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  #11  
Old 05-03-2006, 12:27 AM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by CenturiGuy
*Ooh.* --*That's* a cool idea! I'll have to look into that!

But then where would I attach the Kevlar? (thinking furiously) Hmm...

Thanks, Craig!

--Jay


Run the Kevlar through that liner tube and attach it to the motor mount as you normally do. Make the Kevlar thread long enough for the piston to fully escape the tube. Then attach the other end to a screw eye at the base of the piston. Attach another screw eye to the top of the piston, and your elastic to that. You just "splice" the piston in between.
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  #12  
Old 05-03-2006, 10:38 PM
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Quote:
Originally Posted by CPMcGraw
Make the Kevlar thread long enough for the piston to fully escape the tube. Then attach the other end to a screw eye at the base of the piston. Attach another screw eye to the top of the piston, and your elastic to that. You just "splice" the piston in between.
Overnight, I also considered the idea of drilling a small hole through the (sanded-down balsa tube connector?) piston, and running the Kevlar through it, then tying the elastic to the "forward" end of the Kevlar. Hmm...


Cheers,

--Jay
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  #13  
Old 05-03-2006, 10:58 PM
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Quote:
Originally Posted by CenturiGuy
Overnight, I also considered the idea of drilling a small hole through the (sanded-down balsa tube connector?) piston, and running the Kevlar through it, then tying the elastic to the "forward" end of the Kevlar. Hmm...


Cheers,

--Jay


Another suggestion for reinforcing that transition...

Drill out the entire center to the diameter of the ST-7 tube, then run a very long ST-7 through the transition and all the way to the rear edge of the ST-10. Use one centering ring about 0.5" in from the edge to keep the tube from shifting around. Shove a TR-7 up 2.5" in, and you've just eliminated all of the issues. The forward part of the ST-7 (exposed length) becomes the upper body, while the transition and ST-10 lower body just hang on for the ride, and you attach the fins to it. One central core tube that becomes both the upper body and the motor tube all-in-one.

Come to think of it, you could eliminate the balsa transition and just use a paper shroud with one additional centering ring. Less costly, and easier to construct...
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Last edited by CPMcGraw : 05-03-2006 at 11:05 PM. Reason: A third thought...
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  #14  
Old 05-04-2006, 11:56 PM
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Quote:
Originally Posted by CPMcGraw
Come to think of it, you could eliminate the balsa transition and just use a paper shroud with one additional centering ring. Less costly, and easier to
construct...
Y'know, I had a 13mm design using a BR-58 between an ST-5 motor tube and an ST-8 streamer compartment... but the biggest I could drill out the center was something like 5/32". So I altered the design by making the ST-5 body tube longer (Figure 1 below), and using a paper reducer (transition) with two centering rings. (RockSim thought the revision was less stable, but oh well. )

So while using one big long honkin' ST-7 all the way through this other design's ST-10 is probably overkill (IMO), all I have to do is turn the solution above around 180 degrees. Shove the ST-790 3/4" into front of the ST-10 , use a couple of centering rings (these could be lightweight and thinner than the standard ones) and a 3/4" long paper transition, and... (Figure 2 below)

"--We got 'er done!" Thanks, Craig.


(Talk about needing to think *outside* the box...)


Cheers,

--Jay
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Last edited by CenturiGuy : 05-05-2006 at 12:01 AM.
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  #15  
Old 05-05-2006, 09:32 AM
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Quote:
Originally Posted by CenturiGuy
"--We got 'er done!" Thanks, Craig.


(Talk about needing to think *outside* the box...)


Cheers,

--Jay


The only drawback is that area between the top of the motor mount and the bottom of the forward tube. It is going to be impossible to clean out the crud that accumulates from ejection charges.

(Added) Of course, I've used the same layout in a number of my own designs, so this is not a big issue...
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Last edited by CPMcGraw : 05-05-2006 at 11:49 AM. Reason: Additional thoughts...
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  #16  
Old 05-06-2006, 12:11 AM
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Quote:
Originally Posted by CPMcGraw
The only drawback is that area between the top of the motor mount and the bottom of the forward tube. It is going to be impossible to clean out the crud that accumulates from ejection charges.

(Added) Of course, I've used the same layout in a number of my own designs, so this is not a big issue...
Larry the Cable Guy would probably say, "Crud. 'At's what you need, right there. Git-R-Done!"

Which reminds me of an amusing story Bruce McLawhorn told me in the Vendors Room at NARCON involving grass seed, ducks, and firearms. (It had to do with "Stuff That Brings Out the Redneck in Us.")


Cheers,

--Jay
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