Mounting 1010 rail buttons

[Bill S]

I'm new to rail buttons, and am designing a large (for me) midpower rocket, and I want to add 1010 rail buttons to it. I had planned on using a stuffer tube attached to the front of the motor mount, running about 2/3rds of the way up the body. Having looked at the common methods of attaching rail buttons, I am not sure how I will be able to get that stuffer tube+centering ring past the forward rail button mount on the inside of the tube. The rear mount, I can probably make that work, by installing the button + mount before attaching the rear motor mount ring, but the front button mount?
The only thing I can think to to is put a notch in the front stuffer tube centering ring to allow it to get past the front button mount nut, but that leaves a notch there that the ejection charge gasses can go into, kind of defeating the purpose of a stuffer tube. Otherwise, I may have to use a 2 piece body tube with a coupler right ahead of the centering ring so I can fool with it before attaching the front body tube?

Pic of what I am talking about:

 

[DaHabes]

I'm new to rail buttons, and am designing a large (for me) midpower rocket, and I want to add 1010 rail buttons to it. I had planned on using a stuffer tube attached to the front of the motor mount, running about 2/3rds of the way up the body. Having looked at the common methods of attaching rail buttons, I am not sure how I will be able to get that stuffer tube+centering ring past the forward rail button mount on the inside of the tube. The rear mount, I can probably make that work, by installing the button + mount before attaching the rear motor mount ring, but the front button mount? View attachment 513923
The only thing I can think to to is put a notch in the front stuffer tube centering ring to allow it to get past the front button mount nut, but that leaves a notch there that the ejection charge gasses can go into, kind of defeating the purpose of a stuffer tube. Otherwise, I may have to use a 2 piece body tube with a coupler right ahead of the centering ring so I can fool with it before attaching the front body tube?

Pic of what I am talking about:

I prefer to use Apogee's rail buttons, as they use a weld nut on the backside of a machine screw as opposed to using a wood screw into a CR. I'm not fond of that approach as I prefer not to deprecate the inner plies of the CR. So, I usually have to notch one or more of my centering rings when I install the MMT. Since they get epoxied in, it doesn't affect the strength of the MMT.

 

[Spitfire222]

Is there any way you can cover up the notch in the stuffer tube after you've installed the rail button? Such as with a small segment of a centering ring, simply to block the opening.

 

[Bill S]

Maybe, if I use a 2 piece tube, with the coupler+front part of the tube in front of the centering ring.

 

[David_Stack]

What about a piece of basswood or similar affixed to the back of your forwarding centering ring, shaped to match the contour of the ID of the body tube? You could then secure your forward rail button to that hard point...

From your drawing it would move your forward rail button up a bit, but I don't think it would be too far forward.

Failing that, if you don't want the forward button that far forward, perhaps a hardwood 'pedestal' affixed to the MMT with the top of it contoured to match the ID of the body tube, and again serving as mounting point for the rail button.

Lastly, you could always drill a small hole in the body tube and simply harden the hole and screw the rail button into the body tube. If the rocket is light in weight this approach may be strong enough (I think I've read posts here on the forum of others doing the same).

 

[JimByrne]

I notch the centering ring just enough to slide it by the nut then fill the notch with epoxy.

 

[Bill S]

The rocket should be around 22 oz empty, maybe 25-26 with a motor in it.

I was trying to keep the forward rail button near the CG, maybe a bit behind it; that seems to be the general consensus as to the best location from what I have been able to glean reading here.

 

[jmasterj]

You could always shorten the stuffer tube to just below where you want to put the rail button.

 

[dr wogz]

What about a piece of basswood or similar affixed to the back of your forwarding centering ring, shaped to match the contour of the ID of the body tube? You could then secure your forward rail button to that hard point...

that's typically what I do, double up the CRs with a piece of ply wood. In the case of FG CRs, I would add 2x the 1/4" ply to one side, then 'aim' the button into that..

