Dented CTI Pro75 6GXL Casing

Emailed CTI about this but I just wanted input here as well. Pictures below. Any ideas on how to fix the dent without weakening the tube? I appreciate your consideration.

I would start with a wood dowel and a few taps from a hammer and see what happens. Then make sure the closure and ring fit.

I would email CTI about this...wait... :wink:

Edit: removing rest of comment due to learning more on this below.

I had CTI trim down a damaged (crunched) 75-6G case down to 5G once. They did a nice job, but be aware it wasn't quite the same as working with a "friendly" local vendor, at least in my experience.

After a few email exchanges with CTI, I shipped it to them and heard nothing for 2 months. Getting in touch with them again, I was informed that "my casing was ready and we just need your shipping and billing info" of which I provided.

Several weeks later, the case arrived, but not exactly in pristine condition. The machining and re-threading was done, but the case was still in fairly rough shape and several components were missing. When I inquired about this, I was told that said components (forward closure, thrust ring, etc.) were "badly damaged, possibly from shipping as the box was unsuitably packed. Because of this, we did not attempt to repair them." So it seems as though they tried to blame me for what-they-called shipping damages with little recourse.

Overall, it just felt like they only got away with the bare minimum of what needed to be done and without much further assistance. I guess this is what it's like working with a commercial aerospace business!

I have fixed MANY dinged cases with a wood dowel [1.5-2 in. diameter] by laying case on hard surface.[as Mark stated above +1] Insert dowel round side contacting bad area of threads and whacking dowel/checking fit .....till closure went in easy. Also have used same diameter PVC pipe to do same. Both AT & CTI cases have been brought back this way.

Common sense & basic tool use are all that's required. If you can't change a lightbulb or know which end of screwdriver to use.............then DON"T try it.

Shorten it...I'd strongly recommend against firing this case again in its current configuration. Your chances of torching a rocket have gone way up as a result of the ding...it's just not worth it.

Or if you'd like it shortened and grooved for snap rings, I know a guy (me) that can do it...or if you don't want it I'll take it

patelldp said:

Shorten it...I'd strongly recommend against firing this case again in its current configuration. Your chances of torching a rocket have gone way up as a result of the ding...it's just not worth it.

Or if you'd like it shortened and grooved for snap rings, I know a guy (me) that can do it...or if you don't want it I'll take it

Click to expand...

Would they shorten this case for snap rings at CTI?

Don't know.

AlnessW said:

Overall, it just felt like they only got away with the bare minimum of what needed to be done and without much further assistance. I guess this is what it's like working with a commercial aerospace business!

Click to expand...

So, you sent a poorly pack box, across the border (which takes a STUPID amount of time), with a motor you busted up, back to the manufacturer, who doesn't do custom work, And they fixed up the case, and tossed the stuff that was junk..... But THEY did the bare minimum?

Aris said:

Would they shorten this case for snap rings at CTI?

Click to expand...

Not sure...but anyone who has a lathe probably could.

DizWolf said:

So, you sent a poorly pack box, across the border (which takes a STUPID amount of time), with a motor you busted up, back to the manufacturer, who doesn't do custom work, And they fixed up the case, and tossed the stuff that was junk..... But THEY did the bare minimum?

Click to expand...

It wasn't badly packed. And if they "don't do custom work," then why would they have told me they could trim it down?

markkoelsch said:

I would start with a wood dowel and a few taps from a hammer and see what happens. Then make sure the closure and ring fit.

Click to expand...

blackjack2564 said:

I have fixed MANY dinged cases with a wood dowel [1.5-2 in. diameter] by laying case on hard surface.[as Mark stated above +1] Insert dowel round side contacting bad area of threads and whacking dowel/checking fit .....till closure went in easy. Also have used same diameter PVC pipe to do same. Both AT & CTI cases have been brought back this way.

Common sense & basic tool use are all that's required. If you can't change a lightbulb or know which end of screwdriver to use.............then DON"T try it.

Click to expand...

Sounds like wood dowel fix is making a lot of sense in this case!

KenECoyote said:

Sounds like wood dowel fix is making a lot of sense in this case!

Click to expand...

Banging the aluminum back to round with a dowel will do exactly that...it will restore it to the (almost) original dimensions.

However, the bend has already reduced the tensile strength of the threads and bending it again will only further fatigue the metal. Without understanding the design parameters of all of the CTI motors for this case nor understanding the actual fatigue the case has suffered, it's still true fixing such a ding and using the case again increases the likelihood of a failure.

Ask CTI, it may be fine. Motor cases are probably the last thing you should use a hammer on in this hobby, unless it's removing a bulkhead in a snap ring case.

So just a thought:

From a materials perspective, cold working aluminum will cause strain hardening of the material. This will increase strength and hardness of the material. It should be understood, however, that increasing the strength by cold-working will also result in a reduction in ductility. This is a tradeoff that has some impact on the situation being discussed. Hammering the tube back into shape will actually increase it's strength (to some extent) theoretically reducing the chance of a failure, but it will also increase the likelihood that a failure could result in a brittle fracture of the material in that area, causing an increased risk of high speed flying debris (shrapnel) if a failure was to occur (say due to a motor CATO rather than a case failure). There is no real way to know how much strength hardening has occured when you cold work material like this manually, so how brittle the material will end up is also unknown. A little bit of work, it may still be well into the ductile region and not cause failures, but there's no guarantee after you start messing with the OEM's material (properties).

AlnessW said:

It wasn't badly packed.

Click to expand...

I personally opened the box. When I received it, it had been opened by customs. They placed "CUSTOMS" tape on the box. At that time the casing was shaking in the box. When I opened the package, it dumped a pile of sooth on my carpet in my office. I inspected the parts and they were not salvageable. The forward closure was in the casing sideways and was badly damaged. I decided that we may was well thrown it out.

We did not charge for machining. We completed the customs paperwork and stood in line at the post office. We only charged for the actual shipping cost.

Jeroen

A wooden dowel will do the trick. Or the handle of a hammer.

Jeroen.

Jeroen_at_CTI said:

A wooden dowel will do the trick. Or the handle of a hammer.

Jeroen.

Click to expand...

Thank you. so place the wooden dowel of some diameter in the tube and hit that with a hammer to get it back into shape?

Aris said:

Thank you. so place the wooden dowel of some diameter in the tube and hit that with a hammer to get it back into shape?

Click to expand...

Just use the wooden dowel to tap. Insert it into the case and then tap it outward. Make sure you move the case or dowel around to hit different spots and try to get it round. Keep doing this till the ring fits.

If you are uncomfortable doing this, then there is probably at the field that can show you this trick. You can also return the casing to us, and we will be happy to do this for you.

Jeroen

3 Methods:
Tap it
Hit it
or Wack it

A tail pipe expander might work.

https://m.harborfreight.com/automotive-motorcycle/exhaust/large-tail-pipe-expander-69549.html

Thorfire said:

A tail pipe expander might work.

https://m.harborfreight.com/automotive-motorcycle/exhaust/large-tail-pipe-expander-69549.html

Click to expand...

No, that will expand the whole end. You only want to remove the dent. The best thing to do is follow CTI's instructions.

Adrian