Stanton Instruments Ltd. B15 Balance Restoration

Restoring a bad­ly dam­aged late 1950’s ana­lyt­i­cal balance.

Stanton Instruments Ltd. B15 ape­ri­od­ic auto-load­ing ana­lyt­i­cal bal­ance finished

This project start­ed back in the year 2001, two decades ago when I came across an Ebay list­ing for a work­ing Stanton Instruments B15 ana­lyt­i­cal bal­ance.
I had just fin­ished restor­ing a Stanton Instruments B19 bal­ance which was very sim­i­lar to the mod­el B15, so I thought it would be a fun project.
The bal­ance was locat­ed in England and some­how took three months to ship and reach my doorstep.
Unfortunately, the sell­er P.J.Manison from Swansea, United Kingdom, assured me that he was expe­ri­enced and would prop­er­ly pack the scale for inter­na­tion­al shipping.

Mixture of sin­gle sided card­board, pack­ing tape, and mask­ing tape
Weight knobs pok­ing thru card­board with no padding.
Weight knobs with two lay­ers of sin­gle sided card­board removed

It gets worse as I remove the sin­gle sided card­board wrap­ping and mask­ing tape from the case to find no extra padding under the wrapping.

Damaged Stanton B15 bal­ance due to improp­er packing
Damaged case of Stanton Instruments B15 balance

The ship­per for some unknown rea­son decid­ed to leave all the weights in place, along with the bal­ance beam and pans with no means of secur­ing them. To make mat­ters worse the ship­per decid­ed to place the heavy pow­er trans­former and lamp assem­bly, wrapped in a few lay­ers of news­pa­per inside the case to bounce around dur­ing its trav­els.
Miraculously, some­how only one piece of glass was bro­ken since the only pro­tec­tion for the glass win­dows was a thin piece of cor­ru­gat­ed plas­tic sign board taped on the out­side areas that had glass under­neath. The case also took quite a beat­ing, split­ting sol­id wood and ply­wood.
After receiv­ing the ship­ment, noti­fy­ing the ship­per, and send­ing pho­tos, he denied all respon­si­bil­i­ty and blamed the dam­age on the car­ri­er.
Also since it had been more than three months since the ini­tial pur­chase, Ebay said it was too late to claim a refund or return.

Corrugated plas­tic pro­tect­ing glass win­dows, with no padding underneath

At this point I did­n’t know what I want­ed to do with this bal­ance. I did know that it would have to be dis­sem­bled and cleaned before repair­ing it, or part­ing it out.
Shortly after clean­ing and doc­u­ment­ing all the pieces of the B15 bal­ance, I moved to a new job sev­er­al states away requir­ing me to prop­er­ly pack-up all the pieces for the move.
For near­ly two decades and anoth­er move the B15 stayed secure­ly packed, patient­ly wait­ing for it’s time.
Then came 2020 the year of COVID-19 and extra time to work on near­ly for­got­ten projects.

Stanton Instruments B‑series cat­a­log page with B15 information

Stanton Instruments was found­ed in 1946 by Henry Morton Stanley and Albert W Harrington, in London, England. Stanton Instruments (SI) con­tin­ued build­ing pre­ci­sion bal­ances until 1968, when the com­pa­ny was sold to Avery Ltd.
Luckily I came across a fan­tas­tic web­site curat­ed by Thomas Allgeier.
Stanton Instruments LTD which con­tains a wealth of his­to­ry and infor­ma­tion on SI bal­ances.
The B15 is an ape­ri­od­ic, auto-load­ing, equal-arm, ana­lyt­i­cal bal­ance capa­ble of direct­ly read­ing 0 to 10 mg. from the gratic­ule screen, and up to 100 grams using the “Omni-weight” auto-load­ing attach­ment. It has a sen­si­tiv­i­ty of 0.1 mg.
The Stanton Instruments B15 sold for £ 150 (pounds ster­ling) in 1957 which is approx­i­mate­ly equiv­a­lent to $4,333 USD in ear­ly 2021.

Stanton Instruments B15 Base in primer
Stanton Instruments B15 Base in primer

Restoration start­ed with the base assem­bly and remov­ing all parts attached to it. The base was stripped of all exter­nal paint before struc­tur­al repairs were made, then sprayed with Rust-Oleum sand­able grey filler & primer. After the sur­face was sand­ed and prepped, I used Rust-Oleum “Smoke Grey” gloss enam­el for the final coat­ing of the case. Several of the met­al parts includ­ing inner rails, side door slides, and win­dow glass hold­ers, were paint­ed using Rust-Oleum “Hard Hat” Light Machine Gray enam­el.
Many of the bal­ance pieces are attached to the base, so I took extra time and effort to ver­i­fy dimen­sions and square­ness of this piece.
Next was the rebuild­ing of the arrest­ment cam assem­bly locat­ed under the black glass base. The cam assem­bly has sev­er­al duties includ­ing rais­ing the arrest­ment arm and pan damp­en­ers, along with oper­at­ing a microswitch for the lamp, and sup­port­ing the low­er optics first sur­face mir­ror. Unfortunately I did­n’t get any pic­tures of the work done, but had a pic­ture of the base assem­bly from the orig­i­nal doc­u­men­ta­tion 20 years ago.

