Motor mount

You know I thought about constructing a motor mount out of light ply and using a copper pipe for the tube itself. It would displace the heat and really not add that much weight if you pick a pipe that was fairly thin. I think it would be a unique construction design and would be a good conversation piece.

Cue the safety code wailing and gnashing of teeth.

Copper is one of two metals specifically allowed in high power rockets.

Heat from a motor into a phenolic MMT is not an issue.
You're trying to solve a problem that does not exist.

FredA said:

Heat from a motor into a phenolic MMT is not an issue.
You're trying to solve a problem that does not exist.

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Good point, but it would be no different than someone over building a mid-power kit with 5 lbs of epoxy and 1/2" eye bolts and anchors. Really no point in over building something like that. If anything a copper tubing would at least enhance the appearance of the business end of the rocket, without adding much weight.

FredA said:

Heat from a motor into a phenolic MMT is not an issue.
You're trying to solve a problem that does not exist.

Click to expand...

Also, with copper being better at conducting heat than phenolic or paper, the outside of the copper tube will get hotter than either of those.

Steve Shannon said:

Also, with copper being better at conducting heat than phenolic or paper, the outside of the copper tube will get hotter than either of those.

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what about aluminum?

My concern would be getting glue to stick to the copper. Granted, scuffing and cleaning would be needed, but I would also use a counter bore at the forward end to encase the tube. Kind of like a thrust plate, just at the other end.

AfterBurners said:

what about aluminum?

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Both aluminum and copper are very good heat conductors. Phenolic and paper are very good insulators.

If you want to save weight where you need it least you don't even need a tube. Centering rings will suffice, you'll just lose the ability to glue fin tabs to said tube...

Otherwise, if you do go with copper, Rocketpoxy, at least in my testing, bonds to it just fine..

JB Weld will take care of buisiness too, and wouldn't care about the heat.

FredA said:

Heat from a motor into a phenolic MMT is not an issue.
You're trying to solve a problem that does not exist.

Click to expand...

Not now, but it might be a problem in the future. Take a look at the proposed changes to NFPA 1125 (see Next Edition tab). One removes all temperature limits for non-metallic casings.

UhClem said:

Not now, but it might be a problem in the future. Take a look at the proposed changes to NFPA 1125 (see Next Edition tab). One removes all temperature limits for non-metallic casings.

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Even if NFPA does remove temperature limits, I'd much rather have an insulator between the hot part (motor casing) and the temperature-sensitive parts (everything else). The only exception would be if the conductor was enough mass to be an effective heat sink. That would require a lot more fin area though, so it might not be an improvement.

Are there copper or Al tubes that meet the specs for a motor mount tube?

Mugs914 said:

JB Weld will take care of buisiness too, and wouldn't care about the heat.

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Love Ya Mugs... But... I can't get any even halfway decent (bonding wise, especially with dissimilar materials) results out of JB. Only thing I've ever used it for is At style motor mounts and the way they're designed with all the grooves/surface area you'd probably get away with Elmers School Glue.