Humboldt State University ® Department of Chemistry

Robert A. Paselk Scientific Instrument Museum

Instrument Parts/Repair Help

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

Ainsworth DLB Chain Replacement

Hello Dr. Paselk.

I have acquired an Ainsworth type DLB #8853 balance.  I want to clean it up and restore it to working operation.  It is missing the chain.  Where can I obtain such a chain? Thank you for any information you can share.

Sincerely yours,

Robert J. Vaughan

 

Hi,

I know of no sources for such chain etc. However, I suspect a standard, mass-produced 14 K gold chain would do the trick if it had the proper dimensions. It turns out that modern production techniques tend to produce items of very high precision.

Thus my images on-line which may enable you to make a substitute chain: http://humboldt.edu/~scimus/PartsHelp/index.htm

There is still the problem of the hanger with jeweled bearing. Here you might try using a watch jewel. Obviously you need someone with some machining skill to make this part - a watch maker or competent jeweler could probably do the job.

Good luck,

Rich

 

Hello Dr. Paselk.

Thanks for your information.

I purchased a gold filled chain from a local jeweler.  It was a little too heavy but it was the smallest one I could find for a reasonable price.  I made a small offset bracket that put the pivot support adjustment in the middle of its range.  I machined the hanger bearing out of phosphor-bronze 30 and fashioned the hook as illustrated in the 1937 patent drawings.  The bearing is the smallest piece of machine work I have done on my lathe.  It has virtually no friction as the balance beam swings as it did before I made the bearing. After a calibrating exercise, the chain tracks from 0 through 100 mg to 4 places now thanks to your information.  This has been a fun project.

Sincerely, Robert J. Vaughan

 

Hi Robert,

Would you mind if I posted our correspondence, perhaps with a bit of editing, on my repair pages? I would like to give it as an example that this can actually be accomplished and that I am not totally making this all up!

Cheers,

Rich

 

Hello Rich

I don't mind at all.  I am just grateful for your posting of the Patents and photos for that is the easiest way I could know how to make the chain hanger correctly.

Just a follow-up of the offset bracket.  I calculated that a 280 mm chain should have a mass of .650 grams to fit this balance.  The chain I purchased has a mass of .827 grams at 280 mm.  The jeweler couldn't find one any lighter.  I had to move the pivot support about 5 mm closer to the fulcrum in order to get the chain to track.  The installation of the bracket was such that no physical changes (drilling, etc.) were made to any of the balance components.

My next project is to make a magnetic damper. 

Thanks, Robert

Illustrations and specifications for the chain are given below. All dimensions were determined with dial calipers unless otherwise noted.

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Last modified 10 June 2008