Humboldt State University

Robert A. Paselk Scientific Instrument Museum

Instrument Parts/Repair Help

The information provided via this page is intended to aid those repairing/restoring old instruments. It consists of responses I have made over the years to requests for help with restoration.

If you are interested in replacing missing parts, I have linked a set of emails describing a successful restoration of a missing chain by a user of this site as an example of what can be done - Rich

Chemical Balances

A brief set of instructions for cleaning a balance, originally provided by Fisher Scientific, is provided on-line: Directions for Cleaning a Balance From: Fisher Scientific Company. Modern Laboratory Appliances (Catalog 90). Fisher Scientific Company and Eimer and Amend (1942, reprinted 1946) p 48.

The operation and general care of chemical balances may be found in any vintage (<1975) analytical chemistry text. A fairly thorough early treatment is available here on-line: Weighing from Smith, George McPhail. ...QUANTITATIVE CHEMICAL ANALYSIS ... (1921).

A more advanced treatment on the set-up and repair of balances is also available on-line: The Use and Care of a Balance by Peter J. Krayer (1913). This treatment does not seem to have been superceded in English, and is highly recommended.

A general description of the care and operation of analytical balances focusing on Christian Becker Chain balances is also provided on line: Care and Use of Analytical Balances. This is the complete text of a brochure provided by Christian Becker division of Torsion Balance Company (1952)

Instructions for Assembly and Adjustment of Christian Becker Chainomatic Balances. These typed instructions were found under an instrument in HSU's physical chemistry lab. They probably came with our AB-2 balance in the 1950's. pg 1, pg 2, pg 3, pg 4, pg 5.

Some of the important variations of the Christian Becker line of chain-weight balances are illustated and briefly described on-line in: Christian Becker Analytical Balances from Braun-Knecht-Heiman Co., Catalog No. 40, Laboratory Instruments Apparatus Supplies, (1940)

The directions provided in the lid of the box originally carrying the beam, pans etc. for a SeKo two pan balance is provided in two resolutions: SeKo Directions for Setting up a Balance from Seederer-Kolbush (c. 1960) (Higher Res)

Balance parts: Illustrations and specifications for some parts commonly needing replacement are given below. Linked photos generally include a rule for comparison and/or dimensions. All dimensions were determined with 6" dial or digital calipers unless otherwise noted.

Ainsworth

• Ainsworth Model LCB Chain balance Chain Gold (14 k?) Chain length (not including live bearing on beam end or hanger link on scale end) from ouside to outside of links = 9.46 inchs (measured vertically suspended with a Lufkin steel machinist rule graduated to 1/00"). The weight of the chain assembly (including end pieces) = 0.7068 g (weighed on a calibrated Metller/Toledo electronic analytical balance 6/12/2012). The jeweled hanger (beam) weighed approximately 0.145 g, and the square hanger link weighed approximately 0.037 g (both weighed with chain attached, limiting precision) .
• Ainsworth Model LCB Chain balance beam Weight. 0.5000 g stainless steel: 0.540" long overall; center = 0.089" dia x 0.190 long; shoulders = 0.121" dia. Note that the beam has notches from 0 - 1.0 at 0.1 intervals along the beam, with 0 and 1.0 directly over the pan hangers.
• Ainsworth Model LCB Chain balance Stirrups with hooks.
• Ainsworth Model LCB Chain balance Magnetic Damper Vane.
• Two Ainsworth patents for chain balance mechanisms are provided in pdf format via the links below (the original patents, in pdf format, were kindly provided by Janet Van Doren, a retired analytical chemist).
  • The flexible scale bearing the chain and associated elements, patent 2,022,306 (1932).
  • The live-bearing for the chain on the beam, patent 2,111,842 (1937).

Christian Becker

• Chain Balance
• Christian Becker Model AB-2 Chain balance beam Weight. 0.7172 g stainless steel. (Purchased in 1952. Weighed on a calibrated Mettler electronic analytical balance 11/9/99.) Note that with the dial reading chain balance from CB the notches do not go across the entire beam - they are offset for better visibility (see illustration in Christian Becker Analytical Balances) - thus the heavier weight than is seen in the Ainsworth balance above.
• Christian Becker Model AB-2 Chain balance Stirrup with hook. 2.9898 g aluminum body with polished flat agate bearing surface and brass hook assembly. (Purchased in 1952. Weighed on a calibrated Mettler electronic analytical balance 8/5/04.)The brass parts are of stamped sheet metal (0.032 in thick) with a laquered finish. The brass "U" appears to be press-fit into two holes through the aluminum stirrup body. The two arrest support screws are locked in place with small set screws. Comparison views vs. machinist's rule: Stirrup with hook; top view of stirrup body. Note that the pictures of the stirrup and hook assembly show the assembly upside down.
• Specific Gravity Balance
• Christian Becker Model SG-1 Specific Gravity Balance Weighing Chain. The chain + hanger = 1.2918 g, the hanger alone = 0.2953 g. (Balance purchased in 1959. Chain weighed on a calibrated Mettler electronic analytical balance 17 April 2000.)
• Christian Becker Model SG-1 Specific Gravity Balance beam Weight (rider). The rider = 2.5332 g, (balance purchased in 1959. Rider weighed on a Mettler digital balance 24 May 2010 calibrated during the AY 2009-10.
• Christian Becker Model SG-1 Specific Gravity Balance plummet and weight. The plummet and weight were weighed with the wire attached, however since such devices were made to precise standard weights I suspect they were made to teh exact weights to 0.1 mg (balance purchased in 1959. Weighed on a Mettler digital balance 23 May 2010 calibrated during the AY 2009-10.
  • Plummet = 5.00xx g and has a specified volume of 2.0000 mL (displaces 2.0000 g water).
  • Plummet weight = 10.00xx g.

Voland

• Voland Analytical Balance Riders (5 & 10 mg) Aluminum wire. Note that the 10 mg riders are used on balances with a scale with 0 over the beam center, and 10 over the pan hanger; the 5 mg rider is used on balances with a scale going from 0 - 10 pan-hanger to pan-hanger, with 5 at the beam center-point.

Optical Equipment

AO-Spencer Spectroscope

Prism table:

• A frequently missing part for these instruments is the Prism Table. I have provided a number of photos from different angles of the table from a mid-2oth century "Student" spectroscope. In spite of its name, this is a very high quality instrument that was/is used in college and university physics classes.
• The table and grating holder are made entirely of brass with the exception of steel mounting shaft and steel springs (only parts that are magnetic). The triangular cast brass mount is finished in black krinkle paint, the grating holder is finished in flat enamel, all other parts are chrome plated except the springs and shaft. The two spring brass grating holders are very like microscope slide holders in thickness etc.
• All measurements on the photos were made with a digital caliper reading to 0.001".
  • Table and parts (partially disassembled)
  • Top view of table
  • Bottom view of table
  • Side view of table

HSTC (1921-34)

HSC (1935-1953)

HSC (1954-1973)

© R. Paselk

Last modified 21 June 2012