Got my single outside, wanna try?

[herald948]

Ah, Phil Lynott, master of lyrics...

OK, I have a question that I am fairly confident someone on here will be able to answer.

Think of a big single cylinder engine, maybe 500cc, 600cc. You'll usually only find one on a motorcycle, maybe a large trailie. When a big single like that runs, it isn't smooth. Think of it like a pneumatic drill thumping away at its drive chain. On the bike you'll find a cush drive to stop this jackhammer effect causing damage to the chain, an arrangement of rubber blocks in the rear wheelhub to absorb some of the impact.

But what if you used such an engine on a car? A small single seater such as the 500cc single hillclimbers of yore. If you've got a drivetrain that involves gears and shafts and stuff do you still need the cush drive? Will the thumper strip your cogs?

[popuptoaster]

bikes have gearboxes too ya know and a lot of cars already have rubber doughnuts on the prop.

[jrevillug]

I'd suggest so. The donuts idea is a god one - it's what the Imp uses (there are no springs in the Imp's clutch plate).

[herald948]

Just out of curiosity, would a viscous coupling have the same effect?

[Lewis]

I think the real problem would be that you wouldn't be able to get one to move a car, given the ones I've seen tend to make less than 30ft.lb of torque.

Not even something super lightweight!

This may be slightly off topic but I thought I'd throw it in!

[jrevillug]

I think it would cause lots of slippage - like a Torque Converter, but without being designed for the application.

[Adam]

I'm guessing we're talking 5/600cc 4 stroke here, not 2 stroke? Most of the hillclimbers used multi-cylinder 2 strokes I believe.

[herald948]

A big single wouldn't do much for a road car but it moves something like this very quickly indeed.

[Rich606]

Some of the fastest Formula Student cars at the moment run singles. I think it was the Graz University team who were running a 450cc single, revving to about 19k rpm, in a 145kg (-ish) car.

[10mpg]

As has been said the cush drive aint for the gearbox its just to limit hard impact jerks to the rear wheel which could have an adverse effect on it's road manners...

Singles are no good for cars unless you are planning a super lightweight single seater, my personal choice for a smaller (sub 1000cc) bike engine would be a triumph triple, loads of torque over a decent range and a glorious noise, cheap too..

[Team Blitz]

Sept 10, 2008 8:10:40 GMT herald948 said:

Think of a big single cylinder engine, maybe 500cc, 600cc. You'll usually only find one on a motorcycle, maybe a large trailie. When a big single like that runs, it isn't smooth. Think of it like a pneumatic drill thumping away at its drive chain. On the bike you'll find a cush drive to stop this jackhammer effect causing damage to the chain, an arrangement of rubber blocks in the rear wheelhub to absorb some of the impact.

No cush drive on the Yammie SR500, 1 cyl, 4-stroke. Incredibly torquey. Like a mountain goat. Chain drive to sprocket, and they made this model for something like a decade, well-sorted and robust.

[skinley]

Motocross bikes are all singles and I don't know of any that have a cush-drive.

[mattblack]

"Got my cycle outside, you wanna try?"

[kevfromwales]

pedant mode on:

'sickle' methinks

pedant mode off

- no tech input to add here, years of sidecars as a child have ruined motorcycling for me, but that single seater looks ace!!

- kev

[herald948]

Sept 10, 2008 19:41:25 GMT mattblack said:

"Got my cycle outside, you wanna try?"

Half of the fun of listening to music is mishearing the lyrics. I'm still not entirely convinced that Elvis doesn't want to kill someone.

[Bob the Fish]

2-stroke crossers, different delivery aren't they, so not the same need for cush although my CR250 crosser had one but in the clutch I believe and not the rear wheel.

The cush is to relieve gbox shocks, prolong chain life (singles eat them), and help rideability. Some modern singles have balancer shafts to counter vibes.

Could rubbermount the motor to counter lack of rear cush somewhat.

Singles also eat bores quickly compared to fours.

Singles vary in character: revvy with a pretty steep torque curve that comes in quite sudden higher up, esp newer 4-valve head types. Or traillie thumpers with broader spread and more low down. None imho have a lot of power or grunt as std; check the figures, many are 40bhp or less and that's often the crank figure... Tiny size and light weight helps make the most of it though. Higher hp e.g in the 60's usually = revvy, powerband higher up, shorter life. I know of far more blown-up singles than twins or fours.

Would the gbox hold up I wonder, singles are light, small, dunno.

Might be better with a vee-twin; you have more power+torque, smoother curve and better reliability. Or see Froggy's twin-TL beastie...
V-Max would be nice!!

[Rich606]

Sept 11, 2008 6:54:25 GMT herald948 said:

Half of the fun of listening to music is mishearing the lyrics. I'm still not entirely convinced that Elvis doesn't want to kill someone.

I swear I heard the Red Hot Chilli Peppers singing about ovulation the other day on the radio...

[bodieanddoyle]

Sept 10, 2008 9:28:17 GMT Lewis said:

I think the real problem would be that you wouldn't be able to get one to move a car, given the ones I've seen tend to make less than 30ft.lb of torque.

eh? how much torque does a trabant make? or a fiat 126? or a 2cv?
not putting anyone down but they ain't high in the torque stakes and I'd put money on the fact that a ktm 525 put outs more torque than any of the cars I mentioned.
and correct me if I'm wrong, but all those cars move too

formula juniors are pretty quick little things, manx norton single in a minature single seater.

and I don't think a cush drive would be required at all

[Bob the Fish]

You might not need a cush as necessity, but you sure know when one's needing a coat of looking at, even on a silky 4-cyl UJM* let alone a chain-jerking thumper... Things last a whole lot longer with than without

*UJM = Universal J Motorsickle

[CR500Dom]

Cush is to save the gearbox.... the more grip you have the more you need one

Dirt bikes can slip the wheels on accel and decel easily due to relatively low grip so not needed

Road bikes tend to use them more as generally more weight, more grip, more slow speed driveline shunt etc

My CRF450 Super moto (55hp single 450cc Dirtbike) on super sticky tyres runs quite happliy without a cush drive, and it gets a serious amount of abuse through the rear wheel (Wheelies, changing down early to induce a slide etc)..... on an old brit Pre-unit construction (seperate gearbox) Single, then the cushining is often in the primary drive rather than vehicle chain

HTH
Dom