Rail Buttons

Up to know, simply making a hole in the airframe, and screwing in the screw
for the rail button has worked well. On a few rockets I have put epoxy on
the threads of the screw to hold everything in. Well, I was just test
fitting the Raptor onto the rail. The Raptor is 4", 84" long, and weighs
about 6.5 - 7 lbs. A lot of this weight is in the electronics bay, which is
about 30" from the front of the rocket. Well, screwing in rail buttons
didn't work. As soon as I picked up the rail, with the rocket suspended
beneath, 2 buttons popped, and it fell. It has 3 buttons. One in the aft
centering ring, one 5" from the bottom, and one about 16" from the bottom.
What should I do to more securely mount the buttons?
Reply to
Stephen
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Use ACME conformal lugs. Worked fine on my nice heavy modded Eclipse (c.11# loaded).
G.
Reply to
Graham
If you can get behind the rail guides, use longer screws and T-nuts.
Reply to
Kurt Kesler
I'm reading this to assume that you tried to suspend the rocket sideways from underneath the rail? That's not good for heavier rockets.
I've flown the 23 lbs. M loaded Velociraptor with delrin buttons that were just screwed in place, no epoxy. They are just guides, not structural elements designed to support the weight of the rocket.
As far as the ACME aluminum guides, most clubs are banning them due to rail gaulling.
BTW, 2 buttons=good, 3 buttons=bad.
Mike F.
Reply to
Mfreptiles
You might want to try surface mount as Matt describes on his tips page at:
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-- Best regards, Mark Daughtry, SR Ignorance is bliss unless you are surrounded by it. Ignorance is like bad breath: You usually don't know you have it. NAR 71556 SR L1 MSRS Vice-President NAR Section #550 MSRS #0035 SR
Reply to
M.Daughtry
My own experience with the Acme railguides is exactly opposite yours. The first time I tried loading my ten-pound EV-3 rocket onto the rail, the bottom guide popped right off! Loading my 13-pound camera rocket onto the rail resulted in *both* railguides popping off. And I even used JB-Weld to bond them in place.
Needless to say - my opinion is a little soured by the incident. :-(
Reply to
Len Lekx
'Block of Wood' sounds a little worse than it needs to be. I get scrap pieces of 3/16" or 1/4" plywood that have been left over from fin cutting jobs, then trim them to be roughly a 1/2" x 1/2". Bevelling the edges helps the fit inside the airframe (which I'm sure is what David meant by 'D shaped block of wood'). Sometimes I insert Tee nuts (usually for 5+" airframes); other times, I just drill and tap the holes for #8 threads (then squirt some thin CA into the holes to toughen up the tapped threads).
I'm personally luke warm on the conformal lugs. I've had a couple of them pop off, but haven't had any problems since I started JB-welding them on. I still get nervous, though, everytime a I slot a conformal lug onto a rail; so, I usualy go with Matt Stum buttons (a great value anyway) instead.
cp
Reply to
Chuck Pierce
Options:
1. A nut inside the airframe. Usually not an option if the rocket is already constructed. Epoxy the nut to the airframe, or insert into a piece of wood and epoxy that to the airframe so the screw and button and be removed and replaced.
2. Run the screw into a centering ring. There should be a ring near the top and bottom of the motor tube.
3. Perhaps the hole you've drilled is too large or you are using the wrong type of screw. I've been using nothing more than CA or epoxy in the screw hole to hold rail buttons onto rockets that weigh 10-12 pounds when loaded for flight (phenolic tube, some are 'glassed and some aren't) . Try a dab of epoxy gel (or thickened epoxy) in the hole if the rocket has already been built. The gel will stay in place while it cures.
Dean
Reply to
Dean Roth
Did you use that supplied double sided adhesive? If so, that's the problem. I had a rocket fall off of the pad when I used the adhesive on a 9 pounder on a hot day. Since then, I've used epoxy exclusively and haven't had a problem.
Mark Simpson NAR 71503 Level II God Bless our peacekeepers
Reply to
Mark Simpson
I use a similar trick when istalling T-nuts for my Kaplow Klips. I squirt them full of vasoline or other handy reload grease.
Worst case, a tap will clean out hardened epoxy that accidentally drips into the metal threads...
