[F-FT] Single use motor retention

I like to use the aluminum-foil "duct tape" available at hardware stores for this... since it comes with a removable release-paper over the adhesive, it's easy enough to take piece of the tape several inches long and use a scissors to cut 1/4" wide strips off it as needed... these can be used to build up a thrust ring on single-use motors that is the right size to fit the Aero-Pack retainers. (I haven't tried Slimline, but the dimensional requirements should be similar...)

-dave w

For many moons no motors had either integral thrust rings or motor retainers. So masking tape, that magical substance, was used. Successfully down to 13mm and up to 98mm.

Reloadable motors with their knurled ends and greased surfaces are unfriendly to a masking tape retention, so hooks like Kaplow clips or retainers are typically used.

HOWEVER by simply putting a masking tape band right next to the integral thrust ring on the case, the traditional method can be used.

Some customers of mine put the retention ring at the case right where it extends past a motor conversion mount. So the integral thrust ring prevents blow-through and a ring on the case next to the top end of the motor conversion tube holds it in from ejection.

You will get lots of conflicting advise and therefore others will conflict with mine, but keep in mind I have been doing this almost 40 years and have designed both SU and RL motors and tracked how they are used in the field.

I advise you to at least consider my advise.

Just Jerry

They have a AT-RL (RMS) assumption.

They are SU non-believers and off-brand non-believers.

The benefit of a constructive monopoly to Aerotech I presume.

Errortech, I presume?

First, many motors are made from fiberglass tubing, not exactly "molded." If the motor uses an injection-molded case as some apparently do, it wouldn't be much harder to include a thrust ring, but the benefits are marginal.

In certain applications, also, the rear of the motor has to slide into and out of a tube: some staging methods, for example, and any kind of motor retainer that requires the motor to be inserted from the front, as certain zipperless designs do. I once designed (but never got around to building) a rocket with removable fins in which the motor was inserted from the front and then the fins were inserted with tabs at the front that served as a motor block. So, in a few cases, a built-in thrust ring would be in the way.

Masking tape is so cheap and works so well! For years with little rockets, I built up a ring at the back to the diameter of the motor mount tube, then taped that ring to the tube. Worked great, and then one day I found the same exact instruction in a USR kit -- lending credence to Jerry's reply, whatever you may think of his trollish episodes.

I'd be afraid of the pressure these things can produce. Crank it down a little too much and crack the case, and you have a serious problem.

My humble opinion...

snip!

I have retainers on a few of my 29mm rockets. So when I use a single-use F50 or G80. A take my miter box and slice rings of 29mm PML tubing the width of a AT 29mm aft closure(about 3/8" thick ?), I usually cut several dozen for futur use. Then I scuff the aft of the SU motor with sand paper and glue the ring with 5 min. epoxy. I can put masking tape on the upper portion if there's no retainer or use a Aeropac or Giant Leap retainer, it works every time. NO masking tape thrust rings! Dave Alewine

RocketVision did this for their 24mm relabeled AT motors.

Doing so yourself is fine, except in NAR competition. The Naram-20 "Phil Barnes" rule prohibits it.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

It's not enforced anymore :)

RV used plastic rings BTW.

"Dave Alewine" wrote in news:4I3Zd.54823$755.34641@lakeread05:

Wouldnt using masking tape TR's be easier and quicker?

Shhhhh!

But potentially less strong? I know masking tape is the duct tape of the rocketry universe, but on a really high thrust motor (academic for anyone but Jerry I suppose, but surely USR have some seriously high-thrust SU motors?) I could see it having nasty motor-through-rocket consequences.

Then again, wouldnt JB weld or similar be a better choice for attaching a thrust ring?

Strong enough is strong enough.

It works on a 29mm H640 just fine.

It works on a 38mm I440 and J880 just fine.

It works on a 54mm J1000 and K500 just fine.

It works on a 98mm M1200 just fine.

YMWV

(your mileage won't vary)

Hose clamps work fine, and I use them all the time.

Bah! Less strong? Maybe. maybe not. But strong enough? Yes.

Admitedly, I've used mostly reloads that have aft closures eliminating the need for tape for anything G and above. But the few G and H expendables I've flown, including my original TRA cert back in 1989 used masking tape thrust rings. And in most cases, it's skinny 1/4" masking tape, not big fat wide stuff. That included G125s, G160 Silver Streaks, and an H89.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

You mean to tell me, you never used one of those US Rockets H 160 motors?? (;-)

Fred

I would have said that but I do not want to scare the already fearful masking tape skeptics.

I was merely wondering :-)

I personally get through lots of masking tape - but mainly for taping up quickmatched clusters. Merely unsure how far people had pushed masking tape - clearly to L3!

I have, however, on two occasions demonstrated that duct tape will hold an Estes D12 to a rocket quite happily :-)

LOL!

I have been using hose clamps and have not had any problems, used drem. to cut slites in mm tube, masking tape thrust ring, on 38 mm standard hose clamp and if you look in some dollar stores have thinner hose clamps that I use in 29, 24 mm, Le