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  #11  
Old 06-16-2009, 10:48 AM
timster68 timster68 is offline
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Quote:
Originally Posted by Initiator001
I did not make any modifications to the NCRBE plastic motor mount rings to use them with 'true' 29mm motor mount tube. I did sand the inside of the rings where the motor mount tube would fit to get better adhesion with the cement/epoxy.

Which NCR 'G' motors do you have? The early G50 motors or the G70s?

Bob

I stand corrected. I have 2x F62-4 and 2x F62-6.

I tried the 29MM engine tube with the motor mount rings and they fit, but just barely. They should be fine.

I think I will take them on vacation in July. I should be able to build them both in a day.
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  #12  
Old 06-16-2009, 12:44 PM
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JoeLaunchman JoeLaunchman is offline
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This question may be slightly ahead of its time. My Estes Saturn V (kit#2001) is presently gutted with no motor mount. It's BT-101 based and I want to upgrade it to fly on the soon to be released Quest E & F motors:
http://www.rocketryplanet.com/content/view/2522/28/

The motors are 28mm in diameter and I plan on using this Cygnus mount:

http://www.unclemikesrocketshack.co...tor_Mounts.html

How best to retain the motor in this mount? Would someone suggest a different mount entirely?
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  #13  
Old 06-16-2009, 02:20 PM
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I hand make double engine hooks for all of my mid-powered models. The proper spring steel is free... inside your old windshield washer blades. Some blades have wonderfull 1/8" wide steel which is perfect for mid power hooks. Just bend to shape with pliers. I make mine long enoiuigh to hook just past the thrust ring. The reason I use double hooks is that after I load the motor, I wrap 1/4" wide strapping tape 2 or 3 times around the exposed motor and hooks just to be sure.

Phred
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  #14  
Old 06-16-2009, 08:53 PM
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Mark II Mark II is offline
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On larger rockets, I make the simple modifications needed to allow the use of some form of Kaplow Klips (still one of the best motor retention methods ever invented). The only exception is in certain cluster configurations that allow me to install a threaded rod in the center and retain the motors with a hex nut and a washer.

MarkII
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  #15  
Old 06-16-2009, 09:05 PM
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Bob Kaplow Bob Kaplow is offline
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Quote:
Originally Posted by Mark II
On larger rockets, I make the simple modifications needed to allow the use of some form of Kaplow Klips (still one of the best motor retention methods ever invented). The only exception is in certain cluster configurations that allow me to install a threaded rod in the center and retain the motors with a hex nut and a washer.

MarkII


Seeing someone do that is EXACTLY why I came up with an alternate method. My first thought is "That's a clever way of making sure the motor won't eject". My second thought a moment later was "Wow, that would hurt if it hit me on the head." Or put a nasty scratch on the hood of someone's car.

The idea is to not have anything "pointy" sticking out of the back end of the rocket. For clusters, instead of burying a rod in the cluster, bury a blind nut or threaded brass insert, and then screw a retaining bolt and washer into it.
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  #16  
Old 06-16-2009, 10:40 PM
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Quote:
Originally Posted by Bob Kaplow
...
The idea is to not have anything "pointy" sticking out of the back end of the rocket. For clusters, instead of burying a rod in the cluster, bury a blind nut or threaded brass insert, and then screw a retaining bolt and washer into it.

Great suggestion. I'll try that the next time I build such a mount. The rockets that I have implemented this method on, though, would cause similar damage due to other elements in the design (fins, nose cone, etc.) if they were to come in contact with someone's head or the hood of a car during its descent. I make the threaded rod just long enough to go through the washer and nut when the motors are in place, with none projecting beyond the nut. I don't use any allthread that is any heavier than it absolutely needs to be, either. (I mostly use 4-40.) On occasion, I have used acorn nuts instead of hex nuts. When I mentioned this in another thread last year, someone commented that the rod could stab someone in the hand if they tried to catch it. Aside from the fact that there is no rod end projecting past the nut, when I have used this method, it has been in rockets that you wouldn't want to try to catch on the fly in any event, regardless of what type of motor retention they had. (I'm not talking about Astron Rangers or Cobras here.) But I like your alternative, and I will implement it in my next cluster build if I can find machine screws or bolts that are long enough.

MarkII
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Last edited by Mark II : 06-16-2009 at 10:59 PM.
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