Ceramic bearings

[RiverRat]

Has anyone ever used stainless steel bearings with ceramic balls for their midshaft or pump? how did they work?

I am replacing the bearings in a SN midshaft housing and it was rusted throughout. I am thinking stainless races and ceramic balls would be perfect for this application. They make sealed versions as well. Since the SN housing does not have any grease fittings I think this bearing makes sense.

Im concerned about the durability of the ceramic balls.

 

[madscientist]

ceramic is not at all what its hyped up to be. they will deteriorate at a faster rate and not the best choice for a high vibration application.

there are steel bearings that are just as smooth ( ie: lower resistance) as the ceramics. just harder to find, just as expensive.

 

[SuperJETT]

I've looked into it as well and there is a big difference in application from an electric motor to a jetski driveline. Hybrids are like 10x the cost of a normal one and full ceramic like 30x.

http://www.vxb.com/page/bearings/PROD/Kit7549

http://www.vxb.com/page/bearings/PROD/Kit7680

 

[madscientist]

riding ceramics on my skateboard vs the same quality in stainless i'll chose the stainless. they will last twice as long and spin just as smooth.

how often do you want to have to replace them?

 

[RiverRat]

ceramic is not at all what its hyped up to be. they will deteriorate at a faster rate and not the best choice for a high vibration application.

there are steel bearings that are just as smooth ( ie: lower resistance) as the ceramics. just harder to find, just as expensive.

They make ceramic bearings for crankshaft applications as well. That makes me think they would be ok for the midshaft.

 

[spence]

I dont remember the brand but my race boat had ceramic crank bearings that were around $50 per bearing. It was a spendy crank

 

[RiverRat]

riding ceramics on my skateboard vs the same quality in stainless i'll chose the stainless. they will last twice as long and spin just as smooth.

how often do you want to have to replace them?

Cool, maybe sealed stainless is the way to go

 

[madscientist]

the crank shaft is actually a less violent location and most that run them in race motors don't run a crank for very long.

 

[madscientist]

how hav you been? nice to see you on the boards more lately.

 

[Moadventures]

hybrid/ceramic, stainless bearings

been and engineer for a major bearing manufacturer for over 20 yrs.

Hybrid bearings have been around for 15 plus years in machine tools and aircraft bearings.

I would guess your failure mode is water contamination if u spend a lot of time doing freestyle?

1. Stainless steel balls/races will be great against corrosion, but the load carrying capacity is at least 1/2 less. Also, because the bearings still require good, clean lubricant--if water mixes with the grease, u still have an issue!!
These work better for skateboards because most failure are due to contamination/water.

2. Ceramic balls, steel races are better in high speed applications where lubrication can be marginal, and bearings are subject to "loading and unloading". A ceramic ball has a very low minumum load requirement so they will not be damaged if motor is reving when un hooked.

3. complete ceramic bearings--cost too much. But will work well in marginal lube applications and high speed applications. Most complete ceramic bearings are used in kilns or ovens where temperature are very high.

I have tested many types of cage materials and hybrid bearings in pumps, crank shafts, etc... in my high HP race skis.

PUMPS--I have 4 skis with skat pumps and have never lost a pump bearing. I use a standard sealed bearing with C3 internal clearance and I pack a lot of grease in the housing. Hybrid bearings are not needed in my opinion if your seals are working.

Midshaft: I would use a double sealed bearing and put plenty of grease in the housing. The excess grease will purge under the housing seal. I would not relube using the fitting supplied.

Crank bearings--stick with the OEM bearings. Their was a harmonics issue in kawi SXR race skis, so a polyamide/plastic type bearing retainer was necessary in this application. Ceramics were not necessary. I really do prefer a steel cage/retainer to seaparate the balls. They are stronger, which is needed when a motor/pump is loading and unloading in rough water.

I could get free sample hybrid bearings, and I choose not to use them......

Lastly, be careful of what u get. Very few companies know how to make good ceramic balls!! I have never heard of the company on the above link!

Ya get what u pay for.

Hope that helps.

MM

 

[SuperJETT]

Excellent info, thanks.

 

[RiverRat]

Thanks for taking the time to post. That is some great information to add to the site

been and engineer for a major bearing manufacturer for over 20 yrs.

Hybrid bearings have been around for 15 plus years in machine tools and aircraft bearings.

I would guess your failure mode is water contamination if u spend a lot of time doing freestyle?

1. Stainless steel balls/races will be great against corrosion, but the load carrying capacity is at least 1/2 less. Also, because the bearings still require good, clean lubricant--if water mixes with the grease, u still have an issue!!
These work better for skateboards because most failure are due to contamination/water.

2. Ceramic balls, steel races are better in high speed applications where lubrication can be marginal, and bearings are subject to "loading and unloading". A ceramic ball has a very low minumum load requirement so they will not be damaged if motor is reving when un hooked.

3. complete ceramic bearings--cost too much. But will work well in marginal lube applications and high speed applications. Most complete ceramic bearings are used in kilns or ovens where temperature are very high.

I have tested many types of cage materials and hybrid bearings in pumps, crank shafts, etc... in my high HP race skis.

PUMPS--I have 4 skis with skat pumps and have never lost a pump bearing. I use a standard sealed bearing with C3 internal clearance and I pack a lot of grease in the housing. Hybrid bearings are not needed in my opinion if your seals are working.

Midshaft: I would use a double sealed bearing and put plenty of grease in the housing. The excess grease will purge under the housing seal. I would not relube using the fitting supplied.

Crank bearings--stick with the OEM bearings. Their was a harmonics issue in kawi SXR race skis, so a polyamide/plastic type bearing retainer was necessary in this application. Ceramics were not necessary. I really do prefer a steel cage/retainer to seaparate the balls. They are stronger, which is needed when a motor/pump is loading and unloading in rough water.

I could get free sample hybrid bearings, and I choose not to use them......

Lastly, be careful of what u get. Very few companies know how to make good ceramic balls!! I have never heard of the company on the above link!

Ya get what u pay for.

Hope that helps.

MM