24mm and 29mm motor mounts

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Jan 18, 2009
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I just got a couple new motors a 24mm G37-6 and a 29mm G35-6 they are made by Ellis Mountian Rocket Works and i was wondering how to make my motor mounts versitale to fire a D-12 then turn around and fire a 7inch long G37 and the same for my 29mm?
Don't put a thrust ring in your motor mount. Use a built up tape thrust ring.
Same as hokkyokusei said, don't put a thrust ring in the motor tube. Although, if you want to be able to switch between a 29 and 24mm mount, permanently attatch the 29mm mount and use an adapter when you fly 24mm motors. Loc/Precision sells adapters for this config. By the way, where did buy the new G37's? I have yet to see anyone stock them.
Do I Build up the tape on the back of the motor so it locks in place? Im used to the Estes motor hooks and stuff
I bought the G-37 at a launch in Elsberry Mo. from Giant Leap
What you'll do is build up a wedge using tape (usually masking tape) so that the motor jams into the mount firmly (hard enough that you can't easily pull it out). The trick is to get it tight enough that it doesn't kick out when the ejection charge fires, but loose enough that you can still pull it out with a light grip with pliers. That's a basic friction fit.

You can also buy motor retention kits if you want to go that route. Those screw in to hold the back of the motor in place, but I don't know much more about them. Anyone else want to field that one?

The motor retention kits that wwattles mentioned will keep your motor from kicking out the back, but you'd still need to use masking tape or something as a thrust ring or motor block.

The other option (assuming these are to be used as midpower rockets, not going any bigger than the 29mm 40-120 casing) is to install one of the Aerotech motor hooks. That will eliminate the problems with retention in both directions, and still accomodate the 24/29mm motors you'd be using. Might want to check it against the length of the G37 beforehand though, but I wouldn't think it would be any longer than a G33...

One thing that works very good for thrust rings is 1/4" wide tape. You can find this at some craft stores but usually at automotive paint supply stores. The tape is used for pinstriping. I just put a couple of wraps of 1/4" wide tape around the casing at the nozzle end and it works just as well as any RMS casing.
Another method as far as a thrust ring goes is.
Install a permanent thrust ring at the fdw end of your engine tube to fit your longest motor.
Now take an old used D motor and cut a spacer to be inserted against your thrust ring when using the shorter D motor.
Motor retention at the aft end can be as simple as a blind nut epoxied into the aft cener ring and a small bolt with a screen door window clip thingy to go into nut and onto end of motor.
I put 2 of these 180 degrees apart but only use 1. the other is a backup in case one nut comes loose or threads get buggered up.
on my 29mm ill be useing singel use motors so is a F shorter than a G and a H is longer? Do you use a thrust ring on a 29mm this is new to me
Single use motors do not have thrust rings on them like the reload casings do. If you plan on flying HPR (H and above), you'll want to invest in reload casings. I would say the same for midpower, to tell you the truth. Cost per flight is much lower with reloads.

As to the rest of your question...Since single use does not have a thrust ring, you'll either need to make one on the motor with tape, or install some sort of thrust ring. The method described with installing one for the longest motor you'll use then use adaptors is a good one. If you plan on using reloads, you'll only need to have some sort of retention method to keep the motor from kicking out of the rocket when it firest the ejection charge.

As for motor lengths, larger letters typically are longer motors. But not always. I believe the Aerotech motor matrix has the motor lengths on it...

not to hijack this thread but after talking to a few of my friends im really confused...

what is the highest power engine you can get without any licsence? (spelling)... age doesn't matter because my parents will be more than happy to order... i hope...
AT SU: G80
Pro38: G69 (more expensive than the AT stuff)
Ellis Mountain has some G motors, but I am not sure what they're designated as...

Thanks guys that was a help. Now Im off to work on my 29mm Crayon:D