fossyant
Ride It Like You Stole It!
- Location
- South Manchester
No you attach animal to front and dangle snack on a fishing line. Have you not seen any Looney Tunes cartoons.
Solid verses pneumatic
- Thread starter Biker man
- Start date
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No you attach animal to front and dangle snack on a fishing line. Have you not seen any Looney Tunes cartoons.
I've ridden in Canada there are bears about and they will eat you.
welsh dragon
Thanks but no thanks. I think I'll pass.
andrew_s
Legendary Member
- Location
- Gloucester
There is no such material.
Pneumatic tyres work because there is a single air chamber that distributes any change in pressure round the whole wheel. Take a tyre, and squeeze an inch of it down to the rim, and the volume of the air chamber, and hence the pressure, will only change by about 1%. The force required to get the last 10% down to contact with the rim is almost the same as to get the first bit of movement.
In any non-pnematic tyre there is no mechanism for distributing the change in resistance round the wheel, and all changes are limited to that part of the tyre between the rim and the road. If the tyre is pressed half way down to the rim, the force required to move the tyre is double what is was to start with, at 3/4 down the rim it's 4 times, and at the start of the last 10% it's 10 times.
Since there's a minimum pressure equivalent under steady riding on a smooth surface, from a handling perspective, it's inevitable that any non-pneumatic tyre will give a harsh ride. It doesn't matter whether it's foam, a fancy elastomer, or some arrangement of springs, it's all the same.
I'll give a half excuse to HLaB's bike with the gun. If the tyre is rigid, it's the same as a solid steel wheel with 1" or 1.5" travel suspension.
I dare say the gun gets you more road space tho'
andrew_s
Legendary Member
- Location
- Gloucester
A futher point would be that, because non-pnematic tyres give a harsh ride, they are slow.
All the vibrations that get through to your body are lost energy, human flesh not being noticeably springy, and that lost energy must be replaced from somewhere (i.e. your legs), or you'll slow down.
All the vibrations that get through to your body are lost energy, human flesh not being noticeably springy, and that lost energy must be replaced from somewhere (i.e. your legs), or you'll slow down.
Ajax Bay
Guru
- Location
- East Devon
Show workings please or I'll assume Andrew, that you have plucked this figure from an orifice where the sun doesn't shine.
You are assuming that the tyre's material is elastic in that complete range, which I assert is most unlikely. This latter observation is (agreeing with you - no such material) nugatory (and the deduction you make from this erroneous quantatitive approach is entirely valid), but let's stay within science's bounds.
figbat
Slippery scientist
- Location
- South Oxfordshire, UK
I saw a demonstration once to prove that applied load to a tyre makes no difference to its pressure. A car was on a workshop life, tyres in the air. A tyre pressure gauge was attached. The car was then lowered onto its wheels - the gauge needle stayed put.
- Location
- Essex
I went to canada once to do some bear hunting
As i was driving along i came to a road sign which said "bear left"........so i went home
😃😄😃I went to canada once to do some bear hunting
As i was driving along i came to a road sign which said "bear left"........so i went home
lazybloke
Ginger biscuits and cheddar
- Location
- Leafy Surrey
Seems wrong but I need to think about reasons. Relatively low pressure of car tyre with large contact area and inaccurate gauge: that's my gut feeling.
newfhouse
Resolutely on topic
Surely the pressure will only be higher at the contact point, where the tyres bear the weight. What would happen if you carefully rotated the wheel so that the valve was at the bottom before measuring?
I base my question on the observation that when I pick up a puncture - twice at the weekend - the tyre only deforms near to where it touches the road.
Alex321
Guru
- Location
- South Wales
The pressure is even all across the inside of the tyre, because said tyre is a single chamber.Surely the pressure will only be higher at the contact point, where the tyres bear the weight. What would happen if you carefully rotated the wheel so that the valve was at the bottom before measuring?
I base my question on the observation that when I pick up a puncture - twice at the weekend - the tyre only deforms near to where it touches the road.
The fact it compresses where it is in contact with the road just means the rest of the tyre expand to compensate - but the fact there is so much more not in contact with the road means that expansion is imperceptible to the naked eye.
Alex321
Guru
- Location
- South Wales
Not necessarily inaccurate as such, just with too coarse a scale.
figbat
Slippery scientist
- Location
- South Oxfordshire, UK
Scientifically though, in order for the pressure to change then one of two things must change: volume or temperature. Assuming temperature remains constant then the only vector to increase pressure is a volume change. Does deforming a tyre change the volume, or simple reshape it? The air pressure does not, itself, bear the weight of the vehicle (like, for example, in an air fork) - the pressure provides rigidity to the tyre carcass which bears the weight.
lazybloke
Ginger biscuits and cheddar
- Location
- Leafy Surrey
Yes, having considered various scenarios for the area of tyre contact patch on a unicycle with light & heavy riders, I reckon I agree with you Alex.
Possible next steps are : mathematical modelling, followed by practical experiments with my unicycle.