Rail Button Mounting

[Zippy]

I bought an 8' rail and a bunch of buttons to go with it. What I'm wondering is are there any special techniques for mounting the buttons? The supplied screws seem mighty short. I know I'll have to back up the tube with scrap wood where I don't go into a centering ring but I'd be interested in knowing what others are doing and what works for them. The rockets I'll be using them on will probably all be in the 3 - 5 pound weight area.

 

[Rocketmaniac]

So far, I have only put button on one rocket..... My LOC Expeditor...... It weights about 5 lbs....... I did nothing special to install them........ 2 went into centering rings and the 3rd (middle one) didn't even have the scrap wood behind it....... Just a little bit of 5 min epoxy........

 

[Zippy]

Rocketmaniac,

Well that sounds reassuring, but why did you use a third button?

 

[Rocketmaniac]

Originally posted by Zippy
Rocketmaniac,

Well that sounds reassuring, but why did you use a third button?

Well, the third one might be overkill...... I put the first one at the very end (aft end) (in a centering ring) The next one is up about 7" and the last one is up another 18 1/2" for the second one (centering ring also)....

If you only use 2, they need to be kind of close together towards the aft end of the rocket....... If the front one is too far up, the rocket will wiggle once that button clears the top of the rail.......

My rocket is about 61" long....... The front button clears the rail when the rocket is about half way off the rail, and it still has 2 buttons to keep it pointed in a straight line........ It is only during the last 7" that there is only 1 button on the rail...... By then, the rocket should be going in the right direction.......

Here's the thread where I built the rocket.....

https://www.rocketryforum.com/showthread.php?s=&threadid=4441

I launched for the first time about 3 weeks ago using a hybrid motor...... Pretty cool flight.....

 

[Zippy]

That makes sense, especially for a long rocket. I hadn't thought about "wiggle". I had been thinking one at the bottom cent ring and one at the CG but only becouse thats the way it's done usually with lugs that wouldn't have much wiggle.

 

[rocketkid88]

i've never used butons, but if you check out www.railbuttons.com/ and read the FAQ and the articles sections there is tones of info... good luck!

 

[rstaff3]

I have used buttons on various sized rockets using the techniques discussed on railbuttons.com. (lpr - hpr) I have never used more than two buttons or used a backing. I just make the hole, screw in the button, remove it, add a drop of CA, and reinstall the button. Most times I have them abut to a CR.

In my applications, I generally put buttons pretty far back which increases the time on the rail. So far I haven't had any issues, but it might depend on the thrust of the motor and the length of the rail. I started with a short BSR but now my club has much longer ones. My personal feeling is your rocket has to be pretty marginal if it is still unstable in the last 6" - 1' of a 6' rail.

I didn't mean to bash anyone elses opinion, just to give mine. A third button on a long and/or heavy rocket won't hurt. But you will have to make sure they are well aligned.

PS At the 5 lb range I've used larger buttons. Much larger and I'd also probably go with some sort of backing.

 

[KermieD]

I personally agree with rstaff and attach my buttons pretty much as he does (I use epoxy or JB Weld instead of CA though). I've launched a 12.5 lb. rocket with 2 buttons and no backing. I don't think I even hit the CR on them, but the tube was glassed, so that probably helped.

In short, I personally don't think it's worth a whole lot of worry. 2 buttons on the back 1/3 to 1/4 of a long rocket should work just fine for most MPR to medium HPR applications.

 

[edwardw]

I love my rail buttons. I have some 1010 extrustion (two 6' sections that can be put on a truss I made to make a 12' rail) and also got my buttons from www.railbuttons.com I have yet to use the full 12', just 6' for now.I use three buttons per bird and I rarely hit a CR, just epoxy them in. To keep them inline I use a piece of angle iron. My current setup I put one button 1.5" from the back, measure 2" from that button and then put another. Then usually I go as far up on the fin can section as I can and put the third button. Though if the CG is on the fin can section and not the coupler I put it on the CGI like to get as much guidance out of them as I can. Thats my .02 cents on buttons

Oh also, bring some spares to the launch, I have had the top washer damaged by the rail and being nearly shaved off.

 

[Zippy]

I actually got the buttons from the oftmentioned railbuttons.com. I'll have to go back there and read all the faq stuff. I missed it when I was doing the ordering, all except for the part about rod whip and why rails are better.

 

[lets fly high]

Originally posted by Zippy
I bought an 8' rail and a bunch of buttons to go with it. What I'm wondering is are there any special techniques for mounting the buttons? The supplied screws seem mighty short. I know I'll have to back up the tube with scrap wood where I don't go into a centering ring but I'd be interested in knowing what others are doing and what works for them. The rockets I'll be using them on will probably all be in the 3 - 5 pound weight area.

were did you buy the rail at. I'm looking to build a new pad for the bigger stuff

 

[rstaff3]

McMaster Carr https://www.mcmaster.com/ has the raw materials. railbuttons.com will show you the part number and how-to.

 

[Zippy]

Joe,

Yup Mcmaster Carr and railbuttons.com. Here's the part number for the 6' rail 60585K41, they have 8' & 10' on the same page.

 

[lets fly high]

Originally posted by Zippy
Joe,

Yup Mcmaster Carr and railbuttons.com. Here's the part number for the 6' rail 60585K41, they have 8' & 10' on the same page.

Thank you for the information both of you

 

[edwardw]

I went to a local dealer and ordered my rail. It was the 1010 extrusion. They drop shipped it to my place.I think I paid $32 + shipping which was $15...I was very happy! I used the 1/4 carriage bolt mounting system described on www.railbuttons.com and some 1/2 black steel pipe.

Edward

 

[eugenefl]

Originally posted by lets fly high
Thank you for the information both of you

Joe, check out these pictures of my rail/pad - <a href="https://www.rocketryforum.com/attachment.php?s=&postid=48113">CLICK HERE</a> and another <a href="https://www.rocketryforum.com/attachment.php?s=&postid=48114">HERE</a>. David Logan (aka astrowolf67) was gracious enough to start a thread and document his build. You can see his project thread with my replies <a href="https://www.rocketryforum.com/showthread.php?s=&threadid=4526&highlight=carriage+bolt">HERE</a>. If you need any help at all building your rail, let me know. Then again, there will now be THREE of us with a rail all in the same club. Crazy...

Zippy, let me know if you need any assistance. I can bring out the rail next meet if you want to look it over.

 

[Zippy]

Eugene,

Thanks, I'm mostly done with it allready though. Now I just need something to fly off it like a 3" Jayhawk.

 

[loopy]

I think you really only need the backing for the buttons on larger projects. Personally, I've only used them on one rocket so far, and I've learned that rail buttons are another reason to love PML's Quantum tubing. Mark the tube, drill the holes, put some epoxy in there, and they ain't going nowhere!!!

Loopy

 

[stevem]

all my rockets have Matt Stums buttons on them. From the Big Bertha all the way up to my 43" tall Coyote (all low to mid-power stuff). 2 buttons per rocket, just drilled a 1/8 hole and and drop of epoxy - no backing - never had a failure or a problem.