Aluminium cylinder blocks

Hi, I"d like to know if anyone has any knowledge of using light alloy for locomotive cylinder blocks. My reason for asking is that I want to reduce weight as much as possible to avoid having a front heavy locomotive. The loco in question is the Webb compound Jeanie Deans. On another thread I've been getting a lot of input on this loco so I am not asking for info about it but someone who is building one commented on how front heavy it was with the big cylinder up front. I remember reading an article by Neville Evans on one of his locos some years ago and he suggested light alloy cylinder blocks with cast iron liners. i don't know if he ever tried it. I have lots of alloy blocks so i have the material for nothing at hand. The problem as I see it would be how to manage the port face. I don't know if the alloy would wear satisfactorily or if it would be necessary to let in a piece of iron in which case how could it be made steam tight? I thought of loctite and I have used this satisfactorily to put liners into blocks. I don't know about sealing a flat surface though especially with the differential expansion.

Would there be any wear considering the input of steam oil?

Roger

If you used a liner in the bore and milled a recess for an iron or bronze plate into the port face you could let that take all the wear. Seen it done a few times to rescue castings where the ports were cut or cast badly.

Yes, I intended to use an iron liner for the bore but I couldn't think of how to bond the port face plate except using Loctite and I don't know whether I would get steam leakage from the inlet to exhaust. The valve chest bolts could hold it all together.

It seems a lot of work for possibly not much gain. I'd be inclined to do the maths to work out the saving before committing to metal. It might be better, and easier, to remove excess material from the original cylinder block. At least the cast iron cylinder removes potential problems due to differential expansion. The coefficient for aluminium is more than twice that of steel.

Andrew

I've driven this 4" McLaren which has the CI plate retained to the CI cylinder with Araldite and a few CSK screws, JB Weld would be another option.

I have done a few IC engines where the iron liner is just retained with Loctite in the cast aluminium cylinder and a few machined from solid aluminium too.

Hi, I don't have any cylinder castings so it's not as if I'd be wasting any. Looking at the drawings it looks a definite possibility and it would reduce the weight a great deal. Jason do you mean you have used aluminium without a liner in a I.C. engine?

This makes more sense to me, I've seen quite a few cylinder blocks machined form solid but with all superfluous material machined away. I suspect this would finish up lighter than a composite setup.

Anyway as most model locos are light on their feet, can't you just put a big lump of lead at the back end?

My late friend , Bob Darby, made several Simpexes using aluminum cylinder blocks cast from old I/C pistons. He used standard I/C piston rings running in the aluminum bore. It work fine. He reasoned the conditions in a wet steam cylinder bore were not as severe as an I/C engine, If you want to be really fussy anodize the bore.

Dave Taylor

A possible solution is to have the bores and the valve area hard chrome plated, like the high performance model aircraft engines. The challenge would be finding someone to do it.

No, Cylinders either from cast or solid aluminium, both with CI liners.

Though if you are going to have to make your own cylinders anyway then you may as well machine a lightweight one from CI or fabricate from Bronze. You should be able to keep flange thicknesses reasonably thin and the cylinder wall too which will go some way to compensating for any perceived excess weight. As Duncan says most models lack tractive weight so just put the ballast towards the rear which will stop it being front heavy.

Can you post a photo or scan of the bit of drawing that shows the cylinders?

As traction is affected by weight I would be more tempted to balance the light back end with additional lead.

Just a thought

Regards

Hi, thanks for all the input. I want to keep the weight down also to make it easier to manhandle. When you get over 70 lugging heavy locos in and out of a small car boot on your own isn't easy or a good idea. So I won't be adding lead. I have Don Young;s articles from the '70;s on constructing fabricated cylinders and if they were piston valve that would be the way to go. David, do you know how the Simplexes lasted long term? I don't know what alloy I have but it is 2 inch thick blocks and machines beautifully.

Emma Victoria described by Henry Wood in ME had fabricated slide valve bronze cylinders

I am not a steamie or a Smee, but what about aluminium bronze, good wear and corrosion resistance, light, and although expensive, you could make your own aluminium/copper alloy.

Hi John,

No, I have lived abroad for many years and lost touch with those who might know. The locos certainly worked well initially and gave no signs of cylinder problems.

Aluminium comes in so many grades and conditions that it is not possible to guess what it's composition might be from machinability or visual examination.

As far as differential expansion between the aluminum cylinder and steel or cast iron or bronze piston the main problem would probably be leakage because the aluminum bore would expand more than a steel piston head.

Referring again to I/C practice, aluminum pistons in aluminum bores with cast iron piston rings work very well and there is no reason the same material combinations should not work in a low pressure, well lubricated steam cylinder. Anodizing provides an extremely hard surface which should be wear resistant.

Dave

very little difference in density and an absolute pig to drill and tap. Stick to bronze but machine away as much as possible if you want it light

I can understand wanting to reduce weight for transport reasons, but is the locomotive really front-heavy? I'd be very surprised, since considered just as a dead-weight the cylinders would be balanced very much by the firebox.

Looking at photos of this loco, it seems already rear-heavy by having the cylinders behind the smoke-box and leading wheels, with the much of the load including the cylinders carried on the rearwards-set coupled wheels.

I would think its weight is quite well balanced, but on a miniature, aluminium cylinders might not be significantly lighter than bronze or cast-iron ones with excess metal cut away; as part of the loco's total weight..

Besides, the loco needs to be heavy for adhesion.

Get the bores hard anodised and ground, probably a costly option but better than chrome which would also have to be ground.

I don't think hard anodizing needs to be ground. The layer is very thin but very hard. I suspect it is so thin as to make grinding impractical.

My experience is that it is not so expensive if you can find a firm to do it.