Bearings

[BarryMobbs]

 I need to make some wooden bearing bushes for an old agricultural implement. They will be split and mounted in cast iron split plummer block housings. There is provision for grease lubrication.
 Does anybody know what wood might have been used originally.
 I want to use a native species and have some elm which I know was used to make wheel hubs, would this be suitable?

I look forward to your comments:   Barry

[Bryan Milham]

Lignum Vitae was the wood of choice for wooden bearings as it's hard wearing and self lubricating. Also used as Hull Glands on Ships & Boats for where the prop-shaft goes through the Hull to the propeller.
I believe it's hard to source now, your best bet is an old wooden Lawn Bowl.

Elm was used a wagon wheel hubs,

They are the two that immediately spring to mind ,you need to give us a clue as to the workload they will face to be any more specific.

[Andy Coates]

I'd go for Lignum too. At a push greenheart might also serve. If it's prone to wear I think Elm might be a little prone.

Don't forget to photograph the finished items and show us!

[Roger Groom]

Hi Barry
What about Apple? It was used in mill gearwork.
Roger G

[thebowlerhattedturner]

Hi Barry,
            like the others have said Lignum or Greenheart are good. Canadian Rock Maple was also used in industry for rollers and suchlike, it can handle grease fairly well too.
Regards
John BHT

[admalin]

Hi
I found an intersting website --- lignum-vitae.com.  There's a picture of an unusual form of bearing, presumably made by someone without a lathe.

English hardwood is not as dense as lignum(sinks in water), and it occurs to me you might benefit slightly from having the grain in line with the rotation.

From what you've said I guess the shaft is no more than about 6" dia and probably runs relatively slowly, in which case whatever hardwood you use won't make much difference. Is it for a thresher?

Tony Malin

[BrianH]

Hi Barry
What about Apple? It was used in mill gearwork.
Roger G

I did a mag article on a Dutch wind-powered sawmill, some years ago, and Roger is indeed correct in saying that apple was used to make the teeth for one side of the massive gear train but, if memory serves, it wasn't because of its quality as a bearing but as a safety feature. The opposite set of teeth would be made of (I think) hickory so that should the mill's workings go suddenly pear shaped the apple teeth would strip away, protecting the rest of the machinery.
How's that for a bit of woody trivia??
All the best
Brian

[Andy Coates]

apples and pears! Make your mind up Brian!

[BrianH]

Sorry Andy,I feel such a lemon, I forgot that members getting fruity on the forum gets on your pip.
Or perhaps its just sour grapes?
Brian

[BarryMobbs]

Thanks for your comments everyone.

I think that I will use the elm that I have as this machine is not going to do a lot of work.
I have tried to get some lignum vitae bowling woods in the past but have not been able to find any as they are now made from plastic. I think my chances of finding 16 would be very remote.

I will post some pictures when done.

   Barry

[hughie]

Its around if you really want it.
http://www.lignum-vitae.com/Products_Hydro-Bearings.html
http://www.exotichardwoods.co.uk/Woods_List/Lignum_Vitae-PaloSantowood.asp

[BarryMobbs]

Hello,
 I have made the bearing bushes as you will see from the attached picture.
There are two bushes for each housing.
Each bush has a groove on the outside diameter for a location rib and a hole to locate on the grease nipple bush.
I used elm in the end because I have some and the machine will not be expected to do any real work so wear is not too much of an issue.
Presumably when the elm gets wet it will swell up and make for a tighter fit on the shaft. If the bushes were soaked in oil befor fitting would this help to keep water out or would it cause the elm to swell anyhow?
   Barry

[Bryan Milham]

Interesting job you had there. Did you take any 'In Progress' pictures for us? I'd be interested in seeing how you made them.

Another use I remember for Elm was the making of coffins, as it resist rotting in 'damp' environments.

To throw my 2 pence worth in to answer your questions, All wood swells when it absorbs moisture so yes it will tighten on the shaft but by how much I don't know - I've seen an article on wood absorption etc if I can find it I'll post it.

By oil I presume you are talking about motor (mineral) type oils not our highly refined Danish Oils full of drying agents etc.

Again any moisture that enters the wood will cause swelling, but if it was oil I would assume that yes it would repel water/moisture to quite a high degree and also provide a lower friction, load bearing surface if the wood swells just that little too much. For Wagon Wheels I think Tallow (animal fat) was used.

[BrianH]

Another bit of off thread but (perhaps) interesting trivia from that Dutch sawmill article was that the main shaft bearing was made of stone ...yes stone... and looked like the bottom half of the ones Barry has pictured above. This bearing had apparently worked fine for about 300 years until the mill went out of use about the 1980's.
At the planning stage of the restoration one of the major oil companies became involved and formulated a super duper special lubricant for the job.
When sawing work restarted at t'mill it was found that the bearings and shaft were running hot. After much head scratching by all all involved a local butcher mentioned that the original miller had had a standing order for a certain fatty part of a cow (perhaps sheep, perhaps pig). The oil company walked away in disgust when the stone bearings were smothered in this rancid fat and began to run as sweet as you like. Inside the mill cap it now smells like an abatoir but I know where there are two drums of very expensive, specially formulated stone-bearing oil if anyone is interested.............
Merry Christmas everyone
Brian

[admalin]

Hi Barry

You still haven't told us what sort of machine the bearings are for. Having been involved in rotating machines from 1/4 hp motors to 300 MW generators, I'm curious.

Tony Malin