Hydraulic help:

A friend is building a band saw sawmill. The carriage is powered by a hydraulic motor with a sprocket and chain setup to run the carriage as it cuts the log. He will have an electric switch that will intergize the hyd. motor but really no way of controlling the speed of the hyd. motor. His plan is to put a flow control valve in the line to the motor but to me that seems like a bad idea. So do any of you who know about hydraulics know of any good ideas. Maybe like an electronic valve of some sort that he could control the flow to the motor from his console. As you know he needs to be able to control the speed of the carriage as it cuts down the log, then be able to speed up the return of the carriage back again to start a new cut. I'm sure there are valves out there but we have no idea what to look for or where to look.
Any help with this project would be appreciated.

Thanks,
Dick

Start with a valve that has a motor spool. You change the speed by moving the position of the valve spool.

Go to www.northerntool.com and look at item number 202527. I think that does exactly what you want it to do...flow control in one direction, free flow in the reverse direction.

If he wants to be able to vary the speed, without standing there over the valve, he's going to need an electric flow control valve similar to the one in the link. Not sure if this one free flows in the reverse direction, but that's what he needs if he wants slow speed in one direction, and full speed in reverse.

Valves like this aren't going to be cheap, but it's the only way he is going to be able to do what he needs to do. Another post linked a valve from Northern Tool, and it will work too, but he would have to stand right there at the valve in order to control it.

Tell him to make sure he has enough hydraulic flow to handle every load, at max speed. The guy that figured the flows on the bale buster I built a few years back screwed up, and it wound up costing them thousands for me to add a pump (had to get two new ones and piggy back one off the other) and then to reconfigure the initial single system into two separate ones.

As far as the valve to turn it on and off, if it's going to be a slow speed setup he can get away with a standard valve that just blocks the ports when it turns off. If it's going to be a higher speed deal, then he will need one with a motor spool that puts both the outlet ports to tank when in the off position. Doing it that way will allow it to free wheel when turned off. The alternative is to put a cross port relief in the lines that will allow it to circulate the oil in the motor even with the tank port blocked. This will allow a bit of free wheel, but not like putting both ports to tank.

Hope this helps.
Surplus center flow control valve

Tell your friend to use an electric motor direct instead of hydraulics to move the head of the mill. Much easier to change the speed with a potentiometer on a pulse width modulator to drive the head forward and full power on reverse to speed up in that direction.
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I was just looking in our townships metal dumpster and there was a valve in there off of the sander on the back. It had two dials to control speed. One for the spinner and one for the apron chain. I almost grabbed it but figured it would just be clutter here until I throw it back in their dumpster in 20 years. I can grab it if you think it could be useful to him.

Brenden grab that valve/. I use them every day in my job/. if you don't use it some else will/. Bob

Badger Bob, I'll be sure to grab it. I've got some scrap to drop off anyhow.

Yes your right Wayne, he doesn't want to have to follow the carriage as it travels down the log and returns. His plan is to have a handheld control panel on a long cord to control the saw clutch and carriage travel. I like your idea best of all because he could mount the controls on his handheld panel. The flow control valve from Northern is good but he would have to follow the carriage the length of the log to change to speed. Myself, I would want a 12 volt motor on the carriage drive like RM-MN suggested and I think that would be the cheapest way to go.
I'll pass on all the great idea all of you guys have suggested and see what he wants to do.
Thanks to all of you who have came up with some great ideas.
Dick

It is probably a Gresen. It controls flow in one direction only.

VFD on the pump motor.

