CTI 38mm attempt today didn't end well

My experience today with the CTI 38mm and "reloads" wasn't very much fun.

Setting the delay was a piece of cake, I will grant you that. Disassembling the "reload" is also a piece of cake. Now why would I disassemble a reload? Asking myself the same thing but now I know how the motor is constructed. The "reload" is quite easy to disassemble but make sure you put the dished ends of the grains forward and the black powder pellet grain goes in first. Everything is a slip fit.

The main fit problem appears to be where the delay grain assembly and nozzle assembly o-rings bulge out the flexible liner. Very difficult to push the reload into the case. Do not push on the grains themselves as that will push the delay grain out of the liner which will then block the threads for the nozzle assembly.

Sanding the liner didn't seem like a wise thing to do so I didn't. Thought about greasing the liner/case but I kept remembering how CTI users talk about "dropping the reload into the case" so I didn't.

By this time, I realized I wasn't going to make any progress on my own and sought out the assistance of the club's CTI users. They struggled mightily, uttering words of power, calling for rubber mallets and dowels, but they couldn't do it either which made me feel better...well, in a way but not really.

So now I have 38mm CTI hardware, two I1959R reloads, and no launches today. Joy.

EDIT: Helpful suggestions for fitting CTI reloads into cases would be welcome. Offers to take hardware/reloads off my hands not so much.

Ill take the loads off your hands

At least you didn't have a CATO today Kit. Now I have to find another Kosdon 38/510 nozzle and this time I'll measure the nozzle diameter to be sure it's the right nozzle. That one CATO grounded two of my other rockets due to needing the slimline 54-38 adapter that lost the retaining rings in the CATO.

I spent the rest of my time looking for Thirsty Barbarian (Eric), but never found him. I did leave quite early though.

Good luck getting that reload back in the case . . . never give in . . . which is what I did today

SARG HAS A NEW LAUNCH SITE!!!!

o1d_dude said:

My experience today with the CTI 38mm and "reloads" wasn't very much fun.

Setting the delay was a piece of cake, I will grant you that. Disassembling the "reload" is also a piece of cake. Now why would I disassemble a reload? Asking myself the same thing but now I know how the motor is constructed. The "reload" is quite easy to disassemble but make sure you put the dished ends of the grains forward and the black powder pellet grain goes in first. Everything is a slip fit.

The main fit problem appears to be where the delay grain assembly and nozzle assembly o-rings bulge out the flexible liner. Very difficult to push the reload into the case. Do not push on the grains themselves as that will push the delay grain out of the liner which will then block the threads for the nozzle assembly.

Sanding the liner didn't seem like a wise thing to do so I didn't. Thought about greasing the liner/case but I kept remembering how CTI users talk about "dropping the reload into the case" so I didn't.

By this time, I realized I wasn't going to make any progress on my own and sought out the assistance of the club's CTI users. They struggled mightily, uttering words of power, calling for rubber mallets and dowels, but they couldn't do it either which made me feel better...well, in a way but not really.

So now I have 38mm CTI hardware, two I1959R reloads, and no launches today. Joy.

EDIT: Helpful suggestions for fitting CTI reloads into cases would be welcome. Offers to take hardware/reloads off my hands not so much.

Click to expand...

I had an issue like that once. Fortunately, others were able to help. I thought that I read Jeroen saying in a thread that he sprays a bit of silicon spray on liner before loading. I was going to look this up and try it the next time I launch.

Silicon spray? I have never tried it. There were some defective cases and reloads a few years ago. were these new?

I had a problem getting my first reload in and was advised to spray the inside of the case with Super Lube Dri-Film. That eliminated any further problems. I believe I have seen it at Lowes or HD.

cwbullet said:

Silicon spray? I have never tried it. There were some defective cases and reloads a few years ago. were these new?

Click to expand...

I found the suggestion from Jeroen. It was to use silicone lubricant spray on both ends of case for longer motors. Post #5 in https://www.rocketryforum.com/showt...r-Ablation-Is-This-Normal&p=624839#post624839

Hey Kit,

Seems very odd. The 6 grain or 6xl's can get harder to slide in but a 3 grain shouldn't be that hard. I don't remember any ever being that tough. The case doesn't happen to be "squashed" a little bit by chance? Take the nozzle/rear closure by itself and see if it threads in proper. If it does it shouldn't be a case problem. Not sure what else to think.

You will fall in love with the Pro38 system if you can get it working.

Jason

Sorry to hear about your problems with the loading of the reload. The larger reloads can take a little effort, but the shorter ones should indeed drop right in. Your problem is most likely the result of a slightly oversize liner. The clearances between liner and case are very small.

We can send you some replacement liners. Please PM me your contact information. Is this the first time that this hardware was used? The case material is custom drawn and has a very tight tolerance. But we did find one our two lengths in the last run that had some smaller ID's. Almost as if the last drawing step was skipped by the tube supplier.

Jeroen

4kids49 said:

I had an issue like that once. Fortunately, others were able to help. I thought that I read Jeroen saying in a thread that he sprays a bit of silicon spray on liner before loading. I was going to look this up and try it the next time I launch.

Click to expand...

Based on your advice I tried assembling the motor again today while sitting at my workbench. No pressure, all my tools available. The silicon spray was very helpful but I still encountered difficulty in the last half inch or so. The liner stopped with the aft edge just inside the case and no amount of pushing, words of power, etc. could get it to go further and expose the threads.

jason-and-his-toys said:

Hey Kit,

Seems very odd. The 6 grain or 6xl's can get harder to slide in but a 3 grain shouldn't be that hard. I don't remember any ever being that tough. The case doesn't happen to be "squashed" a little bit by chance? Take the nozzle/rear closure by itself and see if it threads in proper. If it does it shouldn't be a case problem. Not sure what else to think.

You will fall in love with the Pro38 system if you can get it working.

Jason

Click to expand...

I tried threading just the rear closure assembly into the case as you suggested and it worked fine. Case problem? More on that later.

Jeroen_at_CTI said:

Sorry to hear about your problems with the loading of the reload. The larger reloads can take a little effort, but the shorter ones should indeed drop right in. Your problem is most likely the result of a slightly oversize liner. The clearances between liner and case are very small.

We can send you some replacement liners. Please PM me your contact information. Is this the first time that this hardware was used? The case material is custom drawn and has a very tight tolerance. But we did find one our two lengths in the last run that had some smaller ID's. Almost as if the last drawing step was skipped by the tube supplier.

Jeroen

Click to expand...

Thank you Jeroen for joining the discussion. I appreciate your kindness in offering new liners but I don't think the liner is the problem.

After lubing the 3G case and unsuccessfully trying to push the reload home, I decided to try the same reload in my 2G case. With only a bit of residual silicon spray on the liner, the reload went in and fully seated the delay assembly. I went back and examined the 3G case more carefully and discovered two tiny dimples in the exterior case wall about midway along the length of the case. Fearing the worst, I wiped the inside of the case out and found a small barely visible bump by its shadow corresponding the location of the dimples. It was like performing a Foucault test on an astronomical mirror. LOL!

Is this case the problem? Can't say but it seems likely. I tried to insert the reload minus the grains to see if the empty reload would flex enough to pass over the bump but it went no further than previous attempts.

I did buy the 3G case used some time back from a TRF member and this was my first attempted use of it. It was delivered to me in the original clear plastic case and has been stored that way since I bought it. Based on the fact that the reload will properly seat the delay assembly in my smaller 2G case the only conclusion I can draw is that I'm now in the market for a new 3G case.

Thanks everyone who offered suggestions. Much appreciated.

Note to self: Add silicon spray to range box.