Bt50 to bt80 transition a thing?

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mccoy300

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Does anyone know of a manufacturer of a Bt80 to Bt50 hollow transition? Or is that something a guy could reasonably build?
 
BMS has BT50 to 60, and BT60 to 80, but I don't see a single (or hollow) BT50-80. You could make one with a BT50 coupler, centering ring (maybe 2), and printed/glued shroud.
 
+1 on a regular cardstock shroud.
The ace fugue method is difficult and gives you a transition with seams that needs to be filled and sanded.
Even then it will remain faceted, not perfectly round.
A cardstock transition/shroud is smooth and can be toughened with a swipe of thin CA.
 
You can use a regular shroud rather than the body tube “flower petal” style shown in the .pdf. Payloadbay.com has an online tool for doing transition shrouds.
You could model it up in Openrocket or RockSim and it will create the shroud for you
 
So just mount the tubes with a CR, then make the shroud, thickened with CA glue as a cover, instead of being structural? Makes sense
 
For strength and straightness, you may want to use two centering rings. That will keep each tube pointing in the same direction. So you'll run the BT-50 down inside the BT-80 for a short distance.
 
And paint the shroud with thin CA after gluing and drying.
Wood glue doesn't adhere to paper soaked with CA very well.
I'll try and find an assembly picture for clarity.
Like they say, one picture blah blah.....
 
One wide centering ring, like a thrust ring.
Another one at the end of the smaller tube.
I prefer that to thinner rings, it makes for more gluing surface.
Especially if you sand a bevel into it.
Also more length to secure into the larger tube.
 
One wide centering ring, like a thrust ring.
Another one at the end of the smaller tube.
I prefer that to thinner rings, it makes for more gluing surface.
Especially if you sand a bevel into it.
Also more length to secure into the larger tube.
Yes, that works if thick rings are available in that size, otherwise... two rings back-to-back, or other techniques.
 
PayloadBay, a few centering rings and some card stock you are good to go :)
6wyicHd.jpg
 
BT-50 to 80 is a heck of a jump in size! I would guess it would have to be fairly long.
Would you care to show a drawing of what you have in mind?
AS soon as I get home I will sketch it out. It is a pretty big jump, but it is also going to be reinforced with balsa.
 
You can use a regular shroud rather than the body tube “flower petal” style shown in the .pdf. Payloadbay.com has an online tool for doing transition shrouds.
I agree, that looks complex and a pain to do...plus you have to fill all those little gaps at the bottom of each section...the regular shroud is easier and less work no doubt.
 
A single piece of card stock is surely easier for a simple transition. For the two slope transitions that the article shows (it only shows nose cones, but obviously one could do transitions that way as well) do you guys think it would be better than fitting two simple cardstock shrouds together?
1613670643636.png
And for the curvy shapes, is there any other way. OK, it doesn't have to be from body tube, but cutting the curved mating surfaces into a tube or into cardstock, either way might be about as hard as the other.
1613670823247.png
The example worked through uses four panels, and I think one would want to go higher than that to reduce the faceting. The edges, where two panels meet, would wind up lying on the circumscribing circle, so one could build the faces up with filler than sand down to smooth.

The article is © 1984, 1991, 1992, 1997. Nowadays one can 3D print such curvy shapes if one doesn't mind the weight.
 
A single piece of card stock is surely easier for a simple transition. For the two slope transitions that the article shows (it only shows nose cones, but obviously one could do transitions that way as well) do you guys think it would be better than fitting two simple cardstock shrouds together?
View attachment 451234
And for the curvy shapes, is there any other way. OK, it doesn't have to be from body tube, but cutting the curved mating surfaces into a tube or into cardstock, either way might be about as hard as the other.
View attachment 451235
The example worked through uses four panels, and I think one would want to go higher than that to reduce the faceting. The edges, where two panels meet, would wind up lying on the circumscribing circle, so one could build the faces up with filler than sand down to smooth.

The article is © 1984, 1991, 1992, 1997. Nowadays one can 3D print such curvy shapes if one doesn't mind the weight.
Here are Tim Van Milligan's comments on the ace fugue method from the Apogee webpage for the US Rockets Micro Sentra SRB:

ACE Fuge method of transitions


"You can see in the picture here that my own attempt at making the shroud was a mess. I ended up cutting it off the tube, and putting on a traditional paper shroud. This is actually easier to do, and quicker as well. I've created a transition pattern sheet (click here to download) that you can print out on card-stock paper if you'd like to make the same modification. U.S. Rockets has also sent us a replacement fuge shroud cutting template that adds more wedges to the piece, and they say this will make a nicer looking part. Instead of the shroud being conical shape, it will have multiple high-points around the perimeter that give it a unique shape and cool look."


As a build exercise it is interesting to do just for the experience. But if the goal is the best looking transition then there is no contest. I had similar results to TVM.
 
A single piece of card stock is surely easier for a simple transition. For the two slope transitions that the article shows (it only shows nose cones, but obviously one could do transitions that way as well) do you guys think it would be better than fitting two simple cardstock shrouds together?
I have approximated ogive nose cones and boat tails with multiple straight shrouds. See the Apogee "Peak of Flight" newsletters #409 and #410...
 
add more segments, it gets pretty smooth -- this was model I built for the PoF article
 

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Those all look fantastic, thank you all. I got the shroud cut, just holding for centering rings. Can say, cutting it out of card stock, the part is actually pretty stout anyway
 
BT-80 to BT-60
BT-60 to BT 50

Cut the BT-60 shoulders off of both reducers then glue them together.

It probably won't be a straight taper but is that a necessity?
 
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