Sold Any interest in 29mm motor tube

[REK]

Hello TRF,

I finally got around to finding a decent mandrel for making 29mm motor carbon casings. They will be 24” max at $40 each plus shipping. You can specify wall thickness, but I’ll mainly be aiming for 1.125” OD with an ID of 1.062”. Max Tg at 250F. Higher temps can be used, but will cost $14 extra.

Let me know if anyone is interested.

 

[DabCat]

How heavy do you estimate it to weigh?

 

[REK]

How heavy do you estimate it to weigh?

I did one earlier right now and I thought it was going to need at least 100 grams of resin, it only took about half of it. Probably around 75-80 grams. I won’t know until it is out of the oven.

 

[Anthony Claiborne]

Hello TRF,

I finally got around to finding a decent mandrel for making 29mm motor carbon casings. They will be 24” max at $40 each plus shipping. You can specify wall thickness, but I’ll mainly be aiming for 1.125” OD with an ID of 1.062”. Max Tg at 250F. Higher temps can be used, but will cost $14 extra.

Let me know if anyone is interested.

Based on measurements I have made, I found temperatures well above 250 F lasting for more than 2 seconds in my 29mm rockets. I wonder whether melting might be a problem.

 

[REK]

Based on measurements I have made, I found temperatures well above 250 F lasting for more than 2 seconds in my 29mm rockets. I wonder whether melting might be a problem.

It could be, I figured they would get very hot, the high temp resin I have is 390F. Will be planning to get Cotronics soon, I mean 600F is nuts.

 

[Anthony Claiborne]

It could be, I figured they would get very hot, the high temp resin I have is 390F. Will be planning to get Cotronics soon, I mean 600F is nuts.

These were measurements I took just forward of the engine. This was actual time-in-flight. The peak of was 382 degrees at ejection. It seemed that during propellant burn, the temperature was pretty steady. This was on December 30 (in Redmond, Washington) and the ambient temperature was about 50 deg. F.

 

[Rocketjunkie]

Have you checked your dimensions? 29 mm is 1.14", most reload cases are 1.125" diameter. You need an ID of 1.15. For high performance min diameter rockets, I would try for 1.2" OD. For motor tubes 1.25" fits most commercial centering rings.

 

[REK]

These were measurements I took just forward of the engine. This was actual time-in-flight. The peak of was 382 degrees at ejection. It seemed that during propellant burn, the temperature was pretty steady. This was on December 30 (in Redmond, Washington) and the ambient temperature was about 50 deg. F.

View attachment 541988That is very interesting Data, is this also with a linear or was it making contact with the tube? I can most certainly work with Cotronics 600F, but then it would be costly. That resin ain’t cheap for sure.

 

[REK]

Have you checked your dimensions? 29 mm is 1.14", most reload cases are 1.125" diameter. You need an ID of 1.15. For high performance min diameter rockets, I would try for 1.2" OD. For motor tubes 1.25" fits most commercial centering rings.

I figured that having it at 1.14” would match the standard 29mm body tube at the very least. But this way at least the tube would be slightly less and would just require some masking tape to make it fit without me having to get the tube sanded smooth to tight tolerances.

 

[Rocketjunkie]

I figured that having it at 1.14” would match the standard 29mm body tube at the very least. But this way at least the tube would be slightly less and would just require some masking tape to make it fit without me having to get the tube sanded smooth to tight tolerances.

OK, I see you are sourcing casings. My mistake. You will need liners as I've had burn through issues. I like the thinner wall that CF gives. However, the liners will be non standard. I have a source but it will be around $3 per foot in 200 foot quantities. This is convolute wound paper phenolic (Grade XX). They can't make wall thickness less than 1/32" (.8 mm). The larger OD that the thinner wall gives will allow quite a bit more propellant (11.4%).

 

[REK]

OK, I see you are sourcing casings. My mistake. You will need liners as I've had burn through issues. I like the thinner wall that CF gives. However, the liners will be non standard. I have a source but it will be around $3 per foot in 200 foot quantities. This is convolute wound paper phenolic (Grade XX). They can't make wall thickness less than 1/32" (.8 mm). The larger OD that the thinner wall gives will allow quite a bit more propellant (11.4%).

Are the liners 1.062” OD? That is the ID of these tubes. I’m not familiar with liner sizes. This mandrel size was one recommended by someone.

 

[dhbarr]

OK, I see you are sourcing casings. My mistake. You will need liners as I've had burn through issues. I like the thinner wall that CF gives. However, the liners will be non standard. I have a source but it will be around $3 per foot in 200 foot quantities. This is convolute wound paper phenolic (Grade XX). They can't make wall thickness less than 1/32" (.8 mm). The larger OD that the thinner wall gives will allow quite a bit more propellant (11.4%).

If I was going to the difficulty and expense of a SU CF casing, likely I'd cast the liner directly.

 

[Rocketjunkie]

Are the liners 1.062” OD? That is the ID of these tubes. I’m not familiar with liner sizes. This mandrel size was one recommended by someone.

No, you specify dimensions. They are made to order and usually take 6-10 weeks to be made and shipped. You must specify a smaller OD as there are tolerances to consider. I recently got some for 24 mm motors and due to the 1/32 min wall they made the OD .875", the same as my case ID. I have to sand the OD about .003" to get a good fit. They have mandrels for most inch and metric sizes. I have 29 mm liner that fits Aerotech hardware. It's 15/16 ID and 1" OD. Aerotech cases are 1.125" OD and .058" wall.

 

[Rocketjunkie]

duplicate