cesaroni vs forward seal disk

[watermelonman]

Now that Aerotech has certified cross loads we have some more motor options.

However, shortly after, they came out with a statement saying there were some problems with Cesaroni hardware because Cesaroni does not use a forward seal disk. They recommended continuing to use only Aerotech reloads and hardware together.

Fair enough, but how is it that we all fly Cesaroni 75mm and 98mm reloads in Cesaroni hardware and do not need a seal disk? I have never seen or even heard of a single Cesaroni problem that would have been prevented by a seal disk. Maybe the liner to hardware tolerances are different? Maybe Cesaroni tends to burn cooler? Or maybe I am way off and we do see more Cesaroni problems than I know of.

 

[jimzcatz]

There is a seal disk in those loads, just different from Aerotech. No oring.

 

[Dave A]

My Aerotech reloads work perfectly in my snap ring hdw. I used every AT part when building them plus the o-ring I supplied with the nozzle holder.
No reason the AT reload couldn't be used in CTI hdw with the same results taking care in the prep of the motor.
Usually when such a combination has a certain amount failures it's an easy way out for the manufacturer to say it's no longer warrantied.
I have not loaded my AT loads in my CTI hdw yet and I will use the seal disk. I think it's a good design to keep the flame going to the tracking smoke and not to case and fwd closure. Lightly deburring the ends of liner also prevents those sharp edges from nicking the o-ring for a better seal.

 

[caveduck]

FWIW I used an AT M1297 in a CTI 75mm 4-grain casing for my L3 with the AT seal disk and it worked fine, with almost no blowback around the seal disk down the outside of the liner.

 

[watermelonman]

There is a seal disk in those loads, just different from Aerotech. No oring.

Sorry I should have mentioned in the original message, I was told by long time Aerotech users that Aerotech used to supply a phenolic disk extremely similar to what Cesaroni does now. So the question was, if they both started at the same place, why did one decide to make a change while the other did not.

 

[watermelonman]

Phenomenon is described here:
https://aerotech-rocketry.com/news.aspx?y=2016#n2168
And here
https://m.facebook.com/LokiResearch/posts/425986430924179:0

I've read Cesaroni relies on tighter tolerances on their hardware, between the liner and case ID, to reduce the gas flow escaping from the forward end down the outside of the liner. Even so there is still some gas escaping here on long CTI motors, and is why the inside forward end of the case will have some gunk buildup after flight on long motors. With an AT seal disk the top end of my cases are always pretty clean.

Also, the Aerotech disclaimer advises against using CTI Loads in AT cases because AT won't warranty them. Crossloads was the term Aerotech used when they certified AT motors in CTI cases. I don't see anything in the notice advising against using AT loads in CTI cases.

Thanks, that mostly confirms exactly what I was thinking. Or at least, there are a few of us who think the same, so we are not crazy alone!

Sorry it had been a while since I read the notice. Looking back at it now I see they are recommending their own seal disk, which I probably misremembered as recommending keeping hardware and reload the same brand.

 

[Dave A]

FWIW I used an AT M1297 in a CTI 75mm 4-grain casing for my L3 with the AT seal disk and it worked fine, with almost no blowback around the seal disk down the outside of the liner.

Last month I burned the same reload in a 4800n EX snap ring case. With the CTI hub cap & nozzle holder plus the AT seal disc, it worked flawlessly.
Very little to cleanup and you don't have to put any more wear on your graphite nozzles!
I also test fitted it in a Kosdon 6000n case and fit perfectly using 1 CTI spacer.
The 6 grain AT M1850 fits in the 7600n case however I had rocketsaway cut me a CTI spacer minus 0.75", full spacer was almost too long.