Paging Delta22 aka Boris Katan

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

JAL3

Well-Known Member
Joined
Jan 17, 2009
Messages
14,333
Reaction score
268
Howdy,

I know you have the reputation as THE guy to make clusters work and I have a question for you.

I have a long term project I need to get off my backside and finish that involve a 12x18mm mount. Each motor is canted at 30 degrees. I originally planned for a cluster of C6-3s but it looks like they will be lacking in the oomph I need and am considering the idea of using a dozen of the Aerotech D21s instead. While I have been pretty successful at getting BP clusters lit, I have never tried AP. This is going to be a rather expensive proposition so I wanted to get your best advice on getter a dozen of the little monsters to go off. On the bright side, I believe they are Blue Thunder propellant and that should help, from what I understand.
 
I've clulsted 3 D24Ts with wire wrap and thermolite, but this is way beyond that.
I'd try applying a thin layer of pyrogen to Q2G2 igniters. Do some single motor flights and see if you are getting solid, consistant ignition, then go for it. Don't forget the video camera.

John
 
They are blue thunder, which is helpful, but even so, this seems like it might be a challenge. I would definitely fly a few D21s in a single motor rocket using your potential ignition candidates, and make sure that you can get reliable, fast ignition before you try to light 12 at once.
 
John,

Do you have any pictures or diagrams? This sounds like a very interesting project.

Firing a large cluster of 18mm AP motors would be extremely challenging, because your igniter will have to pass deep into a small motor and not block the nozzle.

I am not aware of any igniter or ematch on the market that would be a good match for clustering such a small AP motor. I CATOed or failed to ignite most of the AT E15s I attempted to cluster last year.

To back up a step, has the rocket been built? Specifically the motor mounts?

If not, I would build it for 24mm BP motors. Estes motors have a nice thrust spike at the beginning of their burn. They are also much easier to ignite, both because they are BP and they only require shallow placement of the igniter. They cost less so you will be able to have more flights per $.

If you absolutely must use AT D21 motors in clusters, the previous suggestion to prove out ignition method is critical.

You will likely have to make igniters from scratch using thin twisted pair wire (pulled from computer Ethernet cable), wrap your own nichrome, and dip in Rocketflite pyrogen. It will probably take several rounds of producing and testing these on the ground and in single motor flights before you might have something that could work for a big cluster.

It would be less work and produce more reliable results to do whatever is necessary to fly this rocket on 24mm BP motors.
 
Last edited:
I have not been in for a few days because a big storm on Tuesday left me with a fried server, no email or web access. I have not abandoned this thread and will be back when I can get on my machine.
 
Hmmm...thinking out loud....

The D21's will indeed be a beeeatch to light. You might try 30ga t.p. igniters made with a conductive primer v. a larger gauge wire with a bridge. I've made hundreds of these, and only had a few fail to work. However, it is more difficult to keep the pyrogen layer thin enough for an 18mm reload and you'd need to practice getting matched resistances. I've punted and used the stock copperheads on my 18mm reloads.

Also an H250 is not a very good match for a saucer-like object (assuming this is the aeroshell?).

I assume there is not room to CHAD stage 12 D12's? :dark:
 
John,

Do you have any pictures or diagrams? This sounds like a very interesting project.

Firing a large cluster of 18mm AP motors would be extremely challenging, because your igniter will have to pass deep into a small motor and not block the nozzle.

I am not aware of any igniter or ematch on the market that would be a good match for clustering such a small AP motor. I CATOed or failed to ignite most of the AT E15s I attempted to cluster last year.

To back up a step, has the rocket been built? Specifically the motor mounts?

If not, I would build it for 24mm BP motors. Estes motors have a nice thrust spike at the beginning of their burn. They are also much easier to ignite, both because they are BP and they only require shallow placement of the igniter. They cost less so you will be able to have more flights per $.

If you absolutely must use AT D21 motors in clusters, the previous suggestion to prove out ignition method is critical.

You will likely have to make igniters from scratch using thin twisted pair wire (pulled from computer Ethernet cable), wrap your own nichrome, and dip in Rocketflite pyrogen. It will probably take several rounds of producing and testing these on the ground and in single motor flights before you might have something that could work for a big cluster.

It would be less work and produce more reliable results to do whatever is necessary to fly this rocket on 24mm BP motors.

The thread for the stalled build is here: https://www.rocketryforum.com/showthread.php?t=14

The motor mount is built and pretty well committed to 18mm. I was originally going to use C6s but Art Applewhite told me that was the right choice as far as ignition goes but would not handle the aeroshell. He mentioned the Ds but also said igniting them would be practically impossible. He said that one of the important things with his saucer designs is to get a high enough thrust or it turns sideways very quickly. The ones I have built have born this out.

