Wednesday, April 1, 2015

Nitron Flywheel Motor Postmortem and Observations

So, well over a year ago, I built one local a Nitron. It served well, fired many thousands of rounds without a hint of trouble, and gained a legendary and feared reputation as undodgable full auto Vortex ought to.

Then someone just had to decide that its original 12V NiCd pack was not enough and try a 5S lipo. Okay, I could understand a 3S lipo, that would be almost the same voltage with less IR, less weight and better performance over the life of the charge. I could understand a 4S lipo, even. But, a 5S lipo. Come on, seriously, you guys can tech guns and you know why it was a bad idea.

But end of story, the factory 280 flywheel motor ended up roasted and the RS carbon pusher motor probably on the way out. Now, the pusher motor, who cares, you can just slam any 130 or 180 on there and go, but the flywheel motor...

Just to confirm, it is a generic Mabuchi-type 280. Here it is next to a Sagami "Cyclone" 280

This is going to be the hardest piece of the puzzle. The shaft stickout on the PTO end is 15mm. Most 280 have shorter shafts, 10.4mm and 12mm. Perhaps the 12mm could be made to work? I have not found a single motor with this 2.0x15mm spec for sale yet (except flat can FC-280 which are usually wound too cold to use here as well), it was probably a custom order by Hasbro specifically for this gun. Hell, I'm guessing it was a custom wind as well, see below.

Crispy fride brush gear. These are not EOL and this endbell still has something left but those carbons are about halfway gone. The comm was nuked and jet black with scale/oxide, as well. I suspect why this motor died was the comm.

Armature. I unwound 2 poles which was difficult because the insulation had started melting and the wire was beginning to short and weld together. I counted 112 turns.

This is a good thing, because 280 motors hotter than 112 turns are, almost all of them on the market. The most common wind of stock 280 is -2485 (85t). That should work great for Nitron fly motors assuming the shaft issue can be dealt with.

Custom shafts may come into play here. The comm and armature stack can be pressed off the shaft and a new one fitted. This would be a tedious procedure but perhaps necessary.

I found this interesting. This is the 280 arm next to one out of a FK180. As you can see, there is not a terrible difference here in how much core steel is on these. The 180 arm has a slightly longer stack.

The 280 stack is a bit larger diameter.

The comms are damn near identical. You would think the 280 would be larger, but no. This is probably why the 280 fly motor died as it did, because with 18.5V there would have been arcing going on with that little comm. This is not a 300 series.

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