Setting Clearance on steam engine bearings

How were split bearings on old steam engines (late 18th - early 19th century) adjusted. I mean the type made for crankshafts etc. not the type adjusted using a cotter and wedge.

Presumably the outer cast iron shell would be made undersize so it could be closed up to accommodate bearing wear, otherwise you would have to replace the brasses every time they wore.

Did they use shims or would they have used something malleable like soft lead sheet? Or something else like thin wedges?

Neil

Neil,

Steam engines use a split, 4 part bronze bush for the crankshaft bearings.

The screws on the side adjust the clearance with the crankshaft and are also use to align the crankshaft so it is square with the piston rod.

Shims are added under the retaining cap for vertical wear adjustment.

Paul.

Edited By Paul Lousick on 17/10/2017 13:17:32

Thanks Paul,

That's a specialised arrangement I have never seen used on a real engine. I imagine it might be seen on a big relatively late engine but the sort of engines I'm talking about have much more simple split casting arrangement like here:

I'm assuming shims would probably have been used but in the 1800s you coudln't by packs of shimstock off the shelf.

Has anyone here ever had a 150 year old engine apart and seen what is actually in the gap?

I've restarted work on a model of an early 19th century engine and I am wondering what to use; in models we usually just make the bearing block a close fit, but if I can stick a shim or a twist of lead wire in there, I don't see why not!

Neil

I've no expert knowledge of bearings from olden times, but weren't some made by casting white metal, or Babbitt "in situ" around the shaft? Cut them in half, and hand- chisel the oil grooves.

Don't make them like that any more!

Don't know whether he's still operative, but Stanley Challenger Graham on this site www.oneguyfrombarlick was very much involved in old stationary steam engine renovation and would very likely have chapter and verse.

rgds

Bill

Neil, here is a picture (not a very good one) of the 4 part crankshaft bearing on a Burrell portable.

Brian

Those old chaps had some difficult problems to solve! I've no idea how they did it but this link might help.

The two diagrams at the end of the hyperlink (Figs 12 and 13) both look like simple forms of what my copy of First Year Engineering Drawing (1933), calls a 'Marine Type Connecting Rod End'. It's the only type of con-rod bearing that doesn't have a cotter, the others ('Sliding Strap', 'Fixed Strap', and 'Box End), all have them.

The book shows other bearing variations being used for connecting links. One of them is similar to that in your stationary engine picture; it has an internal cotter.

I can scan the pages if you want.

Dave

Hi Niel.

I have placed 6 scans in a photo album bearings. they are from " Handbook on the Steam Engine" Dated 1893 but translated by HHPPowles from a german original by Herman Haeder . A very interesting book if you should ever find another copy !!

Hopefully they will give you the answers you need.

Thanks folks.

I think this is the one that is most likely to be right:

The method for side to side adjustment is as used on Tubal Cain's Lady Stephanie. He doesn't use the up/down adjustment.

I haven't come across any (many?) models with the more complex block shape, but it's tempting to go this way instead of the usual split on centre line you see in most models.

I note it says: "[to prevent the upper brass from clamping down on the journal when the cap-bolts are tightened, filler sheets to the thickness of the saw cut have to be placed between the two brasses; these can be partially removed to allow for wear]"

so shims should be used, but on the brasses themselves not the housing.

The Pollit & Wigzell has a bearing split into three sections and seperated by wood shims at points A & B.

My model of Agnes has a similar setup.

Phil

I think the examples most people are finding are late 19C engines or later; I want to know what was done in the early days.

Some of the early Fowler Ploughing engines used the octagonal bearings on their shafts which were about 1873.

Real question is whether you will make proper octagonal bearings and housings or just have octagonal flanges

Several of the hit & miss engines I have done suggest putting shims between the bearing halves before they are bored so you can take out a shim and rebore of scrape when they wear. 

Edited By JasonB on 17/10/2017 18:41:00

Good questions!

The engine I'm modelling has round flanges. It';s very hard to see what level the 'pillow block' is split at.

You can often find that the pillow blocks are split on two levels so the split you see either side of the flanges is not always where the split is around the bearing

I think that's the arrangement I should be looking at. See the image I posted higher up.

I doubt many are really spilt straight across the middle although this is how 99% of models are made.

The 'plan' doesn't give much detail, but I think there's a hint of a split above the centre line:

Think I'm a bit late posting, took these yesterday, these are bearings from an engine from around 1880 with the block split at two levels. No sign of shims, probably long gone if they existed, but it's certainly good for a few more years of service.

Peter

In the glass trade we use lead foil and gold size to back mirrors. Old Mo (the mill and engine wright) would pinch the off cuts to shim his bearings. He wouldn't use brass or aluminium foil, only lead or copper.

I saw a variation of the split bearing at the weekend. This was on a Marshall portable engine and one bearing was split in half horizontally and the other was split vertically but the split was offset.

I spoke to the restorer and he explained that the bearings could be adjusted in both directions to line up the crankshaft perfectly. The adjustment was carried out using screws to move the bearings and lock them in position. I took some pictures but it is difficult to see the splits because they are obscured by the housing and the oil. The spinning flywheel didn't help much either!

Brian

Thanks all,

Peter's photo are particularly useful, also the comment about lead/copper foil.

Why am I left thinking I've made more work for myself...

Neil