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Reply to
Bob Kaplow
I used the Tnut clamp trick to glue 4 Tnuts inside the 10" Tomahawk nose. Generally I use JBweld because it's sticky and parts don't move, but this works just as well. Put epoxy on the bottom (the flat side) edges of the permanent Tnut, just a bit to hold it in place. Install a Tnut on the appropriately sized screw and spin it up to the head such that the bottom (flat) is away from the screw head. Dip the screw into grease a little further than the distance through the wall and just out the other end of the permanent Tnut. Wipe off excess. Put the permanent Tnut in position and thread the screw in from the outside of the rocket body. When you see the tip just at the inside edge of the permanent Tnut tighten the Tnut on the screw to the body so it holds the permanent Tnut in position. In this case I laid strips of fiber glass across the Tnut flat to hold it in position, but I would have normally just added JBweld, or epoxy thickened with milled fibers.
Joel. phx
Reply to
Joel Corwith
Or rub wax on an appropriate sized bolt (an old candle will work as a source of wax); put it into the T-nut to hold the T-nut in place, and expoxy all you want. Epoxy won't stick to wax. On small rockets, you can skip the T-nut--use a waxed screw as a mandrel and let the epoxy set around it.
--tc
Reply to
Ted Cochran
"Mfreptiles" wrote in message >
?????????????????????
And 4 ??
3 buttons is bad? Why???????
I always mount my third on a movable section of tube, preferabley on the payload. Because of course the third is only used durring loading.
RDH8 NAR L3
Reply to
Robert DeHate
Any more than two (on the same section) promotes binding unless they are aligned PERFECTLY. On a section of tube that you can rotate into alignment, as you are doing, should work fine.
Mike F.
Reply to
Mfreptiles
I fly a lot of tube-finned rockets, where the launch rail runs up inside one of the tubes. I always use three buttons on these rockets, with a button at the top and bottom of the tube fin, and then the third button up near, and just below, the CG. With only two buttons I'm afraid that once the top button clears the rail the rocket could pivot on the bottom button, with the rail still inside the tube.
With care, it's not too hard to make sure the buttons are colinear.
...Rick
-- ___________ Rick Dunseith /________ | mailto: snipped-for-privacy@dunseith.com /______ / | ___/______/_/____| ***** ___|==| | | |==|*********** _______________________/___|==|______|_|__|==|****************** \\__________________/ |==| | | |==|****************** \\________________________|==|______|_|__|==|*********** -)-==|__| / / / ***** CAR S376 L4 \_________/ / / TRA 7162 L3 \_________/ / NAPAS 1999 \_____________/ BRS 0079
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Reply to
Rick Dunseith
No, but the real question is why. Rear centering ring, forward centering ring.
Joel. phx
Reply to
Joel Corwith
Two rail buttons are not always sufficient for tall, heavy or top heavy rockets.
Two of the small buttons for my 11' tall, 6" diameter, top-heavy rocket aren't enough. A third button further up keeps it stable on the pad. Without the third button the top section leans away from the rail, which puts a lot of stress on the buttons. The third button also helps prevent the rocket from being affected by wind while sitting on the pad.
Two of the large buttons are sufficient for the rocket.
The rocket is equiped with small and large buttons. The large buttons and large rail are preferred.
Dean
Reply to
Dean Roth
Does anyone have any suggestions on mounting the buttons on a standoff for a rocket with a payload section that has a larger diameter that the motor section?
Rocky Firth
Reply to
Rocky Firth
Yes.
1. A small "fin" that is mounted between two fins that is wide enough to mount the button, tall enough to meet with the upper button, and tapered on front and back for aerodynamics. It will make the rocket spin so if that is a problem, put one on the opposite side as a dummy.
2. A small "riser" that is mounted along one fin root, and base, and surface, that is wide enough to mount the button, tall enough to meet with the upper button, and tapered on front and back for aerodynamics. It will make the rocket spin so if that is a problem, put one approximately on the opposite side as a dummy. The disadvantage to this design is it has to be thicker than 1. to give button clearance.
3. A simple "bushing" riser at the rearward button point along the lines of a 1/4" steel tube inside of which is the threaded portion of the button mount. The disadvantage to this is a cylinder has crappy aerodymanics.
4. A ring with a rail button it that slips onto the rear of the rocket. When the rocket leaves the pad, the drag on it slides it off the back of the rocket and ejects it onto the ground near the pad. Paint it orange or pink for revoverability and visibility.
Please pardon the tech post. I apologize in advance.
Jerry
Reply to
Jerry Irvine
Apology accepted, and thanks.
Rocky Firth
Reply to
Rocky Firth

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