power lift help needed

[mroldstyle]

I have been working on putting a power lift on my Timber King 1220, and ran into issue with gravity. I have tried a wheel chair motor, a rv electric jack motor and motor from a boat dock lift, all of which I had in my pile. They will all lift the head without problem, however they will not hold it in place, if I remove the factory hand crank and drive the lift directly. If I leave the hand crank in place, and use motor to turn the drive chain connected to crank, it (crank) binds up when trying to power down. Is anyone aware of a source for a 12-24v motor that would have a brake? or another way to stop the weight of head from causing it to drop freely.
Appreciate any help.

[fluidpowerpro]

Some ATV winches have brakes. I use a Badlands 3500 lb winch on mine and it works good. Plan on also using a pwm motor control so you can adjust the speed.

[mroldstyle]

Thanks and yes definitely plan on the pwm. Using one for power feed and it works well. 

[doc henderson]

I use a gear reduced tarp motor for semi-truck trailers for a conveyor.  it might not stop on a dime but may with a load.  of course, is reverses direction based on polarity.

[mroldstyle]

As soon as you stop upward movement it will start sliding down. I did find a wheelchair motor on ebay that has an electromagnetic brake, just will need to figure out the wiring if I go that route.

[RetiredTech]

 +1 on the ATV winch. Mine is a little smaller than Fluidpowerpro's and also a little slower. It stops on a dime and locks the head in place.

[RetiredTech]

Previous to installing the ATV winch I had plans to use a wheelchair motor to power a worm drive winch. The worm drive doesn't need a lock to keep the head from falling. I became concerned about the bushings on the hand winch not being up to the task.

[doc henderson]

you may want to lift the head from both sides with a cable, so it does not rack.  four post gantry/head.

[mroldstyle]

Thanks all.
Doc, I'm using the original the original timber king system, just trying to incorporate a motor with hopes of putting on a mikron setworks eventually 

[scsmith42]

Doc's advice of using a truck tarp motor is sound.  This is the method that the Peterson swing blade mill uses.

You can buy tarp motors from Surpluscenter.com, and as Doc said they are reversible.

[rliuts]

For lifting/lowering the sawing head I would recommend using a gearbox (motor with gearbox) with a self-stopping effect.

I believe the motor with a mechanical brake (or electromechanical brake) is not a very good idea because this brake might wear off in some time (like the brake in a car). And in some point, the sawing head will start moving down by its weight. The faster the sawing head moves and the more weight it has - the faster the brake will wear off.

I think an electric winch might work. Usually, their gearboxes have a great ratio that enables this self-stopping effect.
To control it is enough to use a winch relay and later you can easily add Micron computer setworks (as you mentioned previously).

Also, when you choose the lifting motor I would suggest choosing it so the lifting/lowering speed is 1-1.75 inch/sec. Higher speed will make it harder to position the sawing head for the first cut and 'catch' the right height for the next cut. And lower speed will decrease the sawmill productivity.

Good luck! 

[Hilltop366]

Could a PWM have a bypass so you could have the best of both worlds?

Thinking that if you had a up/down switch going through the PWM for your main control and a momentary switch that would bypass the PWM so you could get full speed when you want.

That way you could move the saw head up or down fast for big movements using the up/down switch and bypass then when you get close to your target let the bypass go and use the slower (adjustable) speed to hit the target. By default it would always be on the slower speed when using the up/down switch only to avoid sudden rapid movement.

[RetiredTech]

I had the same thought. However after looking at my winch control you'd have to totally ditch it and wire with your own relays. But the good news is the PWM's have a knob you can mount in a convenient space to control the speed. It would be much simpler to mark your preferred high and low speeds around the knob and just select them as needed.

[fluidpowerpro]

I second what retired tech said. I find with mine I'm always adjusting the pot. It's kind of a pain but necessary because the slow setting on the way down is not powerful enough to raise it going up. If I want to bump up just a little the setting is not the same as if I want to raise fast, etc. etc.... I suppose you could figure out a way to wire in multiple pots with switches to select, but in the end just as easy to adjust the pot.

[Hilltop366]

I don't really know a lot about electronics or PWM's and kind of forgot about the relay.

Perhaps a different way to do the full and regulated speed would be to bypass the pot on the control with the momentary switch so everything down stream of the PWM stays the same.

However the more bells and whistles you add the more opportunity for trouble.....I like hydraulics with a handle not with relays.  

[mroldstyle]

Well, I got a tarp motor, just waiting for a rainy day to try that out. I did get a wheelchair motor with a brake, but the postal service rough handled it and busted the end where the wires attach to the brake .   I will use a pwm to control it, that's what I'm using for the drive motor, also a wheelchair motor.
Thanks to all for the responses

[Magicman]

Whatever you use should have a worm gear somewhere to provide the necessary braking stability.

[doc henderson]

I hope the tarp motor works.  they are so gear reduced that you cannot turn the shaft by hand.  I think they can be variable speed.  of course, the final speed depends on the cog or pulley size in the end.

[mroldstyle]

MM, the tarp motor has a 60:1 gear ratio, turns at 49 rpm hooked up direct to 12v

[fluidpowerpro]

Don't let pwm's scare you. They are very easy to hook up. In some ways they actually simplify things because on off and the fwd and reverse relays are built in.

[doc henderson]

In the tarp motor, the shaft is 90 degrees to the motor so likely a worm gear.