Anyone have experience with CTI 614I100 red longburn (Pro54-2G)?

[woferry]

I'll start off saying that I already tried contacting CTI via their webpage 2 weeks ago (about #1 below), didn't get any response. So I end up here. Have also pinged the vendor I bought the motor from, more on the replacement side of things as I'm not sure he'd have the right answer for #1.

I purchased one of these motors last year (part of my local vendor's dwindling CTI stock post-fire), and recently decided it looked like a good sustainer motor for my Osprey 75 2-Stage. At my last launch I started building it on the field, only to find that the liner was way too wide to fit in either my Pro54 cases (3G and 4G). At first I tried 'deburring' the edge, but found that it was much worse than that. After a bunch of sanding of the entire liner I started to get close, but I sanded a LOT of liner away, so I wouldn't feel so comfortable flying it with the mound of liner dust I had wound up with at the field. I also observed a few other "odd" things along the way, compared to other CTI loads I've flown:

1) The aft closure was bonded to the liner. I say "was" because as I was sanding the liner down once I thought I was close I tried getting it to fit, greased it up and managed to get it about an inch into the case before it totally seized (gave up shortly after this point and started building a different motor for the sustainer). While trying to twist/tug it back out at the field, I managed to break the bond on the closure, so they're now separated. I assume these two pieces were bonded for a reason, I haven't seen this on other CTI Pro54/38 loads I've flown. So even if I got a replacement liner that fit, it seems like it would either need to have the aft closure pre-bonded, or I'd have to know how to bond it myself (what adhesive to use, namely, and any prep steps if required).

2) Quickly once I started running into fit trouble I removed the load from the liner (wasn't going to sand it with the propellant in), and it's a strange one. While it's a 2G liner the load is a single grain, and it's quite a bit shorter than the liner, in fact when the grain is all the way against the aft closure there's literally 1.5" to the top of the liner(!!). This leaves me concerned about using this load as an airstart, mainly due to positioning of the igniter. When I first opened it (to set the delay), perhaps just due to handling, the load was all the way against the forward closure, so when I first tried inserting the thin dowel I would have taped the igniter head into I had no trouble inserting it all the way in (having seen that it was an offset core, and after getting past the initial binding point, which I figured was the gap between the 2 grains, but really was the gap below the grain). But if I hadn't wound up taking everything apart I never would have realized that during booster lift-off the grain probably would have shifted down, leaving the match head in the ~1.5" of airspace between the delay grain and the propellant grain. There is the 'pellet' at the top of the grain, but I'd wonder if it would ignite from so far away. I guess I could pre-bias the grain towards the bottom of the motor and figure out exactly how far I'd have to put the dowel/igniter in to line the match up with the pellet, though then it would be pretty far from the delay grain, not that this really matters since the motor eject would only be a backup to my RRC3 in the sustainer, so no biggie if it didn't light. Inserting the igniter at the pad might also be tricky, since the notch in the offset core up the grain doesn't quite make it to the middle (nozzle opening), so with the grain at the bottom the igniter would have to go in on a pretty steep angle and then bend upwards to continue towards the pellet (might end up pushing the grain forwards while trying to insert it, and not sure that it would settle all the way back down once the dowel is in).

I guess all this really says is that if I put the igniter in the 'right place' for the load shifted all the way down, it might end up below the pellet if things shifted up during prep or the first part of the flight, and I guess the worst that would happen is the airstart just wouldn't happen. Or would it be better to have the igniter in the space above the grain, and assume that it will ignite the pellet even if it's an inch or so away from it? But I've never encountered a motor that was configured so strangely before, I guess because it's a longburn? Wondering if anybody has any thoughts, is it just a bad idea to try to use this motor as an airstart? And is the grain supposed to be in a certain position (top, bottom or middle) at ignition? The instructions that came with the motor said nothing special, they were just the generic Pro54 instructions, including saying to insert the match all the way to the top, not sure what it assumed about the position of the grain while doing this.

