Does inserting an engine in the drying motor mount prevent tightness or not?

I have built a few rockets that have very tight motor mounts. I read on here before that some recommended putting a motor which is unfired(fatter) into the rocket while the mount is drying so that it will not shrink. My gauchito, redstone, and eagle are all very tight. The eagle is totally unusable can't even get the motor in. The red stone isn't so bad,, although every time I get the motor in I think I'm going to squash the rocket into oblivion.. The gauchito lets the motor in about 3/4 of the way which seems ok, it still flies just fine. Just wondering because I may build another eagle and try this techniqure.

I do not know about the others but I did have a problem with my Eagle in that it was very difficult (if not impossible) to get any motor (new or spent) into the motor mount after the build.

The design of the Eagle is such that a plastic bulkhead fits on the end of the motor mount. Depending upon the type and amount of glue used to secure this connection the plastic expands which causes the problem.

To fix I simply took a number 11 exacto knife and shaved away at the plastic to expand the hole. After just a few shaves and test fits the motor fit just fine.

Hope this helps!

Michael

Most of my older motor mounts are very tight. I think they get tighter with use.

Originally posted by stizzed
I do not know about the others but I did have a problem with my Eagle in that it was very difficult (if not impossible) to get any motor (new or spent) into the motor mount after the build.

The design of the Eagle is such that a plastic bulkhead fits on the end of the motor mount. Depending upon the type and amount of glue used to secure this connection the plastic expands which causes the problem.

To fix I simply took a number 11 exacto knife and shaved away at the plastic to expand the hole. After just a few shaves and test fits the motor fit just fine.

Hope this helps!

Michael

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I'm glad I saw this thread, since I'm building an Eagle right now and am at the step where I'll be installing the plastic rings on the motor tube.

Quest motors are just a little bit smaller diameter than Estes. so if Estes motor is a tight fit, try a Quest motor.

also, you can peel a layer of paper off of the motor to make it smaller diameter.

The Estes Mercury-Redstone also has a plastic bulkhead ring at the base of the rocket body, and the motor fits in there VERY snugly.

I had to work around the flange of the bulkhead with a Dremel to loosen it up a bit. After that, it was OK. Then the dang thing got stuck in a tree.

Originally posted by LtSharpe
I have built a few rockets that have very tight motor mounts.

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There are only two reasons for this to occur. Motors sometimes have bulges resulting in a tight fit. Sometimes sanding the motors is required.

The other reason is due to getting carried away putting fillets on MMT centering rings. When the glue shrinks, it creates a bottle neck in the tube. I've learned this from personal experience. The first eight or ten MMT's I built as a BAR all had marvelously strong motor mounts, and they needed to be strong to withstand the hammering required to get the motors in

If I was to place a bet, I'd wager you need to use a little less glues on the rings.

Doug

Originally posted by doug_man_sams
There are only two reasons for this to occur. Motors sometimes have bulges resulting in a tight fit. Sometimes sanding the motors is required.

The other reason is due to getting carried away putting fillets on MMT centering rings. When the glue shrinks, it creates a bottle neck in the tube. I've learned this from personal experience. The first eight or ten MMT's I built as a BAR all had marvelously strong motor mounts, and they needed to be strong to withstand the hammering required to get the motors in

If I was to place a bet, I'd wager you need to use a little less glues on the rings.

Doug

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Doug,

I know of one more reason, and so do these other guys who have built Estes X-Prize Eagles. The plastic centering rings are just too tight to fit easily over the ends of the motor tube.