Forward Bulkhead and Nozzle ID

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AlnessW

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Hi everyone - this is somewhat of a continuation of another thread...
https://www.rocketryforum.com/showt...-me-understand-AMW-AMW-Pro-X-Gorilla-and-Loki

Anyways, at a launch this past weekend I swapped some 75mm CTI hardware with a friend of mine for a collection of various EX hardware items. Included in that stash were some different forward bulkheads and nozzles. Out of curiosity, I'm hoping to more specifically identify these - here is my list with some educated guesses:

IMG_3206.jpg
Standard AMW 75mm forward closure.

IMG_3208.jpg
Another AMW 75mm forward closure, but this one with a lip that sits inside the liner as well as a double-stepped smoke grain well? See below:

IMG_3197.jpg


IMG_3207.jpg
75mm Loki forward closure. (Duhhhh...)

IMG_3202.jpg
3 x 75mm nozzles, from left to right I believe we have a 75/2500 (might actually be custom?), 75/6000, and 75/7600. AMW?

IMG_3209.jpg
98mm forward closure, possibly custom also? This too has a smoke grain well.
 
I think the general consensus is that Loki/Fisher/Tru-Core forward bulkheads are very nearly (if not exactly) identical, especially looking at the 75mm and 98mm closures pictured above. (PLUS a 54mm that I have from Mike Fisher.)
Any other thoughts on this?
 
No bites here, I guess...

I'm having trouble sizing O-rings for my 75mm Loki front bulkhead - the grooves are 3/16" (and not 1/8") so -229 is too narrow. -332 and -331 are too wide, as well... ?
 
So your guesses are right on the makes of your parts.

I believe the 2500 nozzle should have a 1/2" throat.

The o-ring can be determined by the ID. If you have a set of calipers, I am pretty sure that the diameter of the groove should be ~2.525", or a depth of ~0.105". The width of the groove is less important, and should be at least 0.135" wide.
 
No bites here, I guess...

I'm having trouble sizing O-rings for my 75mm Loki front bulkhead - the grooves are 3/16" (and not 1/8") so -229 is too narrow. -332 and -331 are too wide, as well... ?

Did you try sending Scott at Loki a message about this?
 
So your guesses are right on the makes of your parts.

I believe the 2500 nozzle should have a 1/2" throat.

The o-ring can be determined by the ID. If you have a set of calipers, I am pretty sure that the diameter of the groove should be ~2.525", or a depth of ~0.105". The width of the groove is less important, and should be at least 0.135" wide.
Yes, Jim Harris of Gorilla Rocket Motors informs me that the nozzle throat of a 2500 nozzle is 15/32. (As well as 49/64 and 59/64 for a 6000 and 7600, respectively.)
Also, that 98mm closure is by Mike Fisher.

Did you try sending Scott at Loki a message about this?
I contacted Scott and while he thinks both of those other 75mm closures are Loki, they are from a very long time ago before he bought the company. He didn't know the O-ring dimensions.
 
Yes, Jim Harris of Gorilla Rocket Motors informs me that the nozzle throat of a 2500 nozzle is 15/32. (As well as 49/64 and 59/64 for a 6000 and 7600, respectively.)

Yea, Gorilla went "aggressive" and dropped the throat dimensions by a 64th over the old AMW sizes.
 
I suggest you download the Parker O-ring Handbook. https://www.parker.com/literature/ORD 5700 Parker_O-Ring_Handbook.pdf

It will provide you with all the information you need to know about O-ring groove dimensioning.

Bob
Thanks Bob for posting this!

Yea, Gorilla went "aggressive" and dropped the throat dimensions by a 64th over the old AMW sizes.
Now this is interesting - it just occurred to me that my nozzles are indeed AMW, not Gorilla. Will need to re-measure just to be sure but would assume I have 31/64", 25/32", and 15/16".

Also, I think I finally figured out the deal on my old 75mm Loki bulkhead. While the grooves are wider than an AMW closure, they are the exact same depth allowing a -229 O-ring to fit in with ease.
 
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