BTW, it was in the high-50's/low-60's at the field, so I don't think the fit issues were due to a large temperature difference, it just wasn't that cold. And even once I got home the liner was still very stuck, I used the warming tray in my oven to get the liner up to ~150F and the liner was still good and stuck, though I finally managed to knock it out with a few more strikes of a PVC pipe through the top of the motor casing (I've probably also buggered the top of the liner enough by now that it wouldn't be safe to fly even if I did sand the OD to the right dimension, at least the case is fine).

 

[Bat-mite]

I had this happen with a Pro38. Finally had my dealer look at it and try to get it to fit and he couldn't. Gave me a refund.

Things have not been quite as good with CTI since the fire. Really hoping they get back into full swing, fix the VMAX delay problem, the Pro38 forward closure issues, get production back up, and get quality control where it needs to be.

 

[Thorfire]

I flew a pre-fire one in my Darkstar 2.6. Great motor. No issues. I used a 3 grain case with a spacer. I hope your experience isn't typical of current CTI production. Both the I100 and J145 moonburners are great motors. I hope to fly more of them.
https://youtu.be/b8AnubA_VgU


Sent from my LG-H811 using Rocketry Forum mobile app

 

[Maxwelljets]

Pro38 forward closure issues

This issue has been resolved for a long time. They sent out replacement forward closures to dealers who will replace forward closures of older reloads for free.

 

[Bat-mite]

This issue has been resolved for a long time. They sent out replacement forward closures to dealers who will replace forward closures of older reloads for free.

Understood.

 

[Maxitout]

I flew one of this in July. The motor was a couple years old, and I flew it in a 3-grain case with spacer. I didn't have any issues at all, it's a great motor. Hopefully, you just had a one-time glitch.

Phil L.

 

[woferry]

Just to clarify, this was not a post-fire motor, it was just purchased post-fire when my local vendor's supply was next to nothing, the motor date stamp is MAR 14 2015.

I flew a pre-fire one in my Darkstar 2.6.

I flew one of this in July.

So for those who have flown this, where did you position the grain in the liner? And especially if the first answer is towards the bottom, how far do you think you got the igniter into the motor? Stopping at the top of the grain, or all the way to the top of the motor? If the grain was towards the top it would seem to be particularly hard to actually get the igniter to go into the grain slot, the wire could easily just bunch-up in the large volume underneath the grain and never make it into the grain itself (though I'm not sure it would light that way). So do you check to verify how far you should be inserting the igniter (the generic instructions say motor length minus around 2"), or just feed it in until it stops regardless of how far that was?

Also, did either of you notice the aft closure being bonded to the liner? Not just a tight fit but actually glued, I can see the residue on my closure where it separated.

 

[Rocketjunkie]

The grain goes forward against the forward closure. You can bond the nozzle into a new liner with CA. I've had several CTI motors with the nozzle bonded in, mostly offset core motors.

 

[woferry]

The grain goes forward against the forward closure. You can bond the nozzle into a new liner with CA. I've had several CTI motors with the nozzle bonded in, mostly offset core motors.

So, impossible to use as an airstart then, since there’s nothing to keep the grain forward under the G-load of the ground motor(s), eh?

 

[rcktnut]

in fact when the grain is all the way against the aft closure there's literally 1.5" to the top of the liner(!!).

I have the 38 cases no 54's. Just a question, you need room for the delay module/ forward closure to fit inside the liner, how much of that 1.5 inches left in the liner is taken up by the delay module?

 

[woferry]

I have the 38 cases no 54's. Just a question, you need room for the delay module/ forward closure to fit inside the liner, how much of that 1.5 inches left in the liner is taken up by the delay module?

