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  #1  
Old 01-04-2012, 03:40 PM
Scott21 Scott21 is offline
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Default 24mm engine in place of 18mm?

Can I do this with a rocket whose lower body tube is 24mm and I just skip inserting the 18mm motor mount? This is for an Estes Photon Disruptor assembled with CA glued fins and body tubes with some sanded wood filler all around (extra strength?) The upper body tube (33mm) is being extended ~ 4 inches as I didn't get the ejection baffle installed low enough.
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  #2  
Old 01-04-2012, 03:46 PM
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Watch the CG but this should flt well on a D motor
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Old 01-04-2012, 04:21 PM
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You will need to use one of those green centering rings that were intended for the 18mm mount as a thrust ring for the 24mm motor. Forget about the motor hook and use friction fit for motor retention.
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Old 01-10-2012, 12:56 PM
Scott21 Scott21 is offline
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I have an expended E motor. I'll saw off a 1/4" and use that in the 24mm tube for the motor block. An I'll cut off a 1/2" piece to use as a spacer and start with a D12-3. I have some Kevlar strings being glued to the top of the baffle to form a 3-string anti-zipper shock cord attachment point.

Unfortunately, I already glued the green ring to the 18mm mount. I 'll work things out so I can slide in the 18mm mount...for windy days.

Thanks all
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Old 01-10-2012, 01:28 PM
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Sounds good.
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Old 01-10-2012, 03:33 PM
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Quote:
Originally Posted by Scott21
I have an expended E motor. I'll saw off a 1/4" and use that in the 24mm tube for the motor block. An I'll cut off a 1/2" piece to use as a spacer and start with a D12-3. I have some Kevlar strings being glued to the top of the baffle to form a 3-string anti-zipper shock cord attachment point.

Unfortunately, I already glued the green ring to the 18mm mount. I 'll work things out so I can slide in the 18mm mount...for windy days.

Thanks all


Buy a rings 'o' plenty from Apogee or get a ring assortment from Semroc (or whomsoever your favourite vendor may be). You can always find a use for rings...

If you are going to use an 18mm adapter your going to have to find a way to engage the adapter in the main tube. Otherwsie it will spit the 18mm on ejection charge.
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  #7  
Old 01-10-2012, 05:14 PM
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Not a warning about the conversion, but an observation about using CA...

They don't hold fins well. In my experience, CA is a bit too brittle for the stresses of launch and landing, so for the fin-to-BT attachment, I'd strongly recommend using something like Titebond (I, II, or the new Translucent formula) instead. A balsa-to-balsa joint may be OK if the glue is fresh enough; but if it has any age on it, go get a new bottle. Use the medium-viscosity, too, not the thin.

Been there, done that, had to un-done it, too...
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  #8  
Old 01-10-2012, 06:51 PM
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I would endorse with only one qualification. If the joint is tight already, then use a thin formula first. The mechanism of CA is to penetrate and then form rigid chains; hence the bond. If the surfaces are gappy, then the adhesive simply bonds on the surfaces. The counter is that no amount of glue is as strong as a solid, tight joint with a good penetrating adhesive. The thinned Aliphatic branded as Super Phatic is IMHO the best of both worlds. It will wick straight from the bottle and penetrates extremely well. Once cured, there is a higher level of flexibility in the joint that you would achieve with a CA.
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  #9  
Old 01-11-2012, 12:49 PM
jamjammer53150 jamjammer53150 is offline
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Default no matter what

always , always go one size bigger on a motor mount , you can always sleeve down.
I know this guy who spent nealy 100 hrs on a project , that in the end nothing in 24mm could fly it ( perhaps with a cti Imax it MAY fly ) , so always over build
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Old 01-12-2012, 03:11 PM
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Quote:
Originally Posted by tbzep
You will need to use one of those green centering rings that were intended for the 18mm mount as a thrust ring for the 24mm motor. Forget about the motor hook and use friction fit for motor retention.

My suggestion is to leave the thrust ring out of the rocket entirely. Instead, use masking tape to create a thrust ring at the end of the motor. That way you can use any length 24mm motors (Estes D-12 or E-9, for example) without worrying about spacers, etc.
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