75mm DMS Single-Use Motors

JD I see no reason why you could not do HE ignition.

I would think this would be a great sustainer motor in a 2-stage. No hardware to worry about losing...etc....etc....etc

Here are the instructions and it looks like you glue the aluminum forward closure in.[with supplied glue] So I see where you could modify the closure to suite your needs.

https://www.aerotech-rocketry.com/resources.aspx?id=4 under single use instructions near top .



Disclaimer for rookies:

"modifying a commercial motor, means you now fly it on research days"

I'm confused. Wouldn't this properly be labeled an LMS? I thought, for Aerotech, DMS meant pre-assembled, almost-ready-to-use motors (other than delay adjustment/ejection, which this one doesn't have).

Actually Jim is right, I stand corrected. I haven't seen these instructions and assumed the 75mm DMS were completely pre-assembled. DMS just means Disposable Motor System, single use motors that are disposed of after use. Now this is an "LMS" kind of feature but the motor is still single use and disposable. It comes partially assembled as well. They probably just put it in that category to keep things simple. Moreover, with LMS you have to assemble the entire motor--all grains, the entire delay column assembly, all o-rings. This looks like you just throw in the grains and epoxy in the bulkhead for this.

marcusSRG said:

Actually Jim is right, I stand corrected. I haven't seen these instructions and assumed the 75mm DMS were completely pre-assembled. DMS just means Disposable Motor System, single use motors that are disposed of after use. Now this is an "LMS" kind of feature but the motor is still single use and disposable. It comes partially assembled as well. They probably just put it in that category to keep things simple. Moreover, with LMS you have to assemble the entire motor--all grains, the entire delay column assembly, all o-rings. This looks like you just throw in the grains and epoxy in the bulkhead for this.

Click to expand...

Still, I think of DMS as "almost ready to use", and I know that LMS implies, "gotta assemble, mix and wait for the epoxy to cure". At least they include the epoxy in these big ones.

Oh I hear ya. It certainly crosses that line... But AT has just standardized this as a DMS. Whatever Gary says is the word!

You have to install the grains and glue in the bulkhead so the motor can be shipped as 1.4. Total propellant weight is over 1400g.

Rocketjunkie said:

You have to install the grains and glue in the bulkhead so the motor can be shipped as 1.4. Total propellant weight is over 1400g.

Click to expand...

That explains it. I was wondering something about shipping and regs in the back of my head but didn't have the facts... Thanks, Tom.

And not a bad price . Very in Line to a reload

Looks like it's going to be $339

These motors makes me want to go L3 with no hardware involved. I guess I need to plan a L3 rocket build.

Well, Aerotech posted some pictures before I had a chance to respond; specifically someone inquired about the thrust ring on the M1350 - it is machined and integral to the case:



I'm not sure what thread the thrust ring question was brought up but I figure this one is as good as any to mention it.

Looks like the M1350 DMS is now going out to dealers. BuyRocketMotors.com shows them in stock for $339.

I picked up a used 75/5120 RMS in the meantime so I'll be looking forward to others experience with this motor.

Looks like I will have to get some on my reorder after next weekends launch.
Mr. Bob
Countyline Hobbies
Grovertown, IN.
574-540-1123
[email protected]
www.countylinehobbies.com

Mr G said:

Looks like the M1350 DMS is now going out to dealers. BuyRocketMotors.com shows them in stock for $339.

I picked up a used 75/5120 RMS in the meantime so I'll be looking forward to others experience with this motor.

Click to expand...

This is true.

And, I would be happy to help you fill that 75/5120 hardware as well . I routinely turn a Pre Order motor(s) around faster than a 'regular' order elsewhere.... Just ask around and you'll see.

No need to throw cash into the abyss and hope you wind up with product months down the road - if at all - and then dispute it with PayPal. Those days are over. :wink:

I bought one of these (M1350DMS) for my L3 last year, AWESOME. Ordered it from buyrocketmotors.com and had it on my doorstep before the end of the week... again AWESOME.
I was looking to get one again this year, but the $339 changed to $399. That is a BIG jump, and honestly, yes, it put me off buying another.

instead I think I am getting that 75mm L Dark Matter....

L1250DM, best 5 grain sparky out now. I have burned 2 and have 2 left!

Salvage-1 said:

I bought one of these (M1350DMS) for my L3 last year, AWESOME. Ordered it from buyrocketmotors.com and had it on my doorstep before the end of the week... again AWESOME.
I was looking to get one again this year, but the $339 changed to $399. That is a BIG jump, and honestly, yes, it put me off buying another.

instead I think I am getting that 75mm L Dark Matter....

