Aerotech M750 Assembly Question

If anyone has any recent experience with the Aerotech M750 I'd appreciate some technical advice as I would like to get the motor assembled over the Labor Day weekend and Aerotech is closed. This is for a Balls project and it needs to be wrapped up before 9 Sep in order to make the trip across country.

The instructions that came with the reload, along with the instructions posted on the website (see the attached .pdf) do not reference the inclusion in the parts kit of 3 ea O rings which are about 1/16th inch thick and roughly the diameter of the grains. Also, the grain spacer O ring, which is listed as 3/16" x 3-3/8 appears to be about 1/8" instead.

I am assuming the small O rings are supposed to go between the grains, and that the grains still need to be epoxied as per the instructions.

Any insights/advice on View attachment M750 - 98_10240w_lb_in_20098.pdfthis motor would be appreciated.

Thanks,
Bill Schworer

The M750 is a moon burner. You need a dowel for alignment of the grains as shown in the instructions.
There are no grain spacers, the grains are glued together to make a single grain. There is a 3/16" thick O-ring to space the grain from the nozzle.
Follow the directions. I've looked them over and they appear to yield a correct motor.
I have 2 of these reloads and they have Medusa nozzles. Check your rear closure - you need the large (3") opening.

This might help

https://www.aerotech-rocketry.com/c...8mm_hp_rms/98-10240/98-10240_m750w-p_assy.pdf

Tony

Thanks, I've put together a 3" M650 exactly as described in the 4" instructions.

But the problem here is the 3 extra O rings plus what looks like a smaller grain spacer O ring as listed in the original post. At this point I cannot assemble the M750 as per the instructions. I am assuming Aerotech has recently made a change to the instructions and has not updated them accordingly. Anybody out there have any recent experience with this multiple O ring configuration??

Thanks,
Bill Schworer

I know they have never done it before, but do you think the extra orings might be for CTI hardware? Just throwing it out there.

Most likely grain spacers. I remember the when M1297 didn't have them and now they do. I don't recall if the instructions were updated right away or not.

Grain spacers for a moon burner?

Possibility that the wrong plastic bag was put in or use the same bag for multiple reloads

Gents -

Thanks for your responses. I'll call AT on Tues AM, when I get the answer I'll post it back here.

Regards,
Bill Schworer

Mystery solved.

Spoke to technical support this AM, the 3 extra O rings were probably put in the bag by mistake.

Regards,
Bill