Woodmizer Close Call...

[VA-Sawyer]

I had a scary moment with my LT40HD yesterday. I had just loaded a new log and moved to hit the up/down switch to the up position. The switch moved up and the head crashed down. The output shaft on the up/down worm gear speed reducer broke inside the housing. It came down pretty quick.  If I or someone else had had their hand under there, they probably would not have had time to move. Scared me pretty bad, but no real damage to me or the saw.
Talked to my engineer friend at WM this morning. He said it was the first such case he had heard of in a long time. Glad to hear that it isn't a common problem.

I always put a chain or blocking on the head when working on the up/down system, as per the manual.  Just beware that parts can fail at any time.  You can bet I will be more careful in the future when reaching behind the battery box to remove bark and sawdust.
VA-Sawyer

[Tom]

......and I have reached beneath that thing a million times without ever considering that it might fall. Whew!  I guess it is in the back of one's head that there is danger there.  But, what could be done to avoid it.  The double chain, if attached to two separate bolts would prevent falling if a bolt or chain broke.  That geared reducer is a difficult thing to protect against.  It's only one point with no back-up or redundency.   I think I'll chain that sucker every time I reach under there from now on.

My 4-post mill has a hydraulic cylinder holding the head up.  I'll bet that would come down with a bang if a hose broke, eh?  I think I'll keep my head out from under there too. ;D

[Corley5]

Never trust a machine. : ;)  

[VA-Sawyer]

Tom,
That is exactly why I posted this.  I have the double chains on mine and thought it was fairly safe. Never thought about the shaft being a single failure point. Have been racking my brain to figure out some sort of safety device. No luck there yet. A chunk of 2x4 about 2 ft long can be slipped behind the battery box and then you can rest the head on that. It is fairly easy and better than nothing. Biggest thing is don't try to move the head up or down if any body parts are under it.
Just the act of thinking of the danger first may save your hand or maybe your head someday.

Corley5 is right about never trust a machine, but it only works so far. Sometimes we have to trust them. If we didn't trust the brakes in our car to work every time, then we would never drive faster than 5 mph. I would never fly in a plane if I didn't trust the engine at least a little bit. The same thing for a lot of other things we end up trusting machines for. We just can't let it become blind trust.

VA-Sawyer

[Tom]

I just had a thought 8)  Now, that's scarey. :D

I wonder if something like a steering damper were attached to the head of the mill if it would keep the mill from "free falling".  It would have to be heavier than one of those that are used to hold the hatch open on a 5 door or station wagon.  I have one on my tractor that is pretty strong but is short stroke.

They allow slow movement but deter fast movement.  Hmmm  Might help :P

[VA-Sawyer]

Tom,
It would need 30" of stroke, be able to slow down about 1000 lbs and not cause so much drag in normal operation as to overload the gearbox or motor. A check valve to allow free motion in the up direction would help with the last item.
It also needs to be very affordable so people will put them on the mill.  It might be cheaper to just change the gearbox every 2000 hours or 10 years, whichever comes first.  Mine failed at almost 3000 hours and 15 years ,so if we throw in a little safety margin the 2000 hr /10 yr  thing might be about right. That is the approach we use in aviation all the time.
I would like to know if anyone else has had such a failure. It would take 3 or 4 more cases to even begin to see a pattern.
VA-Sawyer

[Kirk_Allen]

VA, Did you get your mill used?

I wintessed an LT40 going down the road yesterday and there were two logs strapped to the deck and the saw head was pusheed all the way to the back of the mill and strapped in place.
He had strappes around the loading hooks because they could not come up all the way because of the logs.

I would venture to say that if someone used the mill as a trailer for logs and did not secure the saw head in its resting place the bouncing around of a road trip may weaken the part that broke.

Just a speculation but when I saw this guy hauling logs i thought of your post.

[Tom]

I've hauled a log or two like that but had an awakening one day and quit.  

I came to the realization that the mill weighed 3000 pounds and had 3,000 pound axles.   It just dawned on me out of the blue.  I quit doing it.

I lost the wheel on the rail side one evening coming home from a job.  Man, you should have seen the sparks.  It was running along on the brake drum and didn't hurt anything. The nuts had come loose from the studs and the studs broke. I think someone had tried to steal the tire.

Anyway, I'm impressed with the stability of the mill on the trailer and the trailer itself.  No need to try to break the thing though.  

When the head of the mill is carried somewhere other than where designed, the trailer is no longer balanced and, worse yet, all the locking features are bypassed.  A fellow could find the head of his mill laying in the road.

It's important that we look further in safety than whether we can hurt ourselves and consider whether we could hurt others too.

No sir, I don't haul wood on my mill anymore.

[james]

try an automotive shock absorber , and guide bars that slides up and down on parallel to the hyd cylinder

[Gilman]

If you are using a hydraulic cylinder to lift an object (saw head in this example) where if a hose fails, injury could occur a counter balance valve should be being used.

The counter balance valve is mounted onto the exhaust side of the cylinder (most likely the end away from the cylinder rod) and then the hose is mounted to the CB valve.  The CB valve is an adjustable spring loaded check valve.  The pressure in the cylinder exhaust has to overcome the spring force before it will open.  This way you have to power the cylinder down.  If a hose breakes, the head will stay put.

To adjust one, you would simple tighten the CB valve and raise the head.  From there you would loosed the CB adjuster until the head started to fall.  Tighten the CB valve a bit and you're set.

[FeltzE]

If you wanted a safety device for the event of the saw head falling the ideal device would be an "inertial reel" rated for the weight of the head. An "inertia reel" is essentiall the effective part of your seat belt, when operated slowly they reel in and out, when shock loaded it swings out a set of catches and locks up preventing additional rotation.

Possibly an old inertia based seat belt would work. Many of the newer ones also need a forward G to cause a lockup. You know it's an inertia reel if you just yank the strap out it locks up ease off and it releases.

Eric