4x4 road Mini.