[FFT] Plugging Estes or Quest BP motors

I know the answer to this one for certain as I have done it many many times. First, my experience. I own and fly a VB Li'l Wild Thing. The central motor is a standard 18mm Estes motor and the outer cluster consists of up to 6

13mm motors. The preferred motor for the cluster is the A10-0. To prevent hot gasses from burning the BT, you have to fill the top of the motor with epoxy. Now, A10-0s are getting as scarce as hen's teeth. So, I've tried two approaches. First, I plugged an A10-3. Each and every time it blows the case like a firecracker or it fires the plug foreword like a musket ball. neither option is any good. So, on to plan "B". In this option I scrape out the ejection charge leaving only a small amount of the delay train. Then I seal the top of the motor with epoxy. Works like a charm every time.

no need to waste A10-0s, look for Estes rocket car motors, A10-PT. they are plugged.

Reece Talley wrote:

can you use a D11-P instead?

The ones that resulted in his Big Fine.

Why don't you just buy the very available A10-P?

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

altitude....

In that case, use a solid bulkhead and very positive motor retention because the motor't ejection charge is going to go off just like the firecracker it is. Just remember you are gambling that the nozzle clay is the weak point...what if the nozzle is stronger than your BT at the motor / bulkhead interface ?

Don't think that's going to work very well because the ejection charge goes off in a very short timeline, and probably will have a hard time igniting a delay composition on its own.

Good luck which ever way you decide to go. I know I have frequently designed myself into a trap when I discover my rocket can't be completed without adding some 'unobtainium' to the airframe.

John

You are right of course, but when I bought the VB these motors were not yet on the market.

It wasn't available the last time I flew the bird in 2002.

This had got to be one of the most crazy ideas I've seen on RMR in years.

The ejection charge will still fire, and the "plug" will just be fired into the internals of the bird. (friction fit?)

If you don't want an ejection charge, you got ways to correct for it:

1) buy the motor you really need 2) vent it's charge 3) talk to Gary and get him to issue a press release that none of the testing groups have approved as to "motor modifications". (gary might do it, even though it's BP! He wants sales and happy people....) 4) put the bird on the shelf, as it can longer be flown.

What if I had a bird that used the "short" motors from Estes? (the original Midget comes to mind...) is it Ok for me to cut the casing to the proper length? (heck, it's only cardboard I'm cutting!!) What happens if I make the 6pm news when doing this, as a spark hit the ejection charge? (Model Rocket motor and bandsaw burns down house, more at 11!)

For the first time (to the best of my recollection) in all my years on rmr, I'm turning the flamethrower on full blast.

Woody, pull your head out of your butt.

The rules regarding manufacturer recommended modifications has been on the books for eons. The entire POINT of modifications needed manufacturer recommendations is to allow for 'minor' tweaks that may (or may not) have been fully covered in other material and/or instructions, to allow for either safe operation or a wider range of operation. If, at any point, a manufacturer ABUSES that privilege, the certification organizations would theoretically have the right to ask for corrective action -- which might take the term of a request for clarification, a request for recertification, etc.

The entire POINT of this is that the manfacturer is the one who's butt is on the line in relation to liability issues, so they are very unlikely to 'recommend' modification that might create greater risk or liability.

Just because you've got a hair up your tail about this is no reason to jump on Gary -- he's done what the vast majority of Aerotech composite motors have been asking for for years -- and done it in a very thorough and professional manner.

To suggest that what Gary has done in relation to delay charge modifications is on par with folks 'experimenting' with plugging BP motors with epoxy suggests that you don't have clue one as to what is going on. In the case of delay modification, we have a situation that has been in place for quite some time with other manufacturers, that has no record of any problems, being made 'legal'. In the case of BP motor plugging, all of the folks who have done it are saying DON'T do it, because it's dangerous. For you to imply that what Gary did was in any way similar is unconscionable.

I look forward to hearing your apology (but I won't hold my breath)...

David Erbas-White

Don't forget to say NAR and TRA will go along with teflon-Gary on issues others have been refused over.

- Multiple subcontractors

- modifications of already certified motors.

- field modifications of primary propelling charges - to overcome and prevent recall of known manufacturing defects

Jerry

The problem being real or perceived.

Gary is given wide discretion while others are harassed and expensed to death.

That was not the position taken on Kosdon Or USR or Vulcan or ACS ...

And these all had paperwork, so that excuse evaporates.

There is an OUTSTANDING problem. Different treatments of different vendors. Aerotech was given a pass. You and I agreee it was a good one. Fine. But CTI was not given the same pass on the same issue. Fact.

That fact is going to result in bad vibes from the "excluded class" while some revel in the ability to modify their monopoly sourced errortech motors.

Jerry

Poor pathetic psychotic jerry.

Should CTI have been given a pass on this? Frankly, yes! But, Gary did the SMART thing as a businessman -- he let somebody else blaze the trail and take the arrows, and once there was more history for it, he approved it for his own product. This, Jerry, is known as "conservative business practice".

David Erbas-White

AZ:

thanks for telling me this idea is crazy! Anyway, the ejection charge from the A3-4T motor would indeed "fire", with the idea that above the motor, a delay and ejection charge module of my own making. The idea is the hot particulate of the ejection charge will ignite this delay/ejection charge module. The module will not be blown upwards into the model, as there is a bulkhead above it.....the idea is to get 2-3 extra seconds of delay time so that my A3-4T functions like an A3-6/7-T.. the secondary ejection charge would then pop out the recovery system.

There are NO modifications or alterations made to the actual original A3-4T motor.

I may have to add some exhaust holes to help relieve the pressure and I may have to place the forward bulkhead up an inch or two of the delay/ejection charge module, so that the ejection charge pushes the delay/ejection charge module up these 2 inches and allows more space to pressurize to prevent nozzle blowout or a rupture of the casing....

shockie B)

No, it's not "OK" to make your own short motors by sawing off an inch of empty casing. What I *HAVE* done many times, its take a used casing, saw it down, clean it out, and insert a "T" motor inside it. A standard 18mm casing makes a perfect adapter for them. And a shortened as above 18mm casing makes a perfect Shorty motor. And a cleaned out used D12 casing makes a perfect

18->24mm adapter. I just used one this weekend.

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

-----snip-----

And a cleaned out used D12 casing sawn into 1/4 in rings makes nifty spacers to hold an 18mm motor without adding excessive weight in the tail of the bird.

John

Too late - they were built about 35 years ago. Of course I won't modify them - that's why I think glueing the 18mm centering rings onto the T motors is a good idea.