Need AMW/Gorilla 38/640 delay element washer size

[Viperfixr]

Tried to build a KBA I550R for the last two days--got stuck at the step where the delay assembly goes into the forward closure. No amount of trying got it in there--the o-rings just would not fit (it wasn't a problem with lubrication--the instructions were followed to a T). I tried pushing it in by hand, and the AMW instruction method of pushing the closure down on top of it. The o-rings strip off every time. Even without the delay element, the o-rings will not fit into the well without useless deformation--they just seem too large. Since this was literally my first snap-ring motor build, I took it to the Tripoli Vegas launch yesterday, and no one there could make it work either. I think the KBA supplied o-rings are just too large in terms of OD (ID is right on the money).

Does anyone know the right size or McMaster link to EX useful o-rings? Huge thanks!

 

[COrocket]

From the assembly instructions, it looks like the o-rings are metric sizes. Here is the link to metric o-rings from mcmaster:

https://www.mcmaster.com/#metric-o-rings/=e47ec1

Unfortunately, There does not seem to be any that are 3.75MM thick. It seems like a very weird size... I'd contact Aerotech with your issue.

 

[blackjack2564]

Hey Mark!

I always had the same issue with those loads BUT:

If you are using electronics & don't care about the ejection charge, just use a flat smokeless closure or screw a plug into the well of that one.

It will fly fine. I have gone to using the delay insulator for a plugged closure by filling it with 10 minute epoxy & dropping it into the well with one O-ring mashed in & the charge well plugged with a bolt.
These darn things [front closures] were made with soooo many different thread sizes and hole diameters, it may take carrying one to hardware store for a fitting. Some used plumbing sized threads so a trip to that dept may be needed LOL

I use these cases a lot for EX so plugging them is the norm.

I like those KBA loads, so I didn't mind the work-around., However if you need the delay for ejection purposes, that's a different matter.

I have 4 of these cases & finally gave up on the last one, just filled the smoke well with epoxy and was done with it!!!! LOL

 

[UPscaler]

Hey Mark!

I always had the same issue with those loads BUT:

If you are using electronics & don't care about the ejection charge, just use a flat smokeless closure or screw a plug into the well of that one.

It will fly fine. I have gone to using the delay insulator for a plugged closure by filling it with 10 minute epoxy & dropping it into the well with one O-ring mashed in & the charge well plugged with a bolt.
These darn things [front closures] were made with soooo many different thread sizes and hole diameters, it may take carrying one to hardware store for a fitting. Some used plumbing sized threads so a trip to that dept may be needed LOL

I use these cases a lot for EX so plugging them is the norm.

I like those KBA loads, so I didn't mind the work-around., However if you need the delay for ejection purposes, that's a different matter.

I have 4 of these cases & finally gave up on the last one, just filled the smoke well with epoxy and was done with it!!!! LOL

That's fine and dandy, but I hate to wreck hardware. We have a Kosdon 75-3600 that has an ejection bulkhead, but it's filled with cotronics epoxy...I'd like to get it out just to say I've got a motor ejection bulkhead in 75mm, but I don't think that it'd come out very easy.




Braden

 

[blackjack2564]

That's fine and dandy, but I hate to wreck hardware. We have a Kosdon 75-3600 that has an ejection bulkhead, but it's filled with cotronics epoxy...I'd like to get it out just to say I've got a motor ejection bulkhead in 75mm, but I don't think that it'd come out very easy.




Braden

If you really want it out. It ain't that big deal.

Drill it. Chill it. Whack it.

 

[GRIFFIN]

If you really want it out. It ain't that big deal.

Drill it. Chill it. Whack it.

That needs to be on a T-shirt!!! "Drill it-Chill it-Whack it"

 

[JDcluster]

The real Kosdon loads used metal washers in between the o-rings....
Kosdon delays were cast into a phenolic tubes, not sure about AT loads for Kosdon hardware...



JD

Tried to build a KBA I550R for the last two days--got stuck at the step where the delay assembly goes into the forward closure. No amount of trying got it in there--the o-rings just would not fit (it wasn't a problem with lubrication--the instructions were followed to a T). I tried pushing it in by hand, and the AMW instruction method of pushing the closure down on top of it. The o-rings strip off every time. Even without the delay element, the o-rings will not fit into the well without useless deformation--they just seem too large. Since this was literally my first snap-ring motor build, I took it to the Tripoli Vegas launch yesterday, and no one there could make it work either. I think the KBA supplied washers are just too large in terms of OD (ID is right on the money).

Does anyone know the right size or McMaster link to EX useful washers? Huge thanks!

 

[Viperfixr]

Talked to Karl at Aerotech, and I think the problem is that my forward closure isn't 'stepped' as shown on the instructions where the delay assembly goes in--it's just a straight shot in. My motor is a Gorilla 38-640 motor, and I thought they were 100% compatible with AMW, but it appears not in this case. Karl offered to have me send him the closure to try and find a solution, and I'll probably send it out next week. He thinks there's alternate o-rings they've got on-hand that may work.

CJ, great suggestion--went to Lowe's today and found that a 1/2-13 bolt fits perfectly. I couldn't find anything in that size shorter than 1", so the top doesn't go exactly flush. But, between that and filling the well with grease or epoxy, or Karl's solution, it sounds like I'll be good to go for the next launch. An 1/2-13 eyebolt about 1/2" long would be perfect.

 

[COrocket]

I think that the gorilla and amw are the same in respects to snap ring to snap ring length, and ID/OD. Im pretty sure you need the nozzle and forward closure to match the reload.

