Problem with rail button backing

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NateLowrie

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I was replacing the worn rail buttons on one of my rockets. I replaced 1 just fine.The other 2 I got about 3 turns out when the epoxy on the backing nut let loose. I suspect the threads at the end of the screw got some epoxy or other gunk on them and wouldn't turn through the nut without some force behind it.

So, now I have 2 screws with rail buttons that I can't get out because the nut is twisting. Both nuts are located in between centering rings, so I can't readily get at it. Not the best choice in hindsight. Any advice on the following to things would be helpful:
  1. Removing the screw with the rail button. Preferably removing the nut too so it's not rattling around.
  2. Replacing the nut/reattaching the rail button. I can move the back one back to in between the rear thrust, but I am not sure about the middle. one.
 

Steve Shannon

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Just glue it back into position where it is, then cut the head off and finish it smooth. Put your next buttons into the centering ring if you can.
Personally I prefer two buttons to three, so I would only replace one of those.



Steve Shannon
 

dr wogz

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The only thing I can offer it to cut the button off, and then you can grab the male part of the 'blind nut' and remove the screw. But you've lost the button & will need to replace it..

And for next time, drill a small hole or two into the flange of the blind nut before inserting. or file flats onto the flanges so that the epoxy has something to bite / lock into.. (and add a bit of grease to the screw so the epoxy won't stick to it!)

One thing I've started doing for buttons, it to add a chunk of same thickness ply to the area on the CR where I intend to screw in my buttons. The idea being, instead of trying to aim a screw into a 1/4" piece of ply (the CR), it's doubled up so I have a 1/2" to aim for.. (a larger target!) A 3/4" x 3/4" piece glued to the top side of the CR, then sanded to match the roundness of the CR..
 

NateLowrie

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Just glue it back into position where it is, then cut the head off and finish it smooth. Put your next buttons into the centering ring if you can.
Personally I prefer two buttons to three, so I would only replace one of those.

Steve Shannon
Not sure what your getting at. I think you mean I should glue the screw and nut in place, then cut off the screw at the base of the rocket and finish smooth the cut area with the rest of the airframe. Then put new holes over the centering rings. Does that sound about right?
 

NateLowrie

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Just turn the tube 180 degrees and add new buttons
Good idea and certainly doable. I still have to do something about those buttons though as I can't tighten them down. I could just epoxy them to the tube so they are loose and rattling. I may try to drill a hole right next to the button hole to see if I can slip the nut out through the hole.
 

Bat-mite

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Don't know if you saw my e-mail, but if not, you could drill a hole in the airframe just above the nut, then try to stick in something metal and L-shaped to pull the nut against the airframe. Screw the screw back in. Once it is tight, it won't wiggle.

If you want to try this at the field, I have this set of these.
 

Nathan

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Good idea and certainly doable. I still have to do something about those buttons though as I can't tighten them down. I could just epoxy them to the tube so they are loose and rattling. I may try to drill a hole right next to the button hole to see if I can slip the nut out through the hole.
To remove the old button, how about cutting the rail button off the bolt with a hack saw, then cut the bolt off with bolt cutters. Then to prevent the part in the tube from rattling around, squirt expanding foam into the hole.
 

Steve Shannon

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Not sure what your getting at. I think you mean I should glue the screw and nut in place, then cut off the screw at the base of the rocket and finish smooth the cut area with the rest of the airframe. Then put new holes over the centering rings. Does that sound about right?
Exactly.
 

NateLowrie

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Definitely some ideas to play around with. I think I'll try John's idea first and see if I can't tighten them up. If I can do that, I can turn the buttons already on there 90 degrees to move the worn portion off the rail edges and be fine for this upcoming flight then I can worry about it later.

Plan B is Shannon's suggestion of cutting flushing and redoing the buttons to fall on top of a centering ring.

Plan C is CPUTommy's suggestion of putting buttons on the other side.
 

Steve Shannon

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When I install my rail buttons, I leave just enough slack in the screw so the buttons can rotate around the screw, hopefully allowing them to wear more evenly.
 

NateLowrie

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Well, they are out. I tried drilling a hole next to the button and fishing the pick in to hold the nut, but it did not want to turn. I ended slotting that hole with a file to intersect the rail button hole and I was able to wiggle the button with the nut free. There was epoxy in the top threads and it was from the epoxy injection process :facepalm:. I can tell because of the different filler blend I use on the fillets versus the nut mounting. Lesson learned, moving on. Tonight I will drill over the centering ring and tap a #10 hole about 1/2in into the ring. Then a little thin CA to sure up the threads in the fiberglass and I should be good to go.

Thank you again for all the suggestions.
 

Steve Shannon

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Well, they are out. I tried drilling a hole next to the button and fishing the pick in to hold the nut, but it did not want to turn. I ended slotting that hole with a file to intersect the rail button hole and I was able to wiggle the button with the nut free. There was epoxy in the top threads and it was from the epoxy injection process :facepalm:. I can tell because of the different filler blend I use on the fillets versus the nut mounting. Lesson learned, moving on. Tonight I will drill over the centering ring and tap a #10 hole about 1/2in into the ring. Then a little thin CA to sure up the threads in the fiberglass and I should be good to go.

