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How to mount a HPR 29mm Motor?
#1
How do I mount a HPR 29mm motor?  Do I need a engine block, or does the aft closure butt up against the end of the mmt?
BuiltFromTrash
First RMS Flight: June-17 2015
Pringles Can Rocket
G53-FJ-7 (29-40/120) 92 Newton-Seconds
~1300 Ft
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#2
With a 29mm HPR reload, you will usually (but not always) use a thrust ring that is attached to the motor. This prevents the motor from going to far into the motor mount. However, you will need something to keep the motor from popping out after it burns the ejection charge.
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#3
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#4
Almost all composite motors come with a thrust ring. If you somehow find one that doesn't (or use Estes BP), masking tape works great. To keep them in, most people use positive retention (to keep the motor from popping out at ejection).  T-nuts in the rear centering ring, spaced to use mirror clips, washers or homemade clips (AKA Kaplow clips). You can also buy screw on/snap on retainers that hold the motor. Estes makes some nice PVC retainers in 24mm and 29mm. For larger motors they are all aluminum. Unless you make your own screw on retainers from PVC fittings. Some heretics may do what Rocketman posted.

Many ways to skin the motor retention cat.
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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#5
(07-10-2015, 07:07 PM)rstaff3 Wrote: Almost all composite motors come with a thrust ring. If you somehow find one that doesn't (or use Estes BP), masking tape works great. To keep them in, most people use positive retention (to keep the motor from popping out at ejection).  T-nuts in the rear centering ring, spaced to use mirror clips, washers or homemade clips (AKA Kaplow clips). You can also buy screw on/snap on retainers that hold the motor. Estes makes some nice PVC retainers in 24mm and 29mm. For larger motors they are all aluminum. Unless you make your own screw on retainers from PVC fittings. Some heretics may do what Rocketman posted.

Many ways to skin the motor retention cat.

sonic3100aDSC00996.jpg

tall_tail_10_10.jpg

tall_tail_10_12.jpg

http://forums.rocketshoppe.com/showpost....stcount=20

Tech Jerry
Exemptions not regulations. Please purchase a few rockets from http://v-serv.com/usr/instaship-visual.htm
Thanks. Support eliminating explosive treatment of slow burning solids by DOT.
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#6
Masking tape is a rocketeers friend.
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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#7
There are a lot of commercial 29mm motor retainers, some made of plastic which works fine, some really neato models made of machined aluminum. The thing is to make sure with commercial units is to make sure it is made for the material the motor tube is made of, paper tubes, fiberglass and phenolic each have different outside diameters. Also make sure you leave enough tube hanging out past the rear centering ring. 

Of course home made units like the others describe cost A LOT LESS, they work as well as you engineer them, they just lack the neato part.

http://amwprox.com has a lot of stuff


Bill Clune L3 | NAR#88583
Been a launch Director
Founded a Club
MARS Club|SRC|MDRA - Forever
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#8
(07-10-2015, 07:45 PM)wclune Wrote: Also make sure you leave enough tube hanging out past the rear centering ring. 


I have been saying this for decades with a surprising amount of blast back.

http://v-serv.com/usr/kits/Talon03.jpg

(bad)
Exemptions not regulations. Please purchase a few rockets from http://v-serv.com/usr/instaship-visual.htm
Thanks. Support eliminating explosive treatment of slow burning solids by DOT.
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#9
Wow, a lot of replies in a short time!

I think the thrust ring that rstaff3 is referring to is built into the rear closure of AT and CTI cases as well, am I right?

Sorry, I don't think I was clear in the OP, I am trying to mount reloadable motors so the tape thrust ring isn't going to work.

As for closures, I did not see any ring on the inside of those Aero-Pack retainers that stopped the motor from sliding deeper into the mmt.  I could be wrong.

I guess what I am trying to clear up is this, can the rear closure be used as a thrust ring?

Thank you! Smile
BuiltFromTrash
First RMS Flight: June-17 2015
Pringles Can Rocket
G53-FJ-7 (29-40/120) 92 Newton-Seconds
~1300 Ft
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#10
You are right, all commercial reloadables have a thrust ring. AT and CTI in the rear closure, Loki has a snap ring on the case itself. All need positive retention. You don't want to lose those cases!
Member of MDRA, NAR and NARHAMS;
Level-2 certified but mostly fly G and under;
Volunteer compiler of manufacturer's news for ROCKETS Magazine.
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