Adding a Retainer to a Minimum Diameter Rocket

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3 жыл бұрын

www.ApogeeRockets.com - A common problem with minimum diameter rockets has to do with holding the engine in during flight. You often don't want to add a screw-on engine retainer, because they are fatter than the diameter of the rocket, which would add a lot of extra drag. That defeats the purpose of minimum diameter rockets, which is to be low drag so they go extremely high.
In this video, we'll show you an older technique that still works great on holding the motor in using a twisted steel wire rope that is buried under the fin fillet of the rocket. This was shown in the Peak-of-Flight Newsletter issue #95.
It is easiest to put the wire rope on the rocket before adding fillets. But in this video, the rocket is already built, so we will have to retro-fit the rocket by cutting in some channels into the existing fin fillets. This involves using a rotary tool using a cut-off wheel.
After the channel for the wire rope is cut, it will be bonded in place using thick epoxy. After the epoxy has hardened, the fillets are sanded again, and then re-painted.

Пікірлер: 28

@Bozar069 3 жыл бұрын

I love when I have a question in my head and you answer it with a video.

@neilweinstock4194 3 жыл бұрын

I was actually holding my breath during the cutting part, but I have to say the end result is quite nice. That's a darned good retrofit. Seems to me that you could get a bit more secure retention if you spanned the wire to the root on the *other* side of each of the fins. No inherent reason the wire needs to stay between the two adjacent fins.

@apogeerockets 3 жыл бұрын

On the spread, you have to watch out for crossing the wire rope over the opening in the nozzle. And some motors have nozzles that stick out from the base of the motor, and you have to leave room for those as well. That is why on this rocket, I used to adjacent fin fillets. You will have to make sure that the wire rope also bends sufficiently to allow the motor to be inserted. You are having the exact same thoughts that I did when I was putting this together.

@kernelsmith 3 жыл бұрын

I'm glad you mentioned adding the tape at the end. I was definitely concerned about the wire being shrugged off during flight

@paint57 3 жыл бұрын

Very nice, great tip, Tim!

@billj5645 3 жыл бұрын

A masking tape wrap sounds like a good idea. If you have some small wire like florists wire or even a long tie like you get on a loaf of bread you could hook one of the tie on your retainer wire near one corner, wrap the tie around the nozzle, and then hook the other end of the tie on the retainer wire near the other corner. This would keep the retainer wire from moving off the end of the motor.

@paulrudin5385 3 жыл бұрын

Very clever idea!!

@REAR_rockets 3 жыл бұрын

Slick fix!

@donnieporter7890 3 жыл бұрын

Thank u love your channel

@RonzRocketz 3 жыл бұрын

I'd like to see the sanding and sealing part.

@davidpinter1663 3 жыл бұрын

Love this and will try it. Thought I'd mention that, since that rocket was tip-to-tip glassed, by cutting the channel (and not re-doing the lay-up), you've sacrificed the strength afforded by that fiberglass job, and reduced the overall strength of the fin attachment, at least on the one side of the two fins that got the wire channels. Still, it's an excellent idea for new builds and for retrofitting non-glassed fins.

@epickett63 3 жыл бұрын

I was thinking the same thinG(losing the integrity of the fin layup).

@BryanTorok 3 жыл бұрын

It depends on how the fin glassing is done and how deep the cut it made. It is possible for the fiberglass to be pressed sharply into the junction of the fin root and tube and the fillet to be above that and just epoxy. In that case he could cut just epoxy and avoid the fiberglass. It is also possible that a fillet was added before the fiberglass and in that case the fiberglass would likely be cut as you point out.

@robdaugherty2010 3 жыл бұрын

Another great video, and a smart idea. Thanks, Tim!

@Kevin_OKeefe 3 жыл бұрын

Any videos of the rocket flight after the addition of the retainer?

@apogeerockets 3 жыл бұрын

Yes. See the kit web page, and watch the introductory video on the LASER Loc rocket. It isn't that exciting though. The rocket moves so fast that it is in the camera view only for a split second.

@b.h9186 3 жыл бұрын

how can i modify a rocket to use an aerotech reteiner?

@kirkgroeneveld3191 3 жыл бұрын

What is the name of the rocket you're working on? And how did you clean up all the fiberglass dust without making more aerial problems? Vaccume? Sweep brush? Damp Sponge?

@apogeerockets 3 жыл бұрын

Use a damp sponge. Here is the rocket: www.apogeerockets.com/Model-Rocket-Kits/Skill-Level-4-Model-Rocket-Kits/LaserLoc

@jesuscoria5675 3 жыл бұрын

Is this wire rope also an option for high powered minimum diameter rockets?

@apogeerockets 3 жыл бұрын

This was a high power minimum diameter rocket. So "Yes."

@HPRnut 3 жыл бұрын

I have a question, could you add the twisted wire BEFORE the fillets?

@apogeerockets 3 жыл бұрын

Absolutely. That is what I said at the beginning. You'd ideally want to make this addition to the rocket during construction, so you can bury the wire under the fillet later in the build process. It would be so much easier to do than than to cut the fillet away.

@deepskychaser5707 Жыл бұрын

@@apogeerockets so if I’m understanding this correctly, this should go on the bare cardboard tube and before the fiberglass?

@LoanNguyen-bg5is 3 жыл бұрын

Will this work on rockets that go mach 1+ ?

@alexthekunz 3 жыл бұрын

It should be just fine. The force from the launch is driving the engine into the body of the rocket. This retaining mechanism really just needs to stop the engine from popping out during a parachute ejection charge. That force should typically be pretty low, regardless of how fast the rocket was going up to that point.