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Author Topic: 3-4 feet into a cut when I decided back stops, clamp would be in the way  (Read 3244 times)

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Offline POSTON WIDEHEAD

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Re: 3-4 feet into a cut when I decided back stops, clamp would be in the way
« Reply #40 on: February 24, 2013, 12:03:53 PM »
 smiley_curtain_peek
The older I get I wish my body could Re-Gen.

Offline isawlogs

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Re: 3-4 feet into a cut when I decided back stops, clamp would be in the way
« Reply #41 on: February 24, 2013, 01:06:45 PM »
 He tried to slip one by but I caught him red handed..... :snowball:
A man does not always grow wise as he grows old , but he always grows old as he grows wise .

   Marcel

Offline Chuck White

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Re: 3-4 feet into a cut when I decided back stops, clamp would be in the way
« Reply #42 on: February 24, 2013, 02:20:17 PM »
I've done just as you did several times Tee!

It works, in a pinch, most of us would have a chainsaw with us on sawjobs, so you can always make a wedge out of a chunk of slabwood.
~Chuck~
Retired USAF 1989, Retired School Bus Driver 2012, now semi-retired Mobile Sawyer, 2018 Silverado 4X4
1995 Wood-Mizer LT40HDG25 Kohler - Cooks Cat Claw Sharpener and single-tooth setter, 4-foot Logrite cant hook.
Basic mechanical skills are all that's required to maintain a Wood-Mizer

Offline Brucer

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Re: 3-4 feet into a cut when I decided back stops, clamp would be in the way
« Reply #43 on: February 24, 2013, 03:11:16 PM »
Isn't the motor speed a function of voltage?

Yes, it is. Unfortunately so is motor torque. If you reduce the voltage very much you won't be able to move the head. The preferred method is to power the motor with short, full voltage pulses. Vary the width of the pulse (the "on" time) to change the speed. It's called Pulse Width Modulation (PWM) and it's how Wood-Mizer controls the forward speed. If you move the head forward with the engine off, you'll hear a whine from the control panel; that's the PWM control unit sending out pulses.

The carriage control switch is wired to feed the drive motor from the controller when the head moves forward, and bypass the controller completely when the head moves in reverse.

Theoretically you could re-wire the controls so the PWM unit is used for both forward and backward operation. You would have to be vary careful to reverse the voltage on the output of the controller. If you reverse the polarity on the input you'll toast the unit.
Bruce    LT40HDG28 bandsaw
"Complex problems have simple, easy to understand wrong answers."

Offline rmack

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Re: 3-4 feet into a cut when I decided back stops, clamp would be in the way
« Reply #44 on: February 24, 2013, 03:22:47 PM »
Bruce, what about installing a separate PWM for the reverse travel? are they pricey?

would it be possible to just have one with two settings, available via toggle switch rather than having a rheostat?

Btw, never had grits, never even seen them, except in pictures. It would take something real special to wean me off potatoes. :)
the foundation for a successful life is being able to recognize what to least expect the most... (anonymous)

Welder Bob
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Offline Ga Mtn Man

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Re: 3-4 feet into a cut when I decided back stops, clamp would be in the way
« Reply #45 on: February 24, 2013, 04:03:39 PM »
I couldn’t help myself…it was the  smiley_devil.

Just to make you feel good, I won’t tell what happens when I hit the wrong lever while sawing.  It only happens once. :-[
...I WISH! :(
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2012 LT40HDG29 with "Superized" hydraulics,  2 LogRite cant hooks, home-built log arch.

Offline Brucer

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Re: 3-4 feet into a cut when I decided back stops, clamp would be in the way
« Reply #46 on: February 25, 2013, 12:20:55 AM »
Bruce, what about installing a separate PWM for the reverse travel? are they pricey?

The basic circuit is pretty simple and the parts are cheap. I've made them to control small hobby motors. When you have to control a high-current motor like the carriage drive on a mill it gets more expensive. The PWM circuit is the same but you need some pretty hefty semiconductors at the outputs to handle the motor current. In fact, you'd want to be sure you could handle a stalled drive motor for half a minute or so.

Wood-Mizer's controller has a lot of extra features for diagnosing faults and for protecting the circuit from overloads and so on. That adds to the price.

There's also a PWM unit in the WM sharpener to control the cam motor. It's simpler but I'm pretty sure it couldn't handle the current.

Quote
would it be possible to just have one with two settings, available via toggle switch rather than having a rheostat?

It would be easy to do with a toggle switch or even just a push button. The PWM circuit wouldn't change at all. The potentiometer just varies the resistance at the circuit inputs, so any other scheme to change the resistance would work.
Bruce    LT40HDG28 bandsaw
"Complex problems have simple, easy to understand wrong answers."

Offline kelLOGg

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Re: 3-4 feet into a cut when I decided back stops, clamp would be in the way
« Reply #47 on: February 25, 2013, 06:54:22 AM »
I got my PWM unit at MidwestMotionProducts and thy are pricey ~180$. After 7 years I accidently reversed the input leads and like Brucer said, I fried the unit.  :( >:( .When I installed the 2nd one I protected the input with a diode. It robs a couple of volts from the output but I use 24 VDC so it doesn't make a noticeable difference.
Bob
Cook's MP-32, 20HP, 20' (modified w/ power feed, up/down, loader/turner)
DH kiln, CatClaw setter and sharpener, tandem trailer, log arch, tractor, thumb tacks


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