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I have a Professor Motor Tire Truing Station -- one of the many brands that copy the basic features of the Tire Razor brand stations. Well, at least it used to. I've made a number of modifications to my station. It is more a Bianchi/Professor Motor hybrid these days.
My latest mod has been to replace the comes-with motor and pulley with a 100RPM gearmotor and a custom-printed urethane pulley.
So why? 'Cause I have good reason to think the stock motor/pulley drives the axle/wheels far too fast. I've ruined several sets of tires by overheating them despite being -- I thought -- very conservative in the rate at which I lowered them into the abrasives. Part of that reason may be as the tires get abraded they heat up and expand, increasing their contact with the abrasives and heating up still further -- a positive feedback loop that never ends well. The result is the rubber becomes hot and gummy and starts to grain and shred. Ugly.
I have experimented with wet sanding at 100RPM and not have the success I expected. I've done it with a water/dishsoap solution as coolant, and Mobil 1 motor oil too. For reasons I haven't fully doped out the results have not been encouraging. But that's not what I am here to talk about.
The gearmotor I installed was purchased off of Amazon for US$15. I picked on 100RPM based on a Scientific-Wild-Ass-Guess. The size and shape of the gearmotor was a pretty good fit, and it was designed to operate on 12 volts DC. The motor shaft was larger than the original Professor Motor motor, so I ended up printing a new TPU pulley designed to fit. I had to drill new holes in the mounting plate, but otherwise it was a simple bolt-on fit.
As far as actually sanding a set of tires with the new drive, really, no drama. Most importantly the tires stayed cool to the touch while still sanding up true.
The multimeter you see in the video is measuring the amp-draw of the motor at 12 volts DC. I was lowering the axle/wheel assembly just enough to increase the amp-draw by 10 to 20 milliamps at a time. That seemed to work well.
So how true were the tires? To be honest true like I have never seen before. Normally I'd expect to see something under a thousandth of an inch total indicated runout as measured by a dial indicator skimming the OD of the tire. But no visible runout at all? I figured something was wrong. Uh-huh. The indicator was working fine. The tire was just that round and concentric. Here, see for yourself.
Kinda spooky, yes?
One advantage of re-powering the station is the power supply does not need to be nearly as beefy. The original spec for the Professor Motor power supply was a minimum of 3 amps. I can get by easily with a half an amp.
I guess I should also mention that the revs at the axle is less than 100RPM. The driven pulley is larger than the drive pulley. I haven't bothered to work out the actual speed. Anyway, my model railroad power supply has a variable voltage output, so I can dial in a very wide range of speeds, if that makes a difference.
By the way, the shifter moving the abrasive plate side-to-side is my own design. A lot simpler and compact than some you'll see. I've sold a few of those already as kits for US$30.
My next job is to create one or more additional abrasive plates with finer-grit sandpaper. The objective is to polish the surface of the tires to get even better grip. Stay tuned.
My latest mod has been to replace the comes-with motor and pulley with a 100RPM gearmotor and a custom-printed urethane pulley.
So why? 'Cause I have good reason to think the stock motor/pulley drives the axle/wheels far too fast. I've ruined several sets of tires by overheating them despite being -- I thought -- very conservative in the rate at which I lowered them into the abrasives. Part of that reason may be as the tires get abraded they heat up and expand, increasing their contact with the abrasives and heating up still further -- a positive feedback loop that never ends well. The result is the rubber becomes hot and gummy and starts to grain and shred. Ugly.
I have experimented with wet sanding at 100RPM and not have the success I expected. I've done it with a water/dishsoap solution as coolant, and Mobil 1 motor oil too. For reasons I haven't fully doped out the results have not been encouraging. But that's not what I am here to talk about.
The gearmotor I installed was purchased off of Amazon for US$15. I picked on 100RPM based on a Scientific-Wild-Ass-Guess. The size and shape of the gearmotor was a pretty good fit, and it was designed to operate on 12 volts DC. The motor shaft was larger than the original Professor Motor motor, so I ended up printing a new TPU pulley designed to fit. I had to drill new holes in the mounting plate, but otherwise it was a simple bolt-on fit.
As far as actually sanding a set of tires with the new drive, really, no drama. Most importantly the tires stayed cool to the touch while still sanding up true.
The multimeter you see in the video is measuring the amp-draw of the motor at 12 volts DC. I was lowering the axle/wheel assembly just enough to increase the amp-draw by 10 to 20 milliamps at a time. That seemed to work well.
So how true were the tires? To be honest true like I have never seen before. Normally I'd expect to see something under a thousandth of an inch total indicated runout as measured by a dial indicator skimming the OD of the tire. But no visible runout at all? I figured something was wrong. Uh-huh. The indicator was working fine. The tire was just that round and concentric. Here, see for yourself.
Kinda spooky, yes?
One advantage of re-powering the station is the power supply does not need to be nearly as beefy. The original spec for the Professor Motor power supply was a minimum of 3 amps. I can get by easily with a half an amp.
I guess I should also mention that the revs at the axle is less than 100RPM. The driven pulley is larger than the drive pulley. I haven't bothered to work out the actual speed. Anyway, my model railroad power supply has a variable voltage output, so I can dial in a very wide range of speeds, if that makes a difference.
By the way, the shifter moving the abrasive plate side-to-side is my own design. A lot simpler and compact than some you'll see. I've sold a few of those already as kits for US$30.
My next job is to create one or more additional abrasive plates with finer-grit sandpaper. The objective is to polish the surface of the tires to get even better grip. Stay tuned.
but the proof is in the video. It has to take forever to cut the tires at that slow speed though.
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