test stuff for rail buttons and motor casings

This topic has 13 replies, 6 voices, and was last updated 17 years, 9 months ago by edward.

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April 21, 2008 at 2:02 am #40213
SCOTT EVANS
Im sanding my butt off, or my arms!!!
Got to get “Hair of the Dog” ready for MHM.
Havnt touched this Rocket sinse you Butt heads 😉 had me glassing these tubes last winter! From now on, I will just buy the tubes already done! ((Turn Key!!!)) Plenty of blaze glaze going and primer!!!!
I think I could jump on the fins and they would not break!!!
Its stout!!!

Ok so what are the nuts used inside the tube for the rail buttons?
Are the rails in town, where I coild use one to test my alignment when I put them on? I still need a case (54mm, a long one) for a Rocket motor to test fit.

HELP!!!!

Scott e
April 21, 2008 at 2:08 am #47519
Warren B. Musselman
Moderator
The trailer will be moved to my house IN Longmont sometime tomorrow or Tuesday. I also have multiple rails in my garage for you to test fit with in any event. You would be welcome to come by with your bird and try out the rails and use any of my 54mm cases for a test fit. (I have cases from the shortest Aerotech 54mm up through an AMW 2550.)

Warren

Oh yeah, the nuts inside the airframe are purely up to the builder. Many folks use T-Nuts, with or without a little piece of wood. Some use Riv-Nuts which are inserted with a special tool and crimped into place like a rivet. Some folks just embed a regular nut in thick epoxy… all depends.
April 21, 2008 at 2:22 pm #47520
SCOTT EVANS
where do you get those T-nuts?

Scott e
April 21, 2008 at 2:38 pm #47521
Warren B. Musselman
Moderator
Home Depot.

W
April 21, 2008 at 3:13 pm #47522
SCOTT EVANS
Home Depot.

W

😯 really? that seams to easy!
April 21, 2008 at 3:40 pm #47523
slipstick
Ok so what are the nuts used inside the tube for the rail buttons?

HELP!!!!

Scott e

Scott, I have a rivnut gun if you want to install those in your bird. Blind riv-nuts need about 1/2 inch clearance in the airframe before they collapse, then they stick into the airframe about 3/8 inch.

T-nuts (like used for wood) and other inserts can be obtained at hobbytown as well. I think these are akward to deal with in tubing.

PEM nuts, (I have some of these) can be used but you would need to back them up with epoxy

As a future consideration, I think an ND weld nuts would be applicable because it gives a large surface area to epoxy to preventing torque-out, and they are low profile.

Specification:http://www.on-b.com/pag/onb_004.pdf

The problem with all these scenarios (except for the riv-nuts) is that in small diameter airframes, its hard to reach inside the tube. Threaded inserts for wood (hobbytown has some of these) can be installed from the outside (I would smear some J-B weld on them before insertion)…

http://www.woodworkingparts.com/parts/brass_inserts.html

You might also consider using PML rail guides, as they are epoxied on. Hobby town up in Longmont has a some in stock. After you place them and the epoxy cures, you can drill and tape into the airframe with 6-32 flat head screws for a more finished look. They are lower profile than a round button using a pan-head screw, are slippery on the rails, and will not twist off if J-B weld and screws are used. I think these could be cut in half so one lug could do the job pf two.
April 21, 2008 at 3:59 pm #47524
Warren B. Musselman
Moderator
I know Mike likes those PML resin rail guides, but I’ve never been much of a fan having broken one on one of my early HPR projects. For rail guides like them, I’d choose the Acme cast aluminum guides. Otherwise, I’d go with the classic screw-in buttons with either a Riv-Nut or T-nut epoxied into place to take the screw.

If it’s a sizable project (over 35#) I’d recommend you buy some of my machined stainless 1515 rail buttons. I’ll eventually start making them in 1010 size as well, but that’s a month or three down the road.

Warren
April 21, 2008 at 4:20 pm #47525
SCOTT EVANS
Mike
Hows that rivnut thing work? Also need to get together with you and check out this Dog tracker.

Scott e
April 21, 2008 at 4:52 pm #47526
slipstick
Mike
Hows that rivnut thing work? Also need to get together with you and check out this Dog tracker.

Scott e

It works like a pop rivet gun. You thread the insert on the threaded mandrel, stick it in the hole, and squeeze the handle. I also put a dab of J-B weld on the rim of the hole, to keep them from loosening up later. Here’s the design guide:

http://www.compcoinc.com/pdfs/RivnutDesignGuide.pdf

You can come by any evening if you wish. I’m prepping my two stage, and I have all the stuff you need. I think I may ruined a DC20 last night playing around with change the coax antenna connections on the circuit board.
April 21, 2008 at 6:42 pm #47527
new2hpr
Participant
Mike,

Removing those PCB mount SMA connectors can be a bear, especially with a ground plane on the board. I generally sacrifice the connector, cutting bits of it off at a time with some strong cutters, to reduce the thermal mass before desoldering. I’ve got a nice Metcal iron with both the pencil and tweezers if you want me to do any rework on the DC20. Let me know if you think its repairable. I also have some of the connectors in SMA(threaded) and SMB(snap-on).

Ken
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