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Old 08-01-2016, 08:06 AM
popadoc popadoc is offline
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Default RMS 24mm

In the older posts here it says you can leave off the engine block and hook to be able to use longer engines. What hold the engine in if you leave off the hook? In the attached pic I have the hook install (not glued yet) in the motor mount to hold the RMS 24mm in place. What's the best way to build the mount to accommodate different engine lengths?

Thanks
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  #2  
Old 08-01-2016, 08:13 AM
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Jerry Irvine Jerry Irvine is offline
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Quote:
Originally Posted by popadoc
In the older posts here it says you can leave off the engine block and hook to be able to use longer engines. What hold the engine in if you leave off the hook?
CTI 24mm. You can no longer get longer U.S. Rockets or AT 24mm, but they were widespread for years.
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  #3  
Old 08-01-2016, 08:39 AM
popadoc popadoc is offline
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This is the Aerotech RMS 24/40 case.
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Old 08-01-2016, 09:03 AM
aeppel_cpm aeppel_cpm is offline
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What holds the engine in against the ejection charge if you leave out the hook?

Friction fit
Tape
Use one of the estes thread on retainers.

Its a fairly common tip on the forums to use a little tape on around the engine hook with an RMS case, just to make sure it doesn't slip out.

To leave space for the CTI 24mm casings (2G, 3G, 6G), I've taken to bending the top of the engine hook backwards and gluing another centering ring aft of the hook to hold it in place. Or epoxy it down. Space for long motors, still get an engine hook.

Part of the issue you are looking at is that the recommended gap from motor mount to engine hook is bigger for black powder than for AT or CTI cases. The thrust will slide the motor forward during liftoff, but then there's space for the motor to slide backward at ejection - the extra momentum leading to escaping the hook.

I find that at Bong, the RSOs don't like to see the casing loose. (Neither WOOSH nor TWA.) So I add a tape ring between the casing thrust ring and the motor mount to that it's snug. I find the same narrow tape ring works fine on blackpowder motors when using the estes threaded retainers, too.
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Old 08-01-2016, 09:27 AM
stefanj stefanj is offline
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You can leave off the thrust ring and still use a hook. I do it all the time.

The little dingus on the hook that pieces the front of the hood instead folds outwards, resting against the front of the front centering ring.

I've also turn the front of a motor retaining hook into a loop, and attaching the shock cord anchor to it.
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Old 08-01-2016, 09:40 AM
samb samb is offline
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In your example, I would use a dremel tool to grind down the part of the hook that is protruding through the motor tube. That will keep it from interfering with or scratching the reload case. The larger diameter of the reload case aft closure will seat against the motor tube to prevent forward movement of the motor under thrust and a few wraps of 1/4 or 1/2 inch tape around the closure and the end of the motor tube will keep it from ejecting.
When I use a kit supplied motor hook I bend that forward hook up and out of the way like you can almost make out in this cell phone picture (iphone 4 ).
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  #7  
Old 08-01-2016, 10:18 AM
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burkefj burkefj is offline
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The rms 24/40 case forward delay end is a smaller diameter, all you have to do is make sure the front of your engine hook doesn't stick down far enough to drag on the delay portion, and leave and then install the hook as desired. If you have an estes "e" size hook you just need to make sure the little orange spacer can fit over the delay portion of the casing, by removing some of the cardboard if needed so it slips over then the whole think will insert as normal.

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  #8  
Old 08-01-2016, 10:33 AM
popadoc popadoc is offline
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I believe I am going to go one of threaded retainers. But, I will keep in mind the other suggestion you all have given.

Thanks for your help.
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  #9  
Old 08-01-2016, 02:51 PM
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  #10  
Old 08-01-2016, 04:48 PM
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Beware with some of the threaded closures.
Some are not compatible with the rear closures of Aerotech RMS 24 and 29 cases. Some are too small to fit over the RMS case/closure.
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