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Setting up Contractometer to Measure Stress in Nickel Bath

Can anyone help with instructions on how to set up a Brenner Senderoff Contractometer as we have lost the instruction manual.

Dennis Barnes
support engineer - Perth, Tayside, Scotland
March 24, 2009

Try the web site for the original mfg of the instrument as they are not exactly identical, just close.

James Watts
- Navarre, Florida
March 25, 2009

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March 26, 2009

Dennis,

Are you going to this in the bath or in a beaker [beakers on eBay or Amazon] in the lab?

You first of all have to calibrate the helix with the standard weights provided. You have to wind the weights around and drop them off the pulley and read off the deflection. Repeat in hte opposite direction. From this you can calculate your constant (K) as 1/16 x 1/deflection. Note the compressive and tensile values, you'll need to know the difference later.

Clean the helix and dry. Weigh it to 4 decimal places. Attach the helix to the contractometer, avoid touching the cleaned part with bare hands, this will affect the plating deflection.

Plate the helix for 10 minutes at about 60 ASF (it actually works out to be about 6 amps for a standard helix). At the end of the plating switch off the current and read off the deflection value, note whether it is compressive or tensile. Thoroughly dry the helix and reweigh to 4 decimal places. Calculate the thickness as:

(W1-W2)/[density (in g/cm3) x surface area (in cm2)] = t

Calculate your stress as:

(K x 2 x deflection)/ (t x pitch of helix x thickness of helix) = psi stress.

For K use the tensile value if the plating value was tensile and use the compressive value if the plating was compressive.

Hope this helps.

Brian Terry
Aerospace - Yeovil, Somerset, UK

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Brian,

Thanks for the reply, I will pass that onto the plating shop chemist and hopefully we can make some headway. You have been most helpful (as always).

Dennis Barnes
- Perth, Australia
March 30, 2009