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One aspect that comes to mind is engineering *for* failure; ie engineering the system so that the most likely point of failure is something easily worked on or replaced. So putting in a modern material with a much greater strength may end up causing problems later when it resists breaking and something much harder to replace or work on breaks instead. You might try asking a university with a good Materials Science program if they would actually test a sample of the original bolts and provide a suggestion of the closest modern equivalent. If this was done as say a research project for a senior student it may be able to be done gratis. Thomas Powers > > From: Alan Hardman [mailto:[log in to unmask]] > Sent: 27 February 2013 10:46 > To: [log in to unmask] > Cc: Valerie Bayliss; [log in to unmask] > Subject: Re: Fwd: FW: Caribbean sugar mill and Sheffield steel > > > > As a retired Metallurgist and steel historian I guess I should comment on this enquiry. > > > > I agree with Derek that if the current bolts are the originals from the 1840s it is most likely that they are made of Wrought Iron by the Puddling Process. This was an era well before the Bessemer Process gave the world the first bulk steel at prices allowing its use in general engineering applications. Steel before Bessemer's product from the 1860s was very expensive and its use limited to cutting edges and tools where high hardness for wear resistance was essential. > > > > Assuming that we are dealing with a Wrought Iron product, then the Carbon content would probably be less than 0.15%. > > The Yield Strength would be around 40,000psi and the Brinell Hardness around HB120 - 130. > > If you have access to a Mechanical Testing Facility a Brinell Hardness test is easy and quick to carry out on a bolt, and the result can be converted to an Equivalent Ultimate Tensile Strength. The Yield Strength will be around 55% of the UTS. > > That would confirm the strength level of the original material which has withstood the test of time so well. > > > > I think your proposal to use 50,000psi Yield Strength threadbar locally available is a good solution so long as the bolts are loaded in tension and do not have significant bending stresses applied in use. Threads can be local stress-raisers leading to fatigue failures. > > > > One other observation I would make is that the secret of the remarkable longevity of much wrought iron engineering is its corrosion resistance, associated with the slag stringers present in all wrought irons. It will be interesting to see if modern steel replacement bolts also last 170 years. > > > > I hope my comments are helpful, and I wish you success with the mill refurbishment. > > > > Best regards, > > Alan Hardman. > > Sheffield. > > > > > > > > ----- Original Message ----- > > From: Valerie Bayliss <mailto:[log in to unmask]> > > To: Christine Ball <mailto:[log in to unmask]> ; Alan Hardman <mailto:[log in to unmask]> ; Derek Bayliss <mailto:[log in to unmask]> > > Sent: Friday, February 22, 2013 4:26 PM > > Subject: Re: Fwd: FW: Caribbean sugar mill and Sheffield steel > > > > Christine > > > > I can’t help on the technical issue, but is Mr Croome sure that the bolts are steel and not wrought iron? I checked, some time ago, the products that were mentioned in a large number of Sheffield steel firms’ advertisements of c1860, and bolts were only mentioned once (ditto screws, and rivets). But that may only mean that they were made elsewhere – or taken for granted. > > > > Best wishes > > Derek > > > > From: Christine Ball <mailto:[log in to unmask]> > > Sent: Friday, February 22, 2013 2:40 PM > > To: Alan Hardman <mailto:[log in to unmask]> ; Derek Bayliss <mailto:[log in to unmask]> > > Subject: Fwd: FW: Caribbean sugar mill and Sheffield steel > > > > Can either of you help with this one please? > > Christine > > ---------- Forwarded message ---------- > From: Anthony Ball <[log in to unmask]> > Date: Fri, Feb 22, 2013 at 10:52 AM > Subject: FW: Caribbean sugar mill and Sheffield steel > To: [log in to unmask] > > > > > -----Original Message----- > From: Arch-Metals Group [mailto:[log in to unmask]] On Behalf Of Chris Evans > Sent: 22 February 2013 09:13 > To: [log in to unmask] > Subject: Caribbean sugar mill and Sheffield steel > > I'm passing on an enquiry I've received from George Croome of the River Antoine estate in Grenada concerning the properties of steel made in Sheffield in the 1840s. I'm not competent to comment, but perhaps someone on the list may be able to assist. If so, please contact Mr Croome directly at [log in to unmask] > > "In Grenada, my company operates a small rum distillery, using sugar cane juice grown on the estate, which is crushed in a 3-roll mill made by George Fletcher & Co. of Derby in the 1840's. The mill is still driven by the original water wheel - the only working water wheel in the Caribbean.... > > The mill has eight horizontal through-bolts which take the thrust from the two bottom rolls and are adjusted as the rolls & bearings wear.... > > After 170 years of daily operation, the bolts have started to elongate and break. Fletchers (who are still in existence as Fives Fetcher) are very good, but they tell me that the warranty has expired ! > > I need to replicate the bolts, using modern steel, and I have been trying to 'reverse-engineer'. For that, I need an estimation of the original load-carrying capacity of the bolts. I have engineering data books showing steel properties, going back as far as 1890, but I know that there were huge improvements in steel-making in the 50 years before that time, so the 1890 figures might not be representative . Fives Fletcher are looking back in their archives to try to calculate the theoretical total tensile load on the eight bolts as a component of the thrust from the rolls. > > I am hoping that we could use a continuous threadbar rolled from 50,000 psi yield steel perhaps 1.2 inch OD to replace each bolt, as such threadbar is readily available. > > My question therefore is, can you give me your opinion (i.e. hazard a guess !) at what type of steel would have been used to make these bolts in 1840, and what allowable stresses might have been assumed by the original engineer." > > > > > Thomas Powers