William Hazeldine … Proving Machine

[Michael GilliganParticipant @michaelgilligan61133]

My brother has just sent an interesting snapshot from Shrewsbury Museum:

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Worthy of further investigation, methinks

MichaelG.

[howardbParticipant @howardb]

Abstract from https://www.icevirtuallibrary.com/doi/full/10.1680/ehah.14.00005

Paragraph or section 10

“Perhaps the most celebrated structures on which [Thomas] Telford and [William] Hazledine worked together are the Menai (SH 556714, 1826) and Conwy (SH 785776, 1826) suspension bridges in north Wales”

“Telford dispatched John Provis, the brother of resident engineer William, to Shrewsbury to supervise the testing of all the ironwork. To achieve this Telford (presumably with Hazledine) designed and built a ‘proving machine’, which took from January to June 1822 (Provis, 1828, p. 33ff). This machine was installed at Hazledine’s headquarters in Shrewsbury, to which all the ironwork was brought from Upton by way of the Shrewsbury Canal. After testing, it was sent overland to Weston Wharf, then by way of the Ellesmere Canal to Chester, and finally by sea to Menai; the first consignment of bars for the main chains was delivered to Menai by October 1822 (Provis, 1828).”

But no mention that I could see from a quick visual scan of the document of how the proving machine worked to test the wrought iron used for the suspension chains.

[Nigel Graham 2Participant @nigelgraham2]

Magnifying the image did not help much but the drawing suggests a tensile-test machine using either two racks or a central screw with bevel-wheels, driven from the final gear.

Though how the test was supposed to be quantitative rather than just qualitative, is not clear.

Materials testing was still in its infancy in the 1820s, and even by the early-20th manufacturers were still using quite crude methods such as (for cast-iron) loading the centre of a specimen bar simply supported over a length.

[BazyleParticipant @bazyle]

The weights just to the left of the largest gear are magnified (20:1?) through an arm pivoting on a floor stanchion to lift the substantial lever on the far left which pulls the chain to one end of the test piece. The hand crank far right is wound to take up the slack until the weights are lifted. The weight on the far left is probably used to compensate the weight of the mechanism to make the calculation straightforward.

[duncan webster 1Participant @duncanwebster1]

the gears reduce the rotation of the hand crank (rightmost) to the biggest wheel(centre). Wrapped around the axle of this wheel is a chain, connected to the test piece. At the left hand end a second chain is connected to the test piece, this chain wrapped round another axle. This axle drives a double lever arrangement to lift the pan with 3 weights on it. As Bazyle says, the left hand weight is to zero the whole shebang. It seems reasonably founded to me, the only iffy bit is friction in the left hand axle bearing, otherwise the load in the test bar is the mass of the double weights multiplied by the double lever ratio.

There is a much bigger tensile test machine in a museum in London, Kirkaldy

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the contributions

I have been out for the day, but will digest them later.

Have already written to the museum enquiring whether a full set of drawings might be available.

MichaelG.

[duncan webster 1Participant @duncanwebster1]

Pedantry, but correcting myself, weight, not mass

[Michael GilliganParticipant @michaelgilligan61133]

 

https://stchadschurchshrewsbury.com/wp-content/uploads/2024/11/qr-Simpson-and-Hazeldine.pdf

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

For anyone still interested … the machine is described here:

https://archive.org/details/dli.bengal.10689.19434/page/n253/mode/2up?q=proving

MichaelG.

[DiogenesParticipant @diogenes]

I’m still interested, Michael

– I see that although ultimate tensile strength was known, ‘proof’ was really based on the yield point..

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