Aero Tech motor spacers?

[thobin]

So where does one buy these Aero Tech motor spacers, and do they work? (The kind that let you put a one grain motor in a 3 grain case. And no i'm not thinking of the Cesaroni motors.) I have seen a video on you tube from Apogee but for some reason the site is down. And I can find no information on them elsewhere.

http://www.youtube.com/watch?v=o2VM7...eature=related

TA

[Yoehahn]

Wildmanrocketry.com
Performancehobbies.com

Look under AT hardware, they should have em.

[qquake2k]

I've got a 38mm Special, that I bought when they were available. I liked the theory, but not the practice. It's basically a 38/360 case, standard aft closure, special "floating" forward closure, and two spacers. It allows you to use 1-grain, 2-grain, or 3-grain reloads in the same case. The problem I've run into is that the floating forward closure is a pain in the butt when loading 1 or 2 grain reloads, since the closure sits down inside the motor case when it's loaded. In other words, the black powder well isn't exposed. That means you have to insert the delay grain, put the BP in the well and tape it, then hope the delay grain doesn't come dislodged while you're inserting it. I have since purchased 38/120 and 38/240 cases, and am much happier with them. For me, at least, they're a lot less tedious to load.

[thobin]

Anyone have any more firsthand experience with these AT spacers. This would to me seem to be the ticket to 38mm set. No matter how I work the numbers, paying anywhere from $ 5 to $10 per reload more for CTI PRO 38mm. The startup cost is lower but one year of flying and its irrelevant .

TA

[Zephhyr]

I have used the AT spacer system to fly an I366 (600case) motor in my 720 case (several times) and found it very easy to use, not much different than building up a motor without the spacer system.

[NAR29996]

Anyone have any more firsthand experience with these AT spacers. This would to me seem to be the ticket to 38mm set. No matter how I work the numbers, paying anywhere from $ 5 to $10 per reload more for CTI PRO 38mm. The startup cost is lower but one year of flying and its irrelevant .

TA

I have a set that I've used a couple of times. I've had no problems with it, but I always check the delay element for fit and add a bit of tape if too loose. I would use it more if I had more rockets that the case would fit in.

[jadebox]

I've got a 38mm Special, that I bought when they were available. I liked the theory, but not the practice. It's basically a 38/360 case, standard aft closure, special "floating" forward closure, and two spacers. It allows you to use 1-grain, 2-grain, or 3-grain reloads in the same case. The problem I've run into is that the floating forward closure is a pain in the butt when loading 1 or 2 grain reloads, since the closure sits down inside the motor case when it's loaded. In other words, the black powder well isn't exposed. That means you have to insert the delay grain, put the BP in the well and tape it, then hope the delay grain doesn't come dislodged while you're inserting it. I have since purchased 38/120 and 38/240 cases, and am much happier with them. For me, at least, they're a lot less tedious to load.

I had about the same experience using a 54mm case with the spacers. It's becomes a bit like a juggling act to get all the pieces together. But, it's nice to be able to use more sizes of reloads in the same case.

The CTI spacers, on the other hand, don't make it any more difficult to assemble the motor.

-- Roger

[KenRico]

I've got a 38mm Special, that I bought when they were available. I liked the theory, but not the practice. It's basically a 38/360 case, standard aft closure, special "floating" forward closure, and two spacers. It allows you to use 1-grain, 2-grain, or 3-grain reloads in the same case. The problem I've run into is that the floating forward closure is a pain in the butt when loading 1 or 2 grain reloads, since the closure sits down inside the motor case when it's loaded. In other words, the black powder well isn't exposed. That means you have to insert the delay grain, put the BP in the well and tape it, then hope the delay grain doesn't come dislodged while you're inserting it. I have since purchased 38/120 and 38/240 cases, and am much happier with them. For me, at least, they're a lot less tedious to load.

Thanks for the pics , watched the Apogee Video but except for him sliding it into a case you never really see what goes where and how it fits .

720 case and a seal disk and will be ready for the DARK MATTER !

[gldknght]

I've got a 38mm set of these, used them a couple times. I like them a lot. As others have noted, makes it possible to fly a bunch of different reloads with just one or two cases.

One suggestion, coat the inside portion of your case (forward of the floating closure, but not the floating closure itself) with grease before you load, and coat the spacers too. Makes clean up WAY! easier.

