Oak Bearing replacement

[Shox Dr]

just out of curiosity why do they have to be wood ???

At a guess, for ease of replacement and cost, also can withstand long periods stood outside with little to no maintenance

 

[the artfull-codger]

As nick952 says, lignum vitae, used for ships prop bearings naturally oily,the downside is- [if you can get it] it's sold by weight & as it's the heaviest wood there is it's VERY expensive,probably cost more than the rollers worth!! as bs said iroko might be a good substitute as it's an oily wood & a lot easier to get hold of, one of it's uses is laboratory benches [often schools refurbing the labs throw it out] the d & t depts used to snaffle it but not anymore as it's considered carcinogenic.

 

[WorkshopChris]

Greenheart may be ideal, but nor to easy to come by. Often used for piers and pontoons. It turns well with a razor sharp hss tooling.
http://www.wood-database.com/greenheart/

 

[printcom]

At a guess, for ease of replacement and cost, also can withstand long periods stood outside with little to no maintenance

That why I was thinking of making some out of a block of Nylon or similar. If it will take the shock load it should last forever.

 

[Dieselman 63]

its grown and seasoned not made

Very true. It used to be felled then left for a year, then sawn, milled and air dried for up to two years though

 

[Screwdriver]

That why I was thinking of making some out of a block of Nylon or similar. If it will take the shock load it should last forever.

What sort of dimensions are we talking about? A big block of machinable plastic is going to cost a fair bit, it doesn't grow on trees y'know.

 

[printcom]

What sort of dimensions are we talking about? A big block of machinable plastic is going to cost a fair bit, it doesn't grow on trees y'know.

227 x 140 x 92 Yes I know its not cheap but it might be worth the outlay if its a one off job.

 

[Maker]

Does the plastic part really need to be that big? Could you make a bracket/mount with much smaller piece of plastic pressed in?

 

[julianthegypsy]

I had to pull a twose roller apart to change the bearings once. That was a fun job! The bearing was a mild steel ring welded in. I couldn't believe it. If I'd known I'd have made it myself rather than paying Twose. Disc harrow bearings were traditionally always wood, with a grease nipple. When they wore you turned up new ones and boiled them in grease. Not only were these things not maintained, they were normally left outside all year until they were needed, by which time they were buried under brambles, so it was normal to throw some petrol at them and set fire to them. I wish I could do that with my car!

 

[Shox Dr]

What sort of dimensions are we talking about? A big block of machinable plastic is going to cost a fair bit, it doesn't grow on trees y'know.

There's a guy selling All sorts of 'plastic' off cuts at Rufforth auto jumble, not that expensive.

This was 60p
75x40mm acetal

 

[GW8IZR]

I suspect something like Nylacast or Oilon would maybe work but beware that when left in one position under load the hole might go oval over a time. I use this stuff for a plate with a slowly rotating scaffold pole running through it, its not under massive load and sits in one position for most of the time. The parts need re making every couple of years.

 

[Gareth J]

Some photos.

An ~ 5yrs old twose;

An older one like that blue one above. It has been repainted yellow;

A homemade frame (not by me) for a ring roller;

looks like nothing more exotic than a bit of softwood perlin in this one. But I think the rings do most of the revolving on the shaft rather than the shaft in the bearing.

An ancient ring roller;

I don't know what is going on inside that cast pillow block. Nothing too exotic, I'd bet.

Common to all the wooden ones is either very larger washers underneath or a strip of flat between the mounting bolts. They also all have side supports so the bolts to not have to try to support the dragging force. Do yours have all these bits in place?

 

[Gareth0123]

I thought they used Lignum Vitae for the bearings.

lignum vitae ........ that's the one International Harvester, John Deere, New Holland and Fiatagri/Laverda used for bearings on their agricultural equipment.

Well seasoned and linseed oil boiled Hornbeam bearings came up in a conversation I had a few months ago......... can't tell you what it's for cuz that's a secret at the moment.

 

[Rudi McAnichal]

https://practicalaction.org/docs/technical_information_service/oil_soaked_wood_bearings.pdf

 

[Gritineye]

That why I was thinking of making some out of a block of Nylon or similar. If it will take the shock load it should last forever.

Nylon absorbs water so will rust the shaft when standing

 

[Paul.]

I've used polyethylene for bearings on wet machines, admittedly not as big as those but on some fairly heavy load bearing rollers that are running 70 hours or so per week and they work very well.

 

[Bill Edwards]

If using plastic of some description I would think that the size (cost) could be reduced considerably by boxing it in better with metal, the part that actually has to be a bearing material isn't all that massive.

I still might use my cheap pillow block bearing idea on mine though, should be so easy to do.

 

[Gareth J]

I still might use my cheap pillow block bearing idea on mine though, should be so easy to do.

Can see it surviving ok just rolling grass/vegetation. But rolling in cultivated soil is a really aggressive environment, any precision bearings would need to be really well sealed. You'll save a lot of wear on the shaft but other things will wear out before the shaft is no longer usable anyway.

 

[Keith 66]

My pennys worth as a boatbuilder! Lignum Vitae used to be used for bearings, it is the heaviest wood going & is becoming very scarce & expensive, It is self lubricating under water. Im surprised at the suggestion of Poplar as it is very soft & rots at an alarming rate outside. Oak is hard enough but the tannic acid in it will react with the Iron shaft so this is probably why it doesnt last. Iroko has a lot of silica in it so is pretty abrasive, contrary to popular opinion it is Not an oily wood not good for bearings.
Maple is a good timber for bearings if soaked in oil its hard & relatively easy to get.

 

[Bill Edwards]

Can see it surviving ok just rolling grass/vegetation. But rolling in cultivated soil is a really aggressive environment, any precision bearings would need to be really well sealed. You'll save a lot of wear on the shaft but other things will wear out before the shaft is no longer usable anyway.

The cambridge rollers at work use proper bearings, and must see at least 600 acres per year. Being freshly drilled soil it's a dustbowl, they have a tough life.
I'm soon going to have to change one out (it has six) for the second time as it's showing wear, which is four seasons it's done. That's a cheap £50 bearing and housing Chinese job.

If a cheap bearing can survive cambridge rollers for about 2400 acres in those conditions I don't see that a grass roller is going to give any trouble!