Yes, a VFD would be excellent to run the hydraulic pump but the hydraulic motor is powered by a hyd. pump run by the Perkins diesel on the sawmill. Also, the mill might not always be in a place where there is electricity. It's a portable mill on wheels so he can take it to wherever the timber is. I guess I wasn't real clear on the workings of the mill in my first post.
Thanks for the suggestion anyway.
Dick

Plum hyd motor install a cross over line between the lines to the motor with a ball valve, when the ballvalve is open the motor will stop as you close the valve the motor will start fully closed the motor will be at full speed

The motor would be a good idea in a situation where he had access to high voltage, AC current. With DC current it's not going to work as it would have to be a HUGE motor to handle the load needed to move the carriage, and feed the logs. The amperage required for a motor this size, as well as the cost of the motor would make this idea cost prohibitive.

I know this because we had wanted to run a hydraulic cooler on the bale buster, but to do it with 12V was going to involve several decent sized 12V motors, and it simply wasn't feasible to do it that way. I wound up just custom building a tank about 4 times what was needed, and I partitioned it internally to force the oil to have the most dwell time (to dump heat) before being picked up by the pump again.

With a hydraulic drive he can go with one of the smaller high torque motor's and have the needed torque across the speed range, as well as the compactness of hydraulic operation. Not to mention the cost is going to be far less. On the bale buster we were running one of the smallest CC per Rev gerotor type motors available, running at 2100 psi. They would easily move a 4x4x8+ bale of wheat straw sitting on a conveyor belt much faster than he'll want to be feeding a log into a saw blade, or vice-a-versa.

I don't know what design he has chosen, but if it were me, I'd probably run the drive as a endless chain attached to the carriage at both ends. This would allow him to leave the motor stationary and let it pull the carriage both ways. Too by changing the tooth count on the sprocket he can dial in the best speed, and torque for the job at hand while keeping the motor operating in it's most optimal range instead of at one extreme or the other.

Can't say I know it all, but if you've got any more questions, feel free to ask. If I don't know the answer, I more than likely know where to get it for you.

Thanks again Wayne for you taking the time to provide useful information.
On his mill, he has a chain running the length of the ways or bed of the mill where the log will lay to be cut. On the carriage of the bandsaw with the engine, where the hydraulic motor is mounted, he has three sprockets. So the chain goes under one idler, up and over the drive sprocket, then back down under the second idler sprocket. These three sprockets are mounted in a cluster on one side if the carriage framework. All of the wheels of the carriage are ball bearing wheels and run on a track. The wheels have a groove in them and run on a V shaped track along the bed which is 20' long. Even though the carriage is heavy and well built, it does roll easily up and down the bed of the mill. It looks like a great setup and should work good, in my opinion. The only problem that I can see is, as I stated in my first post, is the speed of the carriage. A slow speed for cutting is fine but I would want the carriage to return at a faster speed than the cutting speed, and the cutting speed could always be different too. That would depend on the size of log you're cutting, and if you're making the first cut or cutting down further in the log. Also, speed would depend on the kind of wood you're cutting, like pine,fir or oak, maple, walnut for example.
He has the one hydraulic pump that will run all of the machine but only one thing at a time. He has about 10 hydraulic cylinders on the mill, for loading the logs, turning the log, clamping the log on the bed. One cylinder for raising and lowering the saw, and the hydraulic motor for the carriage. The bandsaw is run with two belts directly off of the 40 hp Perkins diesel engine.
If you send me your email address I'll take some pictures of the mill the next time I go to his place so you can see what I'm talking about.
I really appreciate you taking the time to answer my questions and the problems you had building your bale buster. This project he has undertaken is a lot of trial and error and if doesn't work he'll change things so it will work. It's a well built machine and he's put a lot of time and work into it. He's looked at several different mills and taken ideas from all of them to build his mill, so it will be one of a kind.

Thanks again for your posts and all your useful information.
Dick

Those electric hyd control valves are technically called PWM valves. They are very common if you know what to google. One thing about the one in the link is that the controller is kind of expensive. The controllers can be found on ebay much cheaper.

Dick
Google " The Forestry Forum" it's all about logging and sawmills. A lot of guys their have built sawmills and will be able to answer your questions..

WOW,, what a great website. Lots of great information.

Thank you very much,,
Dick