I 284 Short liner - Heads up!

Jun 14, 2004 48 Replies

I put an Aerotech I 284 together yesterday. I knew something wasn't right when the aft closure threaded all the way to the case without any resistance at all. It turns out the liner is too short.



I emailed Aerotech but they haven't responded yet. I don't know what the correct length is (can't find it anywhere) but another one I flew on Saturday was 9 3/8 after it was spent. My short one is only 9 7/32".



What's got me spooked is I know for sure that if I would have happened to grab the reload kit with the short liner it would have failed and toasted my rocket. With everything that's going on during a launch, I wouldn't have noticed that the closure went all the way in. The rocket gods were looking down upon me!


Use a design that is not so dependent on liner length :)

Not certified of course.

9 7/16" is the liner length.

Jerry's motors come with hefty shipping costs. 40k or so.

Thanks Chad. Is that one you measured, or is it the spec? Do you know what the tolerance is?

Maybe that's one that needs the seal disc. Check the instructions?

Not so. Casings, closures, liners are exempt.

Unless paper is a flammable solid because it ignites "more readily" than propellant.

Jerry

I just measured one that I have and its length is 9 11/32 (NIP). Are the tolerances so large that we'd be getting such differing numbers?

That is an artifact of non-rocket folks in manufacturing not understanding how the "system works". The AT (now RCS) system is fairly length critical too.

Jerry

I know, I cant even ship sulphur because it is considered an oxidiser (or flammable solid). Yet charcoal can be shipped.

Yes it does need the disc, and it does/did have it in.

That's the first thing I said to myself: "Hey moron, what did you forget?" Everything is in place.

As measurements are coming in, I'm seeing a large varience, but not nearly as short as mine.

Are these AT variances, RCS variances, or some combination?

Makes you think that maybe all that spam in your mailbox might prove useful, huh?!?

David Erbas-White

I'm surprised Gene didn't jump in here....so in his absence:

You said measurements....hehehehehehehe

:-)

John

Doc,

9.375" (9-3/8) is the correct length for this motor. Let me know that they get back to you with a replacement for this.

Thank you for not using the short part, it would have been bad.

Robert Rosenfield Mfg Engineer RCS Rocket Motor Components, Inc.

2113 West 850 North Street Cedar City, Utah 84720 Phone: (435) 865-7100 Fax: (435) 865-7120
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Just a suggestion: perhaps the instruction sheets could include a listing of the correct liner length for various motor types, for reference in the field.

-dave w

Robert wrote:

Guys,

I did make up dimensioned assembly drawings, parts lists assembly drawings, and released the nozzle drawings for the main plant last year. They were going to get them up on the web site eventually, maybe this can help. Not enough room on the instructions for all the data that's on the blueprints. If you need specific motor data they can send you the PDF's. I also have them, so don't hesitate to ask when you want some info.

Robert Rosenfield

I for one would like to recognize and offer kudos for the supplier following the issue and replying quickly and substantively.

Service matters.

Jerry

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