Rail Guidance

Pistons add complication and weight, IMO. Toss the piston, use the railbuttons you want and don't worry about it. Rail buttons affix nicely to PML's Quantum Tube.

-- Joe Michel NAR 82797 L1

We ALWAYS need "one more rocket". 8-}

I'd put the rail buttons down below where the piston will go, use the entire screw, and put a block of wood inside the airframe to back it up. A small piece of pine sanded to approximately match the internal curve of the airframe will work just fine.

-Kevin

I've got the wife almost convinced that if you put two in the closet they produce more. Like rabbits.

John Hornsby

Or some other substrate as a backing plate. If the rail guides have wood screws as I suspect, perhaps a second piece of plastic so 100% of the screw is in plastic that has been predrilled. Then use PLASTIC GLUE to keep it all snug as a bug in a rug.

Ho Ho Ho

And pardon the tech post!

Merry Jerry

Not sure the diameter of this feller. I generally assemble the motor mount and affix a piece of wood to the aft side of the forward centering ring leaving enough room between the wood and the body tube for the thickness of a Tnut flange. Slide the mm into the bt and drill through the bt into the little block of wood. A line on the bt helps keep the 2 buttons aligned :) Now drill out the wood so the barrel of the Tnut fits into the wood. Smaller diameters you will need to bend or shape the flange of the Tnut. When you glue the MM into the bt make sure you can see the threads through the hole in the bt. Aft hole is drilled just forward of the aft centering ring and glue the Tnut directly to the body. Aft centering ring glued in after Tnut (and fins). Grease or other creative methods help keep glue out of the threads, otherwise you might need a tap.

Joel. phx

ever notice the later it gets, the less precise the wrapping becomes?

zzzzzzzz

Rail Buttons hold great on the Quantum tubing. As far as interfering with the piston, place the uppermost button low enough to allow room for the piston, and laundry. I use a stick to apply a small glob of epoxy around the protruding screw inside the airframe, to protect the piston anchor strap. This is what I did with our Tiny Pterodactyl. Jerry, since no one else has mentioned it, the buttons from railbuttons.com come with machine screws. Wood screws are an available option though. David

I wish! Besides, they're rockets. Not Tribbles!

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

Ahhh, *that's* the Trouble With Tribbles; they're not rockets. ;-)

-- Drake "Doc" Damerau

But they make excellent wadding!

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

I have used railbuttons on several PML rockets including my L1. They were applied about 10 minutes before the flight. Both were kept below the MMT centering rings. I drilled a hole in the quantum smaller than the screw threads. Then using a cordless drill I spun the button into the hole until it threaded itself. I removed the railbutton. CA was applied to the threads and the underside of the railbutton and it was reinstalled.......30 flights on one set and no problems. When/if they need replacing I am confident I can snap the CA bond and replace, I'm not so sure I can do it if it's epoxied. For other than quantum I believe a wood backer is necessary, but I've had no failures on the four quantum tubes I've installed them on.

Not if you have a good quality kraft tube and harden the hole with thin CA. I never use backing for my kraft rockets and have never had one pull out.

Mike Fisher

LOL! ...and if you tie one to the shock cord where it meets the opening of the airframe tubing, you get a nice anti-zipper design!

-- Drake "Doc" Damerau

Now you've got problems. Two Tribbles in the same airframe, and if your rocket is out on the pad for too long your wadding will be "over packed" and you will have an ejection failure.

John

Point taken, Mike. I'll give it a try. :-)

Don't tell my daughter that, she has several of them on a shelf in her room.

Randy

And, if there's no quatro trita-kalee, they'll eat your motor instead.

Randy

I installed my railbuttons on QT exactly the same way you did, except I turned the button in by hand. I didn't want to risk messing up the threads. I did have to take one off for some reason, and the CA bond I had on the threads was easy enough to break.

-- Joe Michel NAR 82797 L1

Al, I've used Matt's buttons on a number of PML QT rockets with great success. All I've done is after the MMT is installed is measure where the top centering ring is and drill into that. That way the piston is in no danger of hitting the screw. Then I just screw the button on - I've never even used glue. The bottom button is drilled and mounted into the rearmost centering ring. The QT is thick enough for the machine screws to get a good grip on, and they hold quite nicely. I don't tighten the screw all the way down - I leave it loose so the button can spin on the screw - it seems to slide on the rail a lot more freely that way.

You do need to keep an eye on the lower button. Depending on your rail setup, sometimes the exhaust works its way up the rail channel and can melt the button. It's a simple matter to unscrew the old button and replace it. I always have a handful of extra buttons and screws in my range supplies - they are cheap enough that I can replace them if they look worn or damaged.

Good luck,

Tony Huet

An excellent point and the reason I stick with screws N Tnuts (I swapped out the nut method on the LittleJohnny for Tnut). I've had several rockets with worn plastic due to the rail. Nice not to have to think about it when you need to change them.

Oh, another time I used someone's rail and it wasn't exactly the same gap. I borrowed their buttons and flew because they were removable and mine were too. Another flier couldn't remove theirs and NO JOY!

Joel. phx