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FVTX test channel - pulling off the hose

The test channel, and flow measurements

Walter and I have been following the story of the leaking cooling liquid in the VTX (see VTX emil archive 1st week of Aug 2011), and part of the discussion is of course where the leaks could be. One possible location is the cooling tube attachment to the plastic barbs, the same ones we have on our disks. The question was whether the plastic of the hose relaxed over time, leading to leaks at the barbs. I have seen this phenomenon on hoses with a different type of plastic than the type we are actually using.



I wanted to see how hard it would be to pull the hose off, and inspect the hose for deformation. Despite holding down the carbon with the edge of a (dull) razor blade as shown, the barb, and a piece of carbon skin, snapped off.
(This picture was taken afterwards)


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There is minimal deformation of the hose where it sat on the barb. My conclusion on the leak issue, is that the tubes we use do not relax to the extent that this could be the primary source of of the loss of coolant seen in the VTX.


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So: NEVER try to pull a hose off a barb! Once they're on they cannot be pulled off without risking major damage. The only way is to carefully slice them with a scalpel to make them come off with no force. But don't slice the barb, or you'll have a leak there later. For the FVTX tests and assembly, I would make sure there is strain relief on the hose once it is attached to the disk, to ensure that there are no lifting or twisting forces on our hose barbs, and that all connects/disconnects are made far away from the barbs.  


Aug 2011 HvH