unravelling Gearing theory and formulae

[ColinJ]

A chap I work with has a Raleigh Equip. It weighs 28lb and has a 42 x 24 lowest. It was originally sold as a 'Racer'! Some hopes.... It needs a 30 tooth ring ( a triple ) with a 23 sprocket. 25 to be safe. 27 to be safer.

It's owner is not overweight and he deperately struggles, puffing and panting to climb up Corley Rocks which is about 11% and only 100m duration. At the summit, he should be able to accelerate away to cruising speed. No. Time to recover is necessary. The gear is way too high.

I've been riding around there on my singlespeed bike quite a lot over the past year! I make frequent trips back to Coventry to visit my family.

That little climb is a bit tough on 39/15, especially since I'm about 30 pounds overweight. At least the bike is pretty light.

 

[jimboalee]

Let me just pre-empt some discussion.

I have done some preliminary calcs to get a measure of Peanut's ability.

Peanut's weight is 106 kg. That's not including any clothing so have a ball with your imagination.

I have him climbing up a flight of stairs which are 170 mm lift with every step. He is walking up at 120 steps per minute, or 60 complete reps of alternate leg press in one minute, ie 1 per second.

I get a power requirement of 385 Watts.

When I issue a result, the gear length, cadence and resultant speed should be appropriate to 385 Watts.

More preliminary calcs with PowerCalc give Peanut's 118kg model climbing a 10% at 388 Watts at 10.5 kmh on a 30 x 21 ( 38 ) at 58 cadence.

I am guessing his fat% is 28 ( 28mm of skinfold. educated guess ) so with a bike weight of 23lb, the '10% gear' is 43 – 6 ( for 6% fat over 22% ) = 37.

If anyone says 37 inches is too high, you are also saying Peanut hasn't got the strength to climb a flight of stairs without getting knackered.

 

[Speck]

What about his age?

 

[Steve Austin]

what about his clothes?

 

[punkypossum]

What's his wrist got to do with it? (I suspect this is probably explained somewhere else, but can someone just tell me before I go searching?)

 

[tyred]

What's his wrist got to do with it? (I suspect this is probably explained somewhere else, but can someone just tell me before I go searching?)

Your wrist measurement can be used to come to a conclusion about how overweight you are.

 

[Steve Austin]

Is that why some drivers wave their wrists at me when i ride past them?
They are telling me they are fat?

 

[jimboalee]

What about his age?

Yes, that is the missing question.
Now I'm in front of my calcs, I need your date of Birth Peanut.

 

[jimboalee]

Your wrist measurement can be used to come to a conclusion about how overweight you are.

No, not exactly. It is an indication of a person's Frame Size.
Not bike frame size, but skeletal frame size.

 

[jimboalee]

Is that why some drivers wave their wrists at me when i ride past them?
They are telling me they are fat?

No. That's the universal sign language gesture ( called 'the five knuckle shuffle' ) to say "You're a W****r!"

 

[jimboalee]

Leave the thread Steve. We know you're just cock-a-hoop with anticipation of seeing me disgraced.

It really doesn't bother me.

Am I bothered? Look at me, am I bothered?

 

[peanut]

What's his wrist got to do with it? (I suspect this is probably explained somewhere else, but can someone just tell me before I go searching?)

best not go there possum

we are waiting for jimbo's calcs . They must be pretty comprehensive as they are taking ages

 

[tyred]

Anyone opening a book on whether Jim's right or wrong?

What are the odds?

 

[jimboalee]

What's you date of birth, Peanut?

 

[peanut]

blimey jimbo you'll be asking which primary school I went to next lol

I'll pm you my dob strictly in confidence ok