29mm 40/120 hobby case

Hello all-

I tried to do a search prior to posting this question.

I got a 29mm 40/120 motor from Hobbylinc. The motor is from Aerotech. The entire case, and forward closure is rough with tiny tiny ridges....like it was 3d pinted. The ridges do not go the length of the case....think of stacked "O" rings. Anyway is is not smooth at all. I think this may be a pain to clean. Is this something new? The case feals like a metal file, inside and out. I have never seen anything like it. AHH yes it is like the surface of a record...you know an LP or 45.

Anybody have something like this?

Andrew

Mine have the grooves but they are nowhere near as coarse as a record. I can't really see them but I can feel them if I run a fingernail across them. At a guess they are 200+ threads per inch. They work just fine.

AKVP said:

Hello all-

I tried to do a search prior to posting this question.

I got a 29mm 40/120 motor from Hobbylinc. The motor is from Aerotech. The entire case, and forward closure is rough with tiny tiny ridges....like it was 3d pinted. The ridges do not go the length of the case....think of stacked "O" rings. Anyway is is not smooth at all. I think this may be a pain to clean. Is this something new? The case feals like a metal file, inside and out. I have never seen anything like it. AHH yes it is like the surface of a record...you know an LP or 45.

Anybody have something like this?

Andrew

Click to expand...

It's a fairly coarse autofeed. The rouse-tech cases are the same; the outsides are machined to diameter unlike the drawn-to-spec CTI tubes.

The inside too? Beyond the threads, I've never seen an Aerotech case machined on the inside. Any chance of a picture?

Who cares if it fires the reload without a problem?

My AT 29/40-120 also has the grooves in it. I just use an old toothbrush to clean mine out. It can be a pain though if you don't get it cleaned out well as it will cause the new insulator tubes for your next reload to not fit. Other than that it's worked fine for me without a hitch.

Mine has the grooves as well, they are known as machine marks, they are left over by the machining cutters.

AKVP said:

Hello all-

I tried to do a search prior to posting this question.

I got a 29mm 40/120 motor from Hobbylinc. The motor is from Aerotech. The entire case, and forward closure is rough with tiny tiny ridges....like it was 3d pinted. The ridges do not go the length of the case....think of stacked "O" rings. Anyway is is not smooth at all. I think this may be a pain to clean. Is this something new? The case feals like a metal file, inside and out. I have never seen anything like it. AHH yes it is like the surface of a record...you know an LP or 45.

Anybody have something like this?

Andrew

Click to expand...

If you have worries about a CATO,you should contact Aerotech and ask them about your concerns.It should give peace of mind.Hope this helps.

I know Aerotech had a bad lot of these casings, unfortunately I found out the hard way and had a CATO that froze the threads on one end of the casing. They did warranty it and not only replaced the casing but also replaced the Aerotech Astrobee D that the casing was in at the time of the CATO.

I have 2 Aerotech and 1 Rouse tech 29-40/120 cases, they have micro grooves on the outside, hardly visible, have to look closely to see, but the insides look and feel smooth to me. Pics. would help, otherwise just contact Aerotech.

Mine not only has the grooves, but for about 1/2" on the inside they are much deeper and more noticeable than the rest. I wondered if there was a purpose at first.

I'm going to guess that he wants input before he fires it, hence the reason for the thread in the first place. Otherwise the next thread would be..."when I was loading up my case I noticed it had small grooves inside of the case, but I decided to fly it anyways and it catoed!" Then people one the forum would be like, well you shouldn't of flown it blah blah.....

Preston

Viperfixr said:

Who cares if it fires the reload without a problem?

Click to expand...

I would just contact Aerotech and ask them if about the casing.

The cases should be turned with about .003" - .005" feed per revolution (200-333 grooves per inch). The grooves should only be about .0005" deep. The surface should feel smooth to the touch. If it's rough send it back.

ChrisAttebery said:

The cases should be turned with about .003" - .005" feed per revolution (200-333 grooves per inch). The grooves should only be about .0005" deep. The surface should feel smooth to the touch. If it's rough send it back.

Click to expand...

Feed rate would depend on the tooling used.

Hello All-

Thanks for the replies. The grooves are indeed on the inside and out of the case. They are indeed rough. Also I do not have a camera that could show you in detail. It bums me out to know of a bad lot of these. I hope this one is not bad. As one suggested, I dont want to just load it up and fire it....this is rocketry and I try to mitigate risk, do things safe and have fun. I dotn want to just "wing it".

I think I will contact Aerotech. I just wanted to get some input prior to proceeding. I have had many many cases of all sizes and all are smooth as glass. This rough surface is pretty out of the norm.

Thanks for the input.
Andrew

chadrog said:

Feed rate would depend on the tooling used.

Click to expand...

Yes, but its a finish cut on a thin part. You're not going to be able to take a heavy cut on tubing that thin.

ChrisAttebery said:

Yes, but its a finish cut on a thin part. You're not going to be able to take a heavy cut on tubing that thin.

Click to expand...

A feed rate of .003 to .005 is highly unlikely, especially in aluminum. Unless they're using archaic equipment, which I doubt. Aluminum machines more freely than anything, it's not hard to achieve a great finish in short order.

I just checked my brand new 29/40-120 and it has the grooves/machine marks just like the OPs does. Inside and out also after calipering the tube the aft closure end is .002 smaller than the forward closure end (1.125 vs 1.123 inches) of course the ends can be reversed. The grooves on mine are easy to see and hear when you scrape a fingernail across them.

Has anybody heard anything from Aerotech on this? (the grooves question)

View attachment mr_29-40_120.pdf

I suggest you take a look at the machine drawing of the casing referenced above. Do you see any specification on surface finish? I don't.

The tolerances on x.xxx" dimensions is specified +/- 0.005" so you casing meets all specifications listed in the machine drawing.

Bob

bobkrech said:

I suggest you take a look at the machine drawing of the casing referenced above. Do you see any specification on surface finish? I don't.

The tolerances on x.xxx" dimensions is specified +/- 0.005" so you casing meets all specifications listed in the machine drawing.

Bob

Click to expand...

That's not a machining drawing, it lacks a lot of specific information.

I just received a 29/40-120 casing from hobbylinc. I see the same machining artifacts. I am not concerned in the slightest. Could it be a smoother finish? Yes. Is it a structural concern? No.