The closures only overlap the liner by maybe 1/8-1/4". So most of that 1.5" is empty space after the motor is fully-assembled. It is different than the Pro38's, on those the overlap is larger and the O-ring of the closure goes into the liner, in the Pro54's the O-ring only 'mates' with the casing, and there's just a fairly small lip on each of the closures that goes into the liner. This picture shows it, only the right-most black section goes into the liner.

 

[rcktnut]

If I were you I would just request a new reload, thru vendor or CTI, would not fool around trying to make this one work. You deserve one, should not have to sand the crap out of the liner to get it to fit. That being said I think I have some answers to your questions.

First on the grain only being one in a 2 grain casing: Aerotechs 54 long burns are only one grain whether it be for the 2,3, or 4 grain casings. They have to be or the burn rate would be faster. For the 75 and 98's they have multiple grains, but the grain faces have to be epoxied together to make it one. I looked at the CTI instructions same thing with their 75 and 98's.

On the 1.5 inch space: I think (just think only- IMO) that the grains were bonded to the top of the liner to provide room at the nozzle end to insert the igniter. With the offset core the only other way to get the igniter in is with the bottom grain chamfered. Aerotechs grains have that chamfer on the bottom grain with the nozzle tight to the grain. Is your grain chamfered on the nozzle end?? If not that is most likely why CTI leaves the space. Your sanding most likely broke the grain to liner bond.

On the bonded nozzle with this load, just thinking again, maybe CTI does this just to make absolutely sure that the nozzle does not twist in any way once the igniter is in. Don't really see how it can once assembled and igniter inserted at the pad, but just my thought only again. May be the bonded nozzle is just a side effect of bonding the grains to the liner.

 

[woferry]

If I were you I would just request a new reload, thru vendor or CTI, would not fool around trying to make this one work.

There's no way what I have is going to work, the front edge of the liner got buggered getting it out of the case after it jammed in, so I gave up on that the day of the launch. CTI was contacted 2.5 weeks ago, no response, and I pinged my vendor but he has no stock to replace it with, his CTI 54mm 2-grain bin was literally empty, so not only no I100's but no nothing else that a liner could be taken from, either. What I was asking about here was about the aft closure bonding, which was seemingly intentional for this load (but I was looking for confirmation from someone else who has used this load) and clearly only for the closure, but something I'd presumably have to replicate if all I got was a replacement liner), and what to do about the funny grain in an airstart case (which so far it sounds like I simply can't use this motor for what I wanted to use it for, so besides the fact that I'm not sure I'm even going to be able to get a replacement, it may not do me much good anyway. The rocket I originally intended to use this for is no longer a rocket, and it doesn't have enough kick off the pad to be good for anything I do have right now, it would have been perfect for airstarts but the gap inside the motor is a problem especially if the grain is really supposed to be at the top since there's nothing to keep it there that wouldn't be modifying the motor, but if other people had flown it with the grain towards the bottom that would give me more confidence).

On the 1.5 inch space: I think (just think only- IMO) that the grains were bonded to the top of the liner to provide room at the nozzle end to insert the igniter. With the offset core the only other way to get the igniter in is with the bottom grain chamfered. Aerotechs grains have that chamfer on the bottom grain with the nozzle tight to the grain. Is your grain chamfered on the nozzle end?? If not that is most likely why CTI leaves the space. Your sanding most likely broke the grain to liner bond.

No, there was definitely no glue on the grain or inside the liner, just the aft closure to the liner. The grain was tight (well, not loose) but definitely able to move around, and that was before I did any sanding. All I did at first was to take a hobby knife along the edge to 'deburr' the liner, like AT often says to do, thinking that it was perhaps just the edge keeping it from going into the case, as soon as it was clear that this wasn't the issue I tapped the grain out of the liner like I would on any other CTI/AT load and it came right out, before I did any sanding. The bottom of the grain core is chamfered torwards the middle (similar to the AT J180T I've flown before), it's a pretty steep chamfer though. I'd take pictures except it's on the opposite end of the country from me right now.