View Full Version : How does this work?
jeffyjeep
11-18-2010, 09:36 AM
Over a year ago, I bought a SV 29mm kit from Commonwealth Displays. These are the parts it came with--but no instructions. The parachute, shock cord, and fin inserts are self-explainatory, but I don't understand the engine mount and baffle assembly. Is there supposed to be NO engine hook and thrust ring, or are there parts missing?
Thanks!
Jeff
ghrocketman
11-18-2010, 10:22 AM
With 29mm and above, you use friction-fit or an Aero-pack type retainer, not a motor hook.. The bottom motor closure provides the thrust block so one can use any length motor. I have the same kit for my new Estes kit.
jeffyjeep
11-18-2010, 10:44 AM
Ah So. I get it now. Do you know how the baffle assembles (or is it junk?)
Doug Sams
11-18-2010, 11:26 AM
Ah So. I get it now. Do you know how the baffle assembles (or is it junk?)My guess is that the two conventional rings center the motor tube while the third, funky ring goes just ahead of the motor tube, by a ½" or so. The Brillo-pad thingy (can't recall what's it's called) is manually inserted into the motor tube ahead of the motor. The ejection charge propagates thru the Brillo thingy then flows thru the funky ring. By that point, the hot particles should have been stopped and the hot gases sufficiently cooled to prevent damage to the recovery system.
But I could be wrong ;)
Doug
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ghrocketman
11-18-2010, 11:32 AM
Doug stated the intended baffle operation exactly correct.
GregGleason
11-18-2010, 01:03 PM
... The Brillo-pad thingy (can't recall what's it's called) ...
AeroTech calls it "Permanent Cooling Mesh". It is to be stretched out as much as possible so that if fills the volume available. The PCM is not to be glued, so that it can remain loose inside the volume.
Greg
jdbectec
11-18-2010, 01:10 PM
http://www.cdimodelrocketry.com/proddetail.php?prod=CDIESTESSATURNV29MM
There's a few photos here, a narritive, and a telephone support number. It looks to me like you're missing a baffle ring.
Doug Sams
11-18-2010, 01:16 PM
AeroTech calls it "Permanent Cooling Mesh". Greg"Chore Boy". Finally, it comes to mind...:o
http://www.castlewholesalers.com/media/70300218
.
jamjammer53150
11-18-2010, 01:28 PM
I use chore all the time , except I use the copper rather than the stainless steel . A small wadof that trapped in your BT will choke out nearly any nastyness .
Once i discovered how a combo of chore , a bit of nomex combined works out I went to all ultra thin chutes , and have not damaged a single one
jharding58
11-18-2010, 01:39 PM
Definitely missing the upper baffle ring - the one with the solid center.
o1d_dude
11-18-2010, 02:47 PM
ghrocketman has it right with respect to the motor mount.
No motor block is needed for reasons described above. What you do need is a way of keeping the motor ejection charge from powering the motor out the back of the tube. The least expensive method of motor retention is to wrap the motor with masking tape. You want it to the point that it's very tight...just barely able to extract it. Other methods involve t-nuts, screen clips, and small screws, or threaded sleeves, and more.
See this link for a representative sample. Madcow Rocketry Motor Retention page (http://www.madcowrocketry.com/servlet/the-Rocket-Components-cln-Motor-Retainers/Categories)
jeffyjeep
11-18-2010, 07:29 PM
Thanks for all of the help, gentlemen. No wonder I couldn't figure out how to assemble the baffle--I don't have all of the parts. Now I'll plead my case to Commonwealth Displays and try to schmiekel(sp?) them for the missing part.
Jeff
Commonwealth.net
11-20-2010, 05:27 PM
Jeff,
No need to *shmiekel(sp?)*,we're sorry you got an incomplete kit. Please e-mail us with your name and mailing address and we will get the missing piece out to you.
order@commonwealth.net
Please put rocket in the subject line so our spam filter knows it is from a real person.
The staff @ commonwealth
jeffyjeep
11-20-2010, 06:31 PM
Awesome! Will do. Thanks a ton!
jeffyjeep
11-26-2010, 05:02 PM
Got the missing parts today! Thanks commonwealth!
jdbectec
11-26-2010, 08:32 PM
Got the missing parts today! Thanks commonwealth!
That was quick! Good job Commonwealth!
raohara
11-27-2010, 01:53 PM
The ejection charge propagates thru the Brillo thingy then flows thru the funky ring. By that point, the hot particles should have been stopped and the hot gases sufficiently cooled to prevent damage to the recovery system.
Is there any concern that over time the Brillo thingy will get "gunked up" with particles to point that the ejection gases don't pass through?
- Rich
GregGleason
11-27-2010, 02:04 PM
Is there any concern that over time the Brillo thingy will get "gunked up" with particles to point that the ejection gases don't pass through?
- Rich
There have been anecdotal reports that over time you might have a fire in that area. As long as you shake the rocket on a regular basis and coax as much "gunk" out with a thin, rod of sorts you should be ok.
The best way, albeit with a weight penalty, is use some small diameter aluminum all-thread with a removable cap. That way you can remove and replace it after "x" number of flights.
Greg
jamjammer53150
11-29-2010, 08:32 AM
I have ACTUALLY had a fire in a baffle filled with copper wool. well not actually a fire but smoldering embers that produced a great deal of smoke .
The BT was so hot you could hardley toch it. I ended up using a ABC fire extinguisher on it
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