Treadmill motors - my modifications.

[tonyfoale]

1. I like this modification but have concerns over the heat generated, particularly if used for a belt grinder. A normal fan ventilated motor gets some respite from full load heat when the load is removed and the motor is still running and ventilating. A fully enclosed motor is subject to a continuous build up of heat, slightly less when off load, but still there, and it has nowhere to go. Sealed motors usually have fins on the outside and if necessary have a fan attached to cool those fins.

2. Fitting mesh filters at each end will do very little to improve cooling unless you retain the fan to draw the air through the armature area.

Watch the end part of the video. The heat considerations are explained there. See response to your point 4.

3. Lowering the speed by rheostat reduces the torque as you pointed out but I understand that there may be better electronic speed controllers available that allow a full range of speeds without torque loss. Those fitted on the more expensive treadmills tend to have no loss of torque with speed reduction.

I did not mention rheostat. It never occurred to me that anyone would try to control the speed in that way. A rheostat is more like a torque control than it is a speed control. Totally unsuitable.

4. Retaining the original flywheel fan for its flywheel effect and for the cooling air it might draw over the outside of the motor might help with the cooling. Heat sinks attached to the motor body and retaining the flywheel fan would help more.

These are rotating armature motors and so most of the losses will be in the rotating bits and the cooling heat path will be out through the bearings and the pulley. Cooling air over the outside body will have only a small effect, on the other hand cooling air on the inside, as per a stock motor is effective. On the other hand the common squirrel cage induction motors have a fixed armature attached to the casing and so air drawn over the outside of the casing will cool. That is why those motors often have external fins with a fan designed to flow air over the fins and not through the inside. All motors are not equal.

Many people utilise the treadmill speed controller and RPM indicators. The speed indicators are driven by a sensor on the flywheel, another good reason for keeping it. It is common to attach the drive pulley directly to the flywheel by bolting or welding and your way of truing it up would be perfect for this as well.

You can just as easily put the sensor magnet on any pulley. If the treadmill motor controller is available then that is certainly the easiest way to get a speed control. I do not use one because they have built in delays and other safety features which make the control feel unresponsive. I use the PWM feature of an Arduino to drive a couple of IGBTs. Instant response.

5. There is much debate on the web about whether the drive wheel should be crowned on a belt grinder. Suppliers of ready made wheels generally supply crowned drive and tracking wheels but that doesn’t make it right. There is an excellent explanation somewhere on the web, (I had thought it was your excellent website tonyfoale), that explains how only the tracking wheel should be crowned. If both wheels are crowned they tend to fight each other for alignment.

I don't know why there is any debate on this. Flat belts have been used for hundreds of years to drive machinery and the correct methods are well known. I thought the explanation that you mention was on this forum but a search did not throw it up so I have made a new post Why flat belts need crowned pulleys.

6. I wrote this assuming that you were building a belt grinder but now see pics of a tool & cutter grinder. Heat is going to be less of a problem with such a grinder and the relatively light loads involved. May it last you forever.

Watch the end part of the video. I do not think that I would use one of these motors on a belt grinder. Semi-continuous high loads need cooling air through but the air will contain a lot of dust, even with a dust control vac. A T&C grinder generates very different conditions.