Force in a chain?

[Unclejack]

I have answered my own question. So good night.
:?

 

[We_are_Stevo]

I have answered my own question. So good night.
:?

Indeed you have;

The longer the lever at one end the less effort it takes to lift a given weight at the other...

What does that have to do with the original question posted?

Road v MTB - which creates the most tension in the chain?

This isn't the place to merely post a personal opinion based on guesswork - the math's proves otherwise...

...and once upon a time I could have used it to make my point, just like I used to be able to work out the final drive ratio of a m'cycle transmission given the size of the drive sprocket, the size of the gears in the gear box and the back sprocket - now I look at my old work books and I haven't a clue!

Use it or lose it

 

[petitpal]

In reality I would suspect (guess ) that most chains have broken under conditions giving good traction in higher gears (then you should be in) but at lower cadences ?

The only time I've broken a chain on an MTB was under those exact conditions - gear slightly too big for what I was trying to do and standing on the pedals trying to do it (i.e. low cadence). I guess this is because of an almost 'stretching' effect on the chain - one crank 'pulls' it then the chain relaxes before the next crank and so on... whereas high cadences it's under a slightly more equal amount of pressure. You'd think. Hell, I'm a software engineer, what do I know??? I'm getting no my involved than that!

 

[We_are_Stevo]

In reality I would suspect (guess ) that most chains have broken under conditions giving good traction in higher gears (then you should be in) but at lower cadences ?

The only time I've broken a chain on an MTB was under those exact conditions - gear slightly too big for what I was trying to do and standing on the pedals trying to do it (i.e. low cadence). I guess this is because of an almost 'stretching' effect on the chain - one crank 'pulls' it then the chain relaxes before the next crank and so on... whereas high cadences it's under a slightly more equal amount of pressure. You'd think. Hell, I'm a software engineer, what do I know??? I'm getting no my involved than that!

Maybe so, but at least you know what you're talking about...

 

[02gf74]

Surely that wasn't your original question - you were comparing Road to MTB; which exerts the most?

Using your argument you may as well say that trying to move from a standing start on an incline on the biggest ring front and rear exerts the most force - which is nonsensical!

As I said there are too many variables - rider weight for example?

Original question was due to the orange chain post in > 1998 section - as to whether it will be ok for downhilling.... which lead me to wonder under what circumstances will the chain experience the most force.

The gearing ratio as spotted does relate to road and mountain bike gears but the number of teeth on the rear sprocket does not come into effect. I wasn't not comparing rod vs mtb - the ratios are a red herring.

Other variables don't really come into it either such as body weight, stiffness of frame, incline or if the rider is pulling on the bars to get extra advantage.

No matter how it is done, the rider will at some point exert his maximum torque on the pedals.

It does not matter if he is stationary - track stand and pushing off or the wheel is bolted to the ground or if he is bimbling up a steep incline. His power is max.

The crank and front chain wheel are two levers, the ratio of which mutliples the force going to the chain.

What happens at the other end of the chain makes no different to the force within the chain - for example the chain could be attached to the axle, wheel rim or be on any of the sprockets.

So going on from that - max force in chaiin is when it is in smallest chain ring, I would expect most chain snappings to occur when climbing up steep hills, probably out of the saddle than when zooming along at 27.86 mph on the flat.

 

[WD Pro]

I have answered my own question. So good night.
:?

As that was straight after my post and you seem a agitated, I hope I didn't offend ? :-(

WD

 

[We_are_Stevo]

So going on from that - max force in chaiin is when it is in smallest chain ring, I would expect most chain snappings to occur when climbing up steep hills, probably out of the saddle than when zooming along at 27.86 mph on the flat.

But that's only because that is when the majority of riders are putting in the most effort...

The original question also said;

'I also assume the greatest force is in the lowest gear - is that correct?'

The answer to which is 'not necessarily.'

A heavy road racer suddenly standing on the pedals in a sprint to the finish in top gear is going to be putting a lot more strain on the chain than a lightweight MTB rider spinning slowly up a hill on the granny ring.

It doesn't really matter what gear you're in, it's what you're doing with it that makes the difference...

 

[red_riviera]

Question is about the the force in a chain on a bike - which one would have bigger force going through it:

1. driving gear 39 T, driven gear 23 T (e.g. road bike)
or
2. driving gear 22 T, driven gear 32 T (e.g. mountain bike)

The motor unit (i.e. the cyclist) is generating the same amount of torque.

I also assume the greatest force is in the lowest gear - is that correct?

The same... if you are measuring 'the same torque' at the output point of the system (where the tyre meets the ground)... the only place that isn't subject to variables.

 

[doctor-bond]

Surely the greater the distance between the pivot and the lever the greater the force?

The bb centre is the pivot, the crank arm the lever. The chainring position between those two points is a form of gear that modifies the effect.

Imagine if you had a 200cm long crank arm and a tiny front chain ring that just fitted round the bb spindle; as you turned the crank arm an enormous force would be applied through the chain, regardless of what was attached to it at the other end.

If you replaced the tiny chain ring for one with, say, a 100cm radius, the leverage effect (as far as the chain on the chain ring experienced it) would be lessened greatly.

So, crank length and downward force being equal, a smaller chainring transmits more force to the chain. (And I think that the chain would experience a stretching force not torque, which would be felt at the BB spindle.)

 

[JamesM]

If the ratio's are the same, the load at the rear wheel is the same and the force applied to the cranks is the same. A gear set with smaller cogs (say 32:16) would generate more chain tension than a gear set with larger cogs (say 48:24) for the same outcome.