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  #11  
Old 06-01-2015, 03:45 PM
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Quote:
Originally Posted by tbzep
I believe it changed in the mid 70's from the coupler style to the current style...


Agreed. I built a Bertha in 1977 and it had the 8.5" stuffer but no coupler. The "current style," however, is a regular 2.75" mount with no stuffer tube.
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  #12  
Old 06-01-2015, 05:14 PM
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Quote:
Originally Posted by tbzep
I believe it changed in the mid 70's from the coupler style to the current style.
The coupler style mount remained popular in several Centuri kits until the end.
Back when I was a kid, I recall seeing the coupler style mounts in the catalog. But none of my kits ever had one.

Upon becoming a BAR, I remember studying these more closely, and coming to the conclusion this was a case of over-engineering. Having the coupler tube spanning the gap from the aft centering ring to the front centering ring provided no extra benefit. If the rings were properly sized - ie, sanded to the right size - they would have no problem sliding into the airframe (or outer motor tube) - the coupler tube didn't add any functionality, IMO.

[Conjecture] That said, I suspect it was a vestigial construct. At some point early on, it was needed, but as the centering rings evolved, somebody (at Estes) realized one day that the rings were sufficient, that the extra coupler was superfluous, and they stopped using them.

(Here's where it'd be nice to get input from someone who was there back then )

Doug

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Last edited by Doug Sams : 06-02-2015 at 10:10 AM.
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  #13  
Old 06-01-2015, 05:16 PM
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Quote:
Originally Posted by tbzep
I believe it changed in the mid 70's from the coupler style to the current style.
I want to say my ~1970 Bertha lacked the coupler AND the stuffer. It just had a short BT-20 motor tube with the two white paper rings.

Doug

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  #14  
Old 06-01-2015, 10:00 PM
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I have only built two Estes kits that had the 'coupler' style mount. An early 70's Astron Delta and an early 70's Honest John.
All others have had just centering rings.
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  #15  
Old 06-02-2015, 07:57 PM
mikemech mikemech is offline
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My first BB, early '60s?, had the coupler and no stuffer.
Be careful with a 24x95 mmt. One of my current BBs hit, by altimeter, 501 meters with an E9.
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  #16  
Old 06-03-2015, 01:09 PM
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Quote:
Originally Posted by mikemech
Be careful with a 24x95 mmt. One of my current BBs hit, by altimeter, 501 meters with an E9.



Second that. I flew mine on E12s twice and only got it back once.


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Old 06-03-2015, 01:13 PM
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Quote:
Originally Posted by Doug Sams
Back when I was a kid, I recall seeing the coupler style mounts in the catalog. But none of my kits ever had one.

Upon becoming a BAR, I remember studying these more closely, and coming to the conclusion this was a case of over-engineering. Having the coupler tube spanning the gap from the aft centering ring to the front centering ring provided no extra benefit. If the rings were properly sized - ie, sanded to the right size - they would have no problem sliding into the airframe (or outer motor tube) - the coupler tube didn't add any functionality, IMO.

[Conjecture] That said, I suspect it was a vestigial construct. At some point early on, it was needed, but as the centering rings evolved, somebody (at Estes) realized one day that the rings were sufficient, that the extra coupler was superfluous, and they stopped using them.

(Here's where it'd be nice to get input from someone who was there back then )

Doug

.



My theory is that as yellow glue became more common and popular, they got tired of dealing with complaints about the mount "freezing" in the wrong place.


Bill
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  #18  
Old 06-03-2015, 01:37 PM
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Quote:
Originally Posted by Doug Sams
[Conjecture] That said, I suspect it was a vestigial construct. At some point early on, it was needed, but as the centering rings evolved, somebody (at Estes) realized one day that the rings were sufficient, that the extra coupler was superfluous, and they stopped using them.


While I can't speak for why they removed the coupler back then, I have recently found the need for one. When I built my first Citation Patriot clone, I was concerned about how easy it would be for those wide fins to snap off during landing, so I glued them on with some hefty fillets. The fins stayed on fine when the rocket hit the ground but they tended to buckle the body tube. I still fly that Patriot even though the tube is buckled under all three fins. At least it's symmetrical.

My solution on the second Patriot was to add a coupler to the motor mount, which reinforced the body tube enough to keep it from getting buckled. That change transferred the energy back to the fin and while they still occasionally snap off, it's a lot easier to fix than a buckled tube.

Estes did not make many kits with fins as wide as the Patriot and therefore didn't need the reinforcement. Maybe that's why they eventually dropped the coupler.
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