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blackshire
04-14-2010, 07:15 AM
Hello All,

I'm wondering if anyone else has also had the following problem: I bought an Estes EX-200 RTF rocket last week (it uses the same fin unit & tailcan as the shorter Moon Mutt kit) and upgraded its rubber band shock cord to a Kevlar/round elastic shock cord.

Alas, none of my mini motors will *quite* fit in the rocket! My Estes A3-4T and A10-3T motors, which are about 12 years old, are about a millimeter too long (judging by the gap between the motor lock ring and the tailcan) for the flanges on the lock ring to slide behind the flanges on the rear edge of the tailcan.

There is no dried glue or other debris up inside the front end (or the rear end) of the tailcan to prevent the motors from sliding all the way forward and butting against the forward retainer pins, nor have the motors' cases expanded due to humidity. My only guess is that Estes may have changed the mini motor case length slightly since my motors were made (perhaps shortening it a tiny bit to a "hard-metric" length?).

Shreadvector
04-14-2010, 08:45 AM
There is no change in the motor length at all.

I have seen this "condition" before (other models use the same aft end parts) and it is simply a tight fit of the motor.

The "fix" is to either "roll" away the burr on the leading edge of the motor casing and/or simply push the butt ring on firmly until it pops into position - then rotate it to lock.

CPMcGraw
04-14-2010, 01:25 PM
Hello All,

I'm wondering if anyone else has also had the following problem: I bought an Estes EX-200 RTF rocket last week (it uses the same fin unit & tailcan as the shorter Moon Mutt kit ... none of my mini motors will *quite* fit in the rocket! ... about a millimeter too long ...

Yes. Some of their last 800-series kits, like the Bandito, used the same (or similar) fin can parts, and have had the same problem since they were introduced. The length measurement for the casing was obviously short, and no one caught it before RTM.

blackshire
04-15-2010, 12:20 AM
There is no change in the motor length at all.

I have seen this "condition" before (other models use the same aft end parts) and it is simply a tight fit of the motor.

The "fix" is to either "roll" away the burr on the leading edge of the motor casing and/or simply push the butt ring on firmly until it pops into position - then rotate it to lock.The lock ring on this one requires so much force to "force-fit" it (even with the burrs removed from the motors) that it would probably fracture. I'll cut notches in the front edges of the motors that the retainer pins will fit into.

blackshire
04-15-2010, 12:24 AM
Yes. Some of their last 800-series kits, like the Bandito, used the same (or similar) fin can parts, and have had the same problem since they were introduced. The length measurement for the casing was obviously short, and no one caught it before RTM.I'm sorry to hear that; I'd prefer that this was just my problem (with a fluke "bum" rocket) than everyone's. It sounds like an English/metric conversion error may have happened in a factory far, far, away... :-)

Initiator001
04-15-2010, 01:59 AM
The lock ring on this one requires so much force to "force-fit" it (even with the burrs removed from the motors) that it would probably fracture. I'll cut notches in the front edges of the motors that the retainer pins will fit into.

That's what I had to do. :(

Bob

BEC
04-15-2010, 02:34 AM
My Moon Mutt is fussy about this as well, though apparently not quite as bad as BlackShire's EX-200.

CPMcGraw
04-15-2010, 12:09 PM
That's what I had to do. :(

Bob

That's what I had to do, too. Very shallow "V" notches with a #11, or a few swipes with a "V"-shaped rattail file.

blackshire
04-15-2010, 07:19 PM
My Moon Mutt is fussy about this as well, though apparently not quite as bad as BlackShire's EX-200.The fin assembly of my EX-200 must have been molded at or near one end of the mold's "dimensional tolerance bracket" (either a brand-new mold or a worn-out one). :-)

I may file off the forward motor retainer pins so that the longer Quest 13 mm mini motors will fit all the way into the fin can. (A rear thrust ring made of 1/4" wide masking tape could be taped onto the rear end of the motor, and this could be retained against the rearward kick of the ejection charge by applying a wrap or two of 1/2" wide masking tape around both the rear end of the motor *and* the rear end of the fin can.)

LeeR
04-15-2010, 11:17 PM
I'm sorry to hear that; I'd prefer that this was just my problem (with a fluke "bum" rocket) than everyone's. It sounds like an English/metric conversion error may have happened in a factory far, far, away... :-)

More than likely sloppy mold design, not enough allowance for shrinkage.