Thank you again for all the suggestions.
Nate,
If you have the room, put this kind of insert into your centering ring.



Steve Shannon
 

CzTeacherMan

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For future reference... There's no need for rail button backing at all. You can tap the screws directly into the airframe. Drill the hole, use the screw to self-tap into the airframe. If cardboard frame, remove the screw, drop in some CA, let it dry, then put the screw back in.
Hundreds of flights. Zero issues with this method.
 

djs

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For future reference... There's no need for rail button backing at all. You can tap the screws directly into the airframe.......Hundreds of flights. Zero issues with this method.
Same for me. I've only had one issue where I had a rail button pull loose on my Interceptor 54 when I put it up on an I800 vmax. Pulled about 70 gs on the way up. Flight was straight, and I jb welded the rail button back in later on. Rocket has had probably 6-7 flights since then with no issues.
 

Steve Shannon

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For small rockets (4 inches and under) I absolutely agree, but the need for backing for a rail button may increase depending on rocket weight, distance from centerline, and initial thrust of the motors a person wishes to fly. The ability to change a damaged button is hampered considerably when the threads in a body tube become worn. Threaded inserts have worked for me in larger rockets.


Steve Shannon
 

Bat-mite

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Wind is the enemy of crazy glue/cardboard. Twice I have had the wind jerk my rocket hard enough to rip out the buttons. Now, one could argue that I shouldn't have been launching at all....
 

NateLowrie

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For small rockets (4 inches and under) I absolutely agree, but the need for backing for a rail button may increase depending on rocket weight, distance from centerline, and initial thrust of the motors a person wishes to fly. The ability to change a damaged button is hampered considerably when the threads in a body tube become worn. Threaded inserts have worked for me in larger rockets.


Steve Shannon

I generally agree with this statement, though a nut is sufficient for most all flights. The rocket in question is 53lbs + motor so it's not exactly a small beast. The threaded inserts sound like a decent idea, but the centering ring is FG and smaller in width that the #10 inserts. I figure I can drill on centering ring and tap about 5/8in of threads into the FG tube and ring. I treat all my threads in FG, paper, phenolic, and blue tube with thin CA. It hardens the material and makes it more wear resistant. I think if I do that and screw into all 5/8in of threading I will be ok.
 

CzTeacherMan

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I generally agree with this statement, though a nut is sufficient for most all flights. The rocket in question is 53lbs + motor so it's not exactly a small beast. The threaded inserts sound like a decent idea, but the centering ring is FG and smaller in width that the #10 inserts. I figure I can drill on centering ring and tap about 5/8in of threads into the FG tube and ring. I treat all my threads in FG, paper, phenolic, and blue tube with thin CA. It hardens the material and makes it more wear resistant. I think if I do that and screw into all 5/8in of threading I will be ok.
Didn't realize you were dealing with a beasty...
For my Gizmo XL-DD-V, same approximate weight, 8"tubing... I used 1515 rail buttons inserted with a well-nut. Easily replaced, easily removed, no need for epoxy.
https://www.wildmanrocketry.com/ProductDetail.aspx?product=2855
 
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NateLowrie

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Didn't realize you were dealing with a beasty...
For my Gizmo XL-DD-V, same approximate weight, 8"tubing... I used 1515 rail buttons inserted with a well-nut. Easily replaced, easily removed, no need for epoxy.
Now that never occurred to me to use a well nut. Just so we're on the same page we are talking about these right? https://www.amazon.com/dp/B0149IJQMQ/?tag=skimlinks_replacement-20

I use them on my av-bay's to pass the ematch leads through. Do they really hold well enough for rail button use? How's the wiggle on them?
 
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CzTeacherMan

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Now that never occurred to me to use a well nut. Just so we're on the same page we are talking about these right? https://www.amazon.com/dp/B0149IJQMQ/?tag=skimlinks_replacement-20

I use them on my av-bay's to pass the ematch leads through. Do they really hold well enough for rail button use? How's the wiggle on them?
Yeah, I just added the link from Wildman who sells the buttons and nuts as a package.
https://www.wildmanrocketry.com/ProductDetail.aspx?product=2855
Yeah, they hold great. Tons of guys around here (QCRS) use them on the biggie rockets. My Gizmo was 55lbs on the pad, short and fat, so lots of wiggling on the rail. The buttons held no problem. Once they're in, you'd swear they were glued. And since they're 100% removable... You have every future option available.
 
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NateLowrie

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Yeah, I just added the link from Wildman who sells the buttons and nuts as a package.
https://www.wildmanrocketry.com/ProductDetail.aspx?product=2855
Yeah, they hold great. Tons of guys around here (QCRS) use them on the biggie rockets. My Gizmo was 55lbs on the pad, short and fat, so lots of wiggling on the rail. The buttons held no problem. Once they're in, you'd swear they were glued. And since they're 100% removable... You have every future option available.
Well, I'll be. I haven't really seen this out at MDRA. I am picking some 10-32 well nuts up tonight. I'll let you know how it goes. If it works as advertised I will definitely be using them from now on.
 

