Motor slowing while printing

It could be the brushes. Do you hear the motor “pop” often as if sparking?

You could also try some belt dressing. It’s sold in most hardware or auto parts stores and it adds a little stickiness to the belt.

Carbon brushes can leave a residue. The only time I had a motor slow down like that, cleaning the commutator (is that right?) with emery paper helped. Of course, unplug the motor first.

Do not use emery cloth on any commutator. Not only will it score the copper segments thereby causing excessive sparking,but grit will lodge between the segments and short out the bars. A fine crocus cloth can be used; that is, if a proper cleaning stick is unavailable. In a pinch, a common ink eraser will do the job.
But first, examine the motor. Are any commutator segments discoloured? Is there evidence of thrown solder on or around the segment wires? Is there excessive sparking whilst the motor is operating? Is there evidence of wear in the front and rear bearings/bushings? Are connections tight and bright? Assuming the motor to have variable speed, does shifting the brushes have effect? Is there noticible odour of burnt winding insulation wafting from the motor? Finally, is there adequate lubrication; conversly, is the motor over-lubricated?
The belt pulleys also require attention. Are they slippery with oil/grease film? Are they crowned correctly? Are there discernable balance problems? Then, too, the belt plays vital role. Is it a flat belt? If so, proper tension is vital; there must be deliberate ‘slack’ (this varies with distance involved) else slippage, and overheating, of both belt and motor will occur. That might well be interpreted as a ‘slowing’ of the motor. Ensure the correct side of the belt is facing the pulleys. Should it be a Vee belt, ensure its width is correct for the pulleys, and its tension is measured as well. Never run a Vee belt on a crowned pulley. Belt/pulley dressing is an option of course, but on a small demand such as experienced with an 8x12 is more ‘quick-fix’ than cure.
If the above fails to bring resolution, have a shop check the armature with a growler, and the fields for heat-induced shorts/opens. Then of course, there’s always a foot-treadle.

the motor doesn’t spark or pop while it’s running. the motor isn’t variable speed. there is no odor. the belt is flat. the belt doesn’t slip off. I’ll be honest here, i don’t know anything about motors! I haven’t yet lubricated the motor because I’m not sure where that’s supposed to be done. I’ll have to get someone in there that can run me through inner workings of the motor. Any book suggestions? I’ll do my research anyway. Thank you for your suggestions everyone!

Do the easy thing first: Lubricate the motor. At each end of the motor you will find either a hole leading directly to the shaft, a small cup having a hinged cap fitted to a hole leading to the shaft, a metal clip covering an opening leading to the shaft, a felt pad inserted in a hole leading to the shaft, or a combination of such descript. Using an oil can, squirt bottle, eyedropper, whatever, put oil (ordinary car oil is fine; don’t use 3-in-One oil or any of the ‘instant lubes’) in the receptacle until the hole is filled; the cup is filled; the felt is saturated. Wipe away excess. Run the motor. Look to see if oil leaks past the shaft; if so, the bushing/bearing seal is worn. Also, check the clarity of that oil; if dirty, it indicates lack of maintenance and/or a bearing surface soon in need of attention. Amazing what a little oil can do to make things run smoothly. Despite what the Democrats would say.

thanks forme! question, there are 2 holes on the shaft itself where the leather belt is. fairly large holes. are those oil holes too?

Hi Erika,
The two large holes you mention where the belt is; are they actually on the drive pulley on which the belt rides?
If so, they are most likely to be screw holes for the Allan screws that secure the pulley to the shaft. These screws need to be screwed up tight, so that the pulley does not slip on the shaft. Any oil holes will not be on the shaft itself but on the mountings which hold the bearings for the shaft.
Hope this helps.

Erika
Check to see if your pulley has a keyway. If so make sure a key is in before you tighten the allen screws.My C&Ps require keys on the drive pulley only.I’ll try to attach a picture.

MIke

C&P drive pulley key and set screw hole.JPG

hey mike, didn’t get the pic…would love to see it though! Bern, thanks for the clarification there…i should give this motor a thorough once over it sounds. why is there always a job to do first? :)

Erika

C&P drive pulley key and set screw hole.JPG

Hi Mike,
Thanks for the link to the video. I can’t see anything in it though, the contrast is too dark.

Erika
New vid posted much clearer.
Mike