Low friction tower rails

Any ideas? My first thought was delrin but then hot exhaust vs delrin ... Maybe waxed Aluminum, or even all purpose flour (Ive been baking tonight)... Or, am I over thinking...

Your first idea is on the right track;
I've been flying Teflon (PTFE) Rod faced Aluminum Channel rails on my competition Tower for some time now(1993). The Exhaust Temp has NOT caused a problem.
These 1/4" x 36" rods must be mechanically fastened to the Aluminum rails as even recommended adhesives just did not hold.
They clean up excellently with just a wipe down with Fantastic cleaner.
Hope this helps.

I cannot say that you are overthinking it. If you are flying competition then it makes sense to squeeze every last bit of energy out of your motor, then do it. If you are a recreational flyer, I really don't think that it matters that much.

If you want to go "over the top" and avoid delving into the coefficient of friction of materials, build a frictionless launch tower. I've never seen one, but it's theoretically possible.

Greg

Build a tower that has hollow tubing for the rails. Cap of ends of the tubing. Drill holes along the edge that would be closest to the rocket in the tower. Apply pressured air to the tubes such that air would escape from those drilled holes.

If you did it EXACTLY right, with absolutely even pressure escaping from each of the rail/tubes, your rocket would ride past them on a cushion of air, would not touch the rails themselves, and you would have very low friction.

Better yet, drill your holes in such a way that the escaping air flows upwards rather than horizontally. This might even give your rocket a small boost out of the tower.

s6

Better yet, do a similar thing with magnets. Have magnets in your rocket and in the rails, oriented so that they repel each other. This way your rocket rides a magnetic field up out of the tower, and achieves as low friction as possible.

Of course your rocket would be much heavier due to the mass of the magnets, but hey we're talking about friction here!

s6

Skip the tower completely, go with a compressed air gun launch with your rocket in a sabot. Fire the igniter at about the same time you fire the gun and wooooo.. Of course, you might just get a low altitude lawn-dart if the motor doesn't light.

N

Wingarcher said:

Skip the tower completely, go with a compressed air gun launch with your rocket in a sabot. Fire the igniter at about the same time you fire the gun and wooooo.. Of course, you might just get a low altitude lawn-dart if the motor doesn't light.

N

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I do remember seeing this done. IIRC they had difficulties with ignition.. I believe there was an article at the now gone Rocketry Planet..

I had a thought about a tower which incorporated bearings in the the tower rails. In effect a roller tower.

Not exactly frictionless, but we've had excellent results spraying our 1010 and 1515 rail with McLube Sailkote.



You can get it at West Marine, or, Amazon.

This stuff is frickin amazing. The friction is easily 1/4 of what you'd expect for a clean, untreated rail.


All the best, James

Depending on the diameter of your rails- and of your body tube- there is likely very little contact (surface area) between the two surfaces. I'm really wondering if anything is gained by switching to a lower friction material?? Also, depending on how far out your rails are from the rocket, it's possible that the rocket ascends without always being in full contact with all three rails-- further lessening the affect of using a lower friction material.

I did quite a bit of testing with a piston using brass and Delrin in order to lower the friction and it didn't have much of an effect over other materials. And in that case, the two surfaces were mated with .002" of each other which likely result in a lot of rubbing between the two surfaces.

Fdog said:

Not exactly frictionless, but we've had excellent results spraying our 1010 and 1515 rail with McLube Sailkote.

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Is that just WD-40 or does it work it's way into the metal and dries dry?

Micromeister said:

I've been flying Teflon (PTFE) Rod faced Aluminum Channel rails on my competition Tower for some time now(1993).

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Sell or make me one of those!

My Uncle owns a plastics business and suggests UHMWPE (ultra high molecular weight polyethylene) for that kind of stuff. It's what some auto and motorcycle manufacturers use for chain guides, tensioners and cable guides. I recently made a cable guide out of one and it's great.

Tonimus said:

My Uncle owns a plastics business and suggests UHMWPE (ultra high molecular weight polyethylene) for that kind of stuff. It's what some auto and motorcycle manufacturers use for chain guides, tensioners and cable guides. I recently made a cable guide out of one and it's great.

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Just as slippery as Teflon for substantially less money.....

Bob

majordude said:

Is that just WD-40 or does it work it's way into the metal and dries dry?

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It stays nice and greasy for a long while (months-years), it is mainly a sailing product made by Team McLube that is used to grease shivs (what the mainsheet runs over, not a knife), turnbuckles, winches, whatever needs to run or turn free on a boat. Great stuff, I am pretty sure that every sailboat I have raced on had a can of it aboard.


Sent from my iPhone using Rocketry Forum

Bojangles said:

Any ideas? My first thought was delrin but then hot exhaust vs delrin ... Maybe waxed Aluminum, or even all purpose flour (Ive been baking tonight)... Or, am I over thinking...

Click to expand...

Both Teflon and graphite are available in 'spray' form that can be sprayed on and it dries to a thin film. My experience (limited) is that the Teflon is very temporary but the graphite is a little more longlasting (it's kind of like a dark gray paint). I've either misplaced, used up or borrowed out both, so I can't give you a name, but I think I found them at McMaster-Carr.

The graphite spray has kind of become the 'darling' of the farmers (helping all those rusty ag implements to connect to the tractors), so you might could find it at an Ag (or Tractor) supply place, if that is closer.

-- john.

Try the DuPont Teflon Non-Stick dry-film lubricant, its a liquid the wipes on and drys to a film I use it for lots of things around the house. https://www2.dupont.com/Consumer_Lubricants/en_US/products/non_stick_dry_film.html Says it withstands temps of 480 degress F but i dont know how it would fare on rails and rods, I bought the bottle variety at Lowes or Home Repot...err Depot.

Where the heck would that be in Lowes or Home Depot?

majordude said:

Where the heck would that be in Lowes or Home Depot?

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https://www.lowes.com/pd_213197-39963-D00110101_0__?productId=1059839

https://www.amazon.com/dp/B003UTX0R8/?tag=skimlinks_replacement-20

... and I found my can of the TFE - it's SprayOn S00708 - which looks to be a prior version of this:

https://www.sprayon.com/product-cat.../high-performance-dry-lubricant-aerosol-lu708

(the graphite version is "LU 204")

That should 'get you going'...

-- john.

p.s. It appears the Lowes link is a 'wet' type, not a 'dry film' - but I found this at Home Depot:

https://www.homedepot.com/p/Blaster-9-3-oz-Dry-Lube-with-PTFE-Lubricant-16-TDL/202532762

... that does appear as a dry film. Just Google 'teflon spray' (or 'graphite spray') (and/or add 'dry film' prefix) and you should find several sources. Here's an interesting graphite product called (of all things) "Rail Glide" <g>

https://parts.ectts.com/index.php/slide-rite-graphite-lube-spray.html

-- jhc.

It is a wipe-on liquid that dries to a dry-film.

The "DuPont Teflon Multi-Use" is now sold under its original name, DuPont Chain Saver. Hands down best lube on the market for motorcycle chains. I suspect the "DuPont Teflon Non-Stick Dry-Film" lubricant would be better for rockets though.