 

[troj]

I think that the gorilla and amw are the same in respects to snap ring to snap ring length, and ID/OD. Im pretty sure you need the nozzle and forward closure to match the reload.

I think it's just the nozzle that varies between the two.

-Kevin

 

[Viperfixr]

Just talked to Karl at Aerotech after he examined the motor forward closure that I shipped to him, and it's nearly identical--but not completely. The AMW 38mm forward closures they have are 'stepped' in the delay assembly well, creating room for the o-rings to slide into. The Gorilla forward closure delay area is not stepped, just a straight shot in at a smaller ID. The OD, closure outside o-ring placement and overall length appears to be the same.

So, Gorilla motors might be compatible with AMW, but not 100%. I am either going to buy an AMW forward closure (anyone know where I can get one??), or just plug this one with the 1/2" bolt and grease. I've got a Wildman Darkstar with one test flight under it's belt and itching to ride an I550R or J740G from this motor at Tripoli Vegas' Oktoberfest! Should be about a mile high, according to RS9. Then maybe the Aerotech J510 to 1.1M and 10k :y:.

BTW, according to the KBA I550R instructions, the required AMW nozzle size is the same as the Gorilla nozzle that came with this motor, 0.368". Also, big thanks and kudos to Karl & Aerotech/RCS--he did everything he could to make this work--awesome customer service.

 

[sugardaddy]

Mark,
Gorilla has updatedthe forward closures on the 38mm. The old style were stepped and the newer ones are straight walled. I cant remember exactly why he did this, but i think it was so he can fit a new style of casting tube for the delay element. You may try contacting Jim Harris. If you rather have the old style he might just swap out the one you have.

Danny

 

[patelldp]

All of this variability concerns me slightly. If the instructions say "Animal Compatible Reload Kit" (which the I550R drawing does), then it's Animal compatible, not Gorilla Compatible.

Not trying to burn any bridges, but it appears that Gorilla hardware is dangerously close to AMW hardware, but not exactly the same. This includes some similar nozzle throat dimensions, with Gorilla's being slightly tighter than AMW on the larger sizes.

It's up to Aerotech to look into this issue and then release information on their compatibility/certification.

For example...if I were to have a Gorilla 54-1400, would it be compatible with the KBA K700F that I have in my box?

 

[Viperfixr]

All of this variability concerns me slightly. If the instructions say "Animal Compatible Reload Kit" (which the I550R drawing does), then it's Animal compatible, not Gorilla Compatible.

Yes, I am a little bothered by this as well. I bought the Gorilla motor for all snap ring 38/640 reloads, plus EX. It's not like there's a lot of AMW hardware being sold or easily obtainable today. But, the first AMW-compatible reload I buy doesn't work in it--wouldn't have bought it had I known this. I would have instead looked for a used AMW motor.

It seems like there's a snap-ring void right now where AMW used to be. There's no Gorilla out West (that I know of), plus their prices are commensurate with AT/CTI--thought snap-ring motors were more value oriented by nature. Kosdon looked poised to come back and be that central snap-ring motor figure, but that's of course now not going to happen. There's a whole family of snap-ring motors that are very similar, or supposedly based on AMW. Now that AMW seems gone for all intents & purposes, it's like the standard went away with it.

Now, if somebody like Tru-core came out with 100% AMW-compatible hardware that could fly certified or EX...I'd buy nothing else.

 

[patelldp]

There's a whole family of snap-ring motors that are very similar, or supposedly based on AMW. Now that AMW seems gone for all intents & purposes, it's like the standard went away with it.

I'm not sure how Gorilla motors dimensions came about. I know that Jim Harris is a contributor on this forum, and I would be interested to know. It seems as though his geometries are a direct clone of AMW for all intents and purposes, apart from the previously mentioned nozzle throats.

I have noticed that my Gorilla 54mm bulkhead is interchangeable with my AMW 54mm bulkhead, and therefore I assume that the lengths of everything else are pretty much the same in the 54mm set between the two brands.

Realistically, there should be little to no difference between Kosdon, Kosdon East, AMW, or Gorilla, as they are all just spawns of the prior. Minor changes were made along the way (External thrust rings with Kosdon East, nozzle and bulkhead liner steps with AMW, and then unknown changes with Gorilla), but for the most part the number and length of grains remained the same.

Now, if somebody like Tru-core came out with 100% AMW-compatible hardware that could fly certified or EX...I'd buy nothing else.

There would have to be some agreement between the companies. What makes the most sense to me would be for AMW and Gorilla to sort out the differences in their hardware, normalize everything, and make them fully interchangeable.

As it stands now, as I said before, they are "close, but no cigar," and it appears to be causing people some issues.

 

[COrocket]

Or if you want new Animal hardware, go on amwprox.com, and email Robert. I did a month ago, and he emailed me the next day confirming that he still does. I am still contemplating wether to get a 38/640 motor from him.

 

[JDcluster]

He still has hardware.
I bought a 38mm x 390, 640 cases and nozzles to go with them.
I never flew any AMW 38mm but, have flown a number of Kosdon 38mm back in the day. I still have two 29mm I 385's.

On note of interest:
the Gorilla and AMW forward closures are not as close as one would think.
I saw somebody try to switch a AMW for a Gorilla and it cracked the liner.

JD

 

[patelldp]

On note of interest:
the Gorilla and AMW forward closures are not as close as one would think.
I saw somebody try to switch a AMW for a Gorilla and it cracked the liner.

JD

This pretty much sums up my point. Close enough that it appears they work, far enough away that it causes things to be a pretty major issue if attempted.