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Ceramic Roller Bearings?
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Posted by: xenasdaddy
Ok, not sure if this should go in this forum, but here goes.
I used to be very heavy into 1/8th scale nitro R/C car racing. In R/C engines in particular, we would frequently use ceramic ball bearings. These bearings according to such bearing specialists as Boca, increase performance due to their lighter weight, have the ability to withstand higher operating temperatures and endure greater loads, require less lubrication, are virtually corrosion resistant and almost impervious to wear. This is in comparison to steel bearings. The cost compared to stