Problem is holding the top cover of the valve chest down safely , depending on pressure of course.

For steam, three potential problems. Tufnol absorbs water, about 55mg per gram, and – depending on grade – the max operating temperature will be in the range 90°C to 250°C. 130°C seems typical. Also, Tufnol expands more slowly than a metal liner, which cause a lot of local pressure. With a liner the water problem could be managed, but not ill-effects of high temperatures. I don't have a feel for the effect of different heat expansion rates; I suppose the Tufnol might stop the liner expanding at the same rate at the piston, maybe jamming the piston, or kinking the liner.

Tufnol is pretty strong – about the same as a mid-range Aluminium – but I couldn't find a nice graph showing what happens to its strength as the temperature rises. Most metals have to get up to a few hundred degrees before they soften significantly, most plastics soften far sooner. I'd guess it would be difficult to keep cylinder and liner attached.

As always with unknown scrap no-one on the forum can confirm this is a good idea or not. If Mick's block of Tufnol is the 90°C type, it's certainly no good. If it's the 250°C variety, I don't see why it shouldn't work.

It's a very interesting idea though. In the golden age of steam materials like Tufnol, Aluminium, Magnesium and Titanium were all exotic and far too expensive. In addition weight didn't matter much to steam locomotives, mill engines or ship engines, hence cylinders could be made heavy. No point in exploring lightweight steam cylinders for cars and aircraft, because the weight of whole engine – firebox, boiler, etc can't be reduced usefully just by changing what they're made of. I don't think there's been any serious research into modern materials.

For building an engine guaranteed to work, best stick to time-proven methods and materials. As an experiment, please go for it. Could be Tufnol cylinder blocks are brilliant!

All objections disappear if the engine is driven on cool air.

Dave

Edited By SillyOldDuffer on 30/04/2020 12:37:19

Forget Tufnol for cyl block – just too many issues. You will be fighting that crap all the way. Get a nice piece of continuous-cast cast iron (Meehanite and Durabar are good brands) and make a great running trouble free cylinder.

Just my $0.02 worth. Ready for the onslaught of misguided Tufnol fans saying the opposite. Life is too short, and there are too many FAR better engineering plastics and metals, to fool around with Tufnol in 2020.

Edited By Jeff Dayman on 06/06/2020 00:10:03

Mick

It might be useful for you to know that Myford 7 series lathes use Tufnol for the tumbler gears, I think the idea is the teeth would shear instead of something really expensive should you have a crash.

Tufnol gears also tend to run quite a bit quieter than metal gears.

Brian

+1 for that.

Apparently there have been some replacement tumbler gears in packaging marked as being "Myford" being sold that are made from Tufnol Bar, Purchasers have been "disappointed" with their longevity.

That said, there is another vendor making exact replicas, perfect in every way, by cutting them from the appropriate sheet material.

Brian

Circlip –

Thank you for that point. I assume a sound reason, but could you explain what that is, please?

I do have some small SRBF worm-wheels with associated hardened and ground steel worms, in my "they look useful – I'll keep them" collection, and from your reminder I take it they would have been machined from sheet or even possibly moulded blanks.

'

Jeff Dayman –

With respect you are missing an important point – to the extent of descending into being rude.

That point is of matching any material's properties to intended application; be it natural (metal, wood, stone) or synthetic (plastic, resin, composite); and irrespective of its manufacturer or age.

The thread has established that Tufnol is unsuitable for steam-engine cylinders, and I would agree; but it is not made for that. Neither would many metals and non-metals, be suitable for a steam-engine. (Since you seem to suggest we must use 21C-invented materials even when replicating an 19C machine, I suppose some of the latest aerospace alloys might be technically very good for this purpose, but they might be totally unsuitable on availability, cost and machineability!)

If there are "better" metals and plastics than "Tufnol" – a trade-name for a range of composite materials – if we assume correct choice for application, "better" in what way? You inject into a constructive discussion on whether a particular material is suitable for a singular application, a blanket condemnation of its manufacturer's products, and of their users; apparently based merely on age of invention.

Yet all materials of any age obviously have their own properties making them excellent for some, but unsuitable for other, applications. You may have a basalt (not usually "granite"!) surface-plate, and basalt is melted and cast for certain modern engineering applications, but you would not use it for a steam-engine cylinder. You would use iron or bronze – and like basalt, they are far, far older than SRB-composites.

If the Tufnol range and its ilk were "worse" than their un-identified "betters", they would have gone out of use years ago. The other engineering plastics and composites developed since Tufnol invented what it still sells, only add to the total range of materials available, not replace existing ones wholesale, as you demand.

Adding to gratuitously insulting a professional-grade material and its manufacturer, you end by calling any engineers – amateur or professional – who use 'Tufnol', out-dated fool. Why? Are they foolish and out-dated if they do so from understanding all the materials available, and how to select and use the appropriate ones correctly, for their intended purposes?

Is that what you intended?

Worth remembering that prior to year 2000ish Tufnol might have contained Asbestos so be careful of the dust.