Greatest strain

A bicycle has a pedal sprocket wheel and a smaller back axle sprocket wheel.

I'm curious to know if the strain on the chain is equal at both sprocket wheels.

 

The chain always breaks at the weakest link.

 

Mmm. Well the torque is greater at the front, cos the pedals extend the radius of the front sprocket. But not sure how that theory helps! The 'strain', should only be applicable at the top of the chain, since the return part of the chain is slack enough to need tensioning. So I'm proposing that the 'breaking strain' is equal on both. But hey!

 

If the section of chain between the two sprockets is under constant tension, the stress in the chain will be the same at both ends of the section.

 

The greatest strain is in the middle top surely? I'm no physicist btw. On the front and back sprocket the strain is distributed over the gear teeth.

 

Depends on how the chain is fitted and tensioned.
Usually the pedal sprocket is the driving force so the teeth will be 'pulling' the chain and hence be under the greatest strain. The smaller, wheel sprocket, will be under tension when first starting but once rolling it's own momentum will help to reduce that strain. It's virtually impossible to tension a chain to such accuracy that it is even all the way round. You tend to get a bit of slack on the lower section as it comes off the driving sprocket. As this means it is being pushed as it comes off the driving sprocket it follows that this releases some of the pulling tension by the wheel sprocket. Ergo, the pedal sprocket is the one under greatest strain in most scenarios.

 

On the chain itself, the tension in the upper part between the two chainwheels is the same in every link. How could it be otherwise? if there is, say, 25kg tension in link 3, there must be exactly the same in link 4.

The lower part is slack.

 

Yes when I say middle top I mean the middle bit between the cassette and the chainrings. However, 10 seconds of googling suggest that's incorrect. The greatest strain is at the max angle of deflection so that would be just after the cassette or just before the chainrings, depending on the gear.

So the answer to the question is No.

 

As I tried explaining above in my rather long winded way. LOL

 

If the cyclist is powering the bike along, the chain tension will be equal between both chain wheels. ( on top)

If the rear wheel should slip under traction, then the tension would be very slightly less at the rear, until it bit again.

Willing to be disproved on all counts...........

 

Amazing response. My thanks to all.

 

Well, you lot have done for me.....

Going up a tidy hill over The Chase tonight , I snapped my sodding chain

Six miles of scooting the downhill bits, and pushing the rest, to get home

 

I doubt that you snapped it, the rivets probably gave way, that should be some comfort for you..........

 

It's only been on 50 miles!

 

get yourself a Topeak Mini 18 it has a chain breaker tool, keep it in your kit bag and you just take a link out and ride home.

If you want the good news, if your chain broke, its probably worn and you need a new cassette too