Re: Prototype 'M' motor test flight entirely successful

snipped-for-privacy@propulsionpolymers.com (Marcus Leech) wrote in message


I can't either, Marcus... Silly, Silly, Silly.
I would like to do a real 2" motor line. A MMT adapter for a 2" motor in a 54mm MMT is an easy thing - just a piece of 54mm coupler tube. I say the hybrid MFG. guys get together on this, and buck the system by making 2", and other 'standard' size motors, along with tubing options for them.
Dave has gone standard by going with a non standard rocket motor size of 2.5" (64mm). IMO, A great thing! The beautiful K240 is cheaper to the end user becasue of his standard tube choice, I'm sure.
I think Scott from West Coast is thinking about a standard 3" (not 75mm) tube for his new very nice L motor...
Is it time for a new standard?
What say you?
Todd Moore Sky Ripper Systems.
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snipped-for-privacy@gtlakes.com (Todd Moore) wrote in message

Actually, Todd, 54mm *is* a standard tubing size. 2.125" cold-drawn (ASTM B210) tubing is available--0.065" wall is reasonably easy to find, while 0.095" is somewhat harder (ok, more than "somewhat", but less than "impossible").
I was going to do a 2" line a while ago, but chose to make a "real" 54mm instead. Slightly better mass fraction, since my 2" motors used 2" x 0.125" wall tubing. I have a very happy friend out west (Dave Johnston) who flys the 2" K all the time. Dave recently bought up nearly all of my remaining stock of paper liner tubes for that motor, since I have no further use for them.

LOC 2.6" BT works just great as a motor mount for his motors. My friend Bill Wagstaff has a 2.5" N2O/HTPB motor that he flys at BALLS.

I thought that AT/AMW/CTI 75mm motor tube *was* 3" tube. Am I confused?
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snipped-for-privacy@propulsionpolymers.com (Marcus Leech) wrote in message

Ohh. As a guy who works in the metalworking field, I've never seen 2.125" tube. Been looking for a while, too ;) Would you care to throw a buddy a bone here, and cite a source or two? I have seen 2" and 2.25", but 2.125" is not something I have seen.

I have a source for 2"x.083" wall tube. Not too bad.

As far as I know, all 75mm tubes are smaller OD than 3" - 75mm is 2.95" 3" is 76mm. To fit in a 75mm MMT, 3" OD tube must be turned down some.
Todd
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(Marcus Leech) wrote in message

Close but 3" is actually 76.2mm 8o) I talked to Ken of AMW in the past and they have tubing run at 2.950 or 74.93mm. At Roc Lake we learned just how close MMT are to 3", but we did have to build a make-shift hone and bore out a MMT ( not fun ) I have been bashing this question around for some time! The 76.2mm or true 3" K-M system would definitely have to have a rocket custom build around the motor due to length of the M case.
So, is the rocket community ready for another "non standard" but "standard" type motor? 8o) West Coast's true 3" I'm planning on supplying a MMT with the motor. What the general senses???
Scott ...
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Why do you need a cardboard tube to put a structurally superior aluminum tube into? Why not just build centering rings/thrust rings to fit the motor? I'm planning to do just that for a 54mm mount.
Layne Rossi CAR S767
(Marcus Leech) wrote in message

confused?
bore
true
the
a
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snipped-for-privacy@gtlakes.com (Todd Moore) wrote in message

Yarde Metals stocks the 0.065" wall, and they list 0.095" wall. Tube Service also apparently carries 2.125". Both CTI and Dr Rocket get the stuff somewhere as well.

I know they had to lightly "hone" Andrew Mcmillens BSD THOR a tad to get the West Coast prototype 'L' motor into his 75mm motor mount, but no way did they have to take 0.050" off of it!
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snipped-for-privacy@propulsionpolymers.com (Marcus Leech) wrote in message

Well, I can get whatever I want, as long as I buy a boat-load of it ;) Thanks for the source on the .065" wall, Marcus. Hey, Jerry; I guess you CAN find 54mm tube, right off the shelf.

Woody told me before how much had to come off his 3" EX motors to make them 75mm compatible and IIRC, it wasn't all that much, so you are right. BUT, each one still has to be turned down. Doesn't really matter at that point if it's .005" a side, or .025".. It still has to be done.
Todd
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snipped-for-privacy@propulsionpolymers.com (Marcus Leech) wrote:

