Bearings or bushed

[colin hamiltonParticipant @colinhamilton16803]

So I'm looking to make a rotisserie smoker. Not like a hog roast where the spit is passed through the animal but more like a carrousel where 4 trays rotate round. Basically a smaller version of the attached photo. It will be used at relatively low temp (max approx 180). As with all my builds its about recycling so I'm looking for 'good enough' engineering and the opportunity to make bits. So far it's a barrel for the cooking part and a cut down gas bottle for the fire box.

I'm considering the main bearing options. I've got some spare bearings so was thinking of making some housed bearings which I would bolt onto the outside of the barrel but I'm a bit worried about the temp. Would bushes fair better? If yes would aluminium do (I already have some).

The main shaft us going to be 19mm pipe and it will be rotating at about 3 rpm.

Thanks Colin ⁷

[colin hamiltonParticipant @colinhamilton16803]

[HOWARDTParticipant @howardt]

Ball bearings have a maximum operating temperature usually around 60deg C, and any grease content will run out. Plain bearings would do, even steel on steel with slow running, probably more than adequate for the purpose.

[AdrianRParticipant @adrianr18614]

You could always use a dry lube like Graphite or Molybdenum Disulphide on plain bearings

[SillyOldDufferModerator @sillyoldduffer]

Posted by HOWARDT on 31/05/2022 20:15:41:

Ball bearings have a maximum operating temperature usually around 60deg C,…

I hope that's not universally true – my car engine block runs hotter than that!

But I agree about plain bearings. Apart from the temperature, the bearings in a garden rotisserie have a slow lazy life. Sounds ideal for a steel shaft running in self lubricating cast iron. However, I'd be tempted to try Aluminium for cheapness if the design allowed them to be easily replaced if they seized or wore badly. Smearing the journals with Graphite would provide enough lube.

Dave

[old martParticipant @oldmart]

Plain bearings would be best, and if you are concerned with temperature, you can get a tube of ceramic bearing grease which will be more than adequate, and plenty left over for other jobs.

[John PParticipant @johnp77052]

Aliexpress sell full ceramic bearings for somewhere around £4 each depending on size some will work up to

800 C only at low rpm (200) there are hundreds of them , type in " ball bearings high temperature" to scan through,not able to put reference on here as it will be taken down.

John

[Martin KyteParticipant @martinkyte99762]

Whats wrong with a between centres arrangement. Easy to dismantle.

regards Martin

[bernard towersParticipant @bernardtowers37738]

Lubricate with chicken fat!!

[Nigel Graham 2Participant @nigelgraham2]

Oh, this doesn't need anything too fancy especially if the shaft's bearing surface is just the raw pipe surface, but remember to lubricate the bearings well with grease before storing the rotisserie, as well as prior to use. Especially with aluminium bushes.

[Ex contributorParticipant @mgnbuk]

Graphite bushes, run dry

Nigel B.

[HopperParticipant @hopper]

3 rpm? Steel on steel should be fine.

[Paul LousickParticipant @paullousick59116]

A BBQ is always covered with fat/grease after cooking. So self lubricating. Steel on steel bearings will probably outlast other parts of the grill.

[colin hamiltonParticipant @colinhamilton16803]

Brilliant thanks for the responses. Looks like I have plenty of options.

[not done it yetParticipant @notdoneityet]

Do you have a suitable motor for this project? 10HP would easily cope. Possibly just a little smaller?

Motor speed might be important? 2 or 4 pole motor? Two pole at 2800rpm might be the best?

Three phase with VFD or a brushless DC might be best for wide speed variation choices?

Add to this lot the huge fan required, to supply the combustion air, and you are nearly home. Automatic. ash pan, grate clearing, etc might be a high priority?

Might also need a chain saw to cut down the oak trees for the smoking chips. Saw can be electric, of course – better for the environment than using fossil fuels.

I think bearings are likely fairly low on your list of priorities.🙂

[colin hamiltonParticipant @colinhamilton16803]

Posted by not done it yet on 01/06/2022 09:43:49:

Do you have a suitable motor for this project? 10HP would easily cope. Possibly just a little smaller?

Motor speed might be important? 2 or 4 pole motor? Two pole at 2800rpm might be the best?

Three phase with VFD or a brushless DC might be best for wide speed variation choices?

Add to this lot the huge fan required, to supply the combustion air, and you are nearly home. Automatic. ash pan, grate clearing, etc might be a high priority?

Might also need a chain saw to cut down the oak trees for the smoking chips. Saw can be electric, of course – better for the environment than using fossil fuels.

I think bearings are likely fairly low on your list of priorities.🙂

Yep the things you mention I already have got covered off from when I built my hog roast machine. I'm really interested in improving the bearing set up hence my question but thanks for your input

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