Dear Decision-Makers in Penrose: More Plugged Rocket Engines, Please!

[brockrwood]

Dear Estes Decision-makers (you must be monitoring these forums):

I like the A10-PT plugged rocket engine. Why? Because I have a scratch built cluster rocket with two 13mm “booster pods” on each side of the main body tube. I put an A10-PT into each booster pod and a B6 or C6 into the sustainer. Whoosh! The bird gets off the pad fast.

It would be great if Estes would make other plugged engines. How about an A8–P? Or a B6-P?

I have another scratch built cluster rocket with three 18mm tubes side by side. The two outer tubes are short, booster pods. Since you don’t make an 18mm engine that is plugged, I use A8-3’s in the pods. The pod tubes have vent holes for the ejection charge from the A8-3’s.

I know what you might say, Estes decision-makers: There is not a big enough market to justify making A8-P’s or B6-P’s.

Come now. I don’t mind you being Machiavellian about this. Just MAKE the market.

Just make three or four rocket kits that all REQUIRE A8-P’s or B6-P’s. Break even or lose money on the kits to sell the engines. Remember we are talking about cluster rockets here: It takes a pack of engines for ONE launch. Ka-ching!

 

[smstachwick]

You can make your own pretty easy by putting an epoxy plug in any -0 motor. Lots of people do this for rocket gliders and such.

AeroTech also sells small quantities of plugged reloads. Usually they’re either endburners or Warp-9 monsters.

 

[bad_idea]

Dear Estes Decision-makers (you must be monitoring these forums):

I like the A10-PT plugged rocket engine. Why? Because I have a scratch built cluster rocket with two 13mm “booster pods” on each side of the main body tube. I put an A10-PT into each booster pod and a B6 or C6 into the sustainer. Whoosh! The bird gets off the pad fast.

Although I have high faith in the consistency of ignition in my black powder clusters, there is always a risk that a rocket will clear the pad without lighting all of the motors. What if that happens to the sustainer motor? It's a risk I've taken before, but I'm not a huge fan of it.

I would however prefer more plugged BP motors for flying with electronics. Since they don't exist, the modular cluster I'm working on now will simply vent ejection gasses rearward.

Just make three or four rocket kits that all REQUIRE A8-P’s or B6-P’s. Break even or lose money on the kits to sell the engines. Remember we are talking about cluster rockets here: It takes a pack of engines for ONE launch. Ka-ching!

Based on the trend of the last few years, I doubt Estes will ever release another cluster. I'd love to be wrong though.

You can make your own pretty easy by putting an epoxy plug in any -0 motor. Lots of people do this for rocket gliders and such.

That used to be a gray area, then someone here on TRF recently decided to kick a sleeping dog and ask NAR and TRA point blank if it was allowed. Both said no, it was a motor modification, which NAR does not allow and TRA does not allow for black powder.

 

[cerving]

You CAN legally plug a -0 BP motor with dog barf, and tape it in. You just can't epoxy in a plug... silly distinction, but that's Da Rules.

 

[bad_idea]

You CAN legally plug a -0 BP motor with dog barf, and tape it in. You just can't epoxy in a plug... silly distinction, but that's Da Rules.

Good point. I need to experiment with that again at some point. Had some unfortunate results last time I tried it.

 

[neil_w]

Good point. I need to experiment with that again at some point. Had some unfortunate results last time I tried it.

I think some static tests are called for. I'm amazed that dog barf and tape could hold the burn-through. The tape at the top of the motor (and wrapping around the sides) wouldn't be great for allowing the motor to slide in and out of the mount, though, I think.

 

[Art Upton]

I think some static tests are called for. I'm amazed that dog barf and tape could hold the burn-through. The tape at the top of the motor (and wrapping around the sides) wouldn't be great for allowing the motor to slide in and out of the mount, though, I think

Make a Tape "X" and push it down into the motor well over the barf. Put tape in the well to hold it not the outsides.

 

[neil_w]

Make a Tape "X" and push it down into the motor well over the barf. Put tape in the well to hold it not the outsides.

I guess that would at least work for the motors that are not completely filled (don't recall which but some really have very little open space at the top.) But that's OK, don't necessarily need a -P version of every different motor... A8-0 and B6-0 should both work fine, C6-0 might be tight. Don't have any in front of me to look at at the moment.

 

[smstachwick]

Although I have high faith in the consistency of ignition in my black powder clusters, there is always a risk that a rocket will clear the pad without lighting all of the motors. What if that happens to the sustainer motor? It's a risk I've taken before, but I'm not a huge fan of it.

I would however prefer more plugged BP motors for flying with electronics. Since they don't exist, the modular cluster I'm working on now will simply vent ejection gasses rearward.

Based on the trend of the last few years, I doubt Estes will ever release another cluster. I'd love to be wrong though.

That used to be a gray area, then someone here on TRF recently decided to kick a sleeping dog and ask NAR and TRA point blank if it was allowed. Both said no, it was a motor modification, which NAR does not allow and TRA does not allow for black powder.