In my fantasy world, I was hoping you'd say those new Quest igniters would be just the ticket.:rolleyes:

Farther down the line, I have plans for a 8x24mm version but for now, I have a LOT of time and money into this 12x18mm beast. Sandman turned the parts and Stickershock made up the shrouds. Squirrel works made the truss elements but I am going to have to get new ones because I left a critical part out when I sent him drawings (I went from the scale info instead of my "semi'scale" working drawings. In other words, the blunder was mine: Squirrel Works did a great job with what I sent but I sent the wrong info.
 
Hmmm...thinking out loud....

The D21's will indeed be a beeeatch to light. You might try 30ga t.p. igniters made with a conductive primer v. a larger gauge wire with a bridge. I've made hundreds of these, and only had a few fail to work. However, it is more difficult to keep the pyrogen layer thin enough for an 18mm reload and you'd need to practice getting matched resistances. I've punted and used the stock copperheads on my 18mm reloads.

Also an H250 is not a very good match for a saucer-like object (assuming this is the aeroshell?).

I assume there is not room to CHAD stage 12 D12's? :dark:

You got it on the aeroshell. It already has 18mm mounts. I'm not talking about reloads though. I don't even have an 18mm case. Its the SU D21s I'm thinking about.

I tend to trust Art Applewhite when talking about saucer performance. He says I want a fairly high thrust. Remember also that since the mounts are canted, the vertical thrust will be a product of the sine of the angle.
 
I've clulsted 3 D24Ts with wire wrap and thermolite, but this is way beyond that.
I'd try applying a thin layer of pyrogen to Q2G2 igniters. Do some single motor flights and see if you are getting solid, consistant ignition, then go for it. Don't forget the video camera.

John

I've been hoping somebody would say "Q2G2". I have quickburst pyrogen. I can try coating a few igniters and see what happens. I have not yet ordered the D21s because I really need to finish the rocket. My wife wants it off of her shelf in the garage very badly!
 
You got it on the aeroshell. It already has 18mm mounts. I'm not talking about reloads though. I don't even have an 18mm case. Its the SU D21s I'm thinking about.

I tend to trust Art Applewhite when talking about saucer performance. He says I want a fairly high thrust. Remember also that since the mounts are canted, the vertical thrust will be a product of the sine of the angle.

I realize you were using the D21 but I haven't used one in years and was thinking the D24 RMS should be somewhat comparable for discussion sake.

While you saucer may be heavy and you might need that much average impulse, the quick burn time is still not optimal. But if you can't live with C6's, you are kinda up a creek. That's going to be one expensive H flight!

The Q2G2 might very well be a good option. I haven't tried dipping them but from what I hear the tend to pop when they go off, which is generally not good for a dipped igniter. Also, although easier than a home brew, keeping the diameter down will take practice. A 30ga gap igniter starts really skinny.

Another idea would be to contact Green Monkey to see what they do for their small reloads.
 
How much does it weigh? If 12 18mm black powder motor are not enough to get it into the air, then some design compromises might make a flight possible. Maybe a central 29 mm motor to get it moving (perhaps as a booster engine).
 
Checked out your build thread.

This is a very cool project, really nice work. Remarkable scale detail.

What is the diameter and weight of the aeroshell?

I've built and flown a number of Applewhite's saucers and have been impressed with the very wide range of motors any given saucer can fly on.

For example my 18" saucer has flown well on G to I power. Weight without engines is 28oz. It has done nice flights on 7x D12 motors, low and slow, but a safe and fun flight.

A saucer will weathercock when engine thrust level is modest, but if the engine only burns for 1.5 seconds, the burn will be done well before the saucer nears the ground. This type of weathercock is not a safety hazard.

Unless your project is heavier than it looks, you may get good flights from 12x C6 motors. Estes motors have a strong initial thrust spike which will get the rocket moving and stable quickly.
 
How much does it weigh? If 12 18mm black powder motor are not enough to get it into the air, then some design compromises might make a flight possible. Maybe a central 29 mm motor to get it moving (perhaps as a booster engine).

You can do is use a one inch drill bit (spade bit) and just put as many 1" holes in the aft bulkhead you can, and install the Ds or D mounts in those(whatever fits) I know it's non scale, but a bunch of D's has got to help.

Even if you can get one in it has to help.

If that is not good enough, you could take out all the material in the center of the aft bulkhead and stuff in a cluster of as many 24mm tubes as will fit. This is what I would try. I would draw a circle on the aft bulkhead at a diameter that would not interfere with the 18mm motors when installed, that is big enough to slip fit all the 24 mm mounts glued together that will fit. It looks like at least three will fit but ideally you can cram 5 in there. Drill holes on the circle and use a thin saw to cut between the holes. Glue up your 24mm motor cluster and slide it into the hole so the mounts are flush with the aft end of what is left of the bulkhead. You will have removed a ton of weight and added a lot of peak thrust and total impulse. You can make a cardstock cover for the aft end for scale display to cover the 24mm holes.

To be clear, all the aft bulkhead material visible in this photo inside the tube would be removed and replaced with a 24mm cluster.

