Pressurized Frame...Crazy idea?
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I wouldn't want my frame pressurized high enough to reinflate a tire. Taking into account the volume of, say, a down tube (I can't imagine you'd seal all of them up) you would have to run 2-3 times the pressure of a tire... Seems like a lot of stress on the welds? Maybe an internal sleeve would work... Beats me. Seems like it would be HELL to figure out and make reliable/light/quiet (think rattling), but uh... If anyone does, let me know har-har.
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I don't think you would have enough volume inside the frame tubes for it to be very effective unless it operated at pressures above a standard air compressor.
I have never dealt with it myself, but I have heard people talk about systems where tubing it made more rigid by filling the tubes with high pressure nitrogen. Supposedly this has been done to things like lattice crane booms to make them stronger. Anybody know if this actually done? I have worked around cranes and draglines for years but I haven't come across it.
I have heard several people over the years talk about making the seat tube into a pump. Hook the hose to a fitting near the bottom of the tube, unlock the seat post and pump it up and down with the saddle acting as the handle for the pump. It doesn't seem like it would be hard to do, but I have never been interested enough to try and make one. I suspect there is some reason nobody has put the idea into practice.
I have never dealt with it myself, but I have heard people talk about systems where tubing it made more rigid by filling the tubes with high pressure nitrogen. Supposedly this has been done to things like lattice crane booms to make them stronger. Anybody know if this actually done? I have worked around cranes and draglines for years but I haven't come across it.
I have heard several people over the years talk about making the seat tube into a pump. Hook the hose to a fitting near the bottom of the tube, unlock the seat post and pump it up and down with the saddle acting as the handle for the pump. It doesn't seem like it would be hard to do, but I have never been interested enough to try and make one. I suspect there is some reason nobody has put the idea into practice.
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1,696 Posts
I have heard of ultralites using nitrogen pressure in the tubes
the have a gauge on them
just a few psi
if it ever hits zero psi
you have a cracked weld
the have a gauge on them
just a few psi
if it ever hits zero psi
you have a cracked weld
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15,600 Posts
Not to mention that pressurized air has weight. You might be adding 30-50gs of weight to a frame by having a top tube or downtube full of pressurized air.
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On the flip side go for helium for the ultimate weight weenie expirence or hydrogen if you are really crazy!
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To fill a tire up to say, 35 psi or so, Esp if it was a 29 x 2.3 or something fairly large, you would need to probably get at least 160 psi or so into a large downtube. No problem for a .9mm wall Cromo tube to hold pressure like that, but doesn't seem like it would be worth the work to get the frame done so that you could attach a hose, etc... to pump up the tire. I had a buddy in SoCal years ago that had big tube bumpers on his 4x4 and they were set-up with valves and he pressurized them to about 150 psi with his compressor to be able to either re-inflate or just make pressure changes to his tires when he went out into the sand. Worked well, but the big tires he had were about 20 psi when they are "up". The tube bumpers were pretty huge and had additional cross-pieces and parallel tubes. He made them all one chamber, so a lot of air in the front and a fair amount in the back too.
Odyssey Aeratorkpomtb said:
http://forums.mtbr.com/showpost.php?p=3143905&postcount=17
The pump-inside-seatpost trick worked with Zefal Solibloc, Zefal Lapize, and other similarly skinny frame pumps.
not for pumping tyres but indeed a pressurized frame.
http://www.syntace.com/index.cfm?pid=3&pk=709
"The trials frame's downtube features an air valve and pressure gauge for the ultimate in ride-tuning. Adjusting air pressure changes impact feel and response, for that extra edge."
talked to them at a bike show. The guy told me the down tube would dent less easily if it was pressurized.
Personally I think its a lot of sales BS. Seriously doubt anyone could feel if the frame was pressurized or not, and one would have to put in a rather extreme pressure to make it even a little bit less dent sensitive.
http://www.syntace.com/index.cfm?pid=3&pk=709
"The trials frame's downtube features an air valve and pressure gauge for the ultimate in ride-tuning. Adjusting air pressure changes impact feel and response, for that extra edge."
talked to them at a bike show. The guy told me the down tube would dent less easily if it was pressurized.
Personally I think its a lot of sales BS. Seriously doubt anyone could feel if the frame was pressurized or not, and one would have to put in a rather extreme pressure to make it even a little bit less dent sensitive.
great idea... cause balloons sure like being twisted and bent when they're at high psi... 
let's see, tubes flex/bend/twist (and DO change shape ever-so-slightly) so you want to pressurize the inside of that structure and make sure that the part of the tube being tweaked out by torsion or vertical loading also has the added internal force of a pressurized gas inside trying to resist deformation?
Maybe it helps the frame resist that vertical load, maybe it keeps that part of tube in the same plane while the rest of the tube tries to remove itself... (shear)
This is so weird, pressurized tubes, wire tension frames, those weird arantrix or whatever frames, that dumb belt drive being used offroad...
I have to admit to not being quite so old that I remember ALL of those "for the sake of experiment" years of motorcycling where everything and anything got tried, but I DO remember enough of it to hope that mtb'ing would've learned from the mistake of assuming that because it CAN that means it SHOULD be done.
let's see, tubes flex/bend/twist (and DO change shape ever-so-slightly) so you want to pressurize the inside of that structure and make sure that the part of the tube being tweaked out by torsion or vertical loading also has the added internal force of a pressurized gas inside trying to resist deformation?
Maybe it helps the frame resist that vertical load, maybe it keeps that part of tube in the same plane while the rest of the tube tries to remove itself... (shear)
This is so weird, pressurized tubes, wire tension frames, those weird arantrix or whatever frames, that dumb belt drive being used offroad...
I have to admit to not being quite so old that I remember ALL of those "for the sake of experiment" years of motorcycling where everything and anything got tried, but I DO remember enough of it to hope that mtb'ing would've learned from the mistake of assuming that because it CAN that means it SHOULD be done.
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