Motor Mount Tube Length

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MarkABrown

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How critical is the motor mount tube length? Is it a big deal if the engine sticks out past the end of the MMT? I was looking at some of the Hybrid motors that are available and noticed that no MMT that I've seen will be long enough for those.
 
>>I was looking at some of the Hybrid motors that are available and noticed that no MMT that I've seen will be long enough for those.<<

Most of the time, you will build a rocket *FOR* a hybrid motor, not get a hybrid motor for a rocket. I like the idea of the MMT holding the entire motor and tank. I modified a 4" Yank IRIS for Aerotech Hybrid motors, and made sure that the entire length of the motor was secured in the MMT.
 
That's kind of my opinion too. I'm starting to design a new scratch-built rocket and I'm going to design it with a hybrid motor in mind. My only complaint is that those long motor tubes really take up alot of the payload bay! You have to design these rockets really long in order to get any usable payload bay space. :)
 
Mark,

I always thought that the extra length needed for Hybrids was a plus. The extra length should help with the problems caused by the CG shifting during flight as the N2O is used up.

OBTW has anyone else heard a rumor that Cesaroni is coming out with a 500 to 600 N/S class "I" HyperTek motor?

Ken Holloway, NAR #78336, L-1
 
I hadn't heard that one yet. Sounds interesting though. The one I'm watching carefully is the 38mm "I" motor from Propulsion Polymers. It's currently in the process of being certified by Tripoli and the cost of this motor is significantly less that the HyperTek motors.
 
That sounds interesting, does it use the "floating injector" design like R.A.T.T. works "H", "I", and "K" class motors? I understand that the ground support equipment for "floating injector" motors is less than 1/2 the cost of HyperTek's GSE.

Ken Holloway, NAR #78336, L-1
 
Yes, I believe it does use the floating injector design. At least, that's the way it appears to me. It doesn't really say on their website.
 
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