Power up/down

[BAR]

Just read fred in montana's post for power feed and did a search for his power up/down post and couldn't find it, so am starting a new thread rather than posting an OT question there.

I am in the early thinking stages of adding power up/dn to my WM LT27.  It will most likely include a 12VDC source and wheelchair or similar gearing. 

Here are my early concerns.

1)   The up/dn should be coarse only, perhaps to within 1/2" to 1" of target. I have learned to use the vertical scale pretty well and don't want to get involved in backlash or overshoot problems trying to get a dead on system.

2)  The electrical drive system should be disengaged during final manual adjustment to scale  (thinking electrical or centrifuigal clutch).

3)  The manual adjustment crank can not be allowed to spin during power up/dn for safety reasons.  How would I disengage that?

Anyone done anything similar?  Comments?  Opinions?   Any and all will be appreciated.

BAR

[Tom]

BAR,
Look at some of the early 1990's,  LT30's and LT40's.   The up/down is driven by an electric motor, through a  drum switch, to a V-belt that drives a pulley.  There is a manual lock that just puts pressure on the sheave and a manual handle that can be removed. (It is usually removed)   The accuracy is easily within a half-inch and, with experience, you can manipulate the sheave with a gloved hand to stop "on the money". (as well as use the gloved hand to make minor adjustments by turning the sheave)

What will work on the LT27 might be designed a bit different, but the idea should work.

[BAR]

Thanks for the reply TOM.  I'll look into those if I get the opportunity.
Just to reduce any possibility of misunderstanding,  I want my final adjustment to be within 1/16 of an inch or better by hand.  The power function is just to get the head reasonably close to save wear and tear on 72 year old shoulders and elbows.
BAR

[Tom]

Yep.  That is the same philosophy that Woodmizer used on the old mills with electric up/down. 

If I remember the LT27 correctly; I thought how easy it would be, when I looked at an acquaintance's, to retro-fit electrics similar to my LT40.  I would have done it in a heartbeat too.  He spent a lot of time cranking on that mill.  :D

You won't be able to copy the LT40, but you can sure make something similar.  You already have the gear box.  Just replace the handle/wheel with a sheave that has a hub that will take a handle.  I'll bet you could buy the parts from Woodmizer.

[Hilltop366]

I can see not wanting a handle when using the up/down motor but I am wondering if you used a wheel that set out from the pulley it should be safe, also can then guard the belt & pulley, might save a finger.

Another idea for the drive could be a set up like the old troybuilt tiller with the pulley/friction wheel (tighten belt= one direction,  rub wheel = opposite direction)