Oilite bush cylinder

This topic has 14 replies, 10 voices, and was last updated 10 March 2021 at 09:22 by Nigel Graham 2.

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7 March 2021 at 20:13 #28031
RRMBK
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@rrmbk
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7 March 2021 at 20:13 #532402
RRMBK
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@rrmbk
Hi all.

As I have a number of new old stock Oilite bushes, I was wondering about mounting one inside a suitable block , Ali possibly, by interference fit to create a suitable free running steam cylinder bore. I cant believe it hasn't already been tried by someone, so any info on pitfalls or problems encountered would be greatly appreciated .

Many thanks
7 March 2021 at 20:39 #532420
Nick Wheeler
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@nickwheeler
Isn't Oilite porous?
7 March 2021 at 20:48 #532422
noel shelley
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@noelshelley55608
As Above, it's porous, so unlikely to hold steam. Noel
7 March 2021 at 20:51 #532425
Redsetter
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@redsetter
If you can bore a block accurately enough for an interference fit, why don't you just use that as the cylinder?
7 March 2021 at 21:21 #532438
Nigel Graham 2
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@nigelgraham2
Yes, the material is porous but since RRMBK proposed using it as a liner surrounded with non-porous, solid metal that might not matter very much.

One could argue it might let steam pass from one side of the piston to the other, but I don't think it would, certainly not to any significant rate. What steam does penetrate the sinter from one side would meet that coming the other way.

The OP doesn't state what type and size of engine he is proposing, but if something like a small mill-engine rather than a 4" -scale traction-engine or a sizeable locomotive… try it!

If it doesn't work the Oilite liner could always be replaced with one machined from bronze or gun-metal bar.
7 March 2021 at 22:33 #532458
Martin Kyte
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@martinkyte99762
Why would that be any more free running than a plain bronze bush or bronze cylinder.?

As far as I understand it the point of oilite bushes is that they hold oil in the spaces between the sintered particles so creating a self lubricated bearing. All that oil is going to get washed out by the steam if no cylider lubrication is applied and if it is applied in the usual way the sintered bearing will end up containing an oil water emulsion.

If soft rings are to be used either rubber O rings or graphite packing would the essentially rougher surface wear the ring material faster. Possibly not an issue with cast iron rings but it may affect the steam seal at the ring itself.

I can't see any advantage myself.

regards Martin

Edited By Martin Kyte on 07/03/2021 22:35:35
8 March 2021 at 00:11 #532469
Michael Gilligan
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@michaelgilligan61133
Posted by Martin Kyte on 07/03/2021 22:33:38:

[…]

I can't see any advantage myself.

.

I think the hoped-for advantage was probably expressed in the opening line:

[quote] As I have a number of new old stock Oilite bushes [/quote]

i.e. Expediency rather that technical merit.

MichaelG.
8 March 2021 at 04:08 #532475
Hopper
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@hopper
Yes I would think that where oil can flow, steam will too, from one end of the cylinder to the other where it is not wanted. And the sharp edges of the bronze granules the bushing is made from would rip up piston rings made of the usual rubber o ring or teflon etc.

You'd be better off to run your piston straight in the aluminium or even steel cylinder. No corrosion issues with steel if running on air. Or you can always oil it up after running on steam. Aluminium will wear ok for light duty limited model running too.
9 March 2021 at 19:42 #532831
RRMBK
Participant
@rrmbk
Thank you all for the informed responses. It was for a simple mill engine type cylinder and as much as anything to consider uses for the bushes rather than have them go to the scrap man. I felt that the housing inside a solid bore would alleviate any porosity to exterior, and the Alloy block gives a much easier means to produce external architectural features. It also makes it very easy to achieve the interference fit due to the different expansion ratios,

I was wondering whether using steam oil with its very high viscosity would partially block the pores in the oilite and thus reduce or eliminate end to end transfer. I think Nigel G2 has got the best sloution, – try it and if not replace with a bronze or GM liner.

Thanks again for acces to the wonderful encyclopedia of knowledge.
10 March 2021 at 07:44 #532897
Ron Laden
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@ronladen17547
I was once told if you machine oilite it looses most of its porosity as the granular surface tends to get smoothed over, whether that is true or not I don't know.

Edited By Ron Laden on 10/03/2021 07:47:39
10 March 2021 at 07:49 #532898
not done it yet
Participant
@notdoneityet
Posted by Ron Laden on 10/03/2021 07:44:52:

I was once told if you machine oilite it looses most of its porosity as the surface tends to get smoothed over, whether that is true or not I don't know.

It can do but usually OK if the drill is sharp. I drilled a couple thirty years ago for a fan-shaft and they still pass oil – but definitely don’t ream!
10 March 2021 at 08:13 #532900
Hopper
Participant
@hopper
There is a lot of confusion around that topic. But Oilite's own instruction sheet says you can machine, bore and ream their bushes as long as the cutting tool is good and sharp so it does not smear the bronze granules and close up the gaps in between. Page 4 HERE

They do recommend not grinding or honing though.
10 March 2021 at 09:11 #532910
Ron Laden
Participant
@ronladen17547
I must admit, though I was told it could close the gaps I still machine oilites where needed and I have had no problems. My Shunter axle oilites I machined and they still seem fine plus my in build class 22 has some I,ve machined so fingers crossed.
10 March 2021 at 09:22 #532913
Nigel Graham 2
Participant
@nigelgraham2
Reading the above, I wonder if the common "unofficial" advice not to machine Oilite bores may be from people who have tried it but succeeded only in burnishing the pores closed.

Glad to help, RRMBK, but I'd suggest if you decide you've no use for them, don't scrap them. At least not without a Sales ad on here first for a few quid inc p&p. .
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