Stanton Instruments B15 orig­i­nal dis­as­sem­bly pho­to of arrest­ment cam assembly

The next part involved lot’s of paint strip­ping of the rest of the case in prepa­ra­tion of repair­ing the worst of the ship­ping dam­age. Repairing the case involved lots of glue, and every clamp I owned. This hap­pened in sev­er­al incre­men­tal steps, until every­thing was aligned and stable.

Stanton Instruments B15 stripped, repaired, and sand­ed mid­dle case
Stanton Instruments B15 mid­dle base back
Stanton Instruments B15 mid­dle base side, ready for paint

The mid­dle case sus­tained the most ship­ping dam­age and required the most time to fin­ish. Several areas of the case require a bare wood fin­ish such as the front slid­ing door guide slots, and front glass slots which required mask­ing for each paint coat.

Stanton Instruments B15 mid­dle case with primer / filler coat
Stanton Instruments B15 front door coun­ter­weight hole

Next up was the “Omni-weight” auto-load­ing attach­ment, which after sit­ting for two decades was very stiff from dried out lubri­cant. After a thor­ough clean­ing and relu­bri­ca­tion it was oper­at­ing smooth­ly again. The orig­i­nal rub­ber on the damp­en­ing bars was hard as a rock and required replacement.

Stanton Instruments B15 “Omni-weight” auto-load­ing attach­ment, clean­ing & rub­ber repair

Several of the first sur­face mir­rors in the opti­cal path required replace­ments, before I could reassem­ble the unit. I also decid­ed to build a replace­ment LED light source, instead of reusing the orig­i­nal incan­des­cent light source.

Stanton Instruments B15 new LED light source for optics

After pick­ing up a piece of sin­gle pane glass cut to spe­cif­ic dimen­sions from our local hard­ware store, I was final­ly ready to put every­thing back togeth­er.
New green felt was attached to the low­er front door edge, along with new grey sin­gle sided vel­vet rib­bon between the front glass sup­port and door to pre­vent exter­nal air drafts from dis­turb­ing inter­nal components.

Stanton Instruments B15 instal­la­tion of beam and new brass threshold
Stanton Instruments B15 front door coun­ter­weight cord and rebuilt pulleys
Stanton Instruments B15 ape­ri­od­ic air dampers, pan hang­ers, and beam installed
Stanton Instruments B15 “Omni-weight” auto-load­ing attach­ment installed with weights
Stanton Instruments B15 0 to 10 mg. gratic­ule dis­play read­ing Zero
Stanton Instruments B15 weight sup­ports, rid­er arms, deci­gram and centi­gram weights
Looking thru upper side win­dow of Stanton Instruments B15 balance
Stanton Instruments B15 weight pans and display

Several of the rid­er weights were lost dur­ing the ini­tial ship­ping inci­dent and need­ed to be replaced. I ordered some high per­cent­age chrome / nick­el stain­less steel straight wire in sev­er­al dif­fer­ent diam­e­ters to fab­ri­cate the replace­ments from.
The cir­cu­lar weights were the eas­i­est, requir­ing a round form of the cor­rect diam­e­ter, form­ing the wire tight around it and then twist­ing the ends leav­ing some excess to trim down to their final weight. The bell shaped weights required a bend­ing jig, and a bit more mea­sure­ments to get the lengths and angles cor­rect. The most tedious part was remov­ing extreme­ly small amounts of mate­r­i­al using a dia­mond file to exact­ly match my Class S cal­i­bra­tion weights.

Stanton Instruments B15 beam, sad­dles, arrest­ment arm, agate knife edges, and syn­thet­ic sap­phire (Corundum) planes
Stanton Instruments B15 ana­lyt­i­cal bal­ance fin­ished with upper glass removed
Stanton Instruments B15 bal­ance (left) sit­ting along­side my B19 bal­ance (right)

It was def­i­nite­ly a fun project at times, but I can do with­out any more paint strip­ping for sev­er­al years. The B19 bal­ance was actu­al­ly used for a research project many years ago, but not so much any­more.
The next project for these bal­ances will be a ded­i­cat­ed con­crete or gran­ite weigh­ing table to prop­er­ly sup­port and damp­en vibra­tions.
Many thanks to Thomas Allgeier for pro­vid­ing doc­u­men­ta­tion and answer­ing my many ques­tions, and my wife Leann for her sup­port dur­ing this lengthy project.

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