Lt-70 head speed up and down

drobertson · September 27, 2012, 08:08:28 PM

I have a friend that just bought a used 70, 06' model, The head is extremely slow, it is a 3 phase. I did not time it, (dumb) but you can count the rotations of the key on the motor shaft when it is running up and down.
I checked my 40 super when I got home this evening, 1 sec. per 1 1/8 up or down. consistantly. Any 70 owners with imput?

customsawyer · September 27, 2012, 08:21:09 PM

The gas shocks inside the mast are shot. There are three in there. Go ahead and get them all. If memory serves they are about $90.00 each.

drobertson · September 27, 2012, 08:38:41 PM

Well then, this explains allot. wmz is supposed to come and see him sometime tomorrow. He is a good fellow, just hard to explain things to. You have heard how hard it is to get a word in edge wise, well this describes my buddy. Not a jerk, just a bit in his own world. The only other real issue he has with the mill is the debarker keeps blowing the breaker, and the blades are breaking way to quick, like arond 500 ft, any ideas on this?

stavebuyer · September 29, 2012, 07:48:30 AM

My 70 is diesel so the electrical will be different. I haven't measured the up/down head speed but its faster than I can control accurately without using the setworks. There may be nothing wrong with the debarker; I tripped my circuit breaker all the time when I first got the mill. Make sure its turning before you contact the log, dont start into the end of the log, and try a little less pressure when swinging into the log. As to blade life there could be any number of reasons as with any mill. 70's usually come set up to run the 1 1/2" blades. If he is running .055 1 1/2" blades which really cut; the stiffer blade wll break after "x" number of revolutions regardless of the bd/ft sawn. You should get more than 500' to a blade but I could see if someone was working alone, new to the mill, and edging on the mill the blade could break at 500' sawn with nothing being out of whack. I change mine at least every 4 hours even if they are still sharp.

Magic Smoke · September 29, 2012, 12:23:17 PM

The LT70 electric will have AC drives that run the up/down motor, if you look at the display on the front of the up/down drive it will probably tell you the frequency output while you are running the head, you will have to turn the main power on with the door open though...just don't touch anything in there

AC motor speed is controlled by frequency, if you watch the display you should see at least 60hz displayed while driving the head full speed. Changing the max frequency output (HSP parameter on most Altivar drives) will change the max speed of the motor, just don't go over 90hz on these motors.
If you need help making drive adjustments call WM and they can guide you through it.

Also,
LT70 electric mills don't use the up/down gas shocks, only the DC versions.