Re: [GrizHFMinimill] Re: Counterweight Arrangement



The joist will see the lightest weight attached to the pulley system not the heaviest.  If using a block and tackle or different ratios then it is the lightest weight times the ratio.
 
Richard
 
 
----- Original Message -----
Sent: Friday, January 20, 2012 4:49 PM
Subject: RE: [GrizHFMinimill] Re: Counterweight Arrangement

 

The head itself weighs about 160 lbs so unless you have a mechanical advantage with a pulley arrangement, this is what the joist would see.  Maybe I'm missing something?

Ollie

From: GrizHFMinimill@yahoogroups.com [mailto:GrizHFMinimill@yahoogroups.com] On Behalf Of gerry waclawiak
Sent: Friday, January 20, 2012 2:41 PM
To: grizhfminimill@yahoogroups.com
Subject: RE: [GrizHFMinimill] Re: Counterweight Arrangement

 

The weight to balance the head cant be much above 50lb which should not be a problem provided you have a secure fixing to a joist. If you are worried you could always put in a spreader across a couple of ceiling joists to share the load#

Gerry
Leeds UK

To: GrizHFMinimill@yahoogroups.com
From: ofick@bendbroadband.com
Date: Fri, 20 Jan 2012 13:41:36 -0800
Subject: RE: [GrizHFMinimill] Re: Counterweight Arrangement

 

Be careful.  Ceiling joists are only designed to support the weight of the dry wall and insulation.  They are not designed to hold high point loads.  This is what has discouraged me from using the ceiling joist option.

Ollie

From: GrizHFMinimill@yahoogroups.com [mailto:GrizHFMinimill@yahoogroups.com] On Behalf Of kr98664
Sent: Friday, January 20, 2012 1:37 PM
To: GrizHFMinimill@yahoogroups.com
Subject: [GrizHFMinimill] Re: Counterweight Arrangement

 


Hi Roger,

Thanks for the comments. As far as a pulley arrangement, I'd have to run a cable straight up to a ceiling joist if I wanted the lifting force applied at the spindle end. I wouldn't be able to use David's slick semi-hidden version inside the vertical column. Over the weekend, I plan to play, I mean do a controlled scientific experiment, to see if there any advantage to my idea. One big drawback is an overhead cable will get in the way, versus David's semi-hidden version. It could be that my cure is worse than the disease, especially where David says he is very pleased with his results. I will find out this weekend.

Regards,

Karl

--- In GrizHFMinimill@yahoogroups.com, "Roger Blair" <Roger.Blair@...> wrote:
>
> Karl,
>
> (IMHO)
>
> Issue 1.
>
> To compensate some for gib play, attach the counterweight near the spindle end of the head, and ensure that it is heavier than the
> head weight enough to hold the spindle/tool in the same angular position as when the tool loads into the work. (eliminating slack
> motion)
>
> Issue 2.
>
> In theory, adding a second pulley at or near the spindle end of the head will introduce a much greater moment arm on the vertical
> column than from the center of David's single roller to his attach point, and the higher the head position is on the column, an
> extended arm will cause the column to bend more. If there is a measurable effect, only stiffening the column will correct for that.
>
>
>
> Roger
>
>
>
> From: GrizHFMinimill@yahoogroups.com [mailto:GrizHFMinimill@yahoogroups.com] On Behalf Of kr98664
> Sent: Thursday, January 19, 2012 02:09
> To: GrizHFMinimill@yahoogroups.com
> Subject: [GrizHFMinimill] Re: Counterweight Arrangement
>
>
>
>
>
>
> Hi David,
>
> I like your idea to use a nylon strap, especially how well the bend radius compares to the more typical steel cable. I had already
> been planning to do that.
>
> While brainstorming the installation, I got to wondering if there was anything to be gained by applying the lifting force at the
> spindle end, away from the gibs. There will always be some amount of play as the head rocks up/down on its gibs, so I'd like to take
> out as much play as possible by lifting the spindle end of the head. Granted, the pulley arrangement would no longer be as clean and
> simple as your design, so there would be a trade-off.
>
> --- In GrizHFMinimill@yahoogroups.com <mailto:GrizHFMinimill%40yahoogroups.com> , "a3sigma" <dcclark111@> wrote:
> >
> > Hi Karl,
> >
> > My counterweight scheme continues to work very well for me. See my files at:
> >
> > http://groups.yahoo.com/group/GrizHFMinimill/files/D.C.%20Clark%20stuff/
> >
> > Note also my thrust washer file. I have several sets remaining, and my offer still stands to give a set to any member who sends me
> a SASE. Email me off list for my address.
> >
> > David Clark in Southern Maryland, USA
> >
> >
> >
> > --- In GrizHFMinimill@yahoogroups.com <mailto:GrizHFMinimill%40yahoogroups.com> , "kr98664" <kr98664@> wrote:
> > >
> > > Hello All,
> > >
> > > I've been looking at options to minimize the Z-axis drop on my Micro-mark mill. I've read plenty about gas lifts and
> counterweights. In both cases, the upward force is close to the vertical column. No matter how well the gibs are adjusted, any play
> is magnified and the spindle end can still tip down a tiny bit.. My thoughts are if I apply the lifting force (via a counterweight)
> near the spindle, this will practically eliminate any Z-axis play, even more so than a gas spring or counterweight nears the gibs.
> > >
> > > Any thoughts? Am I out in left field?
> > >
> > > Thanks,
> > >
> > > Karl
> > >
> >
>

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Version: 2012.0.1901 / Virus Database: 2109/4755 - Release Date: 01/20/12



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