Dr. Rocket reloads

I have the Dr Rocket cases for 29/100 29/120 29/180 and 29/240. I have only used the metal grommet in select reloads (H-180 I think) and they are used more in the larger motors (38mm and larger)

The reload gives instructions on when and how to use them. As long as you follow the instructions closely, you shouldn't have any issues.

-Aaron

The "aluminum grommet" you're referring to is probably the "forward seal disc". It should have a hole in the middle, and a groove around the edge.

It's used with some of the reloads in the 29/240 casing. It replaces the forward phenolic washer in some of the higher-thrust reloads, to provide a better seal on the forward end of the motor reload liner, preventing any damage to the case from flames impinging directly on it.

See

Keep it handy. If any of your reloads need it, they'll come with an O-ring that fits the groove around the edge, and the instructions will describe how to fit it into the end of the phenolic liner tube when you assemble the motor.

The hardest thing to remember is not throwing it away when you're cleaning the motor after a flight. Since most reloads don't use it, you have to pay special attention when cleaning up a motor that does, so you don't toss it out along with the rest of the dead guts of the burned-up motor.

- Rick "Burn, baby, burn" Dickinson

I'm assuming you mean the silver-colored disk that has a 'slot' around it that is meant to hold an o-ring. If so, that is the 'front seal disk', and the instructions for using it are indeed with the reload. And you don't need to open the reload to read the instructions -- Aerotech has all of them available on their website (under 'resources') for download.

You will find that reload kits that use a (black) phenolic tube instead of the (white) paper tubes use this disk (instead of a forward insulator disk). Checking my 'cheat-sheet', the H210R and H220T engines use this seal disk in the 29/240 size, so downloading those instructions should answer your questions.

Just to let you know, for these motors, there is a very thin o-ring that goes aroudn that silver disk. The grains are placed within the phenolic liner, and then the seal disk is placed in the forward end (with the o-ring providing the friction seal). The grains for these lines are slightly shorter in order to allow the seal disk to fit in place.

David Erbas-White

I have a very bad habbit of replying to my own posts but....

Dr Rocket's website explains what that is (Forward seal disc) and why it is needed.

-Aaron

Kurt Savegnago

Thanks all. That will give me substance to go on. Need to do some regular ie. smaller reloads to get some experience and then go on to certify with my "bashed" Estes Executioner.

Kurt Savegnago

As others have said, this is only needed on certain loads, and the tricky part is remembering not to throw it away when you clean up the motor after using those loads.

Yes, they will oxidize over time. The packaging slows this a bit. In most reloads, you'll find one grain that is not individually sealed, and often it is beginning to show some oxidization (white stuff). I always put that grain at the aft end of the motor, so that a fresh grain is at the top. Oxidized grains tend to be harder to light.

Where I live, it seems to take a fe months or more for grains to show noticeable oxidization after being removed from the packaging. I've had motors that were assembled for up to a year and worked fine when used. Oxidization may happen faster in a more humid climate, but I still don't think you have to worry about it much if you fly the motor within a few weeks of assembly.