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Yeah me too. I didn't know diff pumps were still in commercial use. My only memory of diff pumps, (besides them working just fine.) Is cleaning/ repairing ones that some previous grad student had burned out... never switched to the backing pump or something.

George H.

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i'm uncertain about this approach; if you start with elastic material under stress, and heat-cycle it (it's a heat pump, after all), the thermal expansion and the strain will interact. A thermal cycle can stretch the member, it'll just become loose. Something that's stiffer than nominally required for the target force would be preferable to a thermoplastic.

Prestressed music wires? Thinned SS bicycle spokes?

whit3rd wrote in news: snipped-for-privacy@googlegroups.com:

I think Delrin 'cold flows' just like Teflon does, so his 'swaged' thread impingement method would likely not work under stress as well as properly formed threads and additional engagement policies (more threads captivation).

The rod end would split easier and if it does cold flow in a similar way as Teflon, they would also 'pull out' (shear) easier as well.

hehe, yes, even more crazy than I thought - I forgot the SEM context and ws thinking of some optical instrument in a vacuum, for some reason.

On Jul 20, 2019, snipped-for-privacy@decadence.org wrote (in article ):

Delrin does not cold flow like teflon.

Joe Gwinn

Always keep the screws you need in stock for now, you can always get plenty more to screw it up later.

Hi,

I was also thinking thin low conductivity metal wire, pre-stressed by coiling the ends together, but a better solution is to use a spring of similar material, and fasten it to each end, this creates a longer thermal conduction path than a straight wire, and also can be more accurately pre-stressed, and is would have less variance in tension with thermal cycling than a straight wire too.

The only tricky part is fastening the ends of the springs so they dont go through the holes but actually if the spring is sized right it could actually act as a screw itself in the holes and allow for adjusting the tension that way.

cheers, Jamie

Joseph Gwinn wrote in news: snipped-for-privacy@news.giganews.com:

It would still follow logically that cut threads would have better shear characteristics than force swaging them in.

As usual, Alwayswrong, you were wrong. So who would trust your logic, Alwayswrong? Do you have any links to back you up?... I thought not.

John S wrote in news:qh2gh0$3h7$ snipped-for-privacy@dont-email.me:

Do you always spout retarded insulting horseshit?

Thread a hole on the end of a (delrin) plastic rod. Which rod will split first? The one with precision cut threads, and the screw nicely captivated fully, or the one with threads swaged in by force, with the entire rod/screw assembly still under (outward) stress?

I am betting that scenario 2 with the ram it, cram it, jam it, and slam it, damn it, Janet version will split first.

You? I don't give a fat flying f*ck what an insulting, retarded bastard like you feels is correct. You can ram it, cram it, jam it, and slam it up your ass for all I care. FOAD, troll punk.

Only when it is deserved.

is there anything wrong with polycarbonite for use in a vacuum.

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I already suggested that. When I looked it up the properties were better t han nylon in the important respects for this application. All plastic will absorb some moisture which it will out gas. But some are worse than other s and it can impact the material properties. Polycarbonate (which is what you probably meant rather than "polycarbonite") is a lot better in this reg ard than many plastics. Mostly it should be a lot better price than some o f the plastics with standard size hardware available off the shelf.

Yep. Mia Culpa.

M3 and M4 $AUD30 for 100, $AUD250 per 1000. Plus postage.

is a lot better in this regard than many plastics. Mostly it should be a lot better price than some of the plastics with standard size hardware available off the shelf.