board return problems

[slider]

need some help from the pro's   I've been using my board return to drag the slabs back now I'm having trouble with the power feed I was thinking maby I've brought this problem on myself by applying too much force on the motor.The brushes look fine and the motor is running cool .Checking the drum switches today .When it stops feeding while cutting a board you can turn up the feed rate and give the saw head a push and it will go.Also the track is clean and free of obstructions.This is on a LT-70 with remote.thanks slider

[WH_Conley]

Don't know much about a 70 but I would check the drive belt and cam follower bearings. If you get a bearing that is a little dry and rough and belt that is a little loose it will do the same thing on my LT40.

[bigmillman]

I recently had a problem that sounds much like yours with my LT40HD.  Drive motor and controls were fine.  WM Technicians told me to check the carriage bearings (they ride on the track) and the bearings were worn so badly the carriage frame was draging slightly on the tracks.  I replaced all the bearings and it works like new now.  Might be worth checking.

Stacey Freeman

[gmmills]

     I had the same problem you describe a while back. Mine stopped feeding completely in the middle of a cut.    First thing I checked was the carriage bearings. They were fine.  Could easily push the carriage down the track manually.
     
        Next was to check the power feed electrical system. You need to attach a 12 volt test light, light only not digital test meter, to the motor terminals.  The groung clip to the neg terminal, black wire, the light probe to the pos terminal,red wire. Turn the key on, engage the drum switch to forward, and have the rate knob turned all the way down. The test light should be on, but dim. Now turn up the feed rate knob. The light should get increasingly brighter. If all of this checks out the circuit is operating properly.  Have to credit Sparks with this test procedure.

       If your circuit checks out than the problem is in the power feed motor. Mine had a brush go to open,no circuit. Only one of the two brushes. They both looked fine, plenty of length. I just replaced the faulty brush and everything is working fine. I always try to keep a spare pair of brushes on the shelf just in case. 

         

     

[slider]

just got back from the mill,cleaned the drum switches,heard a noise when head was moving down the track,found a worn idler gear bearing,though not excessive,the track bearings are fine. I am having the motor checked out monday although the brushes look fine it feels weak,maby just my imagination.thanks for the input.I'm still wondering about draging the slabs with the board return ,just might be asking too much of this little 3/4 horse motor.reguards slider.

[Tom]

Brushes can be fine and still not be making contact.  They slide in a trough and trash might hang them up keeping them from making good contact with the armature.  Lots of times just reseating them and getting them moving freely will solve the problem.  Always put them back in the same way they came out.  There is a wear pattern that might make them have a bad contact if put in backwards.  At least until they wear in again.   Unless broken or the leads broken, there's not much that can go wrong with a brush but wear.

If the motor doesn't stop under load,  I'd suspect worn pulleys (the v-belts will bottom out), loose belts, or a piece of trash hung up under the mill  somewhere.   Trash will make it fail in only one place or in measurable distances down the mill.  I've had stuff stuck in the forward/back chain that causes it too.

[slider]

Thanks Tom, the brushes look almost new.The springs are in place every thing looks good inside the inspection cover.No belts to slip on this 70 the motor bolts directly to the gear drive.The worn idler bearing is the only thing that I found but I just don't think thats the problem.I'm sending the motor to a good shop Monday to be checked out.Next weekend I'll put it all back together and give you an update.One thing the feed chain was sagging some but not bad.I'm just thinking I stressed this motor by dragging those heavy slabs with the board return.By the way great city Jacksonville I deliver there 3 to 4 times a week.  slider

[Tom]

Let me know one of these times and we'll have lunch.  ..or a cup of coffee at least.  I'm up just north of the airport toward callahan.  It's not too far to 95 or 10 either one.

[gmmills]

     I left out a step this morning in the testing of the power feed circuit. You need to disconnect the wires from the motor and then connect the test light to wire end terminals. This isolates the power feed circuit from the motor.

Slider,

     You can very easily test that motor with a Volt -Ohm meter. I thought that I had a brush possibly sticking as Tom suggested.With the motor still mounted on the mill I took the brushes out of their holders and blew all the carbon dust out with compressed air. The brushes looked fine. Good length and no discoloration. Put them back in and tried the power feed. Still no movement. Found the problem by connecting my Volt-Ohm meter to the motor terminals. No electrical connection between the two terminals. Took the brushes out of the motor and tested each one with the Ohm meter. One was good the other was open. No electrical circuit between the ring terminal on the brush wire and the concave contact area of the brush. Replaced that brush and the motor is working fine.

