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Learning how to build Lotus Seven replicas...together!
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PostPosted: Sun Jul 23, 2006 12:17 am 
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Could you just spray wd40 in side the tube and cap it with a plastic/rubber cap with silicone to seal it or weld the end?


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PostPosted: Sun Jul 23, 2006 9:46 am 
violentblue wrote:
drill a 1/8" hole in the solid tube where there is a joint.
it would make the chassis a single chamber, fill it with helium for weight reduction.


You're either kidding or crazy. Surprisingly, I can't tell which (we're always the last to recognize our own disorders). :wink:


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PostPosted: Sun Jul 23, 2006 12:31 pm 
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Locosted Don wrote:
What you could do is drill a hole at every joint, hook a pressure gauge to the chassis, then fill with inert gas. If the pressure gauge drops you've developed a crack. :lol:


Porsche did this with their 917 aluminum chassis, so they'd know when they had a crack somewhere...

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PostPosted: Sun Jul 23, 2006 5:55 pm 
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Location: Lethbridge Alberta
the JoKeR wrote:
violentblue wrote:
drill a 1/8" hole in the solid tube where there is a joint.
it would make the chassis a single chamber, fill it with helium for weight reduction.


You're either kidding or crazy. Surprisingly, I can't tell which (we're always the last to recognize our own disorders). :wink:


they do this with trials motorcycles all the time, cromoly frames filled with helium, not a huge weight savings but every ounce counts.


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 Post subject: Re: Wacky idea?
PostPosted: Sat Jun 12, 2010 2:48 pm 
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I still think it's used to detect leaks. Helium is the smallest At-om that is safe to use for leak detection. It will leak through the smallest cracks. Unless you want to use hydrogen. Then you can say you built a Hindenburg chassis.


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 Post subject: Re: Wacky idea?
PostPosted: Sat Jun 12, 2010 4:44 pm 
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violentblue wrote:
they do this with trials motorcycles all the time, cromoly frames filled with helium, not a huge weight savings but every ounce counts.

Indeed it does, but it takes a cubic foot of air to count to one. On a motorcycle chassis, I'd bet the fitting for filling the frame with helium weighs more than the air that the helium displaces.

This is a pretty common technique (at least at the World Championship level) for engine mounts for competition aircraft, and it does save weight, because you don't have to build with as high a safety margin as you would if you had to wait for your engine to fall off to know you had a crack. The weight savings comes from the confidence inspired by knowing you'll have some notice, and if that pressure gauge drops to zero then you're headed off to the nearest safe place to land.

In practice, we use air, and use tubeless tire fittings as the frame fillers ports. You can find compressed air at any gas station (pretty much) or from a cheapo plug-in-the-cigar-lighter 12v compressor, but where do you find helium in (for example) Poznan, Poland?

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 Post subject: Re: Wacky idea?
PostPosted: Mon Jun 14, 2010 1:37 pm 
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JackMcCornack wrote:
violentblue wrote:
they do this with trials motorcycles all the time, cromoly frames filled with helium, not a huge weight savings but every ounce counts.

Indeed it does, but it takes a cubic foot of air to count to one. On a motorcycle chassis, I'd bet the fitting for filling the frame with helium weighs more than the air that the helium displaces.

This is a pretty common technique (at least at the World Championship level) for engine mounts for competition aircraft, and it does save weight, because you don't have to build with as high a safety margin as you would if you had to wait for your engine to fall off to know you had a crack. The weight savings comes from the confidence inspired by knowing you'll have some notice, and if that pressure gauge drops to zero then you're headed off to the nearest safe place to land.

In practice, we use air, and use tubeless tire fittings as the frame fillers ports. You can find compressed air at any gas station (pretty much) or from a cheapo plug-in-the-cigar-lighter 12v compressor, but where do you find helium in (for example) Poznan, Poland?


Anywhere with balloons. :lol:

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 Post subject: Re: Wacky idea?
PostPosted: Mon Jun 14, 2010 2:11 pm 
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JSullivan wrote:
JackMcCornack wrote:
violentblue wrote:
they do this with trials motorcycles all the time, cromoly frames filled with helium, not a huge weight savings but every ounce counts.

Indeed it does, but it takes a cubic foot of air to count to one. On a motorcycle chassis, I'd bet the fitting for filling the frame with helium weighs more than the air that the helium displaces.

