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  #81  
Old 04-16-2012, 10:22 PM
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SEL SEL is offline
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Quote:
Originally Posted by Carl@Semroc
I am still working on the Ex numbers and decided to put the 29mm back in. It turns out our current machine will make 29mm engines up to 3.25" long. It will take a totally new machine to go over 3.25" (bummer!)

I had missed the fact that Centuri bought the Coaster engine machine that made 1.0625" (27mm) x 8" long engines and sold them for a short while and then changed over to 1.125" (29mm) x 7.75" and 4.75". There was quite an evolution over a few year period.

1963
1.062" x 8" F11-3 49N-sec It and 54 sec Isp (low grade BP) same as Coaster 20lb

1964 1965 1966
1.062" x 8" F11-3 49 N-sec It and 54 sec Isp (still low grade BP ) called Hercules
1.062" x 5" E3.3-2 29 N-sec It and still low Isp called Atlas

1967
1.125" x 7.75" F14-4 37 N-sec It and 65 sec Isp ( higher grade BP) now called MINI-MAX 'PB'
1.125" x 4.75" E3.5-4 25 N-sec and 64 sec Isp now called MINI-MAX 'PB'

1969
1.125" x 7.75" F94-4 52.5 N-sec It and 85 sec Isp (highest grade BP) (metric labelling)
1.125" x 4.75" E7-4 25 N-sec and 54 sec Isp (large throat)

1971
1.125" x 7.75" F16-4 57.8 N-sec It and 94 sec Isp (highest grade BP) End burning
1.125" x 4.75" E15-4 39.6 N-sec and 83 sec Isp

1972
replaced by Enerjets, new case sizes are 1.125" x 3" and 5"

The LT-110 was the engine tube for the early Coaster engines and was replaced by the LT-115 for the 29mm engines and Enerjets.

The new engine survey shows some decision points. The 3/4E21 at 26 N-sec is the largest with 30.0 g or less of propellant. So all the 29mm engines in the 2.75" long casing would be able to be mailed via USPS ground with no additional charges. The full E20 at 3.25" and the 3/4F19 would have to be shipped with HAZMAT. The 3/4F19 at 62.5 g of propellant would be the largest we would ever make. The BATFE discussions we have had made us decide to never go more than 62.5g. We would have to sell them to certified users only, HAZMAT fees, and track each engine from cradle to grave. As long as we keep each engine under 62.5 g, we only track them until they are produced. Once they are packed in the casings, the BATF has no further interest in the BP or the engines.

Let us know what you think about the 29mm engines.



I'm in!!


S.
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  #82  
Old 04-02-2013, 07:33 PM
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gpoehlein gpoehlein is offline
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I know this thread has been dormant for a couple of years now, and I was just wondering if any more progress has been made on this or if motors from Semroc is a totally dead issue? If it is dead, I can completely understand that Carl and crew are putting their energies into producing more and better models. But I would still love to see a few of the low powered motors brought back into production that have not been available for a very long time. At this time, I would love to see the S motors brought back - I know we can use T motors in adapters, but an A10-3T is not the same as an A8-3S in a classic model that was originally designed for the short motors (such as the Midget).

Just out of curiosity, is there enough room in an 18mm short casing for the delay and ejection of an A8-5? And a 1/2A6-4S would be awesome for low power two stagers as well!
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  #83  
Old 04-02-2013, 07:48 PM
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If you use the current Estes thin wall casings (I.D. 0.500"), it is about 1Ż" from the front of the casing to the front of the clay cap over the ejection charge. Estes did offer A5-0S, A5-2S, and A5-4S motors in the 1970, 1971 (both editions), and 1972 catalogs.
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  #84  
Old 04-02-2013, 09:18 PM
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Quote:
Originally Posted by gpoehlein
At this time, I would love to see the S motors brought back - I know we can use T motors in adapters, but an A10-3T is not the same as an A8-3S in a classic model that was originally designed for the short motors (such as the Midget).

Just out of curiosity, is there enough room in an 18mm short casing for the delay and ejection of an A8-5?
I have used, with great results, sawed-off A8-5's and B6-0's. So you should have no problems using a cut-down A8-3 should you try it.

I stuffed some wadding into the end of the motors while I was cutting them to make sure a spark from the sawing process didn't set off the any stray powder.

Quote:
And a 1/2A6-4S would be awesome for low power two stagers as well!
No doubt, a ŻA6-4 would be a great companion to the current ŻA6-2, but I'm afraid the better (ie, more realizable) answer is a ŻA3-4T adapted up to 18mm.

Doug

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  #85  
Old 04-02-2013, 09:54 PM
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Quote:
Originally Posted by Doug Sams
I have used, with great results, sawed-off A8-5's and B6-0's. So you should have no problems using a cut-down A8-3 should you try it.

I stuffed some wadding into the end of the motors while I was cutting them to make sure a spark from the sawing process didn't set off the any stray powder.

No doubt, a ŻA6-4 would be a great companion to the current ŻA6-2, but I'm afraid the better (ie, more realizable) answer is a ŻA3-4T adapted up to 18mm.

