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Model Forum / General / Rockets / December 2003On Topic.... Motor block question
Hi All, Is the motor block really necessary in an Estes motor mount? Or can the little green paper ring be omitted and a drop of Tite Bond be smeared on the tube to stop the motor hook from tearing forward? John Hornsby If you are using the engine hook for retention then you really *should* use the engine *block* as well. If you were to use *epoxy* to secure the hook, this may not be necessary, but not tite bond. *however*, if you choose to use "friction fit", then you can eliminate the engine block AND hook all together. Most of my models use friction fit as I never seem to have hooks laying around when I need them... jim > Hi All, > [quoted text clipped - 3 lines] > > John Hornsby Thank you very much, Mr. Flis. And also keep up excellent work on those very cool kits. I can't wait till pay day as I'm most definitely going to place an order. :o) John Hornsby > If you are using the engine hook for retention then you really *should* > use the engine *block* as well. If you were to use *epoxy* to secure [quoted text clipped - 13 lines] > > > > John Hornsby the engine block functions like a thrust ring, transferring the power to the airframe. To omit it in favor of friction fit means the friction is needed to not only prevent backward ejection of the motor (either falling out from garvity or in reaction to the ejection charge), but also to prevent the motor from flying through the inside of the airframe and coming out the top. just something to bear in mind when considering exactly how much friction you will actually need. if you omit the enine block, I would wrap several turns of a thin masking tape (you can get 1/8 and 1/4" at arts and crafts store, or a good stationery store), around the base of the motor, then a few turns of normal 1/2 or 3/4" tape to provide the friction. like so: +----------------------------- ===| ===|------------------------- MMT ===XXXXXX friction tape +----------------------+ | motor | +----------------------+ ===XXXXXX friction tape ===|------------------------- MMT ===| +----------------------------- where the === is the 1/4" wide buildup beyond the motor tube diameter to function as a "thrust ring", and the XXXXX is the 3/4" wide (less) buildup for a tight fit in the motor tube this way you would have both power transfer with less risk of the motor moving forward in the MT than what the friction fit would provide, and the friction fit to prevent the motor from falling out or being forced out by the ejection charge - iz > If you are using the engine hook for retention then you really *should* > use the engine *block* as well. If you were to use *epoxy* to secure [quoted text clipped - 14 lines] >> >> John Hornsby > the engine block functions like a thrust ring, transferring the power to > the airframe. To omit it in favor of friction fit means the friction is [quoted text clipped - 35 lines] > > - iz On Estes kits? Are you kidding?... No thrust ring required. A little practice on friction fit, and you'll never use any kind of thrust ring *inside* the MMT again.... now a little extra wrap of 1/4 or 1/8 inch masking at the aft end is about the nearest I would come to a thrust ring. If an internal MMT thrust ring is used, you limit your motor options. I friction fit everything I have through G range... not yet had a single frictionfit-related failure. ~ Duane Phillips. > > If you are using the engine hook for retention then you really *should* > > use the engine *block* as well. If you were to use *epoxy* to secure [quoted text clipped - 14 lines] > >> > >> John Hornsby I didn't think you would need it with the way the motor hook is on the Estes kits. Now, the Custom motor hooks, those things need take rubber bands and almost need to be glued in to hold somewhat ok. John > > the engine block functions like a thrust ring, transferring the power to > > the airframe. To omit it in favor of friction fit means the friction is [quoted text clipped - 66 lines] > > >> > > >> John Hornsby > I didn't think you would need it with the way the motor hook is on the Estes > kits. Now, the Custom motor hooks, those things need take rubber bands and > almost need to be glued in to hold somewhat ok. > > John You don't need the hook either. 1) They don't last. 2) Replacement is a pain (extreme understatement). 3) It adds weight to the aft end, where you don't need it. 4) The forward end of the hook limits motor options. 5) Try using an AT RMS casing in a rocket with an Estes hook... the forward end scratches and gouges the delay forward closure. Yes, it can be remedied... but why bother with the hook at all? 6) Having a hook in the thust stream can ruin otherwise perfectly vertical flight. 