Looking for an engine nozzle for Bt-55 tubes

[Bill S]

I'm working on an UN heavy torpedo from The Expanse TV series, and have run into a snag. I need an plastic engine exhaust nozzle that fits a BT-55 tube, and flares out to BT-60 diameter. It needs to be 1" long, and have a shoulder to fit into the BT-55 end.

I found a nozzle attached to the rear of some Estes BT-60 nosecones that are the right size, but it doesn't have a shoulder for the BT-55 end. I'd have to epoxy a BT-55 coupler cut down to the right length, and I'm not sure if it would stand up to landing stresses.

Thoughts as another way to do it?

Picture so you can see what I am talking about:

 

[neil_w]

Such a thing can be made with cardstock shrouds. In fact I just made two of these with *almost* the exact dimensions for an upcoming build; only variance is that it is 1.25" long instead of 1".

I used 110 lb cardstock and double-layered the first one, then made another triple-layered. Soaked with thin CA and sanded smooth. They are very strong (unclear if I needed the third layer).


See also: https://www.rocketryforum.com/threads/how-to-build-a-tail-nozzle-other-than-3d-print.153929/

 

[kuririn]

+1 to Neil's suggestion. Also here's a link to a transition/shroud/nozzle generator where you can input the parameters and it will generate a .pdf you can cut out:https://www.delorie.com/rockets/transitions.html

 

[Bill S]

Well I had been hoping to use something that could withstand an nearly 8oz rocket coming down right on it, and the plastic BT-60 piece looked like it would work better than cardstock transitions. Its got to withstand some heat from the engine as well.

 

[kuririn]

Well I had been hoping to use something that could withstand an nearly 8oz rocket coming down right on it, and the plastic BT-60 piece looked like it would work better than cardstock transitions. Its got to withstand some heat from the engine as well.

Then it sounds like custom 3D printed with ABS is the way to go.

 

[Bill S]

Then it sounds like custom 3D printed with ABS is the way to go.

It probably would be, but I have zero access to a 3d printer, nor software. Shapeways is likely to be way too expensive, even if someone did offer it.

 

[neil_w]

Well I had been hoping to use something that could withstand an nearly 8oz rocket coming down right on it, and the plastic BT-60 piece looked like it would work better than cardstock transitions. Its got to withstand some heat from the engine as well.

Given your picture above, motor heat is not an issue. And anyway, paper can take it just fine (hence rolled paper motor casings).

I will have a 6-oz rocket coming down on my nozzle, which is why I triple-layered it. It is certainly stronger than the body tube by a good margin. Will it survive a landing? I feel confident that it will. We shall see, eventually.

Note that I also will have a centering ring about 3/8" from the back of the nozzle, which adds a lot of strength.

 

[Bill S]

I guess at this point I will try the back section off of that BT-60 nosecone, and epoxy a BT-55 shoulder onto the small end and see how it goes. Thanks anyways guys.