Damaged 38mm 4 grain case recommendations

[dvdsnyd]

I purchased some used snap ring style cases. Not sure brand/home made.
The forward end of this 38mm 4 grain case has a pretty good ding. Will need to file and clean up before using at the very least, as I would be concerned about the o-ring being damaged.
Mostly concerned with the end margin and if this case has substantial enough damage to worry about.
With all that, would you fly it once filed down, or would it be best to shorten the case?
Thanks for looking and providing insight.
Dave

 

[rocket_troy]

I personally wouldn't be concerned. I would try and hammer/beat out what I could 1st though and I would tend to favour that end for the *aft* retention ie. the aft end is under substantially less load than the forward end of the casing end retention.

Snap ring casings should (with correct design) be designed to fail at the snap ring groove at a pinch under the max hoop stress the casing can handle ie. this groove itself should be the weak point. Typical cylinder longitudinal stress is half hoop, so that groove should be brought back/in to approximately 1/2 the wall - despite the recommendations in snap ring groove tables - to allow for the stress concentration points of the (typically square) groove to bring the failure point 5-10% under to ensure the end will fail prior to hoop rupture. Point there is, the weakest point should be the groove itself, not so much the supporting structure behind the groove.

TP

 

[sharkbait]

I purchased some used snap ring style cases. Not sure brand/home made.
The forward end of this 38mm 4 grain case has a pretty good ding. Will need to file and clean up before using at the very least, as I would be concerned about the o-ring being damaged.
Mostly concerned with the end margin and if this case has substantial enough damage to worry about.
With all that, would you fly it once filed down, or would it be best to shorten the case?
Thanks for looking and providing insight.
Dave

Looks like a Loki case
File it off enough on the outside that it fits in your motor mount tube and enough on the inside that you can get your snap ring in. Load your motor from the nozzle end up and the O-ring never gets to the filed area. No worries

 

[3stoogesrocketry]

I purchased some used snap ring style cases. Not sure brand/home made.
The forward end of this 38mm 4 grain case has a pretty good ding. Will need to file and clean up before using at the very least, as I would be concerned about the o-ring being damaged.
Mostly concerned with the end margin and if this case has substantial enough damage to worry about.
With all that, would you fly it once filed down, or would it be best to shorten the case?
Thanks for looking and providing insight.
Dave

Sand it smooth and run it

 

[dvdsnyd]

Thanks everyone! Appreciate the responses.

 

[dvdsnyd]

I personally wouldn't be concerned. I would try and hammer/beat out what I could 1st though and I would tend to favour that end for the *aft* retention ie. the aft end is under substantially less load than the forward end of the casing end retention.

Snap ring casings should (with correct design) be designed to fail at the snap ring groove at a pinch under the max hoop stress the casing can handle ie. this groove itself should be the weak point. Typical cylinder longitudinal stress is half hoop, so that groove should be brought back/in to approximately 1/2 the wall - despite the recommendations in snap ring groove tables - to allow for the stress concentration points of the (typically square) groove to bring the failure point 5-10% under to ensure the end will fail prior to hoop rupture. Point there is, the weakest point should be the groove itself, not so much the supporting structure behind the groove.

TP

Troy,
Thanks for the insight. I will do a little more investigation here on the dims of the case, and use the info you've provided going forward for cases I make myself.