Reply to post: Not sure if I mentioned this before

LOHAN ideas..

imanidiot Silver badge
Boffin

Not sure if I mentioned this before

First off, from the last article I see you are planning to mount the teflon "wing guides" on rubber backing to "give some bounce" to LOHANS mighty lift-generators flapping around. I am curious how you plan to do this mounting. The advantage of Teflon is that nothing really sticks to it. The disadvantage is that this includes any type of glue you can think off. (And I mean ANY glue. I've tried about 20 different manufacturer recommended products in a previous job. All of them failed with little force. NONE would be good to -60 degrees C. Mounting the strips with bolts kinda defeats the purpose of the rubber.

Secondly, in all these plans I see LOHAN's launch rod only supported at one end. (For good reason). But why not make the rod-runner separate from LOHAN and support the other end of the rod too? This would give a lot more support. The runner moves with the plane and has some sort of simple friction or force based release mechanism (my recommendation is a very small ty-rap which breaks easily enough when shock-loaded) Once the runner reaches the end of the launch rod the runner suddenly stops. LOHAN keeps going, breaking the connection to the runner and is then free to keep going.

I've had a bit of a think about the launch rod v. Launch rail conundrum but I've got to ammend my statement about support for a rail. It makes things much more complex, provides more contacts area (and thus more friction and more chances for jamming).

Thus my suggestion becomes making the "runner" not a full tube but consist of a 2 or 3 sections which are clamped by some strong springs. This, if needed the bushing can expand to accommodate rubble but will normally provide a nice tight fit on the rod.

Next, and this is just the engineer in me going, but WHY??: Why did you choose this tubing over fabricating some bushings out of PTFE bar stock on a lathe? This would allow you to choose the fit on the rod exactly as you want it. Setting the play on these tubes is going to be a lot harder. (But can be solved by my previously mentioned multisegment clamp design. Or if the tube if flexible enough, a single slit and some circular springs) How do you plan on affixing these bushings on LOHAN (or the rod-runner, see my first bit). I advise against using the ubiquitous Omega pipe clamps (random google pic example: http://store.eberliron.com/images/products/omega.jpg) They are prone to being overtightened which would seize up the bushings and a slight shift due to buffeting could likewise cause problems. Personally I'd have the LOHAN design boffins design some mountings into her and screw some self designed solid PTFE bushings into/onto those.

(Final note: I pretend to be a mechanical engineer during the day. The above contains some problems I've encountered on the job. Also, as my username implies, I might be wrong ofcourse ;)

Final Final note: when are we going to get some info on LOHANS internals (electrics) so we can shoot some holes into that design too? ;)

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