Mounting of large O-ring on M1350 motor?

[billdz]

Just been assembling an M1350 for my upcoming L3 test. All OK until the final step:
"1.4 Using a stir stick or a flat blade screwdriver,push the forward O-ring completely into the groovebetween the smoke bulkhead and the case.CAUTION: Do not allow any oil or grease tocontact the interior abraded end of the case."
I'm having trouble getting the O-ring all the way down into the groove, it's a tight fit. Any tips? Anything better than the stir stick or flat blade screwdriver to get it in there? The instructions say not to use grease.

 

[Chrisn]

I assembled one last week and it did take a few minutes to get it to go in, its a tight fit. you will get almost all of it in and then have just a small amount protruding from the groove that will need something wider than a popsicle stick to push it all in or you just keep going around in circles. Did you apply grease to the liner oring? Also check the top shoulder of the bulkhead is about level with the top of the casing before you push the oring in as you will have to re do it if you push to check it is seated down on the liner... learned from mistake

 

[billdz]

Thanks for the reply. I'll try some other screwdrivers in the morning.
"you will get almost all of it in and then have just a small amount protruding from the groove"
Yes, that's exactly my problem.
"Did you apply grease to the liner oring?"
No, the instructions say not to apply any grease.
"Also check the top shoulder of the bulkhead is about level with the top of the casing"
Yes, the shoulder is within 1/16" of level with the top of the casing.

 

[Chrisn]

Yes thats right, the instructions don't actually say to grease it but it does refer to it as a pre-greased oring. Mine did not have any grease on it out of the packet so I decided to put grease on it myself

 

[billdz]

It was not easy, but eventually got it in this morning. A tool that is just the right size helps a lot. Poured in the epoxy and hopefully the motor will be ready to go.

Couple of notes to anyone else who is getting ready to build this motor:
* There's a helpful assembly thread for this motor at https://www.rocketryforum.com/showthread.php?70602-Aerotech-M1350W-DMS-Assembly, lots of pictures
* It's not mentioned in the instructions but the nozzle comes pre-attached to the casing. Hopefully it is attached securely as it is all that prevents the motor from flying up into the rocket.
* The 3 thin O-rings that go between the grains do not fit snugly against the liner. This has been mentioned in a few different threads and the consensus is that this is not a problem.
* Mine came with an igniter. Some people said they did not get one.
* The top of the forward bulkhead is tapped for an 3/8" eye bolt.
* In one thread, which I did not see until after I had poured the epoxy, someone mentioned that the epoxy expanded and spilled over the edge of the casing. This got me concerned as I had filled the empty space to the brim, in accordance with the instructions, but so far no expansion or overflow.

 

[Bill KLEIN]

I just finished assembling my 4th M1350 and every time I have had the issue of the large o-ring bunching up in one spot. I removed it started over and tried pushing the o-ring in at different spots rather than starting at one point and working around. I had very little bunching and was able to get the o-ring in successfully a lot easier this time.

 

[RocketDestroyer]

Isn't the motor supposed to be assembled in front of your TAP? Then they are there if you have questions and you know the assembly was done correctly.

 

[rfjustin]

Isn't the motor supposed to be assembled in front of your TAP? Then they are there if you have questions and you know the assembly was done correctly.

BK is L3, why would this be a requirement? Lets assume for a moment he was not L3, where is this requirement published please? Sounds like speculation on your part...

 

[Rocketclar]

I've built several M-1350's. Don't stress over that o-ring and don't use grease. Several years ago, AT told me that it is just to keep most of the epoxy in place. Any grease in there will weaken the epoxy bond.

 

[kalsow]

BK is L3, why would this be a requirement? Lets assume for a moment he was not L3, where is this requirement published please? Sounds like speculation on your part...

See the "Motor" section:

High-Power Level 3 - Tripoli Rocketry Association

tripoli.org

 

[green dragon]

See the "Motor" section:

High-Power Level 3 - Tripoli Rocketry Association

tripoli.org

note *IF* a reload or hybrid motor..

The M1350 is DMS, and MUST be assembled prior to flight so the epoxy can cure, etc