I didn't have any ST-10 tubing. Before ordering parts, I always check the spare parts drawer.
I found some BT-52 tubes left over from an old Thor Agena B build. One piece was 7 1/8", the other at 11 5/8" long. I checked the nose cone and the shoulder fit was good in the BT-52.
Strange thing about those two BT-52 pieces of different lengths. The kit used two 9.4" lengths for a total of 18.8". These two pieces when held end to end were exactly 18.8"!
The smaller rear engine pod nose cones and nozzles fit a BT-20 perfectly. Two pod BT-20s are needed at 2.95" and a engine mount tube at 3" long.
The BT-52 tubes will have to be joined together with a coupler. I don't think one is available to order.
Here's the fit of a BT-50 coupler showing a loose fit in the BT-52 tube end.
The coupler diameter was built up with some cardstock wraps and a glue stick.
After the coupler was sized, I tried a standard BT-50 and it would work as a coupler! Oh well . . .
Perhaps a silly question but eRockets has Semroc ST-10 tubing. If you’re going to have to join it together anyway, why not just get a long piece and save the trouble?
ReplyDeleteHi Anonymous,
DeleteNot a silly question, I'm just cheap! I'd rather use what I have than pay shipping for just one tube. That BT-52 tube fit the 3D nose cone I had printed.
There's also another possible use for having a two-piece tube -- the location of the coupler is probably a convenient place to build in an ejection baffle. If I'm not mistaken some Centuri kits did just that (albeit in slightly larger tube size).
DeleteHi Naoto,
DeleteGood point about the baffle, but on a body tube this diameter I'll use wadding. Centuri did join tubes with a baffle.
Sometimes manufacturers use two (shorter) tubes to get the parts to fit in a certain length bag.
I remember in the Bandit that the BT-50 had a slip-fit within the BT-51 (used within the ejection baffle on the Bandit kit), but I wasn't quite sure of the dimensions of the BT-52. It appears that the inner diameters of the BT-51 and BT-52 only differ by about 0.04" -- so the fit of the BT-50 within the BT-52 would be quite similar.
ReplyDeleteDidn't know about the visual indicator to help differentiate between BT-50, BT-51 and BT-52:
BT-50 doesn't have an inner stripe.
BT-51 has a black interior spiral stripe
BT-52 has a green interior spiral stripe
https://www.rocketshoppe.com/info/Estes_Body_Tube_List_3.1.pdf
Hi Naoto,
DeleteI didn't know about the BT-51 in the Bandit. They used the BT-51 in the Saturn 1B kit. The BT-52 was used in the Thor Agena B.