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ATGM said:
The G71R was a little before my time so I am not sure what the exact issue was but I think there was a delay issue so we stopped making them. Maybe other TRF members can recollect better than I can but it was something like that. That is why a new red load for the 29/40-120 is such a highly requested load. We are developing new loads for the hobby line now and a red to replace the G71R is on the list.
Click to expand...

I love the red flame motors! Can't wait until the new 40-120 red comes out. Here are a couple pictures I took of the nozzel from that G71R that failed today. No idea what would've caused it. ImageUploadedByRocketry Forum1477437342.848059.jpgImageUploadedByRocketry Forum1477437354.458601.jpg
 
ATGM said:
The G71R was a little before my time so I am not sure what the exact issue was but I think there was a delay issue so we stopped making them. Maybe other TRF members can recollect better than I can but it was something like that. That is why a new red load for the 29/40-120 is such a highly requested load. We are developing new loads for the hobby line now and a red to replace the G71R is on the list.
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I think the problem with the G71R was some chemical in the propellant grain was contaminating the delay grain. The problem got worse as the reload aged. The suggested work around was to use new delay grains packaged separately from the propellant grain.
 
mwtoelle said:
I think the problem with the G71R was some chemical in the propellant grain was contaminating the delay grain. The problem got worse as the reload aged. The suggested work around was to use new delay grains packaged separately from the propellant grain.
Click to expand...

I believe you are correct, Karl said something in an email about a similar problem I had with an older (10 year or so) I218R that had a "very fast" delay (ejection charge about 2-3 seconds after motor burn out). One of the chemicals could migrate over time from the propellant to the delay grain, accelerating the delay grains burn rate iirc.
 
rharshberger said:
I believe you are correct, Karl said something in an email about a similar problem I had with an older (10 year or so) I218R that had a "very fast" delay (ejection charge about 2-3 seconds after motor burn out). One of the chemicals could migrate over time from the propellant to the delay grain, accelerating the delay grains burn rate iirc.
Click to expand...

That makes sense. But my "7" second delay ended up being about a 25-30 second delay. I had the opposite problem you had
 
noffie79 said:
This post is definitely not to trash AT. I simply want to know if anyone has any input as to why this may have happened. I know the 29mm G71R-7 is an old motor, but I've launched three of them prior to today and never had a problem. Bad delay grain, ignitor not installed all the way, or maybe even grease on the delay grain? I have no idea. If anyone can share some input, I'd appreciate it. Thanks! https://youtu.be/qKD2t6Jl3mQ
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The G71R had issues with the delay going off immediately or very early after motor burn. However this flight shows something I have seen on old redline reloads. The motor chuffs repeatedly before igniting (using up part of the propellent) before coming up to pressure. The delay grain does not light right away, which results in a long bonus delay. You can see the tracking smoke after the lawn dart in the video. Sand the grains on older redlines to help prevent this. There were also some issues with the delay grain being effected by the redline propellant on older reloads. I remember at some point the delay was modified and sealed up to prevent contact with the grains before use.
 
Anyone know the powder weight included for ejection charge in 38, and 54mm DMS motors? Is it 1.5 grams for 38mm and 2 grams for 54mm?
 
Thanks for the quick turn around on the last few orders. Middle of next week we will have your new H219T DMS, J540DM DMS, and K2050ST reloads in stock and on the web store. With the other major motor company problems I am happy you are keeping up with demand and actually have time to add new product.
 
calambert said:
Anyone know the powder weight included for ejection charge in 38, and 54mm DMS motors? Is it 1.5 grams for 38mm and 2 grams for 54mm?
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I think they all come with vials containing 1.4 grams. You can add (Flier supplied BP) or subtract as needed.

https://www.aerotech-rocketry.com/u...76c23bd97ea_DMS Instructions 7-9-14 Small.pdf

2.2 WARNING: Do not smoke and ensure that
there are no open flames or heat sources nearby
when installing the ejection charge. Open the
ejection charge vial and dispense the desired
amount of black powder ejection charge into the
ejection charge well of the motor bulkhead. Use
about ½ of the contents of the vial for 2.6” diameter
rockets and smaller, and the entire vial for 3” and
larger rockets. Note: additional ejection charge may


Tony
 
Hi Charlie;
Just built my first 98 AT motor for my L3 this weekend and I wanted to point out 2 very small things on my 98 /10249 assembly of an M1939.

In the instructions - Fig 6. Don't say anything or show in the diagram the thin propellant grain O-rings. I watched the video and knew about them - but noted the instructions didn't say anything about it.

ImageUploadedByRocketry Forum1478024953.242397.jpg

Also the smoke grain insulator was oversized by about 0.007" and wouldn't fit into the forward closure which required sanding.

Also in reading the Aerotech Grain Bonding document - it appears the loads needing bonding are the blue. And super thunders - however the N2000W is also on that list which is a load I may plan on flying. Question is - why not just grain bond all the loads in this size? Noticed in the instructions that a load may have slop in the grain length allowing them to move in the motor and that is OK, so grain bonding - Is it a matter of fit and thrust?

Thanks - looking forward to the power of the M1939!