[Viperfixr]

I've got the 'adapter' system for 38mm and have used it on 3-4 flights. It works--I've had no failures at all. That said, it's not as easy as the CTI spacer system for the same reason mentioned above...too easy to let the delay move when inserting down the casing. I was using it to load 38/360 reloads in the 480 casing. But, I fly the 360 reloads a bit, so I just bought a 360 case to eliminate the worry. Depending on motor eject while using the adapter is less confidence inspiring than the normal reload assembly, for me.

It's good to have in a pinch, but I wouldn't recommend it to a newbie learning how to build motors for the first time.

[Zeus-cat]

I have the AT 38mm/480 case and the two spacer kit. I was going to get the 360 case with the spacers, but my local vendor convinced me to get the 480 case. I'm glad I did as I now reaiize that I would never use the 120 reloads; just not enough oomph. I have four launches on the 480 case, with three of them using one or both spacers. They do provide a lot of flexibilty for only a slightly more complex motor build.

qquake2k has a valid complaint; it can be a juggling act. I had a loose delay grain on my last motor. I should have added tape or something to get it snuggly into the forward closure. The thing with AT reloads, and high power rockets in general, is take your time and do not rush anything. Ask someone if you need help. If you are not sure, do not launch!

[thobin]

Thanks for all the info, I have experience putting the motors together just not with the spacers. I was just curious if it worked well or not. Good point about the 360 case I don't have a rocket that would do well on the 120 and you would almost need to have the 120 case to fit in some of these stubby rockets that I see them used. Thanks

TA

[MarkII]

Anyone have any more firsthand experience with these AT spacers. This would to me seem to be the ticket to 38mm set. No matter how I work the numbers, paying anywhere from $ 5 to $10 per reload more for CTI PRO 38mm. The startup cost is lower but one year of flying and its irrelevant .

TA

I used the motor and a spacer from my 29 Special for my successful Level 1 flight last year. I used an H165R reload (designed for the 29/180 motor) in the 29/240 motor from the Special, along with one spacer. I assembled the entire motor at the field on top of my motor box immediately prior to the flight. It was no big deal and the motor performed fine.

Method #1: What I Did

To add the ejection charge into the recessed well after the motor was assembled, I rolled up a piece of paper to make a small funnel. I inserted it so that the end was down inside the well, and then poured in the BP from the top. I then tapped the funnel lightly before slowly and carefully removing it. I was able to place the paper seal disk in with the tip of my finger, and was able to put a small strip of tape over it in the same manner.

A variation of this is to obtain an actual small funnel and modify it to extend the length of the outlet tube by taping a section cut from a drinking straw to it.

Method #2: What AeroTech Recommends

Another way to installed the charge is to attach the plastic canister to the end of a dowel with a wrap of tape around the canister and dowel. Holding it up vertically, open the canister and then lower the inverted motor down onto it until the top of the canister is up against the inside of the charge well in the forward closure. While still holding it against the well, invert the assembly again so that the forward end of the motor is now pointing up, and then withdraw the dowel.

Due to financial pressures, I haven't made any more high power flights since then, so it's my only experience so far with the Reload Adapter System.

With a slight change, Method #2 is the better procedure if your reload kit comes with a plastic cap that snaps on over the ejection well instead of an adhesive paper disk. You just need to pour the charge into the cap, and then attach it to the end of the dowel with something that is only lightly sticky, like roll-on glue or a small ball of glue or tape. Then when you lower the inverted motor down over the dowel and end cap, you can push the cap on and complete the installation right then. Twist the dowel to break its attachment to the cap afterward.

[Handeman]

I have the AT 38mm/480 case and the two spacer kit. I was going to get the 360 case with the spacers, but my local vendor convinced me to get the 480 case. I'm glad I did as I now reaiize that I would never use the 120 reloads; just not enough oomph. I have four launches on the 480 case, with three of them using one or both spacers. They do provide a lot of flexibilty for only a slightly more complex motor build.

qquake2k has a valid complaint; it can be a juggling act. I had a loose delay grain on my last motor. I should have added tape or something to get it snuggly into the forward closure. The thing with AT reloads, and high power rockets in general, is take your time and do not rush anything. Ask someone if you need help. If you are not sure, do not launch!

I don't understand how you can have a loose delay grain on a Aerotech HPR reload. The grain fits inside the liner, and extends outward enough for the o-ring to fit around the delay grain. Those o-rings are snug and hold the grain in the cap quite well, have you ever tried taking one back out?

[MarkII]

I don't understand how you can have a loose delay grain on a Aerotech HPR reload. The grain fits inside the liner, and extends outward enough for the o-ring to fit around the delay grain. Those o-rings are snug and hold the grain in the cap quite well, have you ever tried taking one back out?

