Tufnol - cylinder block?

I have got a substantial block of tufnol lurking under the workshop bench and just wondering whether it could be used to make cylinder blocks, suitably lined.

Mick

IC, steam or air  ?

Edited By roy entwistle on 30/04/2020 10:06:52

Thinking of steam Roy. About 60psi.

Mick

Mick I don't see any problems, but someone else might

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

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

Ah, but just to add to the fun... There is "Tufnol", and there is "Tufnol".

If the piece you have still has the type-label then you can find out its characteristics, but the name "Tufnol" covers a wide variety of two basic classes.

They are SRBF and SRBP: Synthetic Resin-Bonded then respectively, Fabric and Paper. The two are easy to tell apart.

The Fabric shows the weave, giving it in certain angles of section a slightly wood-grained appearance that could even pass as wood on some model-making applications. I have seen it used very effectively for the hand-wheels on miniature steam locomotive manifold valves.

The Paper variety lacks that obvious grain.

They are made in various grades to suit classes and conditions of use, including for the SRBF at any rate, mechanical components such as gears and worm-wheels, bearing bushes, etc. The grades are named, by a rather curious aquatic theme.

A quick look on't www shows the materials are still made, by the company of that name, proudly saying these composites are a British invention and made in Britain! So it should be possible to find the properties, but unless you can identify the specific sample you'd have to err on the side of caution, treat it as the nominally-least suitable for the application and see if you can compromise on working conditions to keep the cylinders made from it, happy.

Also note how you might fit the cylinder covers etc. You can machine most grades of Tufnol though the Paper types chip easily. The problem may be that threads cut in some grades might not be cope with the tightening and operational loads on studs, etc.: I would think the Fabric grades, some of which are based on cotton, would be stronger in this respect.

I should add I don't work for Tufnol, but became quite familiar with using some of the grades at work, though years ago so I cannot now name them.

'

Dave mentions the softening temperatures of plastics. Whilst SRBF / P are classed as plastics they are thermo-setting rather than thermo-plastic. The resin does not soften as polythene or Nylon would, but will still degrade if heated above its operational limit.

Regarding temperature ranges, you can find pressure / temperature tables for steam, and I would go by the boiler pressure unless the engine is to use superheated steam - which complicates the question!

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

I originally asked this question because I have a big lump of Tufnol ( 9x6x2" which has been sitting under the bench for a few years now and apart from a small offcut to make a repair has been unused. On another note, I recently built a two cylinder marine engine with a solid brass cylinder block which has heat loss issues. Putting these two thoughts together I wondered whether a suitably lined Tufnol block might be feasible. As far as stud fixings go, I can forsee no problem with appropriate inserts. A Tufnol retailer has identified my block as Whale grade which has a working temperature up to 130C which would only give me a working pressure in steam of about 25psi so I think the idea has fallen at the first hurdle as far as steam is concerned. So what can I do with my big chunk?

Mick

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

And as a reminder, NEVER use Tufnol Rod/Bar to make gears.

Regards Ian.

+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

I know that Tufnol is not suitable for normal compressed air pistons (about 80lb/ins^2). Water gets into the Tufnol. I would imagine steam would have the same effect..... but... how long will the cylinder run? It might work for a reasonable period.

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?

.

1. Determine, with some certainty, what grade it is
2. Check the prices on ebay
3. Sell it and buy something you want

MichaelG.

.

Spot check, just now: 

https://www.ebay.co.uk/itm/40-MM-X-100-MM-X-62-MM-TUFNOL-WHALE-OR-EQUIVALENT/193498381034

Edited By Michael Gilligan on 06/06/2020 10:41:52

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

.

Nigel,

The answer to that question about gears will be found here: **LINK**

https://www.tufnol.com/technical/tufnol-gears.aspx

Just one of the many excellent items of technical information generously provided by a repected company.

MichaelG.