Timber Harvester Question

Chrisrr · July 04, 2020, 10:58:14 PM

Hello to all. I've been lurking here for a while and joined up so I could pick some brains around here.

First of all, I have a 36HT25 Timber Harvester (97 model) that I have owned for about 6 years. I don't saw for a living, just saw stuff for the farm , a few neighbors, a load or two of cross ties occasionally.

Was sawing today and the bolt in the worm gear for the head lift broke today. Thankfully, it was only up a couple of inches so the crash was minimal. I've got to get the broken bolt out still yet.

So now for the question(s):
1. Would anyone see a problem with drilling out the end of the hydraulic motor shaft so that I could use a 3/8" diameter bolt? Assuming that I can if the shaft isn't as hard as flint. The 1/4-20 bolt that sheared off doesn't instill a lot of confidence.

2. What is the proper way to adjust the lift chains for tightness? Seemed like the steel worm ( the one that bolts to the hydraulic motor) has quite a bit of wear on it. Leading edge of the gear tooth is curled up.

I'm sure that with these answers more questions will come from me as I learn more.

Thanks,
Chris

esteadle · July 06, 2020, 05:55:04 PM

Welcome. You have an excellent sawmill. Yours is an older mill than mine by about 6 years. Can you show a picture of your worm gear box? Is it fully enclosed (the "Motovario 20:1 gearbox") or is it open to the air?

Most hydraulic shafts have a key that fits into a keyway machined into the shaft and mates to the cog that the shaft turns via a hardened key. The bolt is there to keep the cog's collar from slipping up or down on the shaft length, not necessarily to handle the torque of the hydraulic motor or the weight of the sawhead. You should not need to use a bigger bolt than the original. If you think you do there may be something else that needs to be checked -- like that key.

With my 2003 Timber Harvester mill, the gearbox mates to the up/down hydraulic motor using a paired chain that wraps 2 gears that are butted up against one another -- one on the motor, and the other on the gearbox input shaft. It sounds like your worm gear layout is different. A picture might help us see what the differences are.

Also, can you tell us how you were operating when you sheared that bolt? Were you lifting the head? Were you stationary and it just "broke". Or were you doing something else completely (loading a log or ... whatever?)

To adjust the head lifting chains you first loosen up the retaining bolts that attach the chains that come down from the lifting shaft sprockets to the sawhead frame. There should be 4 of them. You can then turn the bottom bolts underneath to raise or lower the sawhead by very small increments. Hold the chain section with an adjustable wrench as you turn the bolts, and make sure you keep the chains oriented correctly so that they continue to track on the cogs of the lifting shaft. You should not need much adjustment. Only the length of a chain link.

If you needing to adjust more than a link of chain, your chains have slipped one or more links over the lifting shaft sprockets (probably when the sawhead was up at full height). In that case, drop the mill to the bottom, loosen the bolts that attach to the hold up bars on the other ends of the chains, and carefully re-wrap them around the cogs. Now it should be obvious from inspection which chains are not evenly tensioned. Adjust the bolts on the lifting chains until they are all just snug. Then finish by re-bolting the other ends of the chains to the hold up bars. Don't over tighten these. Just snug enough to draw the chains up when the shaft is lifting. The lifting shaft and chains below are holding all the weight. These hold up bars just keep the chain out of the way and tight on the cogs.

Let me know if any of that is not clear and I'll try again.

Best of luck,

Eric

Brian_Rhoad · July 06, 2020, 09:19:25 PM

You may be able to drill out the shaft because you are drilling mostly threads. Tapping the hard shaft may be a problem. Like breaking the tap. I'd stick with the smaller bolt.

Tom King · July 06, 2020, 09:41:01 PM

The easiest, and surest way to get out such a broken off bolt, is to use left hand drill bits. If it's a Grade 8, get Cobalt bits. Easy-Outs work if they will come out easy. Breaking an Easy-Out in a broken bolt is no fun. My first try is a left handed bit, and I don't ever remember one letting me down.

