How to work out average effective pedal force for a given

buckles

...power output

Sorry but I have forgotten everything I learnt in maths and physics

How do I work out how much force I'm exerting per pedal stroke, say at 300 watts and 90rpm? 175mm cranks.

Obviously circumferential pedal velocity at 90rpm is 1.5 x 2 x pi x 0.175 = 1.649m/s

Is it simply a case of dividing 300 by 1.649 , which equals 181.89 Newtons? Which would be equivalent to pushing approx 18kg?

drlodge

I'll have a go

Force in Newtons times velocity in m/s = power in Watts

So Force in Newtons = power in Watts divided by velocity in m/s = 300 / 1.649 = 182 Newtons = 18kg

So you're right, but pedal force is not constant, there is almost zero focrce at the top and bottom of the stroke so suggest the maximum force is more than 18kg. Not sure by how much though, may be 30kg?

RChung

Buckles wrote:

Is it simply a case of dividing 300 by 1.649 , which equals 181.89 Newtons?

Yes.

drlodge wrote:

but pedal force is not constant, there is almost zero focrce at the top and bottom of the stroke so suggest the maximum force is more than 18kg. Not sure by how much though, may be 30kg?

For round chain rings, max pedal force for each leg is roughly 4x average pedal force for that leg. If you don't have huge bilateral asymmetry, combined average pedal force for both legs is twice that so the max pedal force is roughly twice average two-leg pedal force. So 30kg is the right ballpark.

Herbsman

So if I picked up a 9kg dumbbell in each hand and moved them straight up and down 0.165m ten times every second would I be doing 300 watts?

RChung

Herbsman wrote:

So if I picked up a 9kg dumbbell in each hand and moved them straight up and down 0.165m ten times every second would I be doing 300 watts?

You remind me of Antoine Vayer.