Motor retention…. Arggg.. again

[Mx2]

After 15 successful launches on my most favorite mid-power rocket with motor held in by tape and wrapping with tape, (Grandbabies rocket) the F motor blew out, no chute, (I suspect the chute and Jolly-Logic was a little too snug in the tube) and dead rocket into ground. I am preparing a rocket that will hold a G motor in which the manufacture clips won’t hold due to an adapter from 38 mm-29 mm, so I’ve opted to use S.S. 0.035 Lock-wire and crimped/soldered the ends through #8 wire terminal lugs. It’s not Pretty but it is lighter than the manufacturer supplied clips. Set up is light, strong & reusable. Any history on this method and/or possible issues?
Signed: Don’t Want to ever lose another rocket that way again.

(Picture is of first build. They got cleaner looking after that with soldered ends)

 

[GalantVR41062]

I would give the rocket motor a good tug, if it stays in place then that looks like a positive retention method to me. I would still do a little tape to help hold the motor and adaptor in.

 

[Sooner Boomer]

That should work great! I've got a rocket that has two screws in the aft centering ring. For a long time (20 years) I used wire, like what you've done. My motor doesn't stick out as far (no adapter), so I switched to washers under the screw heads. Wire is harder to do (but not impossible) with three screws, you just have to be creative how you "weave" the wire around the motor.

 

[Hobie1dog]

The motor should never come out now.

 

[rharshberger]

That should work great! I've got a rocket that has two screws in the aft centering ring. For a long time (20 years) I used wire, like what you've done. My motor doesn't stick out as far (no adapter), so I switched to washers under the screw heads. Wire is harder to do (but not impossible) with three screws, you just have to be creative how you "weave" the wire around the motor.

one of our club members uses a 3 screw arrangement with wire, he has premade wire triangles that slip over the nozzle and tighten down with screws afaik he uses them on many of his 38mm or smaller motors. The wires looked to be formed into a triangle then twisted at each point with a rod to get the right fit, pretty easy to make IMO.

 

[Steve Shannon]

If you’ve never tried the Aeropack style retainers you might want to. Even Aerotech and Estes sells ones for smaller motors.

 

[Bill S]

I'm liking the Aeropack 29mm retainers so far.

 

[dhbarr]

Just be careful not to put too much sideways or clamping pressure on the nozzle. They're not exactly fragile, but it is possible to crack them.

 

[lakeroadster]

Any history on this method and/or possible issues?

I did something similar on my Cygnus Probe Rocket that utilizes 29mm motors, but I used 12 ga copper wire.

It worked... but it was ugly. I had originally used a regular metal motor clip, on the1st flight the F52-5C motor ripped the hook clean out of the motor mount when the ejection charge fired. The chute did deploy though. Rocket was recovered, motor was sacrificed to The Gods Of Motor Retention.

 

[bjphoenix]

so I’ve opted to use S.S. 0.035 Lock-wire and crimped/soldered the ends through #8 wire terminal lugs

I did almost exactly that about 20 years ago.
My first mid power was a LOC Vulcanite, I put 3 T-nuts in the rear centering ring, bought some long bolts, and made a triangular washer from a piece of aluminum with a hole in the middle for the nozzle.
Some time later I built another mid-power and this time I used 2 T-nuts and made a wire thing like in your photo. I didn't use terminal ends, I just formed loops in the wire itself. I did this as an experiment and I thought it would be easier to make.
Both methods work very well. I was using 29mm motors in my Vulcanite, with a homemade 29-38 adapter. My system would work with a 38mm motor too but I might have to enlarge the hole in my washer. If I was using the wire retainer system it would be easy enough to make different wires for each motor type.

 

[bibbster]

Why does the adapter have so much length on the aft end? Seems to me you could cut that way down and likely be able to use your clips.

Maybe I'm not looking at it correctly?

 

[cbrarick]

Aeropack rthen the only way you lose it is if you forget to install the cap.

 

[Mx2]

Why does the adapter have so much length on the aft end? Seems to me you could cut that way down and likely be able to use your clips.

Maybe I'm not looking at it correctly?

Interesting observation. Why indeed. I built it to mfg-design. I will do dimensions. But probably won’t modify-personal preference. (At this time). Nice find and appreciate input. Lots of replies on this.
I try to use those plastic thread motor retainer but wanted to follow mfg kit and although kit does include the adapter it doesn’t show any way to make the original clips work. Thus my question. Thank You for your reply.

 

[bibbster]

Curious to know what rocket and motor adapter we are discussing? Knowledge is power!

 

[Mx2]

Inquiry appreciated but focusing on use of lock wire and possible issues. Some have enlightened a response in that area, such as caution of uneven tension etc. I am trying to build a rocket which will require something other than the plastic retainer nuts, tape etc so not rocket specific albeit it became relevant in recent build as I ponder various motor retention systems. More for my personal gathering of info and not criticizing mfg. It is what it is and everyone has an opinion and an idea.

 

[bibbster]

I was interested in brand, especially the adapter, so I can avoid buying one.

Enjoy your research.

 

[Raketenolli]

Should hold the motor in just fine, but where I don't have a screw-on retainer I like to just cut a retainer from thin steel sheet with one hole for the motor (nozzle) and two holes for the screws. In your case you'd need pretty long screws though. The metal part would look like this:
image source: https://www.zoro.com/static/cms/product/full/Z3u22zqcpIx_.JPG

Oliver

 

[bjphoenix]

Should hold the motor in just fine, but where I don't have a screw-on retainer I like to just cut a retainer from thin steel sheet with one hole for the motor (nozzle) and two holes for the screws. In your case you'd need pretty long screws though. The metal part would look like this:View attachment 538558
image source: https://www.zoro.com/static/cms/product/full/Z3u22zqcpIx_.JPG

Oliver

This is very similar to what I built first, and I used fairly long screws.