I don't either, but I think that Zeus and others were changing the assembly sequence in order to fill the ejection charge well before installing the forward closure in the rocket. As I described in my post yesterday, you don't need to do that. You can fully assemble the motor, and then later pour in the ejection charge using a small funnel and a straw (if needed). Then use a finger or a dowel to push the adhesive paper disk or the cap in to cap the top of the well. I didn't find it to be much different from assembling an AeroTech motor in the usual manner, and I have always regarded that as quite simple and easy.

[Zeus-cat]

Sorry for the confusion; the delay grain was not loose, the liner was. I had the same issue today and wrapped some tape around the liner to get a better fit.

[Handeman]

Sorry for the confusion; the delay grain was not loose, the liner was. I had the same issue today and wrapped some tape around the liner to get a better fit.

Now I'm confused again. Why does a loose liner make a difference? It shouldn't matter what forward closure you're using. If you hold the case vertical when you work with it, you have to have a finger in the case to keep the liner and grains from falling out.

[Zeus-cat]

I was using a two grain motor in a four grain case with two spacers. I can't hold the delay in the forward closure when the closure is in the middle of the case. If you tip the case before you get everything tight the black powder could slip past the delay grain and into the propellant. That happened to me two weeks ago and I had to disassemble the motor and clean up the black powder that got on the propellant.

[qquake2k]

I was using a two grain motor in a four grain case with two spacers. I can't hold the delay in the forward closure when the closure is in the middle of the case. If you tip the case before you get everything tight the black powder could slip past the delay grain and into the propellant. That happened to me two weeks ago and I had to disassemble the motor and clean up the black powder that got on the propellant.

That's the exact problem I've had with using the spacers.

[Handeman]

I was using a two grain motor in a four grain case with two spacers. I can't hold the delay in the forward closure when the closure is in the middle of the case. If you tip the case before you get everything tight the black powder could slip past the delay grain and into the propellant. That happened to me two weeks ago and I had to disassemble the motor and clean up the black powder that got on the propellant.

That's the exact problem I've had with using the spacers.

Still confused

If the delay grain is tight in the well of the forward closure, how can the powder get past the delay grain?

[o1d_dude]

Sounds like the delay grain fits tight in the delay insulator but the insulator isn't tight in the forward closure. This allows the delay/insulator assembly to slide backwards which in turn allows the BP to spill into the the propellant grain area. Yes?

[Handeman]

Sounds like the delay grain fits tight in the delay insulator but the insulator isn't tight in the forward closure. This allows the delay/insulator assembly to slide backwards which in turn allows the BP to spill into the the propellant grain area. Yes?

They said earlier that the delay grain wasn't loose. I shouldn't be, even with a slightly loose insulator tube because the O-ring should keep everything in place.

[MarkII]

Still confused

If the delay grain is tight in the well of the forward closure, how can the powder get past the delay grain?

Even more perplexing: why do you have the ejection charge in the well while you are still assembling the motor? That shouldn't be added until everything is assembled and the closures are tightened down. That's the procedure described in the instructions. That way, no black powder can get past the delay grain.

[qquake2k]

Even more perplexing: why do you have the ejection charge in the well while you are still assembling the motor? That shouldn't be added until everything is assembled and the closures are tightened down. That's the procedure described in the instructions. That way, no black powder can get past the delay grain.

It's because with the adapter system, the forward closure with the BP well is down inside the motor case. You can't get to it to add the powder and seal it after the motor is assembled.

[qquake2k]

There's another thing to think about, too. I don't like putting all my eggs in one basket, so to speak. If I only have a 38/360 case with adapters in my arsenal, and I happen to lose or damage the case, then I'm stuck. With multiple cases and closures, I could still fly 38/240 or 38/120 loads.

[Zeus-cat]

Even more perplexing: why do you have the ejection charge in the well while you are still assembling the motor? That shouldn't be added until everything is assembled and the closures are tightened down. That's the procedure described in the instructions. That way, no black powder can get past the delay grain.

Here is a photo of a motor case and the spacer system. For those who have never seen the system the parts are as follows:

1) The long black tube is the motor case. This appears to be a three grain case.
2) The brass colored part is the rear closure.
3) The two cylinders next to the rear closure are the spacers.
4) The part front left is one of the parts that replaces the forward closure when using the spacers; you are looking down into the well where the ejection charge would sit.
5) The part right front is the other part that replaces the threaded forward closure. This part is the threaded section of the forward closure.

