Rail Guide vs Button

I was given a set (2 pcs) for a 2.6" airframe. They sat for a while & I finally got around to using them. Don't care for the length of them, as I see it a major binding issue / major 'intolerance' factor.. SO, I cut them in half and now have two sets, albeit shorter pieces. Used one on a rocket, a small light weight one. the other set is still sittign around..

much prefer buttons.. much prefer a mechanical 'pull out / pull thru' design that relying on surface bonding.. Also, less obvious on the airframe when standing / diplayed

(Except welding. And even then, I'll add a couple of spot welds, or holes on the backside to plug-weld if needed.. )

Andrew_ASC said:

Thanks. I missed the torque acting on the rail guide as the thrust is off center from the rail and analyzed that one wrongly. Would there be a case were forward of the CG of rocket the tube could strike the rail creating a third frictional point near nose or top of Body tube due to offset thrust from rail position by rocket's center line of thrust and the rail guide height creating a moment?

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Absolutely, many rockets can strike the rail either while sliding on or flying off.


Steve Shannon

qquake2k said:

I've never tried rail guides, and have no desire to. It seems to me that alignment could be an issue. I think rail buttons are more forgiving. If you get one slightly offline from the other, there's still little chance that they'll bind. And if you screw the rail buttons into something solid, there's little chance they could strip off. I epoxy blocks to the centering rings to give more solid mounting points.

https://www.rocketryforum.com/showthread.php?142491-Make-Tube-Fly-With-Fire!&p=1728724#post1728724

https://www.rocketryforum.com/showt...t-Thump-In-My-Down-quot&p=1687812#post1687812

https://www.rocketryforum.com/showt...t-Thump-In-My-Down-quot&p=1688039#post1688039

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You solve the alignment problem by taping a piece of aluminum angle to the rocket and butting both rail guides to that.

That is a great idea! I use Acme guides on almost everything and usually just make careful measurements and accurate marks. I have never had any problems getting things lined up, but your method looks to be quick and foolproof! (even for this fool!)

I cut them in half and use JB Weld to attach 'em. Never any problems at all...

I mounted linear rail guides to my 1/2 scale Nike Smoke. Adding the rocket to the rail resulted in the guides breaking, even though done carefully. Bonding to the rocket was not a problem, but strength of the guides was .

Alignment was not a problem at all.

Since this was my L3 flight I chiselled off the rail guides and screwed on two buttons. The certification ended in success.

I won't use plastic linear rail guides again.

To me the plastic guides look like they would be good for fairly small stuff at the most. The Acme guides are good old aluminum (aluminium, alloy, ally, processed bauxite,whatever...), but even with that, I might go with buttons on a half-scale smoke!

With a 1/2 scale Nike Smoke being 8" diameter it would automatically get 1515 buttons if it were mine. I have rockets with Acme Conformal Rail Guides, PML's (could be GLR too, cant remember) version and rail buttons. I have yet to twist/break a conformal loose BUT I am also aware (from others warnings) that it can happen and I take extra care when putting them on the rail.
As for the Apogee and PML guides, they are plastic so longevity will be an issue. Personally 4" diameter is the largest I go on conformals and usually on the lighter side at under 10lbs RTF.

I've used the rail guides on several rockets, but the first was my L1 cert rocket. They held up fine until the second flight on a I1299 Warp 9. That ripped both guides off although the rocket still flew straight.

I won't say they are any worse than buttons, but the way they are glued onto the rocket is the key, as is the material. When mine got ripped off, the glue didn't fail, the tube did. There was a couple of layers of the tube missing where the guides had been.

Handeman said:

There was a couple of layers of the tube missing where the guides had been.

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I have seen many disappointed flyers either pop off their rail guides, have binding problems, or fitment problems due to paint or adhesive on guides. These are are addressable issues but ones the first time users don't know about. I would also agree that guides are generally too long.

Button users rarely have issues. I wouldn't recommend guides to a new flyer vs. buttons. Ever.

Handeman said:

I've used the rail guides on several rockets, but the first was my L1 cert rocket. They held up fine until the second flight on a I1299 Warp 9. That ripped both guides off although the rocket still flew straight.

I won't say they are any worse than buttons, but the way they are glued onto the rocket is the key, as is the material. When mine got ripped off, the glue didn't fail, the tube did. There was a couple of layers of the tube missing where the guides had been.

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You have just invented the brand new conformal fly away rail guides! You could call it the CFAG.

Been using Acme since they were introduced on 2” through 4” with motors as large as M without major issues. I have always cut them down and reshaped the leading edge, scuffed bottom and sometimes have drilled holes in base. I set them into JB Weld on the roughed up cleaned tube. Alignment is done with a long piece of 1/8 angle aluminum stock inserted in slot of each all (2 or three) to be fastened. On my largest rockets I have successfully used three (no need to comment about possible alignment issues with three- either they are aligned or not!) I have had one failure: all MY fault- very embarrassing making a mistake on 38mm cessaroni load resulting in loss of containment - Heat does release them! That is how I remove them to rework or salvage a rocket- heat them over 450 (jb weld) and they come right off.