PS the motor went together fine and the video made it a breeze.
 
Nick@JET said:
Hi Charlie;
Just built my first 98 AT motor for my L3 this weekend and I wanted to point out 2 very small things on my 98 /10249 assembly of an M1939.

In the instructions - Fig 6. Don't say anything or show in the diagram the thin propellant grain O-rings. I watched the video and knew about them - but noted the instructions didn't say anything about it.

View attachment 304381

Also the smoke grain insulator was oversized by about 0.007" and wouldn't fit into the forward closure which required sanding.

Also in reading the Aerotech Grain Bonding document - it appears the loads needing bonding are the blue. And super thunders - however the N2000W is also on that list which is a load I may plan on flying. Question is - why not just grain bond all the loads in this size? Noticed in the instructions that a load may have slop in the grain length allowing them to move in the motor and that is OK, so grain bonding - Is it a matter of fit and thrust?

Thanks - looking forward to the power of the M1939!

PS the motor went together fine and the video made it a breeze.
Click to expand...

Thanks for bringing the instructions up, it is something I wanted to discuss as we continue to make changes to the product lines. Beginning with the 38mm we have switched to what we refer to as a 'generic' instruction. This eliminates a lot of confusion and we have the 29mm HP line all the way through the 98mm going with the newer instructions. This will address issues like the grain spacer o-rings and other changes that have taken place over the last few years.

The grain-bonding instructions pretty much cover those loads that have higher thrusts along with loads for the 98/15360 case. The N2000W doesn't necessarily have to be bonded to work as it hasn't been bonded previously without issue, however bonding does ensure the best performance and lowers the risk of a grain coming down and plugging that nozzle up.

Enjoy that motor and I wish you well on your level 3! Post some pics too!
 
Where do I find a MESS report? I tried to fly one of your J250W-14A DMS motor at Midwest Power today (11/06). It lifted off the rail approx. 3 feet and the rear closurer let go, spitting out the grains. The Wildman Gizmo rocket fell to the ground and the body ended up on the rail. The rail was inside the body. They have photos. Thanks Greg Olson
 
ATGM said:
75 & 98mm RMS™ Reload Kit Grain Bonding Advisory

....

Therefore, we are advising all our customers to bond the grains of the following reload kits into
their liners with Elmer’s Glue-All Max™. This is a polyurethane glue with minimal foaming and
expansion to prevent the liner from cracking during cure, and has a long working time. The
bonding process itself takes only a few minutes after which the glue should be allowed to cure
overnight before use.

...

View attachment 303926
Click to expand...

I am having a hard time finding Elmer’s Glue-All Max™ locally. I don't have time to order it before this weekend. Can I use 30 minute epoxy instead? Or an alternate glue?
 
dshmel said:
I am having a hard time finding Elmer’s Glue-All Max™ locally. I don't have time to order it before this weekend. Can I use 30 minute epoxy instead? Or an alternate glue?
Click to expand...

Gorilla glue or Titebond polyurethane should work, use sparingly. Titebond is supposed to be low foaming, don't know if that or Elmer's is in comparison to Gorilla glue or not.
 
I've used Gorilla polyurethane alot for couplers and motor mounts (but not to glue motor grains). I would characterize it as NOT low foaming so maybe not the best choice for this application.
 
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ATGM said:
This complaint is 100% accurate. We are working on a matrix right now but that is a small step in my opinion. A larger concern of mine are the websites. It is a large project to be sure but one that we, as an industry leader, need to correct. In fact, here is the list of my current priorities:
-catalog
-website(s)
-hardware

If I had to prioritize them they would be 1a, 1b and 1c. Excellent point. I would say to expect the improved websites by mid-late June.
Click to expand...

Charlie,

I intended to do this a long time ago but... Thanks for all your help and attention at AirFest this year. It was awesome having AeroTech on site. I hope you can make it out next year as well.

What is the status on the improvements mentioned above? It has been about 1 1/2 since those comments were made and not much has changed with the website or catalog. I can tell you one piece of info that I used and still use from time to time is the chart that Rouse-Tech Motor Compatibility chart https://www.rouse-tech.com/motorchart.htm. It shows all the motors that fit in a specific case. I realize that there are new motors now that aren't on this chart but an equivalent chart on the AeroTech website would be awesome. Thanks again for your help with things. I have repaired my rocket that had the deployment failure due to my "excessive" use of grease in the delay well. It will be launched again Saturday on an AT I357R. Photo attached for a reminder of which rocket it was.

ScreamingEagle.jpg

ScreamingEagle.jpg
 
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Is the N dark matter going to be available soon? Trying to convince my dad out would be a good choice to do an L3
 
Mr. Savoie, I just had another 54mm load chew up a seal disk. I haven't filled out a MESS report or warranty claim yet. (Doing that this weekend)

I was wondering if the alloy has recently changed? The seal disk in question was flown with a K375NW and was the first and only flight on the seal disk.

This is the last disk I had replaced (K1103X) and the damage to the new one is very similar:
 
I have sent a MESS report on the failure of an Aerotech DMS J250W-14A at Midwest Power this past Sun. 11/06/2016. I am sending a warranty request to Aerotech.
 

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