Re: Van Norman #12 Milling Machine

Dan Falck wrote:

> From: Dan Falck <dfalck@...>
>
> At 11:31 PM 1/22/2000 , you wrote:
> >From: Jon Elson <jmelson@...>
> >
>
> >If you put a ballscrew on the Z (knee) axis, you will almost certainly need
> >a power-off brake to keet the knee from crashing to the bottom of
> >travel when the power is off, or the system is in e-stop. This may even
> >be true with steppers, depending on how much they drag with power
> >off. The will also be true on machines where the entire vertical head is
> >raised and lowered on a dovetail slide.
> >
> >Jon
> >
>
> On my Rf-45 bed mill/drill the whole head assembly runs up and down on a
> dovetail column. To keep it from crashing into the table when the power
> goes out I have two sets of gas springs and some heavy duty springs counter
> balancing the head. I have sprockets on top of the column and chain
> running from the head, over the sprockets and down the back to the springs
> and cylinders. It works pretty well. Weights would probably work just as
> well.

Neat! Actually, the weight required to counterbalance the head would be
acceptable, but the gas springs add a lot less mass. the counterbalance
weights would DOUBLE the mass when the head is moved. For a knee,
I think gas springs are the only way. Unfortunately, those would be BIG
gas springs. Maybe, one could come up with old oleo struts from aircraft
landing gear. That would be about the right size.

Jon