The FK's brush system works fine but has a limited life as the brushes are fairly short, something that may be improved sooner rather than later. still backwards engineering when it comes to the brushes in those motors being 90 degrees off.May I suggest a chastising letter to the designer of this motor, the Mabuchi Company, which has so far produced nearly one BILLION of these engineering heresies to power the rear-view mirrors of over 500 million cars in the past 40 years? Has anyone here ever had a rear-view mirror motor fail on them?Īs a slot car motor, the specification became more radical (windings, comm design, magnets, brush-holder thickness, brush material) to produce more torque and higher revs, but with more heat ,reducing life due to quicker brush wear. In RetroPro Foamy and I have been running 72 pitch recently in the 5 to 6:1 range with the 4002C Big Dog motors. Running 48 pitch gears limits your gear choices. I think a lot of people bog their Pro Slots and fail to get the most out of them. Expect the Pro Slot arm to be turning in the 28,000 to 34,000 RPM range so gear accordingly. I've never had a Pro Slot register a zero.

It's hard to test brush condition because on the Trinity tester a new motor with as little as 20 minutes of break-in can often register zero. To make a generalization if you have a FK motor above 19,500 rpm at 5 volts you are competitive.įK motors test higher after a race or two than they do when new. I think TonyP tests his Pro Slots at 7 or 8 volts. I chose the 5 volt no load test because at 7 volts some FKs got into brush bounce. Most are clustered in the 18,200-19,500 range. The FK style motors at that voltage have turned from 15,000 to 22,800. Testing at 5 volts no load most Pro Slots vary less than a thousand RPM. If you test rebuilt Pro Slot motors that have been retrued and rebalanced the differences are very small. There is far more variation in rpm between FK motors than there are between Pro Slot motors. You just hoped you got your eight heats in before they died on their last run.

Even the first Falcon motors had the characteristic of speeding up before they died. Combining this with lower drag from reduced spring tension might be contributory.

Another factor to consider is that the bushings are getting polished as the motor wears in and the motor spins easier.

Lsr falcon 7 slot car motor drag racing