PML Quantum Tube experiences

[Toyguy]

I'm just starting to build my L1 cert rocket, a PML Tethys. The stock kit uses their Quantum Tube airframe, which is new to me. Last time I flew any high power it was all cardboard or phenolic. I have to say I am less than impressed with the QT. It seems awfully flimsy and in my case, at least, it is out of round. Neither the centering rings nor the piston would fit inside, even if I squeezed the tube back into round. I was able to sand the rings to get them to fit, but I am reluctant to sand the piston since it's darn thin to begin with.

I've emailed Andy at PML to see if they will send me a replacement phenolic tube.

Anyone else have any bad experiences with the QT material?

Dave

 

[cobra1336]

Nope, strong stuff. Does sound like you got a bad one thou. They will make good.

 

[Chuck Taylor]

I also did my level one on a PML Tethys. It has been a great rocket and I have never had a problem with the QT. I did break a couple of pistons and have since removed the piston. The biggeset motot I have used in it to date has been a J540R. I have nothing but good things to say about the PML kits.

 

[hardinlw]

The Quantum Tube has a different thermal coefficient of expansion than the material of which the piston is made. In cold weather, a piston that slid freely when you built the rocket will often bind. You have to sand the piston to fit in the coldest weather in which you will be flying. Always check the fit of the piston before flight (you need to do that even with the phenolic tubing) to make sure it slides freely. So far, all of my rockets except one are either PML kits or built with PML parts and have pistons. That's up through an upscaled Fat Boy on a K-550. I've never had a piston jam, but I have done some on-the-field sanding to get a loose fit.

 

[DAllen]

That sounds like a rather unusual experience to me. I've built 2 PML kits and neither of them had those kind of issues with the QT. I can't stand the pistons even with a phenolic BT. You are better off putting a baffle in your rocket or spend a little more $$$ for a chute protector.

And remember kids - QT is not made to go supersonic!



-Dave

 

[bobkrech]

That sounds like a rather unusual experience to me. I've built 2 PML kits and neither of them had those kind of issues with the QT. I can't stand the pistons even with a phenolic BT. You are better off putting a baffle in your rocket or spend a little more $$$ for a chute protector.

And remember kids - QT is not made to go supersonic!



-Dave

Dave

Believe it.

Drake "Doc" Dameräu maintains the Rocket Materials website. He is the Chief Metallurgist, and the Laboratory Director of the Scranton Army Ammunition Plant operated by General Dynamics. He specializes in failure analysis, and is responsible for heat treating processes and all material specifications and testing, and he has tested and posted real data on many common rocket materials including QT.

https://www.rocketmaterials.org/research/temp/ has the data on exactly how QT jams phenolic pistons in cold temperatures.

Bob

 

[Toyguy]

Thanks for the input guys. Sounds like I did just get a bad one.

I really like the kit so far - the Kwik-Switch mount is quite nice. The components are very good quality and the instructions are excellent. Once we get the airframe sorted out, I am sure it will be fine.

Dave

 

[Obi-Wan]

Dave

Believe it.

Drake "Doc" Dameräu maintains the Rocket Materials website. He is the Chief Metallurgist, and the Laboratory Director of the Scranton Army Ammunition Plant operated by General Dynamics. He specializes in failure analysis, and is responsible for heat treating processes and all material specifications and testing, and he has tested and posted real data on many common rocket materials including QT.

https://www.rocketmaterials.org/research/temp/ has the data on exactly how QT jams phenolic pistons in cold temperatures.

Bob

Great data = that explains why my nose cone always fits fine but I need to add/remove masking tape to my phenolic ebay depending on the weather/temperature.

It is tough stuff. However, quantum can be squeezed a bit compared to stiff "paper" phenolic tubing. Quantum tube is easy to cut and clean ejection charges.

I flew my DD mod. Ariel on a J820 last month, no problems.

 

[madsen]

https://www.rocketmaterials.org/research/temp/ has the data on exactly how QT jams phenolic pistons in cold temperatures.Bob

Very interesting--especially the relatively large amount of expansion at the higher temperatures. I have only examined Quantum Tube in the hobby shop--but I have always found it to be slightly on the pliable (soft) side. At Rainbow Valley--it is often in the 90's at the start of a launch--and often 110-115 degrees by end of the day--although no one ever makes it to the end of the day. Of course, those temperatures are in the shade--and there is no shade. I have been tempted to purchase a PML Black Brandt X for a number of years--but I have a picture in my mind that it will bend in two as it launches because of the high heat. I could be wrong--but I doubt it.

 

[Brian62]

I have nothing butt good things about the QT.
Considering pistons, never had a problem to date, D-Region Tomahawk.
Sure stuff expands and contracts, and if you pay attention to directions and fit piston properly should be just fine.

 

[cobra1336]

I've had to replace a couple of pistons in my Callisto not from jamming but because the bottom of the piston would develop nicks around the edges. Best I can figure was that I was using to much ejection charge and the piston was cocking against the cord chipping it.

 

[Handeman]

I've had to replace a couple of pistons in my Callisto not from jamming but because the bottom of the piston would develop nicks around the edges. Best I can figure was that I was using to much ejection charge and the piston was cocking against the cord chipping it.

I've had the same problem with the piston in my Callisto. I even got a small crack the went from the edge to half way towards the base. I always thought it was from banging into the tube on the way down. I've never replaced it. I'm still fying the 5 year old, nicked, and crackted piston and haven't had a problem.

 

[ben_ullman]

Great data = that explains why my nose cone always fits fine but I need to add/remove masking tape to my phenolic ebay depending on the weather/temperature.

It is tough stuff. However, quantum can be squeezed a bit compared to stiff "paper" phenolic tubing. Quantum tube is easy to cut and clean ejection charges.

I flew my DD mod. Ariel on a J820 last month, no problems.

You think we are stopping there. I am going to make a 3 grain Super Polish RRRRRRRROJO (as my dad says it) motor. 1376Ns K748!

Ben