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In-wheel shock absorbers

Device that allows tires to act more like full suspension.
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There's an impromptu car show/car people hangout just about a mile from my house every Friday. That has nothing to do with this idea except for that's where I was walking to when this idea occured to me.

A landscape service trailer loaded with tools, mowers and the usual landscape maintenance stuff drove past me on a residential street. It was being towed by a pickup. The pickup truck has nothing to do with this idea either, except for it was making the trailer go. Anyway, the trailer went over a speed bump. Crash, bang, rattle, bounce, bounce said the little red trailer.

"Why does it have to be so noisy?", I thought. "Why doesn't that guy put shocks on the trailer to reduce some of that bouncing?" I watched the trailer bump along down the road for a few seconds and realized that it must not have any suspension, just a solid-mounted axle (or springs so stiff as to render them springless).

"Why doesn't that guy put suspension on that trailer? That's a lot of work. Never mind. Maybe he should let some air out the tires to soften the ride. But, then the sidewalls get all wallery and the tires wear funny and get hot and pop and stuff. There should be some easy sort of retrofit suspension. Easy? I don't think so."

"Hmm, the tires act a little bit like springs and a little less like shocks. Not very effective, but that's what there is to work with. Hmm, what to do? Well, if the tires were softer when hitting bumps, that would help. They'd still bounce. If they were soft when hitting a bump, but firmer at other times, that might work. How about an air cylinder that would let the extra pressure caused by the bump to escape. Okay, how do you put it back? How do you put it back at the proper rate to dampen the bouncy-bouncy?"

"How about a tube that lets 'excess' air pass from the tire into a cylinder with a movable piston? The piston slides to allow a volume of air to escape. Then a spring pushes the air back when the external deflection has been removed and the internal tire pressure drops. So you end up with a thing just like a shock absorber with non-linear valving that lets air in quickly and pushes it back out slowly. Sort of a dynamic inflation adjustment."

"Yeah."

"Pfff, that'll never work. Doesn't the non-deformed part of the tire already do something like this? Maybe I'll dump this one on the halfbakery when I get home just to see what other people might have to say about it. I'll never remember that long. Never mind."

"Hey, I actually remembered. Now, will I remember to come back later and delete this stream of consciousmess?"

"Oh, just shut up and go to bed."

half, Oct 08 2005

Mar Rover http://mars.jpl.nas...light/wheels01.html
[angel, Oct 11 2005]

[link]






       I sure like the way all those little non-linear valves in your mind work, [half]. +
jurist, Oct 08 2005
  

       Thank you, [jurist].   

       GUESS WHAT! It's not just the military that changes tire pressure to accomodate terrain. (Nope, you're right, [Pa've], not that exciting.)   

       This is quite a bit more dynamic than that. And it was an attempt to retrofit cheap, crappy trailers so they're less cheap and less crappy.
half, Oct 08 2005
  

       This is fairly logical. Or else it seems that way when you describe your train of thought in detail. I wonder if you could make any silly thought seem logical if you describe how you reached it? I wonder if is really as logical as you make out? Am I falling into your trap?   

       Back to the idea. My first thought is that you would need a big reservoir of air on the other side of the shock. I don't know why you would, but that's just what I feel instinctively. Anyone else know?
wagster, Oct 08 2005
  

       The thing I don't know, the thing that seems most likely to make it fail is the magnitude of pressure change in the tire when a bump distorts the tire.   

       If there's not a large swing in pressure due to a bump event, this thing would have to somehow be extremely sensitive. Not sure if it could be done without electronic assistance.   

       Internal tire pressure change due to heating under normal use would likely cause some hassles with keeping a mechanical system calibrated.
half, Oct 10 2005
  

       Instead of fiddling with the tyre, why not use a wheel which has a spring-mounted floating centre?
angel, Oct 10 2005
  

       You might have a better idea than I had. I thought of something similar to yours, but couldn't figure out how you'd keep the wheel aligned without introducing a bunch of friction and wear points.
half, Oct 11 2005
  

       Lessee if it works, 'cause I'm curious. For the shock to at least hit neutral pressure with the tire, it's gotta be pressurized to the same psi. No prob there, just have a compression spring resisting. Now, in order for it to accept at least half of the excess air during a bump, it's going to need to have the same expansion rate as the total tire volume deflection. Still no problem there, just design the compression spring with a low rate and set it to a pre-load.
RayfordSteele, Oct 11 2005
  

       "Hey, I remember hearing that this stuff can be modeled the same way electronics systems can. I should go dig out my controls and transform analysis texts and stuff like that. Yeah, transfer functions, Laplace transforms. Ew, my head feels funny. I'm going to get back to work now."
half, Oct 11 2005
  

       Ok. Take 10 shocks and make them extend from the hub of the wheel. Now mount radiuses on each of the 10 shocks so that they form the "rim" of the wheel. On the rim mount a tube and attach it to each of the radius with belts. Now mount the tire over the the tube. When the wheel takes a hard hit, the tire compresses which compresses the tube, the tube then forces down on the shocks it is attached too.
Antegrity, Oct 11 2005
  

       I'm having a little trouble following that at 6 AM. But I am imagining coil-over shock spoked wheels which is interesting, but poses its own set of lateral and radial stability problems.
half, Oct 11 2005
  

       I remember seeing a "suspension wheel" on Tomorrow's World (BBC TV) many years ago, which had been designed to run with solid tyres. It had a funky zig-zag arrangement of springs which were meant to cushion out the bumps in the road, and looked really expensive. I can't find a link, so I might have imagined it...
suctionpad, Oct 11 2005
  

       Funny, I just remembered an experimental wheel that I saw once on TV. The spokes were curved leaf springs. I think it was supposed to be able to allow the wheel to climb over obstacles with a height greater than 1/3 the diameter of the wheel.   

       As I think about the difference that a .5 oz tire weight can make, I think it would be a monumental task to stabilize any such floating rim wheel at high speed without an "active", electronically controlled system of some sort.
half, Oct 11 2005
  

       I knew I'd seen something like how I imagined this (linky).
angel, Oct 11 2005
  

       Larger tires along with external air reservoirs.   

       Think of the number of drunkdialings that halfbakery has prevented.
haywardt, Nov 20 2006
  
      
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