Dr. Rocket reloads

Hi,
I'm that spastic guy that lost the 18/20 RMS 'cause I messed up on the ejection charge. Won't do that again. Am reading instructions
right and left and know how to deal with that now. The video links sent to me really helped out too. I have the 29mm 120, 180 and 240 Dr. Rocket system and wonder in what fashion that aluminum grommet is used? Have no clue from the Dr. R website and no response to my email request for pointers. Now if the information I need is contained in a reload package instructions, then I freely admit I haven't torn into the packages yet. The reason I haven't done that is 1. I'm not ready to launch and 2. Folks have written here that the APCP begins to oxidize with a broken package. Is that true and do I need to worry about it. Am building a large model to try the 18/20 in and will use a streamer to give me a little insurance for recovery. Thanks for any pointers and help.
Kurt Savegnago
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.
http://www.drrocket.com/FORWARDSEALTC.asp
-Aaron
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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 http://aerotech-rocketry.com/customersite/resource_library/Instructions/HP-RMS_Instructions/29mm/29_240t_in_20052.pdf for one example....
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
--
Every parliament or congress worldwide should be equipped with a
hundred-pound chunk of sodium in the entrance foyer, such that any
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Kurt wrote:

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

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Kurt wrote:

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I have some of the Aerotech 3 piece sets at 25% off if anyone is in need. 18mm, 24mm, and 29mm.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Kurt wrote:

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.