This is one of the neatest projects I have ever seen, and I have been following it since you started it.

Good luck!!
 
Last edited:
I realize you were using the D21 but I haven't used one in years and was thinking the D24 RMS should be somewhat comparable for discussion sake.

While you saucer may be heavy and you might need that much average impulse, the quick burn time is still not optimal. But if you can't live with C6's, you are kinda up a creek. That's going to be one expensive H flight!

The Q2G2 might very well be a good option. I haven't tried dipping them but from what I hear the tend to pop when they go off, which is generally not good for a dipped igniter. Also, although easier than a home brew, keeping the diameter down will take practice. A 30ga gap igniter starts really skinny.

Another idea would be to contact Green Monkey to see what they do for their small reloads.

I like the Green MOnkey idea. I'll ahve to give that a try.
 
How much does it weigh? If 12 18mm black powder motor are not enough to get it into the air, then some design compromises might make a flight possible. Maybe a central 29 mm motor to get it moving (perhaps as a booster engine).

That's something I've thought about as a fallback position but I really want to try it the "real way" first.

I'm afraid I don't yet have a weight. THis thing is progressing at its own pace and fairly empirically as opposed to being well thought out rocket science.
 
Checked out your build thread.

This is a very cool project, really nice work. Remarkable scale detail.

What is the diameter and weight of the aeroshell?

I've built and flown a number of Applewhite's saucers and have been impressed with the very wide range of motors any given saucer can fly on.

For example my 18" saucer has flown well on G to I power. Weight without engines is 28oz. It has done nice flights on 7x D12 motors, low and slow, but a safe and fun flight.

A saucer will weathercock when engine thrust level is modest, but if the engine only burns for 1.5 seconds, the burn will be done well before the saucer nears the ground. This type of weathercock is not a safety hazard.

Unless your project is heavier than it looks, you may get good flights from 12x C6 motors. Estes motors have a strong initial thrust spike which will get the rocket moving and stable quickly.

Just for $$$ sake, I might try the C6s when nobody is looking. I need to get it high enough to deploy the laundry, though. This one does not aerobrake. Remember, the original vehicle was to test chutes for the martian atmosphere.
 
You can do is use a one inch drill bit (spade bit) and just put as many 1" holes in the aft bulkhead you can, and install the Ds or D mounts in those(whatever fits) I know it's non scale, but a bunch of D's has got to help.

Even if you can get one in it has to help.

If that is not good enough, you could take out all the material in the center of the aft bulkhead and stuff in a cluster of as many 24mm tubes as will fit. This is what I would try. I would draw a circle on the aft bulkhead at a diameter that would not interfere with the 18mm motors when installed, that is big enough to slip fit all the 24 mm mounts glued together that will fit. It looks like at least three will fit but ideally you can cram 5 in there. Drill holes on the circle and use a thin saw to cut between the holes. Glue up your 24mm motor cluster and slide it into the hole so the mounts are flush with the aft end of what is left of the bulkhead. You will have removed a ton of weight and added a lot of peak thrust and total impulse. You can make a cardstock cover for the aft end for scale display to cover the 24mm holes.

To be clear, all the aft bulkhead material visible in this photo inside the tube would be removed and replaced with a 24mm cluster.

This is one of the neatest projects I have ever seen, and I have been following it since you started it.

Good luck!!


Thanks for the kind words.

As I mentioned a few posts ago, when Art first told me of his reservations, I thought about penetrating the center of the aft bulkhead to add a bigger motor there. I'm resisting doing so for two reasons. One is that I want to try and do it the "right way" but am willing to try that approach if all else fails.

The second reason is that the material you refer to in the photo is supposed to be the anchor point for the laundry. I'd rather not rely on a LOC or Estes style mount if I can avoid it. I was going to put an eye bolt right through the middle there.
 
I just read the first half of this thread, so I hope this hasn't already been answered. An igniter that I have made that works really well for small motors is made from 30 gauge wire from radio shack. I wrapped it with 36 gauge nichrome wire from commonwealth displays, then dipped it with some really hot homemade pyrogen (if you want the pyrogen info PM me).

This has lit everything from D21 - G64. I think that the only failure was me not wrapping the nichrome well. Everytime the pyrogen lit it lit the motor.

Again, sorry if this question has already been answered. :)

Sam
 
I just read the first half of this thread, so I hope this hasn't already been answered. An igniter that I have made that works really well for small motors is made from 30 gauge wire from radio shack. I wrapped it with 36 gauge nichrome wire from commonwealth displays, then dipped it with some really hot homemade pyrogen (if you want the pyrogen info PM me).

This has lit everything from D21 - G64. I think that the only failure was me not wrapping the nichrome well. Everytime the pyrogen lit it lit the motor.

Again, sorry if this question has already been answered. :)

Sam

Don't be sorry. I appreciate all the input I can get.
 
Back
Top