BT-70 classics

SPEV!

Gemini-Titan (with a paper reducer to the BT-60 parachute tube/nose. IIRC BMS makes a BT-70 equivalent of the entire top assy so you can put the chute into the BT-70 and pop the entire top.)

-Fred Shecter NAR 20117

""Remove "zorch" from address (2 places) to reply.

Sprite tail tube.

USR BT-22 is BT-70 ID and a tad thicker and smoother and white. 18", 9" and 5" and we have a tube cutter so 1/2" tailrings are also easy.

Jerry

Rats! Forgot about that one. K32.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

LOC et al 54mm MMT is about the same OD, but smaller ID and much thicker wall. If you want to make something with 29mm or larger motors, I recommend one of these tubes instead of the thinwalled estes clone tubes.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

I'm actually on a "clone binge". I'm doing some old Estes and Centuri kits.

I'm going to moderately upscale a few old kits for school demonstrations too. My BT-80 based Goblin 2X upscale is about ready to be retired and I need some replacements. It is perfect for the school yards. I used

1/4" balsa fins and a home made nosecone to get a better scale shape, though the kids would never know the difference. The draggy fins coupled with a D12-5 motor give the kids a good show and I can keep it inside the playground. I want to keep everything to single D power for simplicity and safety.

I haven't done any HPR in almost two years. I got burned out on traveling long distances to wait and launch one or two rockets once or twice a year.

BTW, thanks everybody for all the suggestions. I'll add some BT-70's to my list.

tim

SPEV

= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Mark B. Bundick mbundick - at - earthlink - dot - net NAR President

I'm gonna build one as soon as I get some BT-70... Sprite is cool but I think I might try Flis's Tumbleweed instead, so I don't have to build half-sized motors.

-- these are the good old days Cliff Sojourner snipped-for-privacy@employees.org

A composite 18mm short would be about a D.

I've seen 18mm regulars with "D" impulse (AT D21, Apogee D10)... those D10's were neat motors... long enough burn with enough thrust to be seriously efficient in a rocket of appropriate weight.

-dave w

The optimum 18mm short would be an endburner ala old USR G15 or AT E10. Scaled to say a Estes equivelent 16.2D would be about a 16.2D4.6-4 and

16.2D3.6-4 respectively.

Fairly easy to make too. A D at an E price :)

Jerry

Even though you asked about old Estes kits that used BT-70 tubes, I like 'em a lot for scratch-building too. I've used BT-70 for a scratch-built Harpoon, Russian AA-10 Alamo (which was an ideal use of the stock BMS BT-70 cone), & on Bender, the robot, among others. The Harpoon & some others used the egg half with a conical paper party hat glued on ala The Launch Pad. There's a size of plastic Easter egg (the kind that opens into two halves) that fits the BT-70 perfectly as a nose cone. Also an Easter egg that fits BT-55 perfectly. Sources for them at non-Easter times are thrift shops, where they are often bagged in the toy section or imposing on friends or relatives who store their seasonal items. You can even exchange wrong-for-rocket purposes-size eggs with friends/relatives for theirs or tell 'em you'll replace by next Easter. Initially, I thought I'd have to extend the shoulder of the egg into the BT, but after a test flight it stayed on fine. I've flown the Harpoon on E15s & E30s with no problems. -- Richard "love that BT-70,..... but I've got to schlep out & by some milk for coffee, cereal, etc." Hickok

THERE ya go! I like the way Cliff thinks....

jim

Cliff Sojourner wrote:

They are USR kit nose cones since 1980. Probably not the first, but certainly the most frequent.

Plans for my Maxi Sprite can be found at

on page 6-7. It was also in Sport Rocketry a year or two later.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

way cool! we've been poking around for a BT-80 project, my kids are going to love this one. maybe we'll do it next week. just gotta find or make some 7.5".

And Bob, I found your crayon-conversion article. the kids want to do that one too. the big question for them is "what color crayon" - it's between blue and purple.

Cliff

No question here: PURPLE! My daughter even found one with the sparkly silver middle, and had Mom buy it for Dad. That's the one featured in the article.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!