Fabtek 4roller on jd490, measuring problems

[dcress]

I have a John Deere 490 with a fabtek 4roller head, shes old buy gets the job done. 

It seems to work fine on pulp, when it comes to 16ft it's all over. Rebuilding the feed rollers, sharpening the knives, helped. 
 
Any ideas or advice would be greatly appreciated. 

Best solution I've come up with is to make a jig 



Thanks

[barbender]

I don't know how the measuring system is set up on those, but I suspect they are a measuring wheel and encoder system. Check for loose bolts, broken springs, and that the teeth on the wheel are in good shape. After that go into the electrical😊 If it works good on small stems but not on bigger diameter stuff I would suspect something mechanical.

[Southside]

I have the same machine.  Does yours have the independent measuring wheel in the center of the head frame or just measure from the rollers themselves?  Which computer do you have? I do have the books for mine and it measures off the rollers, so I can look and see what calibration options exist.

[dcress]

It has the proximity switches in the roller. I have the manual. Just rebuild most of the rollers, I tried it on some birch and it seemed to work fine. I'm thinking maybe the teeth are too aggressive on the measuring roller, when cutting softwood the build up on the longer logs could be throwing it off.

Tomorrow I'm going to change the wheels around and see if it helps. 

[wannaergo]

Is there a chance your calibration is off? When we had our 4 roller, if it was messed up it could be close on shorter wood, but the longer the log, the farther off it would be

[Skeans1]

When cutting out to 40's we would calibrate the independent wheel out to 25' or 27' to find your center. The number you adjust is your center skew the smaller the number the longer the length and vise versa. What sort of lengths are you trying to run? Also when running the long lengths we didn't use the feed wheel encoders unless the bark was slipping you could look at all three measurements to see if it looked right. 

[Riwaka]

How difficult is it to put a fabtek center measuring wheel on the head?
Fabtek    (parts)

Do the track motors have enough oil flow to run a chain saw/ disc saw bunk off the 490s track motor oil feed. (put some grapple arms on the fabtek head. ) (i.e use the head to delimb a pile. then saw a bunch at a time to length & stack/ pile)

See if cypress/ axis have converted any fabteks to their system.
CYPRESS ROBOTICS - Taking over the world, one processor at a time.

[dcress]

Only going to 16ft, there is a lot of  oversize that either pushes the limit of the machine or has to be cut by hand. 

 Calibrating by changing the length settings sorta helps,  the medium to large logs measurements aren't consisten enough to trust the computer.  

[Skeans1]

Only going to 16ft, there is a lot of  oversize that either pushes the limit of the machine or has to be cut by hand.

Calibrating by changing the length settings sorta helps,  the medium to large logs measurements aren't consisten enough to trust the computer.  

Is the independent wheel arm hole open in the tower of the head? One thing I do remember running the feed wheel is diameter could change the distance on long wood, a short say 17' we never saw an issue. Are you running short or long on the measurement?

[dcress]

The hole is closed and it measures long. 
Just have to adjust the length for the bigger logs for now. 7inches less seems to work. 

[Skeans1]

Sounds like you're out of center if I remember it being called, you should need to go up a number or two to find center. Are both sides coming up the same? If not one of the encoders could be going out.