Good points.

I guess the best options would be, in order, the dog barf hack, a plug built into the motor mount assembly, and a Safety Check person who doesn’t really care about this particular issue when nobody’s looking (the last one being a distant third).

 

[bad_idea]

I think some static tests are called for. I'm amazed that dog barf and tape could hold the burn-through. The tape at the top of the motor (and wrapping around the sides) wouldn't be great for allowing the motor to slide in and out of the mount, though, I think.

Yes, my problem was I didn't static test, fix, and optimize, I just packed a few motors and sent them. Had a mixed cluster of two E12-6s and two stuffed-and-taped D12-0s. When the D12s burned through, one (or both?) leaked enough gas to pop the nose cone and cause a mighty zipper while the Es were still burning.

Though I'd always rather be flying, working with composite clusters has forced me to make peace with burning motors on the ground. If/when I return to stuffing -0 BP motors, I'll burn them on the ground first.

I guess the best options would be, in order, the dog barf hack, a plug built into the motor mount assembly, and a Safety Check person who doesn’t really care about this particular issue when nobody’s looking (the last one being a distant third).

Concur 100%. Only pointed out what I did for those who don't know.

Incidentally, my motor-mount plug testing didn't go so well either. Yet another subject of future ground testing.

 

[brockrwood]

Good points.

I guess the best options would be, in order, the dog barf hack, a plug built into the motor mount assembly, and a Safety Check person who doesn’t really care about this particular issue when nobody’s looking (the last one being a distant third).

A plug built right into the motor mount! What a great idea! So, on my scratch built rocket with two booster pods, I could put a cap at the end of the motor mount. Something like a nice, solid disc of 18mm wooden dowel that fits tightly over the top of the engine and seals the tube. Then just put -0 engines into the pods. I like it.

Gotta’ be very careful to remember to put only -0 engines into the pods or I will get a spectacular booster malfunction when the ejection charge goes.

 

[neil_w]

A plug built right into the motor mount! What a great idea!

That is a very intriguing idea. Again, some ground testing is in order.

 

[brockrwood]

Incidentally, my motor-mount plug testing didn't go so well either. Yet another subject of future ground testing.

Dang! When you mentioned that approach it seemed like such a clever idea!

A -0 engine has no ejection charge or smoke charge. We are just talking about the little “pfft” when the flame burns through the top of the black powder. That can’t be that strong, can it?

 

[bad_idea]

Dang! When you mentioned that approach it seemed like such a clever idea!

A -0 engine has no ejection charge or smoke charge. We are just talking about the little “pfft” when the flame burns through the top of the black powder. That can’t be that strong, can it?

Well, my problem was tied to the subject of the other thread currently running about motors we want Estes to make, namely the C5-0. I was trying to plug C5-3s in the absence of a -0. It didn't go well. Again, I should have ground tested. That flight marked the first time the stuffed rabbit we call Thumper that's awarded in Tripoli North Texas for a particularly bad thump came to stay with me (currently hosting that beastly bunny again, but that's another story).

I suspect a -0 would work fine, but I do think it's worth burning a few motors on the ground.

 

[brockrwood]

Well, my problem was tied to the subject of the other thread currently running about motors we want Estes to make, namely the C5-0. I was trying to plug C5-3s in the absence of a -0. It didn't go well. Again, I should have ground tested. That flight marked the first time the stuffed rabbit we call Thumper that's awarded in Tripoli North Texas for a particularly bad thump came to stay with me (currently hosting that beastly bunny again, but that's another story).

I suspect a -0 would work fine, but I do think it's worth burning a few motors on the ground.

Thumper! I love it!

As for a motor mount block “plug” for a -0 engine, I will test said idea on the ground and get back to the participants in this thread.

 

[neil_w]

As for a motor mount block “plug” for a -0 engine, I will test said idea on the ground and get back to the participants in this thread.

I think it should. I suspect that best results will be if the plug touches the top of the motor*, which requires a bit of thought if you're going to support different motors.

Well, my problem was tied to the subject of the other thread currently running about motors we want Estes to make, namely the C5-0. I was trying to plug C5-3s in the absence of a -0. It didn't go well.

I'm not sure plugging a motor with an ejection charge is actually a thing. Which is to say, I don't know if there's a "right" way to do it, or if it's just something that you Don't Do, period. Has anyone ever done that successfully?

If it did work you'd have to have hella strong motor retention.




*on second thought I'm not so sure about this.

 

[bad_idea]

I'm not sure plugging a motor with an ejection charge is actually a thing. Which is to say, I don't know if there's a "right" way to do it, or if it's just something that you Don't Do, period. Has anyone ever done that successfully?

I tired it after seeing someone claim it had worked for them successfully. Claimed the ejection charge gave them some bonus impulse. Of course they might have had a deeper cavity to work with than the one at the end of the C5.