That is not how you actually assemble the motor, I am merely describing the stack up of all the parts. If you use a one grain motor in this three grain case you would use both spacers. First, #2 screws onto one end of #1. Then the propellant, liner, spacers, etc. go in. The delay grain goes into the bottom of #4 and the ejection charge goes into the well. That assembly goes on top of the propellant. Then the spacers (#4) go in. The first spacer slides over #4 and sits on the collar at the base of #4. The second spacer goes on top of the first spacer. And finally you screw on #5.

So now you can see how a loose delay grain can cause problems. In this example, part #4 is closer to the rear closure than to the forward closure when the motor is being assembled. There is no way you can add the ejection charge to the well after you assemble the motor.

[o1d_dude]

Interesting photo up above, Z-C.

My 29mm RAS came with everything shown above plus a seal disk and a third dark gray spacer which I assume is the XL one normally included for use in the case of a 4 grain reload in a 29-360 case.

I had my 29mm RAS out tonight because I'm planning to use an H180W reload in it this weekend. The AT RAS assembly diagram shows the front seal disk in use but this is for a reload with a phenolic liner (H220T) although there is no mention of this in the instructions. The AT H180 reload assembly instructions don't show the front seal disk in place. This is as it should be as the H180W has a paper liner.

I'm wondering if I can use the H180W reload kit in my RAS without there being an "unfortunate" outcome. The portion of the seal disk the protrudes out of the liner looks to be about the same thickness as the standard forward insulator. It all goes to together without any obvious problems but I'm looking for confirmation that this is a perfectly acceptable use of the 29mm RAS.

Thanks.

[gldknght]

Interesting photo up above, Z-C.

My 29mm RAS came with everything shown above plus a seal disk and a third dark gray spacer which I assume is the XL one normally included for use in the case of a 4 grain reload in a 29-360 case.

I had my 29mm RAS out tonight because I'm planning to use an H180W reload in it this weekend. The AT RAS assembly diagram shows the front seal disk in use but this is for a reload with a phenolic liner (H220T) although there is no mention of this in the instructions. The AT H180 reload assembly instructions don't show the front seal disk in place. This is as it should be as the H180W has a paper liner.

I'm wondering if I can use the H180W reload kit in my RAS without there being an "unfortunate" outcome. The portion of the seal disk the protrudes out of the liner looks to be about the same thickness as the standard forward insulator. It all goes to together without any obvious problems but I'm looking for confirmation that this is a perfectly acceptable use of the 29mm RAS.

Thanks.

I would suggest following the instructions for your particular reload. Not all reloads use the forward seal disk. The motor itself builds the same way, whether using a long case with adapters, or using a short case. The way I understand the seal disk use is it takes up the space created at the front of the motor when the motor grains are short and don't fill all the space inside the case. Hope that makes sense.

[troj]

I would suggest following the instructions for your particular reload. Not all reloads use the forward seal disk. The motor itself builds the same way, whether using a long case with adapters, or using a short case. The way I understand the seal disk use is it takes up the space created at the front of the motor when the motor grains are short and don't fill all the space inside the case. Hope that makes sense.

Close, but the grains are short in those motors, to allow space for the forward seal disc -- the disc is there because some motors generate enough pressure to need the better seal provided by the disc.

-Kevin

[qquake2k]

Interesting photo up above, Z-C.

My 29mm RAS came with everything shown above plus a seal disk and a third dark gray spacer which I assume is the XL one normally included for use in the case of a 4 grain reload in a 29-360 case.

I had my 29mm RAS out tonight because I'm planning to use an H180W reload in it this weekend. The AT RAS assembly diagram shows the front seal disk in use but this is for a reload with a phenolic liner (H220T) although there is no mention of this in the instructions. The AT H180 reload assembly instructions don't show the front seal disk in place. This is as it should be as the H180W has a paper liner.

I'm wondering if I can use the H180W reload kit in my RAS without there being an "unfortunate" outcome. The portion of the seal disk the protrudes out of the liner looks to be about the same thickness as the standard forward insulator. It all goes to together without any obvious problems but I'm looking for confirmation that this is a perfectly acceptable use of the 29mm RAS.

Thanks.

As far as I know, the motor would be assembled just as if you were going to put it in a 29/240 case. The only difference is the spacer. The forward closure sits on top of the propellant grains and forward insulator just as in a 240 case, but the spacer and forward retaining ring hold it tight. I have a 29/240 case if you want to use it on Saturday.

http://www.aerotech-rocketry.com/cus...80w-m_assy.pdf

http://www.aerotech-rocketry.com/upl...apter_inst.pdf