NateLowrie

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Low profile weld nuts are way better. No rubber, nothing to cut.https://www.mcmaster.com/#weld-nuts/=18kxojh
I don't understand your reasoning? The key advantage to the weld nut is to be able to drill a hole, stick the weld nut in the hole, and tighten down to seal. I wouldn't have to do any internal mounting or cutting. Just drill a hole. If you want to remove it, just unscrew and the well nut pops right out. With the weld nut, you have to mount it internally right?
 

CzTeacherMan

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The key advantage to the well nut is to be able to drill a hole, stick the well nut in the hole, and tighten down to seal. I wouldn't have to do any internal mounting or cutting. Just drill a hole. If you want to remove it, just unscrew and the well nut pops right out.
Precisely.
 

Bat-mite

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I don't understand your reasoning? The key advantage to the weld nut is to be able to drill a hole, stick the weld nut in the hole, and tighten down to seal. I wouldn't have to do any internal mounting or cutting. Just drill a hole. If you want to remove it, just unscrew and the well nut pops right out. With the weld nut, you have to mount it internally right?
Now you lost me! No matter what you use, something has to be on the inside of the tube. And yes, I epoxy mine in. But even if you use a well nut, it has to be inside the tube. If it is not epoxied in, what happens when you take the screw out? It falls down inside your booster.

Well nuts are light weight with a long shaft. The shaft sticks out through the hole in the airframe. If the shaft is too long, you have to cut it down.

The low profile weld nuts don't need to be cut. They don't stick out of the airframe.

The Wildman ones look like they are pre-measured to fit the button, so that's great. They still go on the inside. But for Unistrut buttons, I'd use a low profile weld nut.
 

CzTeacherMan

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Now you lost me! No matter what you use, something has to be on the inside of the tube. And yes, I epoxy mine in. But even if you use a well nut, it has to be inside the tube. If it is not epoxied in, what happens when you take the screw out? It falls down inside your booster.

Well nuts are light weight with a long shaft. The shaft sticks out through the hole in the airframe. If the shaft is too long, you have to cut it down.

The low profile weld nuts don't need to be cut. They don't stick out of the airframe.

The Wildman ones look like they are pre-measured to fit the button, so that's great. They still go on the inside. But for Unistrut buttons, I'd use a low profile weld nut.
A well nut is a rubber flanged piece... Still a hole, stick it in the hole, it doesn't fall through because of the top flange. Put the button on top. Put a screw through the rail button and into the well nut. As you tighten the screw, it pulls the rubber up to the inside of the airframe, snug as you make it. Tighten all the way, you've sealed the hole and pulled the rail button tight against the airframe. No need for any glue at all. Just a hole big enough for the well nut.
Yes, they go inside, but there's no need to mount them in any way during construction.

1500571720167.jpg
 

Steve Shannon

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I generally agree with this statement, though a nut is sufficient for most all flights. The rocket in question is 53lbs + motor so it's not exactly a small beast. The threaded inserts sound like a decent idea, but the centering ring is FG and smaller in width that the #10 inserts. I figure I can drill on centering ring and tap about 5/8in of threads into the FG tube and ring. I treat all my threads in FG, paper, phenolic, and blue tube with thin CA. It hardens the material and makes it more wear resistant. I think if I do that and screw into all 5/8in of threading I will be ok.
I agree. I'm old enough that my big rocket has half inch plywood centering rings and is laminated PML phenolic.
For my newer g10 rockets I used tee nuts filed flush with the outside surface. I like metal to metal on threads that are meant to survive rough treatment.
 

NateLowrie

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A well nut is a rubber flanged piece... Still a hole, stick it in the hole, it doesn't fall through because of the top flange. Put the button on top. Put a screw through the rail button and into the well nut. As you tighten the screw, it pulls the rubber up to the inside of the airframe, snug as you make it. Tighten all the way, you've sealed the hole and pulled the rail button tight against the airframe. No need for any glue at all. Just a hole big enough for the well nut.
Yes, they go inside, but there's no need to mount them in any way during construction.
Exactly. I didn't think to use them because I thought they would wiggle too much, but I guess I was wrong. The nuts are in hand. I'll post some pictures tonight when I get them mounted.

Also, they are great for sealing the hole your wires pass through in the av-bay bulkheads. Just drill the hole a little bigger to account for the wires. They eliminate the need for terminal blocks on the outside of the bulk plate.
 

Steve Shannon

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Exactly. I didn't think to use them because I thought they would wiggle too much, but I guess I was wrong. The nuts are in hand. I'll post some pictures tonight when I get them mounted.

Also, they are great for sealing the hole your wires pass through in the av-bay bulkheads. Just drill the hole a little bigger to account for the wires. They eliminate the need for terminal blocks on the outside of the bulk plate.
I like the idea of well nuts. I just haven't used them before. I thought they would be less than rigid.
 
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