Grind the broken end flat enough with whatever you have-like a Dremel tool, if you don't have a die grinder, to make it easier to center punch it as good as you can close to the center, for starting the drill bit.

For a 1/4" bolt, I'd use a 1/8" bit, and go up 1/64 at the time until one grabs, and backs the bolt out.

The left hand bit will cut fine until it reaches a critical point, and then the bolt will back out, all of a sudden, which brings a great feeling of relief always.

Dewey · July 11, 2020, 07:52:22 AM

I have a 94 30 HT I bought new .... It's been sawing full time for 26 years.... 6 days a week in the summer...
I had the same problem . The shaft on mine didn't go all the way to the end of the worm gear, I think that allowed a little wobble on it, causing breakage . My solution was to take hydraulic Motor to machine shop and have a piece welded onto the motor shaft that brought it flush to the end of the gear with a 3/8" bolt thread. I haven't had a problem in years...
Another thing I did was to weld light steel over the open air worm gear encasing it with a removable top and putting 90 weight gear oil in it, now the worm gear is lubricated at all times.

Chrisrr · July 15, 2020, 09:01:03 PM

Hello to all and thanks for all of the advice. Sorry for the delayed response but I have been busy.

To Esteadle,
Sometime between my model and yours they went to the enclosed gearbox (from my research one here). I have an open gear system. The worm is attached directly to the shaft on the hydraulic motor. It doesn't go on there very far. The worm is about 2 1/2" long and it has three shaft collars inside the worm as spacers. They are 7/16" thick so that is about an 1 5/16" of the worm that isn't on the shaft. The worm is steel and then that turns a bronze worm gear. The bronze gear has 20 teeth and the worm has five threads so I'm assuming that it has a 4:1 gear ratio(??). When the bolt broke I was lifting the head and POW!! It just let go. As I said earlier it was close to the bed so no other damage.
Thanks about the chain adjustment advice. A difference between your model and mine is that mine only has two lift chains and two chrome rods that the head goes up and down on.

To Brian_Rhoad:
Thanks, yeah broken taps are no fun!

To Tom King:
Thanks for the input. The bolt actually came out pretty easy when I had a chance to work on it. But on further investigation I see that it is not going to be possible to drill out the 1/4"-20 hole to anything larger in diameter due to the cut in the shaft for the woodruff key.

Dewey:
I agree with you on the wobble. I put everything back together and didn't put any tension on anything. Chains were completely off and I could see that there was plenty of play in it. I like your idea about extending the shaft on the hydraulic motor. As a matter of fact, I talked to a guy just a couple of days ago and spoke with him about doing it for me so I have that in the works. I actually stumbled across your post about running your gear in oil and I copy catted you and did the same thing.

Thanks again to everyone for their responses and willingness to help me out. Right now I'm waiting on an idler to come in that goes on my lift chains and going to taker my hydraulic motor to have the shaft extended. Right now I've got some oak logs that are getting harder everyday in this heat and sun, but that's all part of it.

Chris

moodnacreek · July 16, 2020, 01:06:25 PM

Are these sawmills being made again? [Under a slightly different name]

Walnut Beast · July 16, 2020, 02:43:55 PM

What name

Chrisrr · July 16, 2020, 08:32:07 PM

As far as I know, Timber Harvester went out of business around 2007 or 2008. A Cooks sawmill looks somewhat similar but no affiliation there. I turn to Cooks from time to time when I need parts. They carry the right size bands and also roller guides for the TH brand. Just received a roller guide from Cooks in the mail today for my TH.

Chris

esteadle · July 16, 2020, 09:06:40 PM

Quote from: moodnacreek on July 16, 2020, 01:06:25 PM
Are these sawmills being made again? [Under a slightly different name]

It could possibly be Lion Country Sawmills which is part of Clouser Farms Enterprises.
When TH went out of business, my PA rep Ken Clouser and his family started building their own versions.
I talked to him at length about how he planned to improve on TH designs in modest ways.
I believe they offered models very similar for a while, but lost track.
I just found them here: https://clouserfarm.webs.com/Bandsaw/cougar.pdf