MADCOW Motor retainers

[RocketManDan]

I have a few builds coming up and I'm thinking about using this type of motor retention.

http://www.madcowrocketry.com/servle...er-29mm/Detail

It seems pretty popular and the price is reasonable. I do have one Aeropack retainer left, but saving to go on my HPR Level 1 build. With the MADCOW retainers, if something happens to the rocket (loose it) you're not out much money compared to the Aeropack. Also buying the replacement threaded inserts shouldn't be much of a problem.

[follr]

If your concern is price than do a search on kaplow clips for motor retention.

I have used them and they work great.


follr

[Gary Byrum]

That's what I did. Made mine with 1/4" cable straps, single hole. I bought the small Tee nuts and #6 screws to fit. This is way cheaper and not hard to install. My Saturn build is equipped with them. You can also do a search here for Kaplow Clips and find a plethora of info on them.

[Handeman]

If you are installing these on a rocket already built, then it's probably not too bad. Of course once you see what the kit consists of, you can buy the inserts, screws and clips much cheaper.

I used scrap aluminum from a shower door track and made my own plates to fit over the motor. 10 minutes with a tin snips, a drill and some files will turn out some pretty good pieces. The aluminium from the tracks is also much stiffer then you would get if you bought pieces from the box stores.

[o1d_dude]

I just use tee-nuts in the 6-32 size and buy hex head 6-32 screw that I can drive with a ball joint hex key.

The trick is making the clips. Check QQUAKE's build threads as he almost always posts pictures of his retention system with details. I use brass strip, he uses aluminum(?) I think. The retainers are nothing more than a means to keep the motor case from kicking out during the deploy charge going off. I drill a hole in the end, bend the strip in a vise to form the Z shape and file off the rough edges. The trick is to measure the lengths and mark the bend locations with a Sharpie. Tighten the strip into a vise so the marks are just showing and then tap with a hammer to bend the strip. You can get fancy and make sharp bends or you can leave them rounded. I usually make square bends at the bottom and round bends to hold the motor closure lip. YMMV. Like most things, you'll get better at this after you've made a few.

Not shown in the attached picture is that the tee nuts should be secured in place with epoxy, preferably JB Weld. At least that's what I do and I learned that from Jeff the Handeman's builds threads. If you use the toothed tee-nuts and press them in with a vise, I'd still recommend the epoxy. Maybe it's a belt and suspenders thing but if it prevents disaster, it's worth the effort.

[terryg]

I use midget one hole straps from the conduit section at Home Depot. 50 of them for $2.50 , bend to fit.

[Pat_B]

The Madcow 29mm retainers are a little narrow in that the screw holes end up being only a few millimeters outside of the motor tube. By the time you drill holes for the wood nuts they practically break through the centering ring near the inside diameter. They really need to make the metal retainer slightly wider and make the holes wider too.

The other sizes besides the 29mm seem OK. I'm working with a TARC team right now who is dealing with this.

[Boosterdude]

I have a few builds coming up and I'm thinking about using this type of motor retention.

http://www.madcowrocketry.com/servle...er-29mm/Detail

It seems pretty popular and the price is reasonable. I do have one Aeropack retainer left, but saving to go on my HPR Level 1 build. With the MADCOW retainers, if something happens to the rocket (loose it) you're not out much money compared to the Aeropack. Also buying the replacement threaded inserts shouldn't be much of a problem.

I use them, no issues they work fine.

[plano-doug]

Not shown in the attached picture is that the tee nuts should be secured in place with epoxy, preferably JB Weld. At least that's what I do and I learned that from Jeff the Handeman's builds threads. If you use the toothed tee-nuts and press them in with a vise, I'd still recommend the epoxy. Maybe it's a belt and suspenders thing but if it prevents disaster, it's worth the effort.

I agree wholeheartedly.

The barbs (teeth) don't really add much bite at all.

I put the epoxy around the cylindrical portion of the T-nut as well as under the flange, taking great care to not get it in the threads. And if you do, some Q-tips are great for cleaning it out - just screw them thru the threads.

Sometimes, I add wood over the T-nut's flange to sandwich the T-nut in place. I'll cut a piece of birch plywood to fit over the flange, then use a forstner bit to hollow out the wood so that it just fits over the flange. (I wish I had a pic, dangit!)

FWIW, here's a draft page I put together on this topic.

Doug

.

[Gary Byrum]

I use midget one hole straps from the conduit section at Home Depot. 50 of them for $2.50 , bend to fit.

Those are exactly the ones I use. Couldn't find the right Tee nuts & screws at Lowe's where I got my straps so I went to Ace and found just what I was looking for.

[o1d_dude]

FWIW, here's a draft page I put together on this topic.

Doug

.

Excellent resource, Doug. Let's get it posted as an "official" page because this topic comes up pretty regularly.

[Pat_B]

You can also put some Vaseline in the thread hole to keep the epoxy from sticking.

[qquake2k]

I just use tee-nuts in the 6-32 size and buy hex head 6-32 screw that I can drive with a ball joint hex key.

The trick is making the clips. Check QQUAKE's build threads as he almost always posts pictures of his retention system with details. I use brass strip, he uses aluminum(?) I think. The retainers are nothing more than a means to keep the motor case from kicking out during the deploy charge going off. I drill a hole in the end, bend the strip in a vise to form the Z shape and file off the rough edges. The trick is to measure the lengths and mark the bend locations with a Sharpie. Tighten the strip into a vise so the marks are just showing and then tap with a hammer to bend the strip. You can get fancy and make sharp bends or you can leave them rounded. I usually make square bends at the bottom and round bends to hold the motor closure lip. YMMV. Like most things, you'll get better at this after you've made a few.

Not shown in the attached picture is that the tee nuts should be secured in place with epoxy, preferably JB Weld. At least that's what I do and I learned that from Jeff the Handeman's builds threads. If you use the toothed tee-nuts and press them in with a vise, I'd still recommend the epoxy. Maybe it's a belt and suspenders thing but if it prevents disaster, it's worth the effort.

o1d_dude is right, I've been making my clips from 1/8" x 1/2" aluminum. Been working out very well. I have step by step photos of how I make them starting on post #116 here:

http://www.rocketryforum.com/showthr...t=30829&page=4