Rail buttons?

[rsbhunter]

Ok, did the research, and more confused than before. What is good spacing for rail buttons? Madcow DX3 2.6" 44.5" length...marks are at 7" , but before I drill...also,it has a av bay , should I plastic rivet the nose cone on, and should I drill a pressure hole in the av bay? Lots of questions!! Thanks for any help, rsbhunter

 

[David_Stack]

One of the more recent discussions on this topic...

https://www.rocketryforum.com/threads/rail-button-does-it-need-to-be-above-cm.183879/#post-2528894

(bring food and water, you'll be in this rabbit hole a while)

 

[Art Upton]

Use a Sheet metal screw or two to hold the nose cone on a payload bay. [Drill a hole just smaller then the screw for it to tap into the plastic and body tube/coupler.

You AV bay will need a hole for an altimeter. If you have not bought one yet wait till you do and see what they recomend.

You should put a Pressure relief small hole a little below the Coupler on the body tube to keep pressure on a high speed lift off from popping off the AV bay.

Here is a pic of my 3" payload tube over a LOC EBAY held with machine screws. One screw into the Nose Cone shoulder and one into the AV-bay coupler. The big screw on the white "Switch Ring" over the coupler is a screw in switch for the altimeter to arm.

The black tape is not to hold on the nose, it was a "stripe" made of the tape.

 

[kswing]

For the rail buttons, I'd suggest one at the very bottom and one somewhere above the fins. 7" apart on a 44" rocket is probably fine. I've seen many different opinions here on where to place them, but, I think as long as they are in line with each other and a fair bit apart they will work. I don't think I've heard of any failures caused by bad rail button position.

Also, Art's suggestions above about screws and vent holes sounds good to me.

 

[rsbhunter]

Thanks to all of you. I know certain topics are a mix of science, witchcraft and voodoo...I'm going to go with 8"...Hail Mary and full of grace...got the lower button in, epoxied around the T nut, making sure to not get any in the threads...went well. Is the non locking thread sealer ok to use on the button screw? I'll leave it loose enough to allow the button to rotate? Just know, that without you all, I would have $100.00 modern art lamp....Thanks, rsbhunter

 

[Art Upton]

FYI a Delrin button has no need to rotate. I epoxy my threads, threaded into the body tube and then I don't need a T nut. The squish out of epoxy glues the button to the body tube as well.

Any excess epoxy is cleaned up with Iso Alcohol on a paper towel.