The Forestry Forum

I have a 1968 model 127 mobile demension saw. I changed the edger belts and the belts start twisting and come off. Does anyone have any ideas?

Welcome to the forum. I am not familiar with your saw but have had experience with lots of belt driven equipment. Number one is alignment and condition of pulleys. No 2 is belt tension. There have been other threads on this topic so maybe the search function could be of help. I assume these are v belts but same principle applies to flat belts. With misaligned pulleys, when the belt is tensioned one edge becomes longer and tighter and the belt will move in the pulley to that side even to the point of flipping over. This can damage the belt internally and will only stay on if left loose. So the center of the v groove should be aligned and the pulleys need to be parrallel and coplanar. A string stretched across the face of the pulleys should touch each rim or any straight edge across the face making allowance for the thickness  or width of the pulleys. Other problems such as the v worn into a U, loose set screws, sheared keys, bad bearings, etc. should be looked for. A google search will give lots of info on proper belt tension.

I agree with Laup but will say that new vee belts will run for a short time on most any set up. 

Does it have the 5 shive pulley or the 6 shive pulley.  Belt tension and alingment of the roller guides are critical the vertical guide that is beside the pulley on the edger shaft needs to touch the back of all the belts ,set the lead on your saw before you adjust the guide. The horizontal guide must also touch all the belts ,use the bottom adjuster to set the lead which should be about a 32th" down at the front compared to the back of the 12'' edger blade,give or take a 64th". Hope this helps.