CTI Discussion Thread

[OzHybrid]

Remember, CTI is in Canada... there may be other issues involved as well. Importing propellant chems from the US may be "difficult"...

What about producing Hypertek motoer? Is that difficult too? Really.......
If they cannot import HTPB, Aluminium, KP, they haven't got a business model. That's white lightning, which they're not making in amateur rocketry reloads.
It's the fundamental basis of most propellants....ish. So if they're in business, they're just not supplying the amateur community. When war is on, we mean nothing to them in market share. When war is off, we mean more to them. But if they cannot supply us, the vacuum will be filled. Economics 101.

 

[4regt4]

Fired my first CTI motor this last weekend. 29mm 5G "Classic". Flight went well (except delay was about 3 seconds longer than spec...).

When I went to clean it, I found a very badly melted liner. Is this normal?

Hans.

 

[boatgeek]

Fired my first CTI motor this last weekend. 29mm 5G "Classic". Flight went well (except delay was about 3 seconds longer than spec...).

When I went to clean it, I found a very badly melted liner. Is this normal?

Hans.
View attachment 643579View attachment 643580

Totally normal. IIRC, most of the melting happens during the delay burn.

 

[4regt4]

Totally normal. IIRC, most of the melting happens during the delay burn.

Forgot to mention, my altimeter recorded a large pressure spike in the body tube right at burnout (approx 2 seconds into the flight). I was thinking that the liner burn through caused pressure to go up the side of the liner (not through the delay). Residue in the case kind of supports this.

Hans.

 

[3stoogesrocketry]

Forgot to mention, my altimeter recorded a large pressure spike in the body tube right at burnout (approx 2 seconds into the flight). I was thinking that the liner burn through caused pressure to go up the side of the liner (not through the delay). Residue in the case kind of supports this.

Hans.

It probably spit a casting tube out the nozzle causing the spike

 

[jsdemar]

Forgot to mention, my altimeter recorded a large pressure spike in the body tube right at burnout (approx 2 seconds into the flight). I was thinking that the liner burn through caused pressure to go up the side of the liner (not through the delay). Residue in the case kind of supports this.

Hans.

At burnout, the parachute etc will shift forward. Sometimes this will effect the pressure seen by the sensor.

 

[3stoogesrocketry]

At burnout, the parachute etc will shift forward. Sometimes this will effect the pressure seen by the sensor.

A electronics bay should never see a pressure spike from inside. This means ejection gasses are getting into the ebay. No bueno

 

[4regt4]

A electronics bay should never see a pressure spike from inside. This means ejection gasses are getting into the ebay. No bueno

Never said there was an ebay.

The altimeter is in the forward part of the body tube. This is not dual deploy. It is a data logging altimeter, just for informational purposes. So, yes, it is exposed to ejection gasses. The pressure spike at burnout was in the body tube.

Hans.

 

[Handeman]

Never said there was an ebay.

The altimeter is in the forward part of the body tube. This is not dual deploy. It is a data logging altimeter, just for informational purposes. So, yes, it is exposed to ejection gasses. The pressure spike at burnout was in the body tube.

Hans.

I don't think it was from the motor liner melting. Any pressure from the motor getting into the body tube would mean it had to get past the o-rings. This will usually result in more then just residue in the case. Usually there is a melted hole in the case.

 

[Flare]

I don't think it was from the motor liner melting. Any pressure from the motor getting into the body tube would mean it had to get past the o-rings. This will usually result in more then just residue in the case. Usually there is a melted hole in the case.

On Pro29 motors (Pro24 and 38 as well) the o-rings seal on the inside of the liner, not on the inside of the case. So if the liner melted prematurely gases from the motor could escape out the case.

 

[Handeman]

On Pro29 motors (Pro24 and 38 as well) the o-rings seal on the inside of the liner, not on the inside of the case. So if the liner melted prematurely gases from the motor could escape out the case.

wow, I wasn't aware of that. I've only flown Pro54 motors.

 

[Flare]

wow, I wasn't aware of that. I've only flown Pro54 motors.

Note that this isn't really a problem on these motors in the way one might think. Usually sealing on the inside of the liner turns the liner itself into a pressure vessel and it could crack. However since the Pro24/29/38 liners are made of some sort of plastic that's a lot more flexible than the usual phenolic type liners they just basically expand a little bit and there's no problem with getting the case itself to take the pressure.

For what it's worth I've flown several Pro29s and lots of them end up having liners looking all mangled like the picture but I have never had any issues with them performance wise and my casings have been fine if a little sooty occasionally. The consensus is that the liners usually only get like that after motor burnout.

 

[4regt4]

Note that this isn't really a problem on these motors in the way one might think. Usually sealing on the inside of the liner turns the liner itself into a pressure vessel and it could crack. However since the Pro24/29/38 liners are made of some sort of plastic that's a lot more flexible than the usual phenolic type liners they just basically expand a little bit and there's no problem with getting the case itself to take the pressure.

For what it's worth I've flown several Pro29s and lots of them end up having liners looking all mangled like the picture but I have never had any issues with them performance wise and my casings have been fine if a little sooty occasionally. The consensus is that the liners usually only get like that after motor burnout.

Mentioned this on a case cleaning thread, but relevant here...

After doing a normal swab out, bottle brush, etc, there was a bad patch half way into the tube. Looked like pitting. Hard to tell, being several inches in. Ran a paper towel with Hoppe's #9, it now looks like new.

Hans.