Aerotech J800T assembly

[Chris_H]

I am looking through an Aerotech J800T reload kit, and see:

2 x 2" x 1/8" O-Rings, Forward and Aft
1 x 2" x 1/16" O-Ring for the Liner


In looking at the instructions, the 1/16" O-ring is installed on the nozzle, and ends up between the Aft edge of the liner, and the forward edge of the flange on the nozzle. The Aft O-Ring (2" x 1/8") installs between the aft closure and the aft edge of the flange of the nozzle. All good here.

Up at the forward end, there is no O-ring for the forward seal disc? Is there supposed to be an O-ring for the Forward seal disc? The instructions make no mention of this, and no O-ring is included. Does this sound correct?

Actually, in the instructions, there is no mention of the forward seal disc at all. It is not in the drawing, and not mentioned. Is this right? Do some reloads not use the forward seal disc? In the drawing, it shows a small space in front of the forward most grain, then the forward insulator disc, the forward O-Ring, and the forward closure (with delay grain)

I can read and follow directions, so these may be dumb questions. I would rather ask a dumb question than see a cato on this motor.

Why would some motors use a forward seal disc, and others not?

Cheers.

 

[jd2cylman]

It wasn't a J800T, but we tried building a 2 grain 54mm red at Bong last weekend. Absolutely could not get that 1/16" o-ring between the nozzle and the liner to go into the case... Finally gave up and used a forward seal disc w/o-ring and butted the nozzle up to the liner. Burnt flawlessly. Recovery, not so much.

 

[mikec]

Do some reloads not use the forward seal disc?

If AT gives you a phenolic forward insulator disc, then you're supposed to use that and not the metal forward seal disc, which is not required (and they don't give you an O-ring for.)

Why? Originally no AT motor used the forward seal disc, it was added (mostly to the larger reloads) after damage was being caused by leakage past the phenolic insulator.

I suppose you could use the forward seal disc if you could come up with an O-ring for it, but that would not be following the instructions.

 

[Chris_H]

I just assembled the motor, everything fit well. The forward seal disc would not have fit. No problems with that O-ring.

Would still like to hear why some motors use a forward seal disc and some do not.

 

[mikec]

Would still like to hear why some motors use a forward seal disc and some do not.

Did you read post #3?

 

[Chris_H]

Yes, I did as a matter of fact. I was writing my post as you posted your comment. I saw your post after I posted my comment.

Thank you.

 

[jimzcatz]

Are you absolutely sure it was the J 800 blue and not a J415 white? Most white loads don't require a seal disk. If it is a really old reload kit it probably was made before seal disks were introduced.

 

[mikec]

Actually I think it's that four-grain 54mm (54/1706) and larger motors require the seal disk and smaller ones don't, regardless of propellant type. I don't know of a smaller motor that uses the seal disk, are there any?

 

[Chris_H]

Are you absolutely sure it was the J 800 blue and not a J415 white? Most white loads don't require a seal disk. If it is a really old reload kit it probably was made before seal disks were introduced.

There is a pretty big difference between those two loads. So, yes. Dead certain. Unless some scoundrels swapped out the propellent inside the packaging.

 

[Chris_H]

Actually I think it's that four-grain 54mm (54/1706) and larger motors require the seal disk and smaller ones don't, regardless of propellant type. I don't know of a smaller motor that uses the seal disk, are there any?

Either the I600 or the J350, or both, use a seal disc and o-ring. These are 38mm.

 

[mikec]

Sure, I meant smaller 54mm. Anything 38/720 and above also uses a seal disk, and all 75mm and 98mm.

 

[jimzcatz]

I thought all the 54mm blue and red loads needed the disk. That's why I asked if it was a very old load.

 

[Rocketjunkie]

The only 54 mm motors under 4 grains that use a seal disk are the Warp9 J1799 and J1299. (Unless they changed them again.)

 

[Reinhard]

I am looking through an Aerotech J800T reload kit, and see:

2 x 2" x 1/8" O-Rings, Forward and Aft
1 x 2" x 1/16" O-Ring for the Liner


In looking at the instructions, the 1/16" O-ring is installed on the nozzle, and ends up between the Aft edge of the liner, and the forward edge of the flange on the nozzle. The Aft O-Ring (2" x 1/8") installs between the aft closure and the aft edge of the flange of the nozzle. All good here.

Up at the forward end, there is no O-ring for the forward seal disc? Is there supposed to be an O-ring for the Forward seal disc? The instructions make no mention of this, and no O-ring is included. Does this sound correct?

Actually, in the instructions, there is no mention of the forward seal disc at all. It is not in the drawing, and not mentioned. Is this right? Do some reloads not use the forward seal disc? In the drawing, it shows a small space in front of the forward most grain, then the forward insulator disc, the forward O-Ring, and the forward closure (with delay grain)

I can read and follow directions, so these may be dumb questions. I would rather ask a dumb question than see a cato on this motor.

Why would some motors use a forward seal disc, and others not?

Cheers.

I experienced the same thing with a K1100T. In my case, I started to wonder why the thin O-ring was to big for the seal disc. I almost contemplated cutting a piece out of it to make it fit (figuring that on the seal disc you probably can get away with only a 90% solution), before bothering to read the instructions. Turns out this K1100T reload was just much older than the ones I've prepped before, and the seal disc wasn't introduced at that time yet. With AT, it always makes sense to pay attention to the instructions, even if you have built a couple and think that you understand them. There are some subtle differences between various reloads.

Reinhard