I liked and flew Estes Series III engines back in the late '60's. I put away my rockets "temporarily" in 1971, when shorties were still in production. I was surprised and dismayed when I resumed flying in 2004 and found that these engines were not being made anymore. How was I going to fly the replacements for my beloved Midget and my dearly missed Sprite that I was planning on building if there were no shorties?
I read about trimming the cases of Estes 1/2A, A and B motors, and figured that eventually, that was what I was going to have to do. But this posed a real ethical problem for me, because I was always a firm believer in the Model Rocketry Safety Code. And when I finally joined NAR a couple of years ago, I pledged to uphold that code. What did it mean to be a member of NAR if I wasn't going to follow the Code?
I was "thumbing" through old Estes catalogs online at Ninfinger when it finally dawned on me: Estes Industries never stopped making shorty engines! They continued to produce them all through the '70's, '80's and '90's, and the present-day Estes-Cox Corporation is still cranking out them out by the truckload even today. We have all purchased and flown packs of them, and it's a good bet that almost everyone who reads this post has a stash of them in their engine box.
So why does everyone say that Estes Series III "shorty" engines are out of production? Well, because they are - the older 18mm diameter versions of them, that is. In the early '70's, the Damon-owned Estes Industries introduced a new, updated version of the Series III engines. They reduced the size of the case, making the engines more efficient by trimming away some of their dead mass, and also making the engines more versatile, allowing new rocket designs that were not possible with the old version. They called the new version shorty engines Mini-Brute "T" engines. Yes, that's right - the 13mm mini "T" engines produced by Estes ARE their "Shorty" engines, but in a redesigned case. Estes has been producing mini "T" motors continuously since their introduction in 1971. These are the shorty engines, and they never went OOP.
If you want to build a clone of, say, the Estes Sprite, you can still fly it on a current-production shorty engine - you just have to adapt it to fit the repro Sprite's engine tube. You can fly the sustainer stages of repro (or even original) Midgets and Betas the same way. Although Estes still makes 13mm diameter shorty engines, they currently do not make booster versions, which is truly unfortunate, and also a bit incomprehensible. There are stashes of A3-0T and A10-0T engines here and there in the retail channel, so one can still buy small quantities of them with a little bit of hunting around. They are no longer certified by NAR, but that is apparently due entirely to the fact that they were no longer being produced, and not due to any flaws in the engines themselves. I flew a cloned Mini-Brute Midget with an A3-0T in the booster at an official "Old Motor Test Launch" held by my section a couple of years ago, and it performed beautifully. Which leads to a question: whatever happened to the Old Motor Test Program? Is it still being conducted? Has NAR S&T collected enough data yet to draw any conclusions and make any decisions? If not, then let's set up some more Old Motor Test Launches and generate some more data! In fact, let's generate a lot more data! And let's keep the pressure on Estes to start producing short-length 1/2A and A booster engines again.
Mark \\.