 

[MidOH]

On a four inch rocket:

I drill the mount holes in the body tube. Cut out two 4" plywood rings. Remove two 1" sections of the ring. Glue that, stacked up on the rear centering ring. Now that side of the rear centering ring is 3/4" thick. Very easy to get that lined up. Epoxy and slide in the fin unit mmt. Drill through the button hole into the ply, then use a wood screw.

The front button, I simply reach in and use a nut. I guess on a smaller rocket, you could easily do the plywood trick to the forward ring as well.

 

[Cl(VII)]

Warning, shameless plug incoming…

Not for every case, but handy when you need it: Conformal Rail Button Nuts

Available for 6-32 (for mini-RB), 8-32 (for 1010 RB) and 10-24 (for 1515 RB).

 

[beeblebrox]

Use bonded on rail guides.... These are 3D printed. What tube size are you using? I could make you a set. if you don't have access to a 3D printer. If you do, I can send you STL files. You want one near the base of the rocket and the other one at least 2 calibers up from the CG. You want to span the CG with the rail guides or buttons....



These are Apogee ones, on my Cluster Duck. My rail guides don't have the slot in the middle which is not necessary and weakens them anyway. For this size rocket, they are certainly fine. (2.6" Dia tube)

 

[beeblebrox]

Alternatively, if you want to use the screw in type, (Which I prefer if the rocket is heavier.) I made a positioning tool using a 12" piece of basswood with a magnet on it. Drill the hole thru the body tube where you are putting the top one, 8-10" from nose cone or separation joint, make the hole a little loose. Put a little epoxy on the flange of the rail button nut. (Usually a weld nut) Use the magnet stick to hold the weld nut and position it carefully thru the hole, screw in the button loosely and pull the weld nut shaft part thru the tube and then tighten it.

 

[Bill S]

That sounds like a good plan, beeblebrox (using the screw in type).

 

[Bill S]

Got the buttons mounted. Rear one is 1.25" from the rear of the rocket, clearing the centering ring. Easy to install.

The front one, I put the hole in front of the stuffer tube centering ring. I took my new piece of 3' aluminum angle, put a rolled up piece of painters tape on it, stuck the button backing to it, put it in the tube and basically held it in place while moving it around until it hit the hole, tightened it up, done.

I now have to remove them and epoxy the backings in place, as the first time was just a test run.

 

[Starfire73]

I'm new to rail buttons, and am designing a large (for me) midpower rocket, and I want to add 1010 rail buttons to it. I had planned on using a stuffer tube attached to the front of the motor mount, running about 2/3rds of the way up the body. Having looked at the common methods of attaching rail buttons, I am not sure how I will be able to get that stuffer tube+centering ring past the forward rail button mount on the inside of the tube. The rear mount, I can probably make that work, by installing the button + mount before attaching the rear motor mount ring, but the front button mount? View attachment 513923
The only thing I can think to to is put a notch in the front stuffer tube centering ring to allow it to get past the front button mount nut, but that leaves a notch there that the ejection charge gasses can go into, kind of defeating the purpose of a stuffer tube. Otherwise, I may have to use a 2 piece body tube with a coupler right ahead of the centering ring so I can fool with it before attaching the front body tube?

Pic of what I am talking about:

What’s a ”stuffer tube”?

 

[Bill S]

What’s a ”stuffer tube”?

When you attach another tube to the motor mount running forward in the body tube (with a centering ring at the front end glued in) to reduce the volume of body tube that needs to be pressurized. Some rockets are rather wide/long and the ejection charge tends to not pop the nosecone or deploy the parachute reliably, and so this can help. Say an BT-80 main body tube, with an BT-55/60 stuffer tube running most of the length forward of the motor mount.

I found it helps greatly with my Estes Vapor, Super Big Bertha, and Executioner.

 

[Ez2cDave]

What’s a ”stuffer tube”?

Dave F.