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afadeev

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Just so you know, our production staff has been briefed on this potential issue and our production manager has changed the motor assembly procedures to specifically address it. I don’t expect it to be a problem moving forward.
Thank you for following up on this !

a
 

jrap330

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That was a real strange one because no epoxy is used in the delay assembly of our standard single use motors. Apparently what happened was that the employee building the motors got a drip of epoxy in the touch hole during the process of applying the bead of epoxy at the case/bulkhead interface.
Leads to this question..so all SU motors are hand made.....no automatic machinery used? Just thinking about Mabel.
 

PatD

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Just so you know, our production staff has been briefed on this potential issue and our production manager has changed the motor assembly procedures to specifically address it. I don’t expect it to be a problem moving forward.
I really wasn't trying to cause a dustup over this. As I said in my post this was just a heads up for folks to check for issues prior to launch. Aerotechs response has been great. I did have one question. If I find another of these can I just drill through the epoxy? Don't really want to pay the hazmat fee to send it back.
 

AeroTech

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Our production manager informs me that this problem has been resolved and corrective action taken. Please be sure to contact Karl at warranty@aerotech-rocketry.com.

I flew an F67-6W Economax motor on Saturday. The flight was good; the recovery, not. There was no ejection. Afterwards I checked the motor:
View attachment 422762
No scorching from ejection charges...

I checked the other one, still in the package:

View attachment 422763

So check your motors for ejection charges, otherwise your Leviathan may end up like this:
View attachment 422764
 

AeroTech

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Yes, you can drill it or cut it out with a hobby knife.

QUOTE="PatD, post: 2017140, member: 24024"]
I really wasn't trying to cause a dustup over this. As I said in my post this was just a heads up for folks to check for issues prior to launch. Aerotechs response has been great. I did have one question. If I find another of these can I just drill through the epoxy? Don't really want to pay the hazmat fee to send it back.
[/QUOTE]
 

AeroTech

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There are automated processes involved in the production of most of the motor components, but the final motor assembly is indeed performed by hand. The quantities being produced do not justify the cost of automated assembly equipment.

Leads to this question..so all SU motors are hand made.....no automatic machinery used? Just thinking about Mabel.
 

Mike Haberer

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Had two core samples at the last club launch. First HP ballistic recoveries that I can recall. I believe I know what caused the second one, an IO on a G77R. Yes, I have filed a MESS report and yes I have communicated with AT about it and they are replacing the motor, great warranty response. This is in the vein of a public information announcement. Normal motor function and coast. Motor recovery charge failed to fire. This was determined by post mortem exam. The bp charge chamber on the motor was not singed and the unsinged charge cap (along with the bp I assume, hard to tell on a well flown bird) were found in the bt. After I cleaned the dust from the motor charge well I observed what appeared to be epoxy in the touch hole above the delay column. I had checked to ensure that there was bp in the well, but didn't remove it. Guess that is one more thing to check with single use motors in the future. The glint in the photo is the epoxy in the touch hole. AT requested, and I sent to them the casing. The request was framed to use the casing as a training tool. I can understand that. :) I don't have the manufacturers code for the motor because it was one of the motors with a stick on label that precluded inserting it into the motor tube and I scraped it off. Guess I'll have to record that info before I peel a label in the future. Another lesson learned.
View attachment 422587
View attachment 422588
That's my one beef with AT SU engines. I almost always have to remove the labels to get the motor to fit into the MMT.
 

AeroTech

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Hi Mike, that’s interesting and concerning. When we designed the molded cases, we deliberately reduced the case diameter by 0.005” to eliminate this problem. In theory.

Who produces the MMT in question?

That's my one beef with AT SU engines. I almost always have to remove the labels to get the motor to fit into the MMT.
 

crossfire

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Hi Mike, that’s interesting and concerning. When we designed the molded cases, we deliberately reduced the case diameter by 0.005” to eliminate this problem. In theory.

Who produces the MMT in question?
I think it had to do with the MMTs. The fiberglass MMT are right on. But I built 2 kits from different vendors with paper mmts. One fit perfect and one was tight.
 

ChicagoDave

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I think it had to do with the MMTs. The fiberglass MMT are right on. But I built 2 kits from different vendors with paper mmts. One fit perfect and one was tight.
I just flew 2x AT J270 in a LOC Sandhawk 38mm MMT with the Aerotech retainer -- basically as standard and Aerotech as you can get. In both cases I had to use my knife to strip off the paper label on the J270 to get it to fit in the MMT. I don't remember if I had the same issue on the I205 (A 29mm LOC MMT + Aeropack retainer) but I keep my knife in my kit just in case.

Dave
 

Mike Haberer

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Hi Mike, that’s interesting and concerning. When we designed the molded cases, we deliberately reduced the case diameter by 0.005” to eliminate this problem. In theory.