      I contacted WM and was told that there have been isolated issues with faulty brushes in the Leeson motors.

      This brush problem really surprised me. The 3/4 hp Leeson motors are very durable. My My old LT 40 Super had 3 of these motors. Only changed brushes in one motor in 4000 hrs. This was the power feed motor and they were getting pretty short in length.

       

[slider]

Gmmills,thanks for clarifying that test procedure.The saw head will travel it just gets stuck.I was wondering how I was going to hold the test light on the terminals and boogie down the track while watching that little light go from dim to bright.Sounds like a two man opperation.I just tested the brushes ,they are fine also checked the terminals I have continuity so I assume the motor is fine.I will replace the worn idler gear bearing next weekend and go from there.   slider

[MartyParsons]

The LT70 Feed system should have no issues pulling slabs back. I have customers pulling 7 x 9 ties back with the board return. There is an over load sensor in the power feed ( this depends what year your LT70 is) If you control the Return speed with the feed control it is an early model. If it is an early model it will also have solenoids.
  The newer LT70 have a curcit board that opertates it. No selonids.
Remove the wires on the Power feed. Can you push the saw head? If not you have a bind or a bearing failing. Next look in your manual under Power feed trouble shooting there are lights to help you. One for over load, one gets brighter when you turn the Feed control. I have not seen many solenoids fail but that would be my guess from what is listed above. I have heard about the Lesson motor burshed sticking but this is not real common. Also check the wires on the motor where they enter the motor frame, I have seen these get loose and not make a good connection. The last one the customer had a log fall onto the motor and then the frame became bent a little letting the bolts and wires get loose. If the wires look burnt at the brushes there is your problem.
Hope this helps. 
Marty

[DR Buck]

When it stops feeding while cutting a board you can turn up the feed rate and give the saw head a push and it will go.

Check the speed control potentiometer.   I had one stopping in the middle of the cut and if I increased the speed it worked.  Replaced the control and the problem went away.

[sparks]

The easiest thing to do is when the head stops, remove the power feed motor from the gear box and see if it starts running. If it does, electrically your ok. You have a mechanical bind.   Thanks

[slider]

Thanks,Marty,Sparks and Dr buck.I m off trucking for a week I'll get back on the problem this weekend.I will replace the idler first then go from there.I really was concerned about dragging the heavy stuff.I'll let yall know the outcome.   slider

[customsawyer]

Slider you might want to check your fluid level in the gear drive. As for over loading the motor on the return with heavy slabs come over and watch me drag 8X8X18' beams off. If your slabs don't wiegh more than 500 lbs than it wasn't the slabs.

[slider]

Jake,someday when I get through your part of the woods I'd love to stop and check out your setup.I'm replacing the idler sproket and potenonmomiter,spell/spell,switch saturday when I get home.The gearbox oil is fine.Had the motor checked out also,it's fine.I suspect the switch.Was that your rig under the shed with the roller table and log deck? I built 2 roller tables and boy what a difference.log deck is next just need a pattern.See you some day.  slider

[slider]

Thanks for all the advice,found the problem.After replacing the idler,checking the motor ,greasing the drum switches I went over the track bearings one more time and found the bad bearing . This culprit would work fine and then hang up.Thanks once again for all the input  slider

[MartyParsons]

Slider make sure you check the lower ground brush under the battery box. If the lower rail gets dirty or rusty it will not make a good connection. the ground will then go through the lower track bearings and arc on the needles making the bearings fail. Some units had the lower rails painted, the area that needs to be clean is about 12" if front of the contact strip and towards the the front of the mill ( hitch end) lower rail.
Marty

[slider]

Thanks Marty,I understand your point of having a good ground but why just 12 inches at the front of the mill? Am I missing something?   slider

[ronwood]

slider,

I believe Marty indicated that it was 12 inches in from of the contract strip. No need for a ground on the rest of the mill since there is no power strip on the rest of the mill.

Ron

[MartyParsons]

Ron is correct. You will only need it when the hydraulic pump is working. The LT70 does have the rear strip I almost missed that. If you have a LT70 Remote mill you will need to check the rear also. If it is a walk mill only the front.
Marty