LOHAN gasps at stiff and slippery tube We do like a bit of unboxing down here at the Special Projects Bureau, so there was a decided frisson this afternoon when we took delivery of a stiff and deliciously slippery tube. Click here for a bigger version of the LOHAN graphic Low Orbit Helium Assisted Navigator (LOHAN) regulars will be aware of the ongoing debate …
"We also have a tube of lube to hand if required – Molykote 33 low temperature grease, which works down to -73°C."
As my other half could be described as frigid, and KY jelly doesn't work for her at room temperature, can I try a bit of that, if you've some spare? "To hand" is a nice way to destroy another keyboard....
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How much condensation is the Ti rod going to gather? I'd me more concerned about condensation droplets freezing and creating a knobbly rod that'll jam in the tube than it bridging the gap between the rod and tube as there's potential for it to build to a much larger thickness than the tube can accommodate where the build up isn't restricted by the tube shrouding the rod.
How about a hydrophilic coating? Unless that'd just make it bead up worse and be even knobblier... Better still, a hollow rod with a hand warmer filling that someone mentioned before.
I think I've crammed enough innuendo into that.
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I offer a suggestion that can solve the problems related to the rearward motion pressing against the aluminum back plate.when the rocket motor is ignited. Replace the back plate with two small narrow pieces of metal welded to the top and bottom of the titanium rod directly behind the rear collar that is used to hang the LOHAN from the titanium rod. The metal pieces will provide stops that will prevent the LOHAN from falling backward when the carrier is in a semi-vertical position and will not in any way interfere with the forward motion when the rocket motor is ignited.
... Some kind of heated windscreen-based device for the rod? IE a very low electric current to keep it warm enough to resist condensation, droplets of ice, etc?
I should state that I'm extremely non-technical so am fully prepared for the numerous and obvious reasons why this would be impossible. Eg titanium being the best insulator known to man or titanium requiring something the size of a car battery to provide sufficient current to create a temperature-differential, etc.
Sometimes, having things slack is the right approach.
Sooooo, please define a "tad"
my experience with cylinders as bearing surfaces is that if you get misalignment they jam.
To mitigate against this make the teflon insert MUCH bigger than the tube, and trumpet shaped so that any icing obstacles are ramps rather than stops
(Why does it need to be a close tolerance?)
This IS a problem in my day job.... we have to accurately align a part in a rail switch machine which did NOT need to be a close tolerance but was made one because it looks better, and is unreliable as a result.
The answer to icing is simple. You slip a closed ended light sleeve over the rod in front of the aircraft and another shorter one between the suspension bushes. Any icing will be on the outside of the sleeve, where it doesn't matter. These fall away as the the aircraft clears the rod. But I still think that you should dispense with the aluminium plate set athwart the frame and replace it with one running lengthwise. The impingement of the exhaust stream on this plate could do do some strange things to the attitude of the truss before the aircraft has cleared the end of the rod. Particularly when the leading bush has cleared , and the trailing bush is still engaged
"when we'll take the opportunity to plunge the rod and tube into the cold box, and see what happens"
Is this such a good thing to do - I would have expected a more gradual drop in temperature rather than a sudden plunge into something so frigid !
Mine's a cold one for obvious reasons
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