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Expanding foam to fill bike tires

Mushy. Popproof. Not the best ride but you get there.
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Outside my workplace is a university communal bike. It has been there a long time. It has flats. No-one is fixing them. The tragedy of the commons.

I propose that communal use bikes have the tires filled with expanding foam. This foam would need to be more resilient than the stuff commonly used for insulation, which is sort of crispy.

A tire full of foam would not go flat. The ride would not be as cushy as a pure air wheel, but the many airspaces in the foam would compress so it would not be like a wooden or sand-filled tire either.

A can of this foam could also be an emergency flat fixer for cars or bikes, though it would need to be a big can for a car. Puncture sites would be evident as the foam would extrude from them, and they could then be occluded with a thumbn until the foam set up.

bungston, Jun 05 2009

A description of Fix-a-Flat and it's uses http://www.kk.org/c...archives/000721.php
[21 Quest, Jun 05 2009]

corrected link air free tires http://www.airfreet...eel-john-deere.aspx
[dentworth, Jun 06 2009]

[link]






       This is baked in the form of foam tyres, but not as a foam applicator.
nineteenthly, Jun 05 2009
  

       You used to be able to buy this foam in a can in bikeshops in the '80s, not sure if it's still around. it was used for fixing punctures
simonj, Jun 05 2009
  

       Was it foam or was it some gluey runny stuff that was intended to fill puncture?
bungston, Jun 05 2009
  

       //A can of this foam could also be an emergency flat fixer for cars or bikes, though it would need to be a big can for a car. Puncture sites would be evident as the foam would extrude from them, and they could then be occluded with a thumbn until the foam set up.//   

       How is this different than Fix-a-Flat? Or the spray foam sealant used in home remodeling?
21 Quest, Jun 05 2009
  

       Fix a flat is mostly gas, with some runny stuff to fill the puncture from the inside.   

       The foam sealant for remodeling that I have seen is too brittle for this use. I am hopeful that there might be a more plastic foam sealant that I could press into service for this poor bike parked outside. I was thinking I would just cut the fill valves off and fill thru those holes. We will have the bike sign an informed consent first, of course.
bungston, Jun 05 2009
  

       Yeah it was foam in a compressed air canister. you just attached it to the valve to reinflate and seal the tyre.
simonj, Jun 05 2009
  

       What may be possible, Bungston, would be to replace the inner tube with a solid nerf ring that goes inside the tire in its place. That's pretty robust. Not sprayable, but I don't think you're going to find an insertable liquid foam more robust for this application than the stuff used in Fix-a-Flat. (btw, not my bone)
21 Quest, Jun 05 2009
  

       I like the Nerf ring but you would have to butterfly the tire in half to get it in there. I suppose you could just glue the tire to the ring and hope for the best.
bungston, Jun 05 2009
  

       What do you mean by "butterfly the tire"? Hm... maybe make it a 2-layered ring. You put the first layer in the tire, and it sits flush with the outer part of the tire. then you put the second layer in, held to the first by some sort of adhesive, or just lego-like interlocking parts, which fills the gap between the first layer and the rim. It would take some finagling, alright... ok, so maybe not.
21 Quest, Jun 05 2009
  

       Foam tires have been available at various points, and I guess still are. For communal bikes they might be a valid solution. The real problem is the increased risk of damage to both the wheel and the rider. A pneumatic tire has the entire diameter of the tire to distribute impacts, a foam tire can only do it over the immediate contact area. This provides a much rougher ride, and a greatly increased chance of spoke breakage.
MechE, Jun 06 2009
  

       "I am hopeful that there might be a more plastic foam sealant ..."   

       fess up, what you really want is custard- UK version
dentworth, Jun 06 2009
  

       If you are using foam from a pressurized can to inflate a tire, will this repressuization tire not turn your foam back to goo?   

       Where I come from, the term "communal bike" has an entirely different meaning.
Custardguts, Jun 08 2009
  

       You're referring to the Village Bicycle, then?
21 Quest, Jun 08 2009
  

       [2Fries] Most expanding foams are a two part reacting material, they won't reverse under pressure.
MechE, Jun 08 2009
  

       Those buggars lied to me when I wanted to fix a leaky Zodiak by making it a solid foam boat then!
Perfectly good bullet proof boat and I let it go for a song. <mutters under breath>
  

       I think what you need is liquid nerf foam. They have to have a way to inject it into the molds they use. It might be a hot liquid though, which would make portability a problem. Perhaps you could suggest this product line to the Nerf company.
gryphon327, Jun 09 2009
  
      
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