Doug

.


No can do - the only place I get to fly is at our club launches, so NAR rules are always in effect (no modified motors). So cutting down a regular motor is not an option. And I thought of using the adapter with a 1/2A3-4T (I have the Semoc Midget that comes with T motor adapter sleeves), but as with using the A10-0 and A10-3T, it adds weight to the motor end of the model that wouldn't be there with an S motor using the current style casings. Granted, not a big deal, but still worth thinking about.

Greg
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  #86  
Old 04-03-2013, 01:49 AM
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blackshire blackshire is offline
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Quote:
Originally Posted by gpoehlein
No can do - the only place I get to fly is at our club launches, so NAR rules are always in effect (no modified motors). So cutting down a regular motor is not an option. And I thought of using the adapter with a 1/2A3-4T (I have the Semoc Midget that comes with T motor adapter sleeves), but as with using the A10-0 and A10-3T, it adds weight to the motor end of the model that wouldn't be there with an S motor using the current style casings. Granted, not a big deal, but still worth thinking about.

Greg
And don't forget the Centuri birds that were designed for the shorties--the original Lil' Herc and the Firefly two-stager! Maybe Carl could make a vacu-formed (or cast polyurethane resin) version of the new Estes two-piece red plastic motor adaptors, but sized to "convert" 13 mm mini motors to shorty S motors. Also:

Regarding your NAR club difficulty (Re: using "cut-down" shorty motors at club launches), I see a niche market for motor, er...re-printing... I'm a NAR member, too, but if one -secretly- breaks a rule that is a "victim-less crime" anyway, I have a hard time working up righteous indignation against violators. To me, it just isn't in the same category as, say, launching rockets at angles of less than 30 degrees to the local vertical, or launching flammable or explosive payloads--those are clearly dangerous activities, while using "cut-down" S motors is a "paper/political" violation. If I were in your situation, I'd keep my own counsel and enjoy some S motor nostalgia flying.
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Last edited by blackshire : 04-03-2013 at 01:59 AM. Reason: This ol' hoss done forgot somethin'.
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  #87  
Old 04-03-2013, 02:46 AM
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Quote:
Originally Posted by gpoehlein
...but as with using the A10-0 and A10-3T, it adds weight to the motor end of the model that wouldn't be there with an S motor using the current style casings. Granted, not a big deal, but still worth thinking about.
Greg,

Most of the old motor cases had extra thick walls, similar in thickness to a T motor inserted into a spent case. The mass is fairly close. I've flown stock Midgets using the 18-mm adapted combo of A10-0T to ŻA3-4T many times with no stability issues.

Doug

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  #88  
Old 04-03-2013, 03:23 AM
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Quote:
Originally Posted by Doug Sams
Greg,

Most of the old motor cases had extra thick walls, similar in thickness to a T motor inserted into a spent case. The mass is fairly close. I've flown stock Midgets using the 18-mm adapted combo of A10-0T to ŻA3-4T many times with no stability issues.

Doug
I had equally good results flying an Estes Sprite clone using a 13 mm-to-shorty "conversion" motor adaptor made from BT-5 with two centering rings and a mini motor clip. It could also be used in an original (shorty motor powered) Centuri Lil' Herc. It would even be "NAR Kosher" for club launches if a streamer was taped to the mini motor adaptor's BT-5 tube and wrapped around it before the adaptor was slipped into the rocket; the shorty motor adaptor would descend under its streamer while the Lil' Herc used tumble recovery as per its design.
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http://www.lulu.com/product/cd/what...of-2%29/6126511
All of my book proceeds go to the Northcote Heavy Horse Centre www.northcotehorses.com.
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Last edited by blackshire : 04-03-2013 at 03:28 AM. Reason: This ol' hoss done forgot somethin'.
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  #89  
Old 04-03-2013, 09:29 AM
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Would also REALLY like to know if we are going to see any sort of Semroc motors in the NEAR future.
I for one would gladly like to see them come out with say half a dozen new motors not on the market (one of which MUST be the B14) soon rather than any new kits.
The LPR/MPR market needs new MOTORS far more than kits.
They already offer more kits than all the other major LPR/MPR suppliers combined.
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  #90  
Old 04-03-2013, 11:33 AM
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Quote:
Originally Posted by Doug Sams
I have used, with great results, sawed-off A8-5's and B6-0's. So you should have no problems using a cut-down A8-3 should you try it.

I stuffed some wadding into the end of the motors while I was cutting them to make sure a spark from the sawing process didn't set off the any stray powder.

No doubt, a ŻA6-4 would be a great companion to the current ŻA6-2, but I'm afraid the better (ie, more realizable) answer is a ŻA3-4T adapted up to 18mm.

Doug

.


Indeed, after accidentally flying a couple of 1/2A6-4's in an Astron Scout at NARAM-50 (didn't realize they were LONG decertified), and finding they were the PERFECT motor for the Scout, I've used adapted 1/2A3-4Ts in it for even better flights.
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