CTI 29 case seized

[SamK]

Good day,

with my local club launch in a week, I need to get this case ready ; the aft closure has seized terribly and nothing I have tried so far has been successful.

So far I have tried, WD40, lubricant, hot water, knocking it against a hard surface, rubber grips, water pump pliers, and all combinations of the above. The last time the closure was removed was in September.

Are there any techniques with a good track record I should know about? (Apart from not storing the case with the closure installed)

Thanks!

 

[pugachu]

I only have CTI in the 54mm size, and the closure is SS. looking at pictures, it looks like the 29mm case is internally threaded. If the closure is SS on the 29mm, then try gently heating the case (as long as there is no motor in it). the aluminum should expand more than the SS, and that may be enough to break it free. heat should also soften organic residues that may be causing it to stick. I know you've tried hot water, but that might not be enough heat.

 

[terryg]

Strap wrench?
Temperature cycling, freezer to boiling water?

 

[SamK]

I'll give more extreme temperature cycles a try, would it be ok to hit it with the blowtorch a little?

 

[SolarYellow]

I'll give more extreme temperature cycles a try, would it be ok to hit it with the blowtorch a little?

NO!!!! That will anneal the aluminum, which will destroy its mechanical properties and make it suitable only for the recycle bin.

I'd go as hot as boiling water, not from the tap. If that doesn't work, maybe put it in a ~300F oven, but no hotter.

SS against aluminum creates a galvanic cell that attacks the aluminum. Add any carbon to the mix, and it gets worse.

For penetrating oil, I haven't really tried that until I've tried Kroil. The stuff is amazing. Soaking for a day or two may make a difference.

 

[SamK]

NO!!!! That will anneal the aluminum, which will destroy its mechanical properties and make it suitable only for the recycle bin.

I'd go as hot as boiling water, not from the tap. If that doesn't work, maybe put it in a ~300F oven, but no hotter.

SS against aluminum creates a galvanic cell that attacks the aluminum. Add any carbon to the mix, and it gets worse.

For penetrating oil, I haven't really tried that until I've tried Kroil. The stuff is amazing. Soaking for a day or two may make a difference.

Thank you, I put it in the freezer earlier today. I will try after dipping into boiling water and loosening then.

 

[SolarYellow]

If it's at freezer temperature, heating the aluminum with boiling water on the outside while keeping the closure as cold as possible would be a good approach. Stainless does expand more than plain carbon steel, but not as much as aluminum.

 

[ThirstyBarbarian]

On 29mm, I don’t think the aft closure is stainless steel. Mine are anodized black. I’m not sure what the metal is. If they are aluminum, you won’t get the difference in expansion. You could still try heating it.

 

[SamK]

On 29mm, I don’t think the aft closure is stainless steel. Mine are anodized black. I’m not sure what the metal is. If they are aluminum, you won’t get the difference in expansion. You could still try heating it.

I will give it a go.

 

[Voyhager3]

Don't do anything extreme temperature wise, as almost everyone so far has said that, as I say that from experience. Not from motor casing, but RC car parts. I had a control arm I reshaped countless times through heating and cooling. Then one day, in a hard, but good landing, it just snapped. Now with a motor casing, it's already being temp. cycled every time it was flown. So it could rupture and sha-bing, sha-boom, it goes kaboom. So boiling and freezing wont be too much past normal operating temps, so it will be fine.

EDIT:
Just don't forget to wear gloves when it is hot. I've done that too many times, because I forget how well aluminum can sometimes hold the heat.

 

[rocket_troy]

Add as much lube as possible and keep tapping the closure against something rigid but not too hard as to mark the alloy (eg. hard wood or plastic). Tap tap tap and occasionally try screwing/unscrewing (both directions) without applying too much force (that'll seize it more).

TP

 

[ThirstyBarbarian]

I tend to think the penetrating lubricant is going to be the best route. Something designed with penetrating properties. Spray it on and let it soak for hours.

When you get it off, you can use lubricants on the case and closure when you fly the next motor. I‘ve been told that spray silicone or spray Teflon work well. They told me it doesn’t take much. Just spray it on the threads and inside the casing tube. Then wipe most of it away. Then assemble and fly the motor. It’s supposed to make cleaning easier, and I assume it would make removing the closure easier. I haven’t actually tried it myself since being told about the technique.

I’m terrible about cleaning cases and other things after a launch. I think I have 3 waiting to be cleaned. I was also told that gun cleaning solvent works well for cleaning residue from cases, so I’m going to try that the next time I clean the blasters.

 

[KenECoyote]

PB Blaster soak + rubber jar gripper (on casing) + big adjustable wrench or pipe wrench on the closure.

 

[prfesser]

It's the difference in expansion/contraction that you want to exploit. Freeze the whole thing. Put on insulated gloves with a good gripping surface (silicone dots or similar). Remove from freezer, stick the casing into boiling water nearly up to the closure. Remove after a few seconds and immediately attempt to unscrew.

If you had access to dry ice or liquid nitrogen, those might work better.

 

[asm109]

dry ice in an alcohol bath will give you -90 C

 

[rocket_troy]

dry ice in an alcohol bath will give you -90 C

Are you sure you don't mean -78C?

TP

 

[asm109]

No I don't.
https://melscience.com/US-en/articl...re's tem­per­a­ture can reach -90°C (-130°F).
Its a mixture that gets colder than the phase change temp of the co2 alone. Same principal as using salt in an ice water bath to get it colder for ice cream making purposes.

 

[rocket_troy]

No I don't.
https://melscience.com/US-en/articl...re's tem­per­a­ture can reach -90°C (-130°F).
Its a mixture that gets colder than the phase change temp of the co2 alone. Same principal as using salt in an ice water bath to get it colder for ice cream making purposes.

Color me skeptical. This backyard youtuber's hunch assertion is the only reference I can find to achieve -90C from dry ice and ethanol. If he at least showed a thermocouple measurement of that temp, I'd be convinced. Got any more scientific links or at least where it's measured?

I'm trying to theorize a mechanism- like, once the solution (or at least the localised interfacing solution) hits the freezing point of the dry ice, what's left to absorb heat and evaporate?

TP

 

[KenECoyote]

Good day,

with my local club launch in a week, I need to get this case ready ; the aft closure has seized terribly and nothing I have tried so far has been successful.

So far I have tried, WD40, lubricant, hot water, knocking it against a hard surface, rubber grips, water pump pliers, and all combinations of the above. The last time the closure was removed was in September.

Are there any techniques with a good track record I should know about? (Apart from not storing the case with the closure installed)

Thanks!

Any luck with any of the suggestions?