Inflation Chart

[Tim Hall]

Internal radius = 0.622/2 = 0.311m
External radius = 0.627/2 = 0.314

Volume = 1/4 x (pi)squared x (a+b) x (b-a)squared

V=1/4*3.14*3.14(.311+.314)*(0.314-0.311)*(0.314-0.311) = 0.14l

But this is very old maths - I may well be wrong and the external radius looks wrong anyway ....

I think your external radius should be larger, as it's only 3mm bigger than your internal radius.

 

[cisamcgu]

I think so too..looking at http://www.bikecalc.com/wheel_size_math I see I got the tyre diameter wrong.

Hence:
A 700C wheel has a diameter of 622mm => radius of 311
A 700C/28 tyre has a diamter of 678mm => radius of 339

Therefore :
volume of 28mm tube = 1.26l

Now, you correctly state that : "A 16g gas bottle, molecular weight 44 (c=12, O=16) has 16/44 = 0.36 mol of gas"

Therefore 0.36mol equates to 0.36 x 22.4 = 8.06l

Therefore : P = (8.06/1.26) * 14.9 = 120psi

Et voila, you are right

 

[Tim Hall]

I think so too..looking at http://www.bikecalc.com/wheel_size_math I see I got the tyre diameter wrong.

Hence:
A 700C wheel has a diameter of 622mm => radius of 311
A 700C/28 tyre has a diamter of 678mm => radius of 339

Therefore :
volume of 28mm tube = 1.26l

Now, you correctly state that : "A 16g gas bottle, molecular weight 44 (c=12, O=16) has 16/44 = 0.36 mol of gas"

Therefore 0.36mol equates to 0.36 x 22.4 = 8.06l

Therefore : P = (8.06/1/26) * 14.9 = 120psi

Et voila, you are right

Excellent! Except bar to psi is a factor of 14.5 not 14.9, according to wiki. (I used 14.5, you went for 14.9)

 

[cisamcgu]

Well I never, I always thought 1bar was 14.9psi but it seems I have been living under a misapprehension for a long time

live and learn

 

[NorvernRob]

You could just get a decent mini pump.

 

[byegad]

Any beggar that punches me will get a kick in the goolies!

 

[junkie_ball]

Good work guys nice to see some maths on this have to trust your workings though.