Who produces the MMT in question?
Hard to know at this point. The two rockets I've flown 29mm SU's in is an NCR 1/4 scale Patriot that I swapped out the stock MMT tube since it was odd sized. I can't remember where I sourced it from (over a decade ago). The other is a Sheri's Hot Rockets Mercury Redstone. I've had it for years as well, so I can't recall if I bought it from Sheri directly or from Red Arrow Hobbies after she sold out to them. Either way, I don't know where they sourced their parts, could have been anyone's. I've designed some 3D printed parts for marking fins and such; they have to be sized for the largest diameters in any given "standard" sized airframe or MMT. I learned that the hard way.

I've attached a spreadsheet I put together of body tube dimensions from every vendor and source I can find. All I can say is there is no standard, ODs and IDs can be all over the board.
 

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Walter Longburn

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I use public missiles tubes and I never have had to take the label off the motors to get them in. I'm talking about 29mm, 38mm, and 54mm.
 

Mike Haberer

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I use public missiles tubes and I never have had to take the label off the motors to get them in. I'm talking about 29mm, 38mm, and 54mm.
I can confirm that. My PML Bullpuppy died a tragic death, but I have the engine from the fatal flight and the label is on it.
 

rcktnut

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I have some G71's and G33's that have been around for a few years. I remember hearing a few years ago that some delay grains "age" with time and was wondering if it would be good to buy some new HDK's for them. Also have some older HP redline motors and Black jack motors, would it be good to get new delay kits for those also? Any other propellant types that have been stored for quite some time (10+ years} that might need new delays? Time to burn these up!! I had one G75 {the good old ones} BJ motor that I used and the delay was way long. Got 4 more of those also. THANKS.
 

beeblebrox

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I have some G71's and G33's that have been around for a few years. I remember hearing a few years ago that some delay grains "age" with time and was wondering if it would be good to buy some new HDK's for them. Also have some older HP redline motors and Black jack motors, would it be good to get new delay kits for those also? Any other propellant types that have been stored for quite some time (10+ years} that might need new delays? Time to burn these up!! I had one G75 {the good old ones} BJ motor that I used and the delay was way long. Got 4 more of those also. THANKS.
Simple solution, get a cheap altimeter like an Eggtimer Quark. Even if you have it built for you it is the cheapen dual deploy out there. <$50 including shipping. Then you don't need no steeeenking delays... just take out the BP to use in charge wells...
 

DankMemes

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Am I mistaken or did I see something a while back on AT facebook page about a Redline load for the hobbyline case?
 

ChicagoDave

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I have some G71's and G33's that have been around for a few years. I remember hearing a few years ago that some delay grains "age" with time and was wondering if it would be good to buy some new HDK's for them. Also have some older HP redline motors and Black jack motors, would it be good to get new delay kits for those also? Any other propellant types that have been stored for quite some time (10+ years} that might need new delays? Time to burn these up!! I had one G75 {the good old ones} BJ motor that I used and the delay was way long. Got 4 more of those also. THANKS.
You definitely can purchase delay grains from AeroTech directly. I've done so when I accidently drilled a delay too short. I would recommend replacing the delay grains if they are in question and you plan on using motor ejection.

Otherwise, as mentioned, chuck the delay grains and use altimeter ejection and you won't have to worry about the delay :)
 

rcktnut

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I guess I'll just get some delay kits to be sure. Want to use on MPR rockets that have no DD. Some of the HPR I will use the DD.
 

djs

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Am I mistaken or did I see something a while back on AT facebook page about a Redline load for the hobbyline case?
There was one about 2 (3?) years ago. I flew a prototype at Midwest Power that year. I don't think it ever got made though.
 

Retrospace101

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Just Curious, Is it possible for the G40 or G80 to have their total impulse increased to 150 or 160 Ns? As 160 is the Total Impulse limit, or would it be harder to certify?
 

AeroTech

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Not in the existing form factor. Not enough room in the casing for the extra propellant. However, now that I think about it, if we used the short bulkhead that is in the G74 and F67 motors, we could increase it a bit. That, and using Super White Lightning would increase the Isp. The trick would be to keep the average impulse under 80 N. Also, the short bulkhead would limit the maximum time delay length. It would likely be something other than a G40 or G80.

Just Curious, Is it possible for the G40 or G80 to have their total impulse increased to 150 or 160 Ns? As 160 is the Total Impulse limit, or would it be harder to certify?
 
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Retrospace101

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. The trick would be to keep the average impulse under 80 N. Also, the short bulkhead would limit the maximum time delay length. It would likely be something other than a G40 or G80.
Hmmmm, Curious as to what that would make, a G60, G65, G90, G95?
 
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