Weather resistant low friction miniature bearings

[Gina]

I'm looking for anyone with experience of miniature low friction bearings?  I am looking at bearings for the wind sensors for my weather station.  Previously I have used miniature ball bearings but being in damp conditions (even though well shielded), these have corroded.  Probably oil (which collects dust) could be washed out and replaced with dry PTFE lubricant but I would still need SS bearings and I can't find these in miniature sizes.  I'm wondering about using PTFE tubing eg. Bowden tube 2mm ID and 4mm OD and either 2mm SS bolts or round rod.

Any thoughts, please?

[Gina]

Thanks Kev they look good.

Edited July 1, 2020 by Gina

[Chriske]

I'd go for PLA.

[Gina]

Do you mean a hole in a PLA part with a stainless steel bolt?  We need very low friction.  Could easily try it though.

Edited July 1, 2020 by Gina

[Chriske]

Hold on, I make quick drawing...

[Gina]

If I can get a reading with a Force 1 - light air, I shall be well satisfied.  That's 1-3mph.  Anything less is Calm anyway.   I get that with nice new ball bearings.  I'm thinking of reading wind speed in integer mph anyway.  Accurate enough.

[Chriske]

Keep it simple, cheap and sturdy at the same time.
You most likely have all the component in house.

Print a tube with a hole(grey)
At the bottom of the tube place a small piece of brass or other material. In the centre of that piece of metal drill a very shallow hole. In that hole place a small ball, you need to crush an old (broke) ball bearing. Fill that compartment with grease. Put axis with a (very)flat bottom on top of that little ball and your done.
No ball bearing at hand : drill a hole and tap - M8 or so- put a fitting bolt with a pointy end upward in that (grey)main unit.

[Chriske]

The red is a safety ring fixed onto the axis, to keep it from flying away during storm.
The blue cover is also fixed to the axis to keep water out of the unit. It needs to be lowered of course.

[Chriske]

[Gina]

I think I shall use something like that for the wind vane but I was hoping to have the anemometer underneath.  That arrangement will only work for something on the top.  I could have the units side by side rather that one above the other though as in my original design and like the ubiquitous Fine Offset WS.

Edited July 1, 2020 by Gina

[Gina]

I have steel bearing balls that I used in my Marble Machine of about 12mm diameter.  The current wind vane has a 5mm hole for an M5 bolt and I think I'll try the same with PLA bearings and bearing ball at the bottom with the bolt head resting on the ball and the ball resting on a flat plate (something hard preferably, or maybe PTFE).

OTOH I think those balls are a bit big and they are not stainless.  I think it may be worth buying some smaller stainless steel bearing balls - only a few quid.

What size of bearing ball would you recommend please @Chriske

Edited July 2, 2020 by Gina

[Chriske]

Any steel ball is ok, I'd use a somewhat bigger ball. See to it that the ball is fixed(not glued) in the centre of the device. Make a shallow pit in the bottom preventing the ball rolling around at the bottom.
As long as you insert lots of grease in the device. It'll do the job for years to come. Don't use that thick grease that will stiffen up when it gets colder.
Did you already drew the device, how will it look like..?
 

[MarkAR]

Hi Gina, I think the smallest BB you can get away with. I can send you a selection of small ones down to 5/64"

I would also consider using a light oil rather than grease. Something like the sealed design above would allow you to fill the bearing cavity with oil.

[Gina]

Hmm...  Two opposing answers about ball size and grease or oil.

If the cavity is filled with grease or oil a SS ball would not be necessary.  I would worry about grease getting stiff when we get frosts.

Another point - if filling the cavity with a light oil I could use a standard 5x10x4mm standard ball bearing I already have though a single bearing ball resting the the hex hole in the bolt head has appeal.  That means the ball turns with the bolt and the ball to flat plate forms the end bearing.

@ChriskeI'll draw a model with the 12mm (or 1/2" ball I already have).

Edited July 2, 2020 by Gina

[Gina]

Actually that bearing ball is 14mm not 12mm.  I see I should also have 9.5mm bearing balls from searching my Amazon purchases.

[MarkAR]

33 minutes ago, Gina said:

Hmm...  Two opposing answers about ball size and grease or oil.

Yup, my way of thinking was smaller ball = less friction and lighter oil = less resistance.

The 5 x 10 x 4 would work well in an oil bath.

Also if you need anything machined on a lathe, let me know. Might be able to help.

Edited July 2, 2020 by MarkAR

[Astrobits]

If I was designing something like this I would make sure that it was easy to maintain/repair using the simplest, readily available, components possible as a first requirement. Any friction implies that there will be wear that will eventually cause the component to malfunction so the easier it is to replace the better.

Nigel

[Icosahedron]

These do not require lubrication.

[Gina]

Bearings decided.  I'm going for an SS ball bearing for the anemometer.

S605ZZ EZO Stainless Steel Miniature Bearing 5x14x5 Shielded

 

[Gina]

For the wind vane where slow and back & forth motion is involved I'm going for PLA sideways bearings and a point contact single ball on a hard surface.  The ball is a 14mm chrome steel bearing ball and the hard surface is a Neodymium Magnet (these are coated with a very hard material).  Lubrication will be Liqui Moly 3510 LM 47 Long-Life Grease + MoS2 100 g

This is the basic arrangement.

Still developing the wind vane sensor and bearing unit but this is getting near.  8 reed switches held in holes.  The weather hood will have a magnet to operate the switches.

Edited July 6, 2020 by Gina

[Gina]

They have rounded front edges.  (Can't play your video because the sound isn't working on my computer ATM).