Aerotech forward insulator question

[Nathan]

I usually fly only CTI motors but last spring a bought a couple of AT 75mm reloads to use in my CTI hardware because 75mm CTI reloads were so scarce. So now I am attempting to assemble a motor for the first time. It is a 2 grain K1000T Blue Thunder. I opened up the packaging and the forward insulator disk appears to be missing. So I looked at the other AT reload that I bought (3 grain L1150 Redline) and it appears that I didn't get a forward insulator with that one either. So where is the forward insulator disk supposed to be included with an AT RMS reload? With a CTI reload the forward insulator comes packaged with the liner. But there were no forward insulator disks with the AT liners.

 

[Handeman]

You probably need the aluminum forward seal disk. Is there an extra o-ring in the kit? Probably 1/16" diameter and slightly smaller then the other o-rings?. That would be the o-ring that goes in the aluminum forward seal disk.

I don't have 75mm AT hardware, but the 29, 38, & 54mm hardware all have the aluminum seal disks for the larger motors. I can only assume the 75mm is the same way.

 

[Nathan]

You probably need the aluminum forward seal disk. Is there an extra o-ring in the kit? Probably 1/16" diameter and slightly smaller then the other o-rings?. That would be the o-ring that goes in the aluminum forward seal disk.

I don't have 75mm AT hardware, but the 29, 38, & 54mm hardware all have the aluminum seal disks for the larger motors. I can only assume the 75mm is the same way.

Yes I do have the 3rd smaller O ring. I was wondering what that was for since it is not mentioned in the instructions. So I guess maybe I need the aluminum forward seal disks. Looks like I won't be able to fly the Formula 150 this weekend because I can't assemble the motor. I got these from Kenny Allen last spring. Do you know if he will be at BattlePark this weekend?

 

[qquake2k]

According to this, there is no seal disc, but there should be a forward insulator and o-ring.

https://aerotech-rocketry.com/uploads/2e49771b-3b02-485e-9fb4-d376499d0089_75-2560_k1000t-P_assy.pdf

https://aerotech-rocketry.com/uploa...-84a3-9cc25869e2cb_75_1280-2560t_in_20081.pdf

 

[qquake2k]

This shows the o-ring sizes.

https://aerotech-rocketry.com/uploa...6-c43695b64781_hp_rms_o-ring_spacer_guide.pdf

 

[tfish]

it sounds like. if his reloads came with the medusa style nozzles, he'll need to purchase single throat nozzles to fly the AT reload in CTI hardware..

https://www.rocketryforum.com/showthread.php?131802-So-what-am-I-reading-on-the-Aerotech-site

Tony

 

[Nathan]

Yes they are medusa nozzles. So then not only am I missing the forward insulator disks but I would also have to buy new $55 nozzles for each of these reloads before I could use them in CTI hardware? :eyepop:

 

[ben]

Ken will be at Battle Park this weekend.

Ben

 

[Nathan]

After doing a little research it looks like I should be able to use the AT medusa nozzles with the CTI hardware. None of the outer orifices are drilled out in these nozzles so they are really single throat nozzles.

And the bag that the parts came in has a label that says "AT Crossloads" so I assume that they are designed to be used in either AT or CTI hardware.

 

[tfish]

not to add more issues. But according to the online drawings, both those motors use the same nozzle.

01750-2 NOZZLE ( 75MM MEDUSA)1x .344"/ 4 x .242" (which shows four of the outboard throats are used)

I'd contact Aerotech and make sure you have all the right pieces to fly those reloads in CTI hardware.

Tony

 

[Steve Shannon]

Ask for the supplemental instructions also. Here’s what the cert document says:

RMS/CTI Case Cross Certification

Finally, most all Aerotech 75 MM 2, 3 and 4 grain motors have been certified for use in the equivalent CTI 75-2g, 3g and 4g cases, WITH the following restrictions. The supplemental instructions are required to be followed to the letter in regards to both seal placement and positioning of the nozzle bushing. Also, as any Medusa nozzle reload will be recessed in said bushing, certain Medusa motors will not be compatible due to expansion restrictions. All Single Throat motors (including single throat Medusa) should be good to go in that regards. Contact Aerotech for specific details on both the instructions and specific motors not applicable to this certification (especially older, legacy reloads!).

From the above it sounds like your Medusa nozzle should be okay.

Steve Shannon

 

[Handeman]

I got these from Kenny Allen last spring. Do you know if he will be at BattlePark this weekend?

Kenny is planning to be there. If his AT order arrives at the DC address on Thursday, he plans to be there on Friday. If it arrives Friday when it's promised, he will probably be there Saturday.

It looks like rain on Sunday so that day may be a wash out, but it depends on the forecast.

 

[Nathan]

I talked to Kenny Allen and he confirmed that the problem is that Aerotech is switching from fiber forward seal disks to reusable aluminum disks on 75mm motors. The aluminum disks cost about $35. Unfortunately the instructions with the reload still say to install the nonexistent fiber forward disk. The aluminum forward seal disks are currently backordered. And the aluminum disks require an O-ring which was also not included with the reload.

 

[tim cubbedge]

This is where I got mine, shows in stock.
https://www.siriusrocketry.biz/ishop/aerotech-rms-75mm-fwd-seal-disk-1648.html

If I recall, my reloads did come with the seal disk 0-ring.

[video=youtube;d0xjmJ-Yur8]https://www.youtube.com/watch?v=d0xjmJ-Yur8&index=5&list=FLf2RoMTsTGmo6iwigZv5S8w&t=6s[/video]

 

[ChrisAttebery]

I have purchased 5 AT 75mm reloads over the last 2 years and all of them had the deal disk o-ring. Were these old loads?

I'd call AT. They will probably send you the o-rings for free. I'm sure if you asked around at a launch you could find one. You should be able to find someone with a seal disk you could borrow.

I talked to Kenny Allen and he confirmed that the problem is that Aerotech is switching from fiber forward seal disks to reusable aluminum disks on 75mm motors. The aluminum disks cost about $35. Unfortunately the instructions with the reload still say to install the nonexistent fiber forward disk. The aluminum forward seal disks are currently backordered. And the aluminum disks require an O-ring which was also not included with the reload.