Motor retainers...38mm/54mm...no love for plastic screw on (à la Estes)?

Just curious why there are no plastic or 3D printed motor retainers for 38mm (or larger)?

I have the Estes 29mm plastic screw on retainers, and there are a few 29mm retainers on Thingiverse, but nothing for 38mm.

Why?

If I can (with my LOC 4" Goblin) use a pair of screen door window retainers (or similar) up to 54mm motors, why aren't there any Estes style plastic 38mm & 54 mm screw on retainers? Yes, I've seen the aluminum ones (Aeropac, LOC), but why no plastic?

I print them... work like a charm. Have printed them for lots of folks in the board, but only up to 54mm. No issues with anything up to that big

swatkat said:

I print them... work like a charm. Have printed them for lots of folks in the board, but only up to 54mm. No issues with anything up to that big

Click to expand...

Now that is innovative and very cool

54mm JUST fits in a 75mm tube.

swatkat said:

I print them... work like a charm. Have printed them for lots of folks in the board, but only up to 54mm. No issues with anything up to that big

Click to expand...

What'll a couple sets of 38mm's cost me?

Cheap Cheaper than Estes 29mm sets online. PM me. I have two different styles.

Just watch out which direction the prints are oriented. I can imagine the rear ring failing in tension due to over-tightening and/or the larger ejection charges firing. If you print them using FDM with the retainer essentially horizontal you have the stress across the z-axis weakness. Printing them side-on might give some extra strength.

Strengthening with an acetone treatment, or similar, will help of course.

OverTheTop said:

Just watch out which direction the prints are oriented. I can imagine the rear ring failing in tension due to over-tightening and/or the larger ejection charges firing. If you print them using FDM with the retainer essentially horizontal you have the stress across the z-axis weakness. Printing them side-on might give some extra strength.

Strengthening with an acetone treatment, or similar, will help of course.

Click to expand...

I print on a continuous rotating 30 degree axis at a 0.1mm layer height. No issues so far even with the bigger motors. Only issue to date was a little melting on a friend's low and slow kit on a J350W. Nothing close to failure, but some visual melting on the back of the retainer due to the blast shield/slow liftoff combo. Just printed a second retainer... the threaded part was perfectly fine.

Should clarify the wording above, my prints rotate the orientation of the print 30 degrees each layer.

Fair enough. Just raising awareness of something that some people might not know or think about. 3D printing strength can be very process-specific.

Yes, have to be careful about delamination, especially with PETG.

swatkat said:

Cheap Cheaper than Estes 29mm sets online. PM me. I have two different styles.

Click to expand...

PM sent!

I have one of his 54mm. And it is amazing. That rocket won't get tones of flights, so I'm not worried about it at all.

Can always just print another end cap if it gets too melty. The threaded portion will be fine.

I like putting a ring of ductape on the back of my plastic estes retainers. Seems to protect them from the blast splash melting, so it may work for the 3d printed ones too

I just paint them with the spray on pottery glaze, but duct tape would work too. I've yet to really see a ton of damage from flights though aside from the one J350W on the low and slow. I've got a Mach 1 Portia that has seen 7 I impulse level flights and barely shows any signs of use and that one I printed in white, so it would be really obvious.

There are the two different style caps, a smooth one and a knurled one. They come in two depths, only the smooth one has the second depth shown, but there's a knurled one like that too it gives extra room if you are using an adapter/spacer for a smaller motor inside the 38mm mount. . The white one on the red rocket in the back has seen 7 I-impulse flights, it is only very slightly discolored, no physical issues to the retainer at all. The white round one has seen two H flights and a 38mm G67R flight, so issues at all.

Apparently there is a demand for these. Thanks all who expressed interested, ordered. I'm kicking off a batch of 8 sets now.

If you offered a smooth bt60-29mm cone ( e.g. to fit Star Orbiter ) I believe you might find some additional demand.

Specifically, I would buy 3-4 of them :-D

a BT-60 tailcone with a threaded end? Hmmm.

Launch lab rocketry currently sells polycarbonate (I believe injection molded) 38mm retainers for 17$ a pop. They come in blue and grey. I do not have one of these retainers but I have purchased things from launch lab rocketry and they have been great. I am posting this just in case anyone was still watching this thread and hoping for someone to sell them!