OzVMX Forum
Clubroom => Tech Talk => Topic started by: kurraboy on August 29, 2016, 05:09:02 pm
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Hi all,
Does anyone know of someone that can dings out of my shiny new 2 stroke pipe?
Many thanks,
James
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or plenty of dents in my1973 cr250 pipe
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try Geoff Morris
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Um, not me anymore. Last one I did (have done many over the years) exploded @ 35psi & took out 3 bones in the back of my hand. Very lucky it went sideways & not upwards into my face. Not worth it when new pipes are available at pretty reasonable costs & only an option for something unobtainable. That's just my opinion gained from personal experience.
K
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Where are you located?
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Bloke i knew used water. Plugged ends, filled pipe with water and applied heat sparingly. Good method for smaller dings.
Was relatively safe - but you wouldn't want to melt the metal with high pressure steam behind it! He always used caution and full cover safety gear!
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How about that, I was pumping out some dings with compressed air @50psi and using oxy/acetylene to heat on the week end.
The whole time I was wondering if the juice was going to be worth the squeeze as you warn of in your reply Big K.
It is a sketchy process, even small pressures can make a big bang. So 50 PSI is going to go big.
Any how, moral of the story is that it is potentially catastophic heating a vessel under pressure while observing the process at arms length - especially a thin metal chamber not rated or built for these pressures.
The result was very impressive in any case, nicely repaired pipe for minimal effort. I will build a cage to do this in the future. Similar to a tyre inflation cage, the concept is to contain the pipe if it blows.
There is still scope for the pipe to blow fragments and the potential for injury is still very present but hopefully the hazard can be reduced with the use of protective devices and protective gear.
I would be very interested to hear a blow by blow recollection of events from Big K to assist in designing a cage to contain a blow out. Maybe a Ned Kelly suit?
Hydroforming using high pressure water - you tube it. Looks real good and the operator can stay at a respectful distance from the pipe.
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There is a guy over here in WA called Pipe King.. look him up..he is on Friend Face.. pretty impressive work.. and will build to your needs also..
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Pipe King = Richard - very good but thought maybe long way away?
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I, ve done a couple of dint repairs on chambers lately using compressed air and oxy. You need to organise tethered bungs and a calibrated leak which can be as simple as a bolt loosely screwed into a tap.ped hole in one bung. When the air pressure rises from the temp and probably the burning carbon yit will not go over about 25psi. I use a air line connector and the line from the compressor with the reg. Set at no more than 25
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Thats interesting Momus, I could not get the dents to budge at 25 PSI. Initially I thought that it would not take a great deal of pressure, I estimated 10 PSI with heat. I actually needed the 50 to do the job.
Pro circuit Platinum, FMF Gold series and a stock YZ - all took 50 Pounds
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There's lots of theories on pressure but I always used 40psi & never had an issue till the one that went pop. Took off like a missile & one of the mounting tabs sliced the back of my hand open, breaking 3 bones. Shit injury, 6 weeks with 18 gauge pins (nails) in them sticking out the end. I know people who regularly use 100psi, maybe I was just unlucky but never again for me.
K
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Thats a major bummer what happened to you K, I suppose the result could have been lethal given the force and the damage to your hand.
So the pipe spun or shot forward and smashed into your hand? Did the seam split or did a bung let go? Do you think a cage would have prevented your injury?
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Bung let go @35psi, didn't even get the hot spanner near it. I usually clamp them in a vice but was only putting the air in (gently) & had it sitting on the bench. Yes a cage would have probably restricted the damage.
K
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You can get one these kits on evilbay they work well.
http://www.ebay.com.au/itm/191581736279?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
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when testing Industrial hoses for pressure only a fool would use compressed air. if an end lets go or the hose fails , Air goes off like a bomb so Air is not used to test. Water and ONLY water is used as if there is a failure as above, you will get wet and thats all. Water being a liquid absorbs the energy and releases it in a more linear way.
Think about your safety and the safety of everyone in the block as Ive seen just how far a projectile can travel when an oversize air rifle goes off without warning.
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I have seen a 5 tonne carbon vessel let go at only 5 psi - not pretty.
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olmate had an "apprentice" undo a 3" bung that had 850 cfm at 1000psi up its clacker...it travelled 250 metres dead level and cracked a concrete wall on the local post office. just clipped ol mates apprentices left ear...luckiest man alive... the bang was nothing short of sensational.
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This one is for Kev
Mate - when it blew up could it have been the presence of oil inside the chamber (just wonder if it was the air at 35 psi or an actual explosion of gases released from the burning oil along with enough air to support ignition at the hot spot of the oxy heated spot ? That aspect has always worried me even though so many have done it OK.
Sorry to hear of the injury - that would have hurt like F !
Dave Mac ?
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when testing Industrial hoses for pressure only a fool would use compressed air. if an end lets go or the hose fails , Air goes off like a bomb so Air is not used to test. Water and ONLY water is used as if there is a failure as above, you will get wet and thats all. Water being a liquid absorbs the energy and releases it in a more linear way.
Think about your safety and the safety of everyone in the block as Ive seen just how far a projectile can travel when an oversize air rifle goes off without warning.
The reason water is used is that being non compressible it stores very little energy to build the necessary test pressure. Using compressed air the amount of energy stored is much much larger, as the air compresses it stores energy as you build pressure.