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[FFT] Plugging Estes or Quest BP motors

I know some motors come pre-plugged from the factory, ie A10-PT. But lets say I wanted a A10-6T which doesn't exist. Only an A10-3T is avilable.

Let say just for the sake of illusion, that I create a small external plug that either fits within the top of the motor casing and/or sits right outside the end of the motor casing. This plug is not "glued" or adhere to the actual motor case in any way other than perhaps a friction fit, if the plug extended into the well of the motor casing.

From my POV this is not "altering" the motor per se.... The plug itself is a temporary device designed basically to prevent the ejection charge already in the motor from going up into the actual body tube and pressurizing and ejecting the recovery system. It essentially acts as a bulkhead.

Lets say for the sake of this illusion that I want to "plug" the motor and not use its "native delay train and ejection charge" due to the fact that there is only say a 3 sec delay avilable for use with this motor, and I want to use a microtimer based delay charge/ejctiion charge assembly in place of the actual motor delay train and ejection charge.

If the motor is taped securing into the model body tube by use of tape, when the ejection charge fires at clay cap breakthrough, then I assume since the ejection charge gases cannot escape out the top of the motor, it will pressurize the now empty motor casing(except for residue )and be exhausted through the motor nozzle....

questions:

Would you expect that the above would result in X amount of forward momentum?

If I do this will it result in the motor nozzle being blown out due to the pressurization of the ejection charge?

Could the pressurization be so much as to cause a paper motor casing failure due to temporary over pressurization?

Somebody once posted the amounts by weight of actual BP in Estes motors...would somebody please post those amounts again?

TIA

shockie B)

Reply to
shockwaveriderz
Loading thread data ...

Yes.

Yes.

Reply to
Jerry Irvine

An easy test would be to epoxy said engine into a 3/4" dead-end hole in a block of wood and test fire.

Reply to
bit eimer

jerry: are you sure or are you trying to feed me disinformation? If the ejection charge in Estes motors is lets say producing 15 lb/sq ft(?) of pressure, to eject the recovery system, surely the burn pressure on the casing and nozzle is way above 15 lb/sq ft?

shockie B)

Reply to
shockwaveriderz

And clearly fail.

And also demonstrate this guy did NO real world tests before posting.

Reply to
Jerry Irvine

Get a life.

Or not.

Reply to
Jerry Irvine

who says you have to do real world test before posting? Is that a JI requirement in this group. The reason i asked was, why should i waste X amounts of motors testing them, if somebody has already done this successfully or not?

shockie B)

Reply to
shockwaveriderz

Not you.

observation?

Yes.

To learn?

Like me?

But you would disregard that.

:)

Reply to
Jerry Irvine

What's the matter? Are you afraid you might learn something by doing it yourself? To cheap to buy a few motors?

Because Jerry said so is the only reason I can come up with to not do it yourself and that shouldn't stop anyone..

Reply to
Phil Stein

Aren't you in more danger of blowing out your (Estes-type I would assume) body tube by doing this? Unless you can assure a gas-tight seal between the motor and plug, I think this could be a problem.

Is kicking the motor an option? Would be far simpler, just block off the MMT with a bulkhead and loosely friction fit the motor.

Another option would be to vent the gases, perhaps you could have a section of BT ahead of the motor with a simple baffle and small holes in the airframe to vent the gases evenly in all directions.

My thoughts are that if you want to avoid modifying the motor, there may be more ways to skin the cat (or something like that ;) ).

HTH.

Reply to
Niall Oswald

And what "real world tests" did you do?

Reply to
Dave Grayvis

Yes.

Point.

Reply to
Jerry Irvine

When I have glued the forward section of the motor, it sounds like a shot gun blast and blows the nozzle out the rear end.

Reply to
AlMax

That sounds cool :) was the rocket ok?

Reply to
Dave Grayvis

almax:

interesting....

what motors were you using? I am only really interested in a3 or a10 motors....

thanks shockie B)

Reply to
shockwaveriderz

most of the time. once in decades , I had one blow the motor tube from a D13 , ouch !

Reply to
AlMax

D12s.

A3s, same thing, but sounds like a 22 rim fire instead. b

Reply to
AlMax

-----snip-----

-----snip-----

I'm personally not a fan of motor ejection because I once had one actually hit my shoulder in a one-in-a-gazillion chance. Made me worry about lightning strikes, too.

Two 1/4 in diameter vent holes 180 degrees apart below the solid bulkhead will vent the ejection charge nicely.

John

Reply to
John Bonnett

Usually, ejecting motors is frowned upon. Most clubs use some type of farm land and motors can be a hazzard to livestock or machinery, so leaving motor liter all over the place from dozens of launches, isn't a good thing. I've flown them so that either way was an option, depending on the field and who I'm flying with. Some will say there is also a fire hazzaed but fire is more of a problem at liftoff, than from a fallen burned out booster.

On the other hand, if these conditions are not an issue, a falling A-D type engine doesn't pose too much of a threat, they tend to tumble quite a bit and 999 times out of 1000, arch away from the launch area. To date, I've made over 50 flights where the engines ejected and never had a problem of any kind. I like the idea of lightening the chute load AND ejecting can make spent engine extraction easier. Ever had an engine get stuck in your favorite rocket?

If you want to fly a bird that ejects it's engine, you can scotch tape a short piece of orange caution tape to it. That will allow you to track it as it falls and locate it later.

Randy

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Reply to
<randyolb

john:

I'm not sure venting the ejection charge gases is what I am after... I was hoping to use the ejection charge gases, whether it blows out the nozzle or not, as a secondary source of energy.... to get some additional altitude.... If I vent then I have potentially 2 problems:

  1. the vented gases may cause some instability as it is exhausted..
  2. drag due to 2 holes in model..

I guess I might as well go ahead and give "the rest of the story"....

Instead of using a microtimer as I posed in the 1st post, what I am actually considering doing is making my own delay train/ejection charge module.... and having the "real" ejection charge ignite the add-on delay train...

I figure that I only need 3-4 more seconds to give me an actual 6-7 delay time...

the idea is that with the A3-4T or A10-3T motors is their delay times are way too short for altitude..

I figure that a small delay/ejection charge module like this should not weight more than 2 grams max... and it would give me the effective 6-7 s delay time that I am looking for.

shockie B)

Reply to
shockwaveriderz

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