7) The hooks do not always retain the engine.... hot hook... ejecting engine... Need I go on? I find that a good friction fit with masking tape works perfectly for average G and smaller motors. ~ Duane Phillips. > > > the engine block functions like a thrust ring, transferring the power to > > > the airframe. To omit it in favor of friction fit means the friction is [quoted text clipped - 69 lines] > > > >> > > > >> John Hornsby > You don't need the hook either. > [quoted text clipped - 5 lines] > end scratches and gouges the delay forward closure. Yes, it can be > remedied... but why bother with the hook at all? With the cost of the 18mm hardware and reloads have me off of the idea of that. Three reloads for 15 bucks versas 5 bucks at Wally World. Not to mention that I have this very bad habit of feeding the tree gods on a regular basis. I've already lost too many 24mm cases to them for comfort. At least I should say, to live a comfortable life with the wife. Yes that many. :o) John > 6) Having a hook in the thust stream can ruin otherwise perfectly vertical > flight. [quoted text clipped - 90 lines] > > > > >> > > > > >> John Hornsby > > You don't need the hook either. > > [quoted text clipped - 13 lines] > least I should say, to live a comfortable life with the wife. Yes that many. > :o) This raises the obvious question. AeroTech designed the 18mm RMS specifically to retrofit the Estes products. So why doesn't it fit? And why do they get called errortech so often? And why do they keep filing bankruptcy? Inquiring minds want to know. Jerry  SignatureJerry Irvine, Box 1242, Claremont, California 91711 USA Opinion, the whole thing. <mail to:01rocket@gte.net> Please bring common sense back to rocketry administration. Produce then publish. http://www.usrockets.com My articles valuable? Donate at iKobo.com c/o my email. "> This raises the obvious question. AeroTech designed the 18mm RMS > specifically to retrofit the Estes products. So why doesn't it fit? > [quoted text clipped - 5 lines] > > Jerry Absolutely! John > This raises the obvious question. AeroTech designed the 18mm RMS > specifically to retrofit the Estes products. So why doesn't it fit? Doh. Because you have to take the "Estes" motor out first. ;) > And why do they get called errortech so often? What does this have to do with motor blocks? > And why do they keep filing bankruptcy? What does this have to do with motor blocks? > Inquiring minds want to know. What does this have to do with motor blocks? Inquiring minds want to know. Cheetah > > > You don't need the hook either. > > > [quoted text clipped - 16 lines] > This raises the obvious question. AeroTech designed the 18mm RMS > specifically to retrofit the Estes products. So why doesn't it fit? ours fit, without modifying the hook > And why do they get called errortech so often? because end users never want to blame themselves? > And why do they keep filing bankruptcy? They've done so more than once? > Inquiring minds want to know. I tried Jerry, anything else minds want to know? SignatureTater President of MARS Club (NAR #660) www.treece.org/mars.htm KC9ESF NAR #79654 L1 AMA #747769 EAA #703312 remove spam spelled backwards to reply Duane, your post reminds me of one I saw about fin fastening the group was going into the finer points of fin fastening, including filleting with fiberglass strips and carbon fibers mixed in the epoxy, fillets both outside the body tube and where the fin joins the motor tube, etc. etc. someone (I think an EX flyer from an Arizona club) popped in and said he never bothers with fillets at all. He just puts a few holes in the fins in the area that is between the body tube and motor tube, and uses two-part expanding foam, saying the foam has enough adhesion, stiffness and strength to hold the fins just fine, and never had a fin come off a rocket (and he flew pretty big motors) there was a dead silence in the thread after that - iz :) >>if you omit the enine block, I would wrap several turns of a thin >>masking tape (you can get 1/8 and 1/4" at arts and crafts store, or a >>good stationery store), around the base of the motor, then a few turns >>of normal 1/2 or 3/4" tape to provide the friction. > On Estes kits? Are you kidding?... No thrust ring required. A little > practice on friction fit, and you'll never use any kind of thrust ring [quoted text clipped - 5 lines] > I friction fit everything I have through G range... not yet had a single > frictionfit-related failure. jhijack |
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