I'm now starting to build clusters to vent to the rear so I don't have this problem, but that restricts them to electronics.

 

[SolarYellow]

A plug built right into the motor mount!

My ever-expanding list of future projects includes printing up a version of this to use in the top of -0 BP motors. Then you can also integrate motor retention for MD rockets.

https://www.amazon.com/gp/product/B000H5WVQY/?th=1

 

[brockrwood]

My ever-expanding list of future projects includes printing up a version of this to use in the top of -0 BP motors. Then you can also integrate motor retention for MD rockets.

https://www.amazon.com/gp/product/B000H5WVQY/?th=1

What meaneth “MD”?

 

[Titan II]

What meaneth “MD”?

https://www.rocketryforum.com/search/553669/?q=MD&o=relevance

 

[bad_idea]

Minimum diameter.

 

[BABAR]

Thinking outside the box, what are your field rules And conditions?

outside of competition, there is nothing in NAR rules nor the safety code that says you can’t eject a motor, and there are number of kits including the Semroc Hawk glider (which I believe is a repro of an Estes and/or Centuri kit), and the Sprite and of course the Mosquito which are motor eject.

so skip the vent holes, make sure the pod nose cone is glued in firmly or add a bulkhead, throw some JB weld or other heat protectant on the base of the cone or rear of bulkehead. Usually don’t need anything to hold the motor in place, if really “falling out” loose on pad put a loose friction fit, and let her rip.

I’ve been doing this for years with 13-24 mm motors (D12s, E motors might be pushing it) without any issues.

I look For and when found I pick up the casings if I can find them, I don’t sweat it if I can’t as they are biodegradable.

some fields have rules that disallow free falling casings, and Miiiight want to skip it if high fire danger due to dry field conditions.

there are ways to add streamers if you feel the need, even on minimum diameter. See post 20
https://www.rocketryforum.com/threads/glider-front-motor-eject-feasible.181457/#post-2476414

 

[jmasterj]

That used to be a gray area, then someone here on TRF recently decided to kick a sleeping dog and ask NAR and TRA point blank if it was allowed. Both said no, it was a motor modification, which NAR does not allow and TRA does not allow for black powder.

All we need is Estes to say it's a manufacturer-approved modification and we'd be good to go. I doubt that will happen, though.

 

[prfesser]

All we need is Estes to say it's a manufacturer-approved modification and we'd be good to go. I doubt that will happen, though.

I agree, though I'm not sure why Estes wouldn't approve (other than the time-honored "easier to say no"). It'd be easy enough to do. Prepare a statement such as: "Booster motors, which have neither delay nor ejection charge, may be plugged with two-part epoxy glue or other strong adhesive that will retain chamber pressure during flight and does not contain water. Motors so modified shall be used only where and when their use does not constitute a hazard."

It would undoubtedly increase sales of booster motors to a (small) fraction of rocketnutz who want to do bigger and better things with -0 motors, though it wouldn't be enough to make a blip in Estes' bottom line.

 

[2-0turbo]

Not permitting an epoxy plug for this purpose is nonsense. It in no way impacts the structural integrity of the motor. Calling this a modification and prohibiting it seems like an over reach.

 

[mh9162013]

Not permitting an epoxy plug for this purpose is nonsense. It in no way impacts the structural integrity of the motor. Calling this a modification and prohibiting it seems like an over reach.

Maybe, maybe not. But to keep things simple, the rules/guidelines may just use a "belt and suspenders" blanket approach as to what's allowed and not allowed with motor modification.

If they allowed certain types of plugging, what about shortening rocket engines? For example, cutting an A8-3 in half as much of the motor casing is just empty space. Or how about removing some or all of the clay cap covering the ejection charge to make it less powerful (or for some other objective). You can see how this would create a slippery slope type of problem...

 

[2-0turbo]

As a follow-up, I have an old LOC Viper IV with a 4X 24mm cluster. I should be able to install 2x D12-5 and plug 2X D12-3 and use only the two 5-second delay motors for motor ejection. Having to find 4X of the same motors can be a pain. Perhaps I should have bought the Viper III. And honestly, 4X Estes BP motors is too much boom for this rocket.

 

[jmasterj]

As a follow-up, I have an old LOC Viper IV with a 4X 24mm cluster. I should be able to install 2x D12-5 and plug 2X D12-3 and use only the two 5-second delay motors for motor ejection. Having to find 4X of the same motors can be a pain. Perhaps I should have bought the Viper III. And honestly, 4X Estes BP motors is too much boom for this rocket.

You could use 2x D12-5 and 2x D12-7. The latter will just eject into an empty body tube.

Edit: darn phone autocorrect

 

[Art Upton]

Putting an epoxy plug over an ejection charge rather than a -0 motor well, could blow your epoxy plug out like a shot gun shell wad.

 

[jmasterj]

Putting an epoxy plug over an ejection charge rather than a -0 motor well, could blow your epoxy plug out like a shot gun shell wad.

Nah, it just goes out the nozzle.