Pushing Buttons... My builds have turned a corner.

I don't know why I've sat on the fence over this issue for so long, but I finally decided that in the future, all my 29mm+ powered rockets (within reason) are going to be using rail buttons. I suspect that the reason was that I hadn't had any experience with them until I finally broke down and bought (then built) Mike Fisher's (Binder Design) 2.6 Dragonfly, and my LHS doesn't carry them. Now that I've had almost 9 months to get familiar with MPR that are more powerful than D/E engines, I realize that despite my personal lack of owning a rail shouldn't mean that I only build for launch rods.

As it stands now, only the Partizon and an Argent are stuck with 1/4" LL's. I may need some advice on how to handle the Ventris/Ventris-like builds for rails.

Now I put "within reason" as rockets like the Apogee Aspire (29mm minimum diameter) and the Enerjet Egg Crate (BT-56 based 29mm powered rocket), use such thin cardboard for body tubes, and I'm not certain about techniques for attaching buttons to rockets like them (Read: I'd like advice).

Pointy Side Up!
Jim

For the smaller 29mm or so rockets, take a look at the new mini buttons at rail-buttons.com. 1010 buttons are kind of large for these smaller diameter rockets. The mini buttons are about 1/3 the size!

https://rail-buttons.com/minimicro.html

90% using ACME 1010 rail guides-the rest are 1515 buttons.

ACME Conformal Rail Guides are AWESOME!!!

https://www.giantleaprocketry.com/p...nch_systems.aspx#Acme_Conformal_Launch_Guides

I just started launching from a Rail recently, and I love it.

I like these airfoil rails - they look great on the rockets. https://www.scpconcepts.com/rocket-accesories.html

Specfically for the Ventris I shaped a double layer of Basswood to the same shape as the airfoil to use as a stand-off.

Here's a set of Randy's micro buttons on an Alpha

edit:
I first poked a small hole with a compass point, put a drop of CA in the hole, and let it wick into the tube. After the CA hardened, I drilled a #46 hole which is a little smaller than the screw OD. I threaded the rail button in place, removed it, put a drop of 5 min epoxy in the hole and re-tightened the rail button screw. The lower rail button is going into the centering ring, just like the big boys

Here is how I mount my buttons on a Ventris:

https://doghouse.blastzone.org/rail-button-standoffs.html

So this question came up at this weekend's launch.
How do you attach rail buttons or such to piston rockets and quantum body tubes like those from Public Missiles?

kweaver said:

So this question came up at this weekend's launch.
How do you attach rail buttons or such to piston rockets and quantum body tubes like those from Public Missiles?

Click to expand...

A PML Callisto is the first rocket I put buttons on. I just drilled a hole slightly smaller then the screw I was using and let it thread itself into the plastic as it went in. They have been on there and working perfectly for 7 years now.

kweaver said:

So this question came up at this weekend's launch.
How do you attach rail buttons or such to piston rockets and quantum body tubes like those from Public Missiles?

Click to expand...

For QT, the same process is used to mount them as with a kraft tube bird. Some vendors suggest you drill through the BT into the CR's, and use a wood screw (with epoxy) to hold the screw into the CRs, but my preferred style is you mount t-nuts just forward of the bottom and top CR's. That way if the button gets damaged (it does happen), they can easily be replaced.

As far as pistons, there are two methods. The one preferred by me is DUMP THE PISTON. They might be fine for a few flights, but are prone to fail when residue from the ejection charge builds up on them. If you want to keep the piston, you can attach an acme rail guide on the outside of the bird

RecoRocket said:

As far as pistons, there are two methods. The one preferred by me is DUMP THE PISTON. They might be fine for a few flights, but are prone to fail when residue from the ejection charge builds up on them. If you want to keep the piston, you can attach an acme rail guide on the outside of the bird

Click to expand...

I've been using the same piston in my PML Callisto for 11 years. It's never been an issue. I run a bottle brush through the tube to clean residue every 4 or 5 flights, but that's about it. The piston has been sanded so it's a loose fit in the winter time so it's really loose in the summer. There is plenty of room in the tube and the piston only has to go down far enough to get the chute and cord in the rocket. I screwed the upper button into the BT about in the middle and it acts as a stop for the piston. This keeps the weight of the piston and recovery in the upper half of the rocket which is good for stability.

This has worked so well for so long, I've started adding pistons to some of my 29mm & 38mm powered scratch built rockets.

A piston can use a smaller ejection charge and would solve a lot of the ejection issues people have with the G-Force and other large diameter/small MMT rockets that are flying on MPR motors.

I think the Sumo uses a piston, but would it work on the G-force where you would have to deploy the entire top BT (at least 10-15 oz, more with payload)?

I'll just chime in to point out the mistaken impression that the ejection charge is primarily directional and "pushes the parachute out". Black powder explosions and CO2 cartridge discharges generate gas which expands in all directions. You need two things for successful ejection: 1) enough force to separate the rocket, 2) the recovery system not to be jammed in so tightly as to not come out. This is true with or without a piston.

But, back to the OOP question, the forward button should be aft of the laundry (or piston) so that it doesn't cause a snag and deployment failure.

JohnCoker said:

I'll just chime in to point out the mistaken impression that the ejection charge is primarily directional and "pushes the parachute out". Black powder explosions and CO2 cartridge discharges generate gas which expands in all directions.

Click to expand...

Unless the expansion is contained like in a bullet cartridge, then it most definitely is directional.

dixontj93060 said:

Unless the expansion is contained like in a bullet cartridge, then it most definitely is directional.

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It is contained, by the air frame. It's actually the increase in pressure that separates the bird.

Hey guys, chill and keep it civil. Everyone has different ways of doing things. It's hobby rocketry, so most of them work just fine.

Rails are a technology I can get wholeheartedly behind, though, for sure. Good call on making the switch, OP!

Thanks to all who replied, and I'd like to say thanks to davyfire for the... let's just say "pruning" of the discussion.

Peace
Jim

What Jim said. Sorry everyone for letting this get away, I should know better by now.

Back to the subject at hand. I you don't want to use screws through the BT with conventional buttons, you can use just epoxy to attach Acme Confromal Rail Guides which are metal, or do the same thing with the PML rail guides which are nylon. The PML guide do come with screw holes so you can use flat head screws to attach them if you want. I had the PML type on my El Juan rocket and they were just epoxied on. They held up just great until the second I1299N-P Warp9 flight. The flight was great but I never found the rail guides again.

RecoRocket said:

It is contained, by the air frame. It's actually the increase in pressure that separates the bird.

Click to expand...

Yes, I put together an animation from some frames from the latest video I'm working on. Sorry about the large size (it's made for 1920x1080 video frames).