How do you deal with a too tight motor case?

[pfhorwath]

I have a Dr Rockets 29mm 180 motor case that is about 20 years old but in very good condition. my problem is that now that I've gotten back into the hobby 20 years later, it seems like it is to tight for the modern Aerotech reload kits. Did they change the dimensions? Is there a fix out there? I was able to get a H220 to work but I had to sand the liner a bunch and use an arbor press to seat it. I got away with it because it was one of the black liners but I tried the same with one of the paper lines and ruined the liner. anyone have any suggestions other then to get a new case?

 

[dhbarr]

Usually folks just peel the outer layer.

 

[tsmith1315]

I have a Dr Rockets 29mm 180 motor case that is about 20 years old but in very good condition. my problem is that now that I've gotten back into the hobby 20 years later, it seems like it is to tight for the modern Aerotech reload kits. Did they change the dimensions?

No change, many of us are still using our old hardware.

 

[cls]

yeah, peel the very outer layer of the liner tube. use lots of superlube so it slides out after use.

 

[terryg]

I have an older Rousetech 38/480 case that is slightly out of spec. I have to sand the crap out of the phenolic liners to get them to fit the case. If I borrow a case the reload fits fine with no effort.

 

[pfhorwath]

I wonder if I change out the case if that will make a difference. This is really annoying, I don't have any trouble with my 38MM and 54MM cases. Strange thing is, I don't remember it being a problem in the past with this case but that was 20 years ago. I can't image any scenario where a case could shrink.

 

[waltr]

The liner diameter issue can happen with any of the AT reloads.
Peeling a layer or two off the outside of the liner tube is fairly common for me. I have had to do this with 18 through 29 reloads. All have worked fine at launch time.

 

[tsmith1315]

I can't image any scenario where a case could shrink.

Liner tolerance would be a more plausible explanation. Peeling the outer layer is acceptable practice. AeroTech has nodded approval for that in the “AeroTech Open Thread”



FWIW, my 29mm hardware is from ‘95 and still in service.

 

[Handeman]

I have Dr. Rocket cases from 29 to 54. The only one that has the issue you mention was my 38-480 case. Whenever I got a phenolic liner that didn't fit, I would barrow an AT 38-480 case and the liner would slide right in. It only seemed to be every 8 - 10 reloads were this happened. I ended up buying a AT 38-480 case. I had to peel the label off that so it would fit into the rocket, but the tight liners in my Dr. Rocket case always fit in the AT case.

I think the Dr. Rocket case is near the minimum diameter tolerances and when a liner at the outer diameter tolerances meet, they don't fit.

 

[Voyhager3]

Well I guess you don't have to worry about it now!

 

[pfhorwath]

LOL your correct there Jacob and thanks for helping me look for it. This problem solved itself as the motor retainer failed in flight yesterday and the motor casing is lost somewhere in a corn field at the ROCC launch. Try looking for a 29mm red anodized Dr Rocket case in a field of stripped corn cobs (same size and color). Thanks to Ken and my Visa card I've already replaced it with a new Aerotech casing!
BTW the IRIS is already back in flying condition which is nuts as it lawn darted in and buried the nose cone so deep we couldn't get it out. That rocket has nine lives, which means it only has about four left as this is the FIFTH time I have rebuilt it! I think its the only rocket in history to have crashed in three different states, four different decades and two different millennia (1997 VA, 2006 MD, 2011 VA, and twice in DEC 2023 NC)