Intermittent, travel, speed

[69bsa650]

we have two mills, a 40 with 5000 hours and a 35 with 500 hours. The 35 is struggling with travel speed. It's intermittent at best sometimes. Sometimes you can get two or three logs cut and it's perfectly fine other times it struggles with, stopping jumping and then when you try to accelerate with the speed control, it takes off like a rocket and then of course can't keep up with that cut. We are looking for an answer of course and would appreciate input. Have a great day. Thank you. 

[GAB]

we have two mills, a 40 with 5000 hours and a 35 with 500 hours. The 35 is struggling with travel speed. It's intermittent at best sometimes. Sometimes you can get two or three logs cut and it's perfectly fine other times it struggles with, stopping jumping and then when you try to accelerate with the speed control, it takes off like a rocket and then of course can't keep up with that cut. We are looking for an answer of course and would appreciate input. Have a great day. Thank you.

I'm not familiar with a 35 so I may be way out of line.
I'm thinking it could be the speed potentiometer, or it could be a roller that is occasionally locking up on it's way to total failure.
I suggest lowering the head with the cantilevered end supported and then try turning the rollers by hand to see if any are the problem.  I do not know what to tell you to do to check the other rollers.  Maybe a hydraulic jack might work.  On my 40 there are 7 rollers and only a few can be checked by supporting the cantilever end of the head up.
Please let us know what you find out as being the problem.
As an FYI: Some rollers are made in China and some are made in Mexico.  I have some of both as I changed the 2 problem ones and ordered 2 more spares to have a complete set on hand.
GAB

[SawyerTed]

Check the brushes in the motor.  It's an inexpensive check and fix.  If they are ok then you can check it off the list.  

My 35 did similar things.   I replace the potentiometer and cam followers.  It was brushes.  

[Ben Cut-wright]

we have two mills, a 40 with 5000 hours and a 35 with 500 hours. The 35 is struggling with travel speed. It's intermittent at best sometimes. Sometimes you can get two or three logs cut and it's perfectly fine other times it struggles with, stopping jumping and then when you try to accelerate with the speed control, it takes off like a rocket and then of course can't keep up with that cut. We are looking for an answer of course and would appreciate input. Have a great day. Thank you.

"Taking off like a rocket" would negate most mechanical faults those mills might encounter, IMO.  Intermittent "stuttering" forward travel and obvious changes in behavior when manipulating the "pot" seem to pinpoint electronic *control as primary concern. Forward travel comparable to reverse speed has been loss of variable speed control, in my experience.  The pot and its wiring would be my first area of concern.  Poor pot or control connections can cause stutter or full forward speed, same thing can happen with a failed or failing pot. 

The last two pots I purchased from WoodMizer are from different mfgs than the originals and do not preform in the same manner. Rotation of the shaft is extremely loose. As installed any vibration caused rotation.  I had to put o-rings between the knob and the base to limit vibration rotation of the new pots. There were other modifications but they relate to my particular (older model) speed control unit.

It is easy to test the pots with digital meters or scopes, easy to check the connections, and simple to replace one.  Keeping a new replacement on hand is a good idea. IF all these checks do not reveal a fault of resolve the issue, it is wise to contact WoodMIzer before getting in over your head. 

[DanielW]

I second what Ted says: I helped a friend out with a 40 that was behaving similarly - in that case it was the pot, but id doesn't hurt to go over the motor/brushes while you're at it. Both easy & inexpensive fixes.

[Southside]

How old is the 35?  Does it have joysticks or the side controls? 

[WV Sawmiller]

   Don't forget to check the power feed belt. Is it tight, worn or any sawdust or chips in there?

[barbender]

 I've experienced the same symptoms on mine from several different causes. Like cam followers going bad and dragging. The reason that they don't make a consistent amount of drag is that the load is transferred among the rollers due to variances in the rails. 

 The second most common one is either my drive belt getting loose, or sawdust getting inside the guard and packing in, causing the belt to slip.

 The last episode I had was the drive system solenoid going out. Instead of dieing all at once, it must've been making an intermittent contact that caused the speed to jump all over the place.

[WV Sawmiller]

  BB reminded me I had very similar issues with mine that was indeed the cam follower bearing. I'd sure check that!

[Stephen1]

Start with the simple...belt, then cam follower bearings, that where my money goes, and then the expensive fix of the potentiometer, I changed my POT and then found out it was the bearings after all.  

[LeeB]

Check the posts on the motor where the wires connect. They can get loose causing intermittent loss of connection. The wire may still be tight but the post itself can be loose. If this is so, make sure you don't let the post turn when you tighten the bottom nut.

[Sixacresand]

This week the mill head would stall several times in a cut.  By switching the travel drum switch off and on and rotating the pot switch back and forth, and physically pushing, I could get the head to lunge a few inches at a time and finally get through a cut. 

I watched the WM You Tube video.  I did a inspection and found all cam followers to turn easy, no excess grooves, etc. I did see where the paint had rubbed off the frame next to the round top rail, but did not find anything that might have scraped it.  Chain and sprocket looked fine.  Belt is clean and tight.  

I did find that sawdust had caked up inside the middle track cover, but did not seem to cause enough friction to stop travel.  It got cleaned out and resoaked with ATF.  

The final check was the mill level, which it was not.  It had been set up on soft dirt and the operator end had sunk slightly, causing the head to travel up hill.  I made a few adjustments to make the operator end slightly higher, dosed the cam followers with ATF and it ran fine.  In my opinion, releveling the mill so the head to moving slightly down hill "fixed" the problem. 

I have replaced the pot switch, which seems to spin way too easily.  I have not changed out the motor bushes, but will order some.  

I do not see how this system could pull an operator in a seat. or drag back slabs, but I know it can.  

[barbender]

My 40 Super doesn't care much if the mill is level, and will pull somebeefy 16' oakslabs back without issue. I can't see an operator seat being a problem either, but I've never used one on it. I'd keep an eye on that power feed solenoid. It's a little more difficult to diagnose because it is transmitting the correct voltage, but not amperage, when it starts to fail.

[Ben Cut-wright]

This week the mill head would stall several times in a cut.  By switching the travel drum switch off and on and rotating the pot switch back and forth, and physically pushing, I could get the head to lunge a few inches at a time and finally get through a cut.

In my opinion, releveling the mill so the head to moving slightly down hill "fixed" the problem.

I have replaced the pot switch, which seems to spin way too easily.  I have not changed out the motor bushes, but will order some. 
 

Sorry to hear you had the same results with the replacement pots that I have had.  The first new pot would not preform properly at all.  The second was so finicky I had to call Woodmizer support. They gave me instructions to modify the PCB and that solved the finicky problem but not the "spin way too easily".  Adding o-rings between the knob and the housing created enough friction to control the rotation.  Only later did I discover  the first new pot could be made to work by adding o-rings.  Seems the internal wiper wasn't making secure contact and the added o-rings acted as spacers to tug the wiper contact a bit closer to the resistive track. None of the new pots would have worked without the PCB adjustments.  The new pots would occasionally cause stuttering forward travel, no-travel, and full-forward speed. 

I'll keep my fingers crossed that "leveling" solved the travel issue.