Re: Re: Home-Built Beam Balance

From: Bill Gowen <b.gowen_at_earthlink.net>
Date: Sun, 10 Dec 2006 11:54:05 -0500

Lee
Maybe you have a bearing for your beam balance that you like. I put a picture of mine in the "Tools" folder. It works real well and is simple. I don't depend on my scale too much for absolute weights but I can see weight differences down to a milligram or so.

  ----- Original Message -----
  From: Lee Dammann
  To: Indoor_Construction_at_yahoogroups.com
  Sent: Saturday, December 09, 2006 9:53 PM
  Subject: [Indoor_Construction] Re: Home-Built Beam Balance


  Gary
  Your right about the rigid pans and the possible error. I just went
  down and put a 120 mg EZB motor stick on the pan. When moved all
  the way in and all the way out on the pan, I can get a 10 mg
  difference in weight. (+5, -5)
  Hanging the balsa pan on 3 or 4 threads would be an easy fix. Thanks
  for the heads up. Although in the back of my mind I knew there
  would be an error, so I have always set the piece in the middle.

  All your other ideas are great. Its part of the fun of a 2 dollar
  homemade scale. You could but into it as much as you'd like.

  I have fould that dampning is not necessary for what I'm doing. If
  you keep the limit bars close, settle time is not bad. I would like
  to have a centered pointer with scale so I wouldn't have to wait for
  settle, just check that the ossilations are even on the scale.
  You may also be able to put a magnet under the T-pin. With the
  right strength and distance, it may be good enough. Something more
  to play with.

  Thanks
  Lee
  --- In Indoor_Construction_at_yahoogroups.com, dgbj@... wrote:
>
> LD,
>
> This is very good. Thanks for sharing it with us. Having the
  pads glued to
> the bar introduces a serious error. Because the pads are rigidly
  attached
> to the bar, placement of the object to be weighed will influence
  the balance.
> Placing the object close to the blade will show a lower weight
  than placing
> it farther out. Try it. The pads must be suspended with a
  nonrigid
> attachment from a point on the beam.
>
> There are some refinements to consider.
>
> Trim nut. Having a machine screw with a nut on it sticking out
  from the end
> opposite the scale will allow fine trim of the balance by moving
  the nut
> along the screw..
>
> Vernier. A vernier is a small scale attached to the sliding
  weight that
> allows reading one finer division of the scale. It has 10
  divisions, but is
> 9/10 of the length of 10 scale divisions. If the index point on
  the vernier is
> between two of the divisions on the scale, the subdivision
  corresponds to the
> value where the vernier marks most closely approximates the
  corresponding
> mark on the scale.
>
> Damper. The oscillation of the beam can be slowed with a
  magnetic damper.
> A damper consists of a thin aluminum plate attached to the end of
  the beam
> and a strong magnet near by. As the aluminum plate moves through
  the magnetic
> field an electric current is induced. The induced current
  opposes the
> magnetic field and exerts a force on the aluminum that is
  opposite to the direction
> of movement.
>
> Gary Hinze
>
>
> [Non-text portions of this message have been removed]
>



   

[Non-text portions of this message have been removed]
Received on Sun Dec 10 2006 - 08:54:27 CET