Router Rotation Direction

[John Hasler]

Jim it is a universal motor and you can indeed change the direction of rotation. Unlike some tools which are designed to run in both directions this router will likely have a leading commutator brush angle which gives it better performance in the normal direction. If it is reversed you may notice a bit more sparking at the commutator, although it should not be excessive.

Also see if the brushes are angled. If the brush angle exceeds 20 degrees reversing the motor may break the brushes.

 

[Billh50]

I had forgot about mounting the motor behind the toolpost. That would make it turn the wrong direction. That's why photos of a setup are always better.

 

[David S]

I am not quite sure what the brush angle of 20 degrees means. In all my years of designing power tools the brushes were perpendicular to the commutator, but the "brush angle" was the amount that they were rotated with respect to the field neutral position. It could be mechanically by moving the brush gear around the comm..or by shifting the comm during the armature pressing process.

My experience is mostly with fractional hp universal and PM motors.

Could you clarify your comments so I don't lead anyone astray.

David

 

[John Hasler]

I am not quite sure what the brush angle of 20 degrees means. In all my years of designing power tools the brushes were perpendicular to the commutator, but the "brush angle" was the amount that they were rotated with respect to the field neutral position. It could be mechanically by moving the brush gear around the comm..or by shifting the comm during the armature pressing process.

My experience is mostly with fractional hp universal and PM motors.

Could you clarify your comments so I don't lead anyone astray.

David

In some DC motors the brushes are not perpendicular to the commutator. I've seen this in treadmill motors and some older industrial motors (all integral horsepower).

 

[David S]

The other consideration would be cooling. Usually incoming air comes over the much hotter commutator / brush gear then as much as possible drawn through the armature air gap and around the field. For reversing motors we would use a straight radial fan, which would "suck" in both directions. However if the trimmer uses an axial fan it may not cool very well due to reverse air flow. This may not be an issue if the tool post grinding loads are much smaller than as a laminate trimmer.

David

 

[John Hasler]

The other consideration would be cooling. Usually incoming air comes over the much hotter commutator / brush gear then as much as possible drawn through the armature air gap and around the field. For reversing motors we would use a straight radial fan, which would "suck" in both directions. However if the trimmer uses an axial fan it may not cool very well due to reverse air flow. This may not be an issue if the tool post grinding loads are much smaller than as a laminate trimmer.

David

Good point. You also don't want to be sucking air into the motor from anywhere near the stone.

 

[Billh50]

I did not understand that the router was DC and thought it was an AC motor.

 

[John Hasler]

I did not understand that the router was DC and thought it was an AC motor.

It's undoubtedly a "universal" motor which is actually a series motor. It's called "universal" because it works on both AC and DC.

 

[Cobra]

I had forgot about mounting the motor behind the toolpost. That would make it turn the wrong direction. That's why photos of a setup are always better.

Hey Bill, not at a physical presence as yet.
This is a sketch of the proposed grinder. It will bolt to the toolpost stud through the hole in the centre.
This sketch shows the OD grinding spindle; there will also be an ID grinding spindle.

 

[Keith Foor]

Because of the speed involved in that type of motor. There may be a timing issue with the brushes. Advancing the brush timing can make the motor faster in one direction. Since the motor would normally never be reversed. So it may turn slower when you reverse it. Now, the other issue with that is the current draw and heat will also go up in the motor is run with the brushes retarded. If you reverse it and it seems slower. It probably is and shouldn't be run in that configuration. If the motor seems to run the same RPM it will be fine to be turned backward... the only thing you may notice is increased brush wear.