Maximum Torque on Bike Chain?

Question

I don't want advice on how to do this, or people telling me to get it shape instead of doing this. For the record, I bike about 10-40 miles every other day. And I don't want people telling me not to do this.

Sorry about that, that's all from my last question.

Anyway, my friend and I are putting a chainsaw engine on a bike, and the engine will go on the back of the bike on a bike rack, connecting to the first gear of the bike via a bicycle chain, or something like it. I briefly looked online, but could not find anything telling me the maximum torque of a bicycle chain, and I would rather not have a broken chain embedded in my back... Any help on if a chain is strong enough would be nice. The engine is 1.5-2 horsepower, 40cc. Also, if not, are stronger chains made that will fit around a gear?

Thanks

Answer 1

Humans develop only 1/4 of a horse power and are known to break bicycles chains.  Make sure you have a good quality new chain.

Answer 2

Here are the specs of a standard bike chain. This one is rated to 1300 kgf. (Kilograms force). It is the force that will break chains not power or torque.

http://www.harobikes.com/2004/parts/chai...

A chain rated to 1300 kgf should be able to lift a weight of 1300 kg (2860 pounds). This might sound a lot but when you get a fairly large bloke jumping on cranks fitted with tiny sprockets forces can get quite high.

E.G. a 250 lb bloke standing on a 170mm(6.69") cranks fitted with a 12 tooth sprocket(1.91"radius) will cause about 875 pounds force in the chain at the sprocket. ( Torque = force x distance). If he jumps, it will be much higher.(This is when chains break)

A cyclist riding with a cadence of 90 rpm and putting out about a quarter horse power will only be applying about 28 lbs force to the pedals. (not 250) (power = force x speed).

The bike chain should be plenty strong enough to handle a 2 hp chainsaw engine. Chainsaw engines are pretty gutless in terms of torque. The big challenge is gearing the thing down.I doubt first gear will be anywhere near low enough. Most chainsaws need to run at over 7000 rpm to get rated power. (low force, high speed)

It would be very unwise not to use a chain guard. Chains will fail eventually with wear, all sorts of things can get caught in it,(including body parts) and you are still in danger of a sprocket or chain coming off and embedding itself.