LOC Cyclotron Motor Tube Length

[BobCox]

I am building a LOC Cyclotron with the intention of using it for my Level 1 certification. This is my first experience with 38mm motors.

The motor tube in the kit seems exceptionally long, at 27". Since the lower mainframe tube is 34" and the transition shoulder is 2.5" long, that leaves only 4.5" for the parachute, shock cord, and chute protection. It is a very snug fit, and I don't think it has to be. If I shortened the motor tube, that would leave more room for the recovery equipment.

How long should the motor tube be?

The Nuke Pro Max from LOC Precision only uses a 10" motor tube. I have seen other kits in that size range that use motor tubes from 8 to 10" long. The directions say to spread a ring of epoxy 12" from the bottom of the airframe when installing the motor mount. All of this makes me think that the correct length should be about 12" long.

 

[JDcluster]

I've never built this kit, but it sounds like the motor tube is intended to pass through the transition.

The RocSim file that I have has a 8" long 29mm mount in it.
That's under version 9.




JD

 

[BobCox]

I've never built this kit, but it sounds like the motor tube is intended to pass through the transition.

LOC has a similar kit (NORAD Pro-Maxx) that does extend the motor tube up through the transition, but the Cyclotron does not. The 27" motor tube stops 4.5" short of the transition's rear shoulder.

The RocSim file that I have has a 8" long 29mm mount in it.
That's under version 9.

I found several mistakes in the RockSim file that is in EMRR and in the Version 9 library, so I don't trust it much. If the motor tube is only suppose to be 8 inches long, why would the directions call for a ring of epoxy 12 inches into the airframe? Is that a mistake in the directions, or did I get the wrong length tube in my kit?

 

[madmax]

Trust your kit. In my experience Rocksim files are sometimes incredibly inaccurate that are put out by other "fliers". It seems the creator just put in what they were going to use at the time or they were lazy and didn't bother measuring parts or they didn't even have the parts to begin with. LOC has pretty good quality control so if the directions say a ring 12" up I would trust that.

Also I thought the Cyclotron came with a 38mm mount not a 29mm.

 

[BobCox]

Trust your kit. In my experience Rocksim files are sometimes incredibly inaccurate that are put out by other "fliers". It seems the creator just put in what they were going to use at the time or they were lazy and didn't bother measuring parts or they didn't even have the parts to begin with. ...

Also I thought the Cyclotron came with a 38mm mount not a 29mm.

I just checked, and the published RockSim model does say 29mm. That's another mistake in the published model. I will have to submit a new version based on accurate measurements and part numbers.

The kit comes with a 38mm x 27" motor tube. It also includes a 38-to-29mm adapter.

LOC has pretty good quality control so if the directions say a ring 12" up I would trust that.

I have already cut the motor tube into two pieces - one 12" long, the other 15" long. The 15" piece will be a little heavier, with more weight in the rear where it will degrade stability. The 12" piece will result in a larger volume for the ejection charge to pressurize. Realistically, it probably won't matter much which of the two pieces I use.

 

[redsox15]

My motor tube on my 4" LOC Fantom (which i used as my level 1 cert rocket) was 18" and it flew nice and straight with the whole tube in there. it did not mess with the stability of the rocket


good luck with the build and your level one!

 

[DAllen]

I have already cut the motor tube into two pieces - one 12" long, the other 15" long. The 15" piece will be a little heavier, with more weight in the rear where it will degrade stability. The 12" piece will result in a larger volume for the ejection charge to pressurize. Realistically, it probably won't matter much which of the two pieces I use.

Bob,

The difference between the 2 tubes is minimal. Flip a coin for which to use. Remember that 4" green and silver rocket I had at NSL? I would bet that my rocket has at least 50% more volume to pressurize than the Cyclotron and I have always used the stock ejection charges without adding any BP. I've had exactly zero problems getting the laundry out.

Good luck on your L1!

By the way...I really like how your kit came with a 38mm mount. Do you have any idea what you can put in that thingy now? MMmmmmm...38/1080 case....mmmmmm...J570....mmhmm.

-Dave

 

[BobCox]

Bob,

The difference between the 2 tubes is minimal. Flip a coin for which to use. Remember that 4" green and silver rocket I had at NSL? I would bet that my rocket has at least 50% more volume to pressurize than the Cyclotron and I have always used the stock ejection charges without adding any BP. I've had exactly zero problems getting the laundry out.

Thanks. That's good to know.

By the way...I really like how your kit came with a 38mm mount. Do you have any idea what you can put in that thingy now? MMmmmmm...38/1080 case....mmmmmm...J570....mmhmm.

Since there is no thrust ring in the front, I imagine you could in any motor up to 31.5" long in there. It would stick out the front of the motor tube, but that's okay.

Not sure I'd trust it with that much thrust, though. LOC only rates it up to an I170.

 

[Rocketjunkie]

Not sure I'd trust it with that much thrust, though. LOC only rates it up to an I170.

The biggest motor I put in mine was an Ellis 38/910 J330. It flew fine.

 

[cls]

I built my Cyclotron completely stock, used WEST epoxy for all the joints. It's flown on J420s a few times. it's a great rocket, don't worry about how sturdy it is.

I watched this thread with some curiosity, people frequently ask about how long should the motor mount tube be. you got good answers here.