Click to expand...

Yes, the price change caught me off guard as well. It's a great motor and all that I've sold have worked as advertised (pretty much everyone sends me pics and video ) but I was disappointed to see such a big jump, too.

Robert
Yes it was a good price increase. I was going to purchase one soon but I now might wait to find a used case and by the reload.

Ouch. No more of those for me, like, ever.

Too bad, too. I thought it was a great idea but now buying hardware is the better deal.

Glad I recently bought my second one at the original price, it was a fabulous deal.

Since you have to glue in the grains, i.e. actually build the motor, does it qualify for a TRA Level 3?

cerving said:

Since you have to glue in the grains, i.e. actually build the motor, does it qualify for a TRA Level 3?

Click to expand...

Of course.

cerving said:

Since you have to glue in the grains, i.e. actually build the motor, does it qualify for a TRA Level 3?

Click to expand...

I'm sorry, but why is this even an issue? Of course you can.

You don't glue the grains IIRC, just the forward bulkhead. But yes it qualifies for certs.

cerving said:

Since you have to glue in the grains, i.e. actually build the motor, does it qualify for a TRA Level 3?

Click to expand...

Cerving,
When TRA, NAR, or CAR, certify a motor, they certify the instructions also. If the instructions say something needs to be glued, that's what you must do. That has no effect on whether a motor may be used to certify at a particular level.
Choosing the right motor to certify with is part of the process also. Choose a motor that you are comfortable with. If you're not comfortable assembling a motor that requires extra steps, choose a different motor, or even a single use motor.


[emoji1010] Steve Shannon [emoji1010]

The Tripoli L3 Certification rules are published here. https://www.tripoli.org/Level3

The requirement for the motor to be used in a TRA L3 Certification rocket is stated as:

Motor – The certification flight must be with a single certified M or larger motor (tested total impulse greater than 5120.01 n-secs). Staged and/or Clustered rockets may not be used for certification flights. The flyer shall be observed by the TAP member or their designated representative during the assembly (if a reload or hybrid) and preparation of the motor.

Here's the certification for the motor. https://aerotech-rocketry.com/uploads...20jun%2019.pdf

For the motor to maintain certification it must be assembled according to the instruction sheet listed here. https://www.aerotech-rocketry.com/upl...14%20Small.pdf

Provided the motor is assembled according to the instructions, and everything is approved by the TAP, and the flight is successful, you're an L3, and submit your paperwork to record it.

When building an M1350, please note that the epoxy that you will use to seal the fore closure in WILL expand as it cures.

This can become a problem if, like me, you prop said motor up inside a mortar can overnight, then come to find the next morning that the can was at a slight angle, that the epoxy expanded over the edge, and that the nice L3 motor has now been epoxied to the inside of the mortar can.

This lead to half an hour panic and fun starring myself and my TAP (Pete E of Team Numb) and culminated in the use of a mallet to the outside of the can, then another 1/2 hour with a craft blade peeling the epoxy off the outside of the motor case so that it would again fit in the rear end of the L3 rocket.

I'm not sure what epoxy you use, but I've never had a problem with expansion with Aeropoxy.
I could see a fast cure epoxy that was mixed in a deep container expanding with heat, but if you're cooking off your epoxy that's different problem. One of the advantages of epoxy is the fact that it neither expands nor contracts as it cures. I wonder if the epoxy reacted with something else to out gas, or if air was entrained in the epoxy when mixing.

Salvage-1 said:

When building an M1350, please note that the epoxy that you will use to seal the fore closure in WILL expand as it cures.

This can become a problem if, like me, you prop said motor up inside a mortar can overnight, then come to find the next morning that the can was at a slight angle, that the epoxy expanded over the edge, and that the nice L3 motor has now been epoxied to the inside of the mortar can.

This lead to half an hour panic and fun starring myself and my TAP (Pete E of Team Numb) and culminated in the use of a mallet to the outside of the can, then another 1/2 hour with a craft blade peeling the epoxy off the outside of the motor case so that it would again fit in the rear end of the L3 rocket.

Click to expand...

I wrapped blue tape around the top to keep it in place. Mine did not expand enough to be an issue, but I wanted to make sure it would be fine either way.

watermelonman said:

I wrapped blue tape around the top to keep it in place. Mine did not expand enough to be an issue, but I wanted to make sure it would be fine either way.

Click to expand...

good idea there!!!

mine cured inside an ammo can, in the bathroom of an RV, outside temp in the 100's..... it bubbled a little and overflowed just enough to be a problem.