FLASHBACK FRIDAY: Recreate RC's most tedious task with this incredible comm lathe simulator
Friday, Apr 24, 2015 02:43pm
By Aaron Waldron
Everybody knows that Friday is meant for reminiscing old times. Each week we take you back in time as we flashback to some of R/C racing's greatest moments, products, drivers, and more!
RC's most tedious maintenance task
Today's brushless motors are so easy to maintain that many racers don't take care of them at all - you'd be amazed at the reaction of some racers when told they should take them apart and clean them every once in a while! A well-maintained brushless motor's performance on its 200th run might be just as fast as its first. If you only started racing electric cars in the last 7-8 years, you may never have experienced what it was like to feel as though you had a completely new motor every few runs. That's what the power difference was like for a brushed motor when you disassembled it completely, installed it onto a special lathe, and used a diamond or carbide bit to reshape the commutator into a completely round and smooth cylinder.
See the shiny portion on the left edge of the comm? That's freshly cut. PHOTO: RCCrawler
HUDY was one of dozens of companies that made their own comm lathes, but they all functioned the same way. The armature was aligned along either bearings (like the HUDY lathe below) or V-shaped notches (like the Cobra lathe above), and driven by a slave motor spinning a tight rubber O-ring wrapped around the armature. Two sliding blocks were used to move the bit: one determined how bit the cut would go (controlled by the dial on the left), and one to move the bit across the comm's surface (controlled by the dial on the right).
Before the days of rebuildable stock motors, truing the commutator on a locked stock motor required a special lathe (or at least a lathe that could be fitted with a mount for stock motors.
Because the motor endbells were sealed, the bit had to reach through the opening created by removing a brush hood.
That's all the room the lathe had to work with. PHOTO: RCCrawler
The process left shrapnel all over the inside of the motor that needed to be cleaned out completely, but the performance gain was more than worth the trouble.
Along with truing the commutator, racers often replaced (or at least re-serrated) the brushes.
Judging by the destroyed comm and severely worn brushes, this motor hasn't been torn apart in a long time.
PHOTO: Traxxas forum
PHOTO: Traxxas forum
For large races, motor companies like Reedy, Trinity, Orion, Peak, and more would send representatives tasked solely with taking care of the team drivers' motors.
Sean Cochran (left) and Mike Reedy soldering new brushes onto motors for Reedy team drivers.
Good comm lathes costs a few hundred dollars, so not every racer owned one. Many hobby shops offered to cut comms for a small fee, but if you were really lucky the racer pitting next to you would do it.
The new Comm Lathe Pro computer game by devotid Media dutifully recreates the process of truing commutators, all the way up to the total destruction of an armature should the comm snag on the lathe. Here's a demo:
If there's any one single reason to be glad brushed motors are gone forever, this is it!