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How to mount a HPR 29mm Motor?
#11
estes retainers-
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aeropack-
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#12
Since motor retainers typically presume a particular thrust ring length, SU motors with tape thrust rings should have compatible width tape thrust rings.  What thrust ring lengths are you seeing in the field these days?
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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#13
(07-10-2015, 07:34 PM)rstaff3 Wrote: Masking tape is a rocketeers friend.

Both the Blue and the White kind, each type of masking tape has its place. I like the white (old school) for thrust rings and taping dog barf over my ejection charges due to its greater stickiness. The blue I use for friction fitting and taping the igniter to the outside of my rocket for transport out to the pad, since it removes easier after usage, and wont damage my finishes (white wont necessarily hurt the finish its just harder to pull off sometimes).
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#14
(07-12-2015, 11:41 AM)Rocketman Wrote: Since motor retainers typically presume a particular thrust ring length, SU motors with tape thrust rings should have compatible width tape thrust rings.  What thrust ring lengths are you seeing in the field these days?

It's been a long time since I've needed tape for APCP motors but use it all the time on Estes. I use either 1/2" or 3/4" when the motor retention system allows or thin 1/4" when using Estes retainers. I wrap the full length tape overhanging the base and trim the excess with an Exacto or equivalent.
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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#15
(07-12-2015, 07:38 PM)rstaff3 Wrote:
(07-12-2015, 11:41 AM)Rocketman Wrote: Since motor retainers typically presume a particular thrust ring length, SU motors with tape thrust rings should have compatible width tape thrust rings.  What thrust ring lengths are you seeing in the field these days?

It's been a long time since I've needed tape for APCP motors but use it all the time on Estes. I use either 1/2" or 3/4" when the motor retention system allows or thin 1/4" when using Estes retainers. I wrap the full length tape overhanging the base and trim the excess with an Exacto or equivalent.

That's my exact question, what is the net trimmed length.  It appears to be 3/8" for AT/CTI and not sure about Estes if you omit the airframe thrust ring  Might be zero.
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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#16
(07-13-2015, 01:21 PM)Rocketman Wrote:
(07-12-2015, 07:38 PM)rstaff3 Wrote:
(07-12-2015, 11:41 AM)Rocketman Wrote: Since motor retainers typically presume a particular thrust ring length, SU motors with tape thrust rings should have compatible width tape thrust rings.  What thrust ring lengths are you seeing in the field these days?

It's been a long time since I've needed tape for APCP motors but use it all the time on Estes. I use either 1/2" or 3/4" when the motor retention system allows or thin 1/4" when using Estes retainers. I wrap the full length tape overhanging the base and trim the excess with an Exacto or equivalent.

That's my exact question, what is the net trimmed length.  It appears to be 3/8" for AT/CTI and not sure about Estes if you omit the airframe thrust ring  Might be zero.
When I can't just use the full tape width, I try to mimic the 29mm Hobbyline thrust ring. I do it by eyeball so I don't have an exact measurement.

Thrust rings are evil. Except maybe on 13mm and MicroMaxx where there aren't any real options.
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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#17
In case it hasn't been perfectly clear, you need two forms of retention. One that keeps the motor from blasting forward into the airframe. For all SU and RMS and CTI motors, this is accomplished by the thrust ring on the motor. The thrust ring is larger than the MMT, and will not allow the motor to slip into the MMT.

The second kind of retention is what keeps the motor casing from falling out of the rocket after burnout. This is accomplished with some kind of retainer, be it Estes, Aerotech, AeroPack, Slimline or whatever. Or, as others have shown, a homemade retainer with screws and washers. With purchased retainers, there is usually a screw-on outer piece that hold everything in place.

Purchased retainers have two pieces. The male threaded piece gets glued directly to the MMT and causes the first type of retention. The female threaded piece screws on outside and causes the second type of retention.

However, there is nothing wrong with the bent metal motor hook that smaller rockets use. Aerotech kits come with these. The only catch is that since motors are of different lengths, you need cardboard slide-on rings to accomplish your forward rentention.

Go to a club launch and walk around and ask people to show you stuff. Best way to learn.
John S.
NAR #96911
TRA #15253
MDRA
Level 1, 2014-Mar-15 -- Aerotech Sumo, H133BS
Level 2, 2014-Jun-21 -- Giant Leap Vertical Assault, J240RL
Level 3, 2016-03-12 -- MAC Performance Radial Flyer, M1101WH, 13,028 feet
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#18
(07-17-2015, 01:01 PM)Bat-mite Wrote: In case it hasn't been perfectly clear, you need two forms of retention.  One that keeps the motor from blasting forward into the airframe.  For all SU and RMS and CTI motors, this is accomplished by the thrust ring on the motor.  The thrust ring is larger than the MMT, and will not allow the motor to slip into the MMT.

The second kind of retention is what keeps the motor casing from falling out of the rocket after burnout.  This is accomplished with some kind of retainer, be it Estes, Aerotech, AeroPack, Slimline or whatever.  Or, as others have shown, a homemade retainer with screws and washers.  With purchased retainers, there is usually a screw-on outer piece that hold everything in place.

Purchased retainers have two pieces.  The male threaded piece gets glued directly to the MMT and causes the first type of retention.  The female threaded piece screws on outside and causes the second type of retention.

However, there is nothing wrong with the bent metal motor hook that smaller rockets use.  Aerotech kits come with these.  The only catch is that since motors are of different lengths, you need cardboard slide-on rings to accomplish your forward rentention.

Go to a club launch and walk around and ask people to show you stuff.  Best way to learn.

Thank you!  Just the info that I needed!

Has anyone flown a 3D printed Retainer?  I am thinking about attempting this as a interesting project.
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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#19
Rosenfield Aerospace makes a 3-D printed retainer for some of their rockets.
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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#20
The Estes retainers(29mm) work well for the Aerotech Hobby line 40/120 hardware /CTI hardware and Aerotech SU motors and Aerotech DMS motors. With the Aerotech 29 mm high power hardware though , you only get 1 -1/2 turns on the cap. I use the Estes retainer for my Aerotech H180 flights without issue. Has worked every time . I use pliers to snug the ring down tight. The rear closure is just a bit bigger than the the other motors and hardware.
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