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Old Oct 01, 2012, 01:09 AM
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clipper's Avatar
United States, CA, Lake Forest
Joined Sep 2005
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Question
RMS-24/20-40 R/C case

Can any one tell me why the RMS-24/20-40 R/C cost three X's the other casings?
Has anyone looked into the possibilities of using the 24mm R/C reload in the RMS 24/40 casing with a end plug?


Thanks, Eric
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Old Oct 01, 2012, 09:24 PM
Registered User
St Catharines Canada
Joined May 2002
908 Posts
I looked at it but never acquired a RMS 24/40 case to try. Both grain lengths are the same from what I could tell. The front closure as you know needs to be plugged. It would be heavier than the standard RC case I think and more complicated to assemble both of which are not good for competition. The RC market is a small nitch so small runs are more expensive but I too believe the price is out of proportion and big A wants to make money, money, money. Too bad Cesaroni doesn't make something.

Richard
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Old Oct 01, 2012, 09:49 PM
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ttabbal's Avatar
United States, UT, Herriman
Joined Jan 2012
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Is there some reason you can't just leave out the ejection charge? I wouldn't change the motor setup. Just leave the black powder out. I do that all the time on bigger motors and have never had a problem.
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Old Oct 01, 2012, 11:28 PM
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Joined Oct 2006
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I think he wants to use the rc reloads which have a very different, lower and longer thrust curve, in the standard case. The reloads do in fact cross between the cases as far as liner and grain length. A friend of mine made an aluminum insert which uses o-rings to fill the ejection charge area of a normal case and then I have to re-use a fiber washer from a normal reload with the rc reload in a standard case and it works fine, but is longer and heavier than an rc case/reload.
Alternatively you could use a normal delay grain/orings in a normal case, without ejection charge and swap in an RC reload and nozzle, but then you would wind up with a bunch of normal reloads without ejection charges...


If you were to use a screwed in plugged closure, you really need a forward o-ring/washer to seal the threads from being erroded, and that means that the reload grain would have to come with different parts and a slightly shorter grain. Having the forward end one piece, that doesn't seem to be an issue.

The rc reloads take about a minute to wipe out and reload, so you buy one case and that's really all you need....find one used.....

Frank

Quote:
Originally Posted by ttabbal View Post
Is there some reason you can't just leave out the ejection charge? I wouldn't change the motor setup. Just leave the black powder out. I do that all the time on bigger motors and have never had a problem.
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Old Oct 02, 2012, 12:50 AM
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United States, UT, Herriman
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heh.. I was on my phone and totally missed that. I pulled up the catalog, I've always been surprised that there aren't more long burn loads. That's really the big difference. Perhaps I'm one of the weird rocket fliers. Fast is fun too, but something about a slower liftoff just is more fun to me. I'm a noob at the RC side, but L2 for plain rockets. I'd just use I49 or I59 loads, but that's easy to say when I already have the cert and cases. For 24mm, the E11/F12 might be a good choice. And F22 for the 29/40-120 case..

For the original topic, Aerotech does sell delay parts. HDK1 is a part number for them. Might be able to use those to fill the forward delay chamber along with the fiber washer thing burkefj mentioned and any O-rings you might need.

Of course, that's now a "modified motor" and you can't fly at a NAR or non-research TRA event. And if you blow up the case, Aerotech isn't going to care.....

I suspect the cost difference has more to do with supply and demand rather than malice though. It would be nice if AT just sold a plugged end closure for the 24mm case that would work with the RC loads though, but then they would probably have to pay for certification and such, and it seems like a pretty niche market for them. And for the slower loads I like in general..
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