3" motor mount tubes are 3.00 ID 3" motor casings are ground to 3.97" to slide fit properly
The only sizes that do not have to have a 2nd operation grind are 29mm 1.125 38mm 1.500 64mm 2.500 152mm 6.000
24mm 0.935 typically has to be ground from 1.00 54mm 2.125 typically has to be ground from 2.250 75mm 2.970 typicaly has to be ground from 3.000 98mm 3.875 typically has to be ground from 4.000
It is less work to grind a single reuseable casing that someone is paying the big bucks for in the first place than grinding thousands of installed base paper rockets :)
Jerry
Standards. They matter. Set a good one that has legs.
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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Jerry:
I do standards in my other life. Heck, I spent several years as a senior management type in an important internet standards organization.
The notion of "standing on the shoulders of giants" is an important currency in standards.
The fact that you have to take standard, OTS, metal tubing, and muck with it to fit some ill-conceived other standards is just wrong. It's the state of the world, but it's *wrong*.
Take 75mm, for example. There's simply *no* reason that 75mm motor mount tubing couldn't have been made as 3.015" ID, allowing OTS 75mm aluminum tubing to be used for corresponding motors. But no, some weeny probably thought that if the motors were 3.00" OD, then the corresponding MMT should be exactly 3.00" ID. Bing! Or it may have been that they went to the paper tube maker, asked for 3.015", and the lame-ass folks said "we don't have a mandrel for 3.015, but we can make 3.000". Pick a different paper tube manufacturer, one that uses more modern equipment with extreme flexibility in ID and OD. In bulk, tubes up to about 4.5" ID x 34" long can be made for about $1.50 each. Contrast that to a turning operation on aluminum tubes.
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snipped-for-privacy@propulsionpolymers.com (Marcus Leech) wrote:

So how about we set ONE new standard right here and now.
3.00" tubing shall now be 3.02" actual. The blow molded cones will need tape and the rings will have to be resized and the motors will fit right.
Or grind the tube OD at the same time you cosmetically prep it for anodizing and save all the 5 company kit retooling cost. In some cases it is simple economics.
But if you pick one I say pick 3".
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Dave Ross is a craftsman of some considerable skill. He can make schemes like that work, and make it seem easy, cheap, fast, and straightforward.
To be fair, he did luck-in to a source of fairly thick LE phenolic sheet for next-to-nothing. Cutting rings for this motor from this material was fairly straightforward, and structurally sound.
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snipped-for-privacy@propulsionpolymers.com (Marcus Leech) wrote:

Sweet.
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Which is why the East Coast guys have taken to 115mm motors, with a 4" ID. I just use 4" body tubes and couplers as the liners and casting tubes.
It's also the same reason 2.5" is wonderful...
-Darren
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snipped-for-privacy@dca.net (Darren Wright) wrote:

For EX purposes 2.5 (our 66mm) and 115mm (no equivelent here) that is great where each part is a one off. But when you get into manufacturing you have to sell into an installed base. I installled the first installed base BTW.
The installed base has 24mm, 29mm, 38mm, 54mm, 66mm, 75mm, 98mm, 152mm.
Period.
115mm is in a sense the most INCOMPATIBLE size possible. To me that makes it yet more perfect for EX. No confusion.
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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But every time a new size is created, there isn't an installed base.
Until the CTI O5100, there was no installed based of 152mm rockets out there of any significance. The attitude of "let's take an existing airframe size, and make motors that fit it" leads to the unpleasantness I've described. Having custom paper tubes and corresponding centering rings made up is quite cheap. For a $200.00 investment, I can get 75-150 custom paper MMTs made up, depending on size. For the same $200.00 investment, I can get about 5-6 motors turned-down to fit existing airframe sizes. Which makes more economic sense?
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I should, I guess, have said "no installed base of any significance in the HPR market". Granted, there were some EX 152mm motors around, and as you point out, some/many military motors at this size range. That doesn't count when you're looking at the HPR market.
The way I look at it is this. CTI introduced a 152mm 'O' motor into the high-end HPR market. How many people were/are screwed by the fact that it's a new size. How many people just said "it's the only O motor currently available in the HPR market, and I'll just build my rocket accordingly, rather than whine about it not being 98mm, 75mm, 54mm, 38mm, 29mm or 24mm?"
If you're building rockets at the 98mm size range, and you are utterly stopped by the fact that new motors in this range are actually 100mm, then I'm kinda scared about the degree of competence in the hobby...
How about this. When I do bring my 100mm hybrids into production, the first 50 customers get a complementary set consisting of an MMT, and centering rings to match either 5.5" or 7.5" "standard" airframe tubing? I'm willing to bet that grumbling would stop pretty quickly, and the PMLs and LOCs and BSDs and...of the world will start carrying the appropriate parts.
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snipped-for-privacy@propulsionpolymers.com (Marcus Leech) wrote:

All of them because of the strange coupler technology making install a brute. It's not like it's JUST an oddball size like your cool hybrid. Maybe the solution is for you to commission some kits from LOC tailored to your kits and both you and he sell the kits as needed.

The utterly stopped language is not right. I simply pointed out 90% of the installed base or more have standard sizes.
There will always be a small minority of people willling to make purpose built rockets.
Or do as I do. Put fins on the case and be done with it.

Point.
Jerry
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Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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Marcus Leech wrote:

The other components to carry would be a rubber sleeve and a flanged aluminum bushing to adapt "standard" 98mm hardware to your new tubes.
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The O5100 is *not* 152 mm (6"). It's more like 160 mm. I have a rocket with 6" mount that I built in 1995 and the O5100 *will not* fit. CTI is very misleading calling it 152 mm.
Tom
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snipped-for-privacy@propulsionpolymers.com (Marcus Leech) wrote in message

Sure it is, but overkill means a huge margin of error and less CATO's. Especially for EX guys. I've run 115's WAY higher than 1200psi.....
It is also standard size drawn tubing and uses standard casting and liners... you have to weigh time vs. motor mass.
-D
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