This is a pretty common technique (at least at the World Championship level) for engine mounts for competition aircraft, and it does save weight, because you don't have to build with as high a safety margin as you would if you had to wait for your engine to fall off to know you had a crack. The weight savings comes from the confidence inspired by knowing you'll have some notice, and if that pressure gauge drops to zero then you're headed off to the nearest safe place to land.

In practice, we use air, and use tubeless tire fittings as the frame fillers ports. You can find compressed air at any gas station (pretty much) or from a cheapo plug-in-the-cigar-lighter 12v compressor, but where do you find helium in (for example) Poznan, Poland?


Anywhere with balloons. :lol:


Or HeliArc welding.

On the helium filled tubes...In the old days when all of the Phone company's underground cables were under constant pressure (dry air) to prevent water from entering; water doesn't have a chance to get in if there is always air squirting out, we used helium to detect leaks in the sheath. The helium was injected at the closest splice case and then a combustible gas detector was used to detect the inert Helium. Since inert is the opposite of explosive, the gas detector would go negative in its readings when it sniffed helium coming out of the ground. Worked like a charm.

But back to the subject at hand. My wifes granfather re-built many a crop duster frame (for the normal reasons, pilot ran out of good judgement too close to the earth) and they used the two hole method of filling the tubes with oil after all welding was done. One at the top to completely fill each tube, and then after all were completely filled, another small hole at the bottom to dain it all out. The holes were then brazed shut, the frame clean up and then some zinc chromate ( can't rember if that was the exact compound) sprayed over every tube. He said they used any and all left over oil, but never used "used" oil.

Tom

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Last edited by Off Road SHO on Fri Jun 18, 2010 9:03 pm, edited 1 time in total.

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 Post subject: Re: Wacky idea?
PostPosted: Fri Jun 18, 2010 8:47 pm 
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instead of filling the frame volume with something that isn't water and hoping it doesn't leak out..... do what A/C techs the civilized world over do to rid confined spaces of trapped water.

seal it up and draw a huge vacuum on it. you'ld be surprised how low the boiling point of water is at negative 30 psi. put a vacuum guage on your tubes where you can see it, put an R-12 fitting on your frame where you can reach it, and dust off your local mechanic's old a/c machine.

if the pressure normalizes, you have a crack. it won't leak anything out, so it might be nearly impossible to find, but i guess you could fill it with water, find the leak, drain it, fix it, and vacuum it.


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 Post subject: Re:
PostPosted: Fri Jun 18, 2010 10:33 pm 
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violentblue,
Awe come on now, helium? I used to ride trials and I never heard of this. If you wanted to be light just go take a crap before riding. The trials bikes are specially made for balance but one or two ounces of weight savings is nothing. Some did modify their frames but that was to add an even thicker skidplate.


Mark.


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 Post subject: Re: Wacky idea?
PostPosted: Fri Jun 18, 2010 10:39 pm 
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Pete,

If it really bothers you go online to Aircraftspruce and buy some of the crawling oil they use in aircraft frames. Better yet go to Academy and buy a can or two of CorrosionX. If not at Academy Sports in your area any place they sell boats should have it. CorrosionX is basically a thinned out cosmoline in a spray can.

Mark


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PostPosted: Fri Jul 02, 2010 10:40 am 
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I do it 2 ways, either I fill up tubes with diesel, tip it back out or I get the whole chassis galvinised.

Making sure there is no way for air to get in anywhere on the chassis is good too and except for competition rolls bars this is entirely possible.


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PostPosted: Fri Jul 02, 2010 4:29 pm 
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There is a specific product made for this called frame saver that is meant to coat the inside of your steel frame to prevent rust.

http://www.universalcycles.com/shopping ... hp?id=7824

They just think you own a bicycle.


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PostPosted: Sat Jul 03, 2010 1:53 am 
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milo wrote:
There is a specific product made for this called frame saver that is meant to coat the inside of your steel frame to prevent rust.

http://www.universalcycles.com/shopping ... hp?id=7824

They just think you own a bicycle.


For motocycles you can get a similar thing to coat the inside of your fuel tank, bit exxy on price though.


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PostPosted: Sat Jul 03, 2010 8:35 pm 
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Just got a quote on t-304 stainless tubing 1" x 1" x 16 ga.- $2.43/ft, in stock. Cheaper than powdercoating.


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