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Old 02-16-2007, 06:02 PM
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Doug Sams Doug Sams is offline
Old Far...er...Rocketeer
 
Join Date: Mar 2005
Location: Plano, TX resident since 1998.
Posts: 3,965
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Quote:
Originally Posted by SaturnV
I wish to fly some of my "S" engine rockets, not with the mini-brute engines but with actual S engines. For the upper stage of my Midget I simply made a little fixture that holds the 1/2A engines and cut them on a saw to the S size. However, Estes stopped making the 1/2A or full A booster engines so I am stumped here.
Basically, your only choice is Estes, although there are a few Quest B6-0 boosters out there you might could cut down to "S" length.

If you use a cut-down Estes 1/2A6-2 in the sustainer, you should be OK for single stage flights, but for staging, you will want a longer sustainer delay. Otherwise, you're likely to get ejection while the rocket is still moving fast on the way up resulting in a zippered airframe or shredded chute and crash. I zippered my ~30yo Midget 'cause of too short a delay and was mightily bummed.

Unless you find someone willing to part with actual shorty motors, you're gonna have to roll your own. The S motors are pretty scarce. They went out of production around 1972, so they've been gone a long time.

I have a fleet of over 20 Midgets in various sizes and scales, and fly them on everything from 1/8A's to J's. The common motor combos I use with my K-40 clones are A10-0T and/or B6-0 boosters with A8-5 or 1/2A3-4T sustainers.

With the T motors, you take a spent 18x70mm casing (ie, standard size motor) and saw it down to 1.75". Actually, saw it to 1.8" then sand it to the exact length - you want a nice, clean, square end to tape flush to the other motor. Insert the T motor in it and add a couple drops of white or yellow glue. Voila! Home made S motors.

If you use the 1/2A3-4T in the sustainer, try to find some with the all-purple printing on the motors. These are a bit older and work great. Some of the newer ones, with the multi-color printing, have nuclear ejection charges which have been know to break the shock cords and even rupture the airframes

With the standard sized motors, you can, as you have stated, cut them down to length. Both the B6-0 and A8-5 have over an inch of open space you can saw off. I like to stuff a bit of flame proof wadding into the end before I begin sawing just in case the sawing produces a spark which might make things hot Be sure to remove the wadding before you tape the motors together. Also, make sure you scrape, eg, with a small drill bit, the sustainer nozzle to ensure it's clean and unobstructed for staging. One wrap of cellophane tape is the standard for joining the motors.

I love staging and fly lots of them besides my Midgets. (Sunday's outing was four 2-stagers and a cluster.) If you get the motors prepped well, you'll have lots of success.

Here's a shot of my 2.2X upscale Midget just coming up to pressure. That's 3 outboard B6-0's (or C6-0's) and a centerline D12-0 in the booster. I think that's the burn string falling away just below the burn stick. Or maybe it's one of the ignitor lead extensions.


Doug
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