AeroTech Arreaux motor fit

[McRick]

So after buying this kit nearly 8 years ago, I've started to build an Arreaux. When building the motor mount, I've noticed that if you put the retainer hook where the directions indicate that an AeroTech 29 40-120 doesn't fit all the way in. It sticks out about 1/4 inch from the end of the mount. It also has about 3/4 inches of play in that the hook won't "grab" it until it has dropped out of the back another 1/2 inch.

Normal, or has anyone done anything different to retain this motor?

Thanks!

Rick

 

[fyrwrxz]

If it's not too late-ditch the clip and motor block-aeropack retainer. If built- wrap some tape to take up the slack so it doesn't slam back and past the retainer. I also eliminate the metal mesh. Dog barf or nomex. Replace the underwear elastic with kevlar BEFORE you glue it in the tube-it's too far down to fix later without cutting open the patient after it fails (and it will)

 

[ksm2001]

Agree with fyrwxz, This was my first MPR build and still a great rocket to fly. I just wish I would have left out the motor hook, thrust ring, thrust ring flange, mesh and ejection baffle shoulder. You will be limited to what motor casings you can use if you install these parts. My 29 40-120 fits in mine but I'm not sure if I used the motor casing as a guide for fitting the pieces first or if I went with measurements off the instructions. I like to dry fit first before gluing parts to make sure they fit.

It could also be that the motor hook is hitting the top of ejection charge part of the case, if it is and you already have it assembled use a file to take a bit off so it fits.

In any case ditch these parts if its not to late.

I'm in the process of making mine as a duel deploy but limited to the 29 40-120 case length. The plugged closure for the 29/40-120 casing wont allow the motor to fit either so I have to use motor ejection deploy for the drogue chute (or both motor and altimeter as redundancy for drogue) and altimeter for the main.

Ken

 

[McRick]

It's not too late, I was just messing with dry fitting. I see a PML and Loc Precision version for 29mm. Oh and there's also a plastic Estes version. Which one would you use? I'll pick up some Kevlar too and leave out the "canned" ejection system and just use nomex.

I'm glad I asked as you guys have made some terrific suggestions. Thank you!

 

[chadrog]

If the motor tube is recessed into the body a bit, you could do this: cut two rectangles out of the motor tube near the end.

Put a 1" hose clamp on it.

Taa-daa. Believe it or not, a rocket can fly without an aeropak retainer. This has never failed me where I've used it, total cost is about a dollar.

 

[dpower]

Rick,

This doesn't seem right. I've built a bunch of the Aerotech 1.9" kits, and if IIRC, the RMS case should fit with the hook without much slop. The RMS case length is 4 7/8", same as a modern Single Use "G". The hook should fit in the slot of the rear closure. The aft closure of the RMS case will not seat against the motor tube, unlike the Single Use motors, but this is ok with a stock build, as the motor block acts as a thrust ring.

For my recent Aerotech kit builds, I no longer use the hook or motor block, and just use a wrap of tape to hold the motors from kicking. The RMS and all modern SU motors have a built-in thrust ring. For the Arreaux and other 1.9" kits, the motor tube needs to be mounted a bit further aft, to provide access for the tape wrap.

 

[Initiator001]

Double-check your measurements for the motor hook placement. I've never had a problem with getting any of the recommended motors/RMS cases to fit.

I built my Arreaux stock just like the instructions 10+ years ago and it's still going strong. Motor hook, baffle, elastic still fine.

Enjoy building/flying your Arreaux model!

 

[rcktnut]

Double-check your measurements for the motor hook placement. I've never had a problem with getting any of the recommended motors/RMS cases to fit.

I built my Arreaux stock just like the instructions 10+ years ago and it's still going strong. Motor hook, baffle, elastic still fine.

Enjoy building/flying your Arreaux model!

I built mine stock at about the same time, mine is just fine also.

The way it sounds with your sloppy mount is that you are missing the thrust ring. There sould be a thrust ring just aft of the motor hook. Building it stock works just fine, unless you plan on using larger motors in it.

 

[McRick]

I really appreciate the feedback! I thought that the 29/40-120 would seat normally against the motor tube and when it didn't, assumed that there was a problem. I see now that if I had inserted the thrust ring assembly there would not have been any play, as Paul and Jeff mentioned (thank you!), although the motor still would not have mounted flush.

In the end, I'm going to modify it by using a Slimline retainer, as I already had an order with Giant Leap that I've added to. I'm going to go ahead and replace the elastic with Kevlar and the mesh baffle with nomex.

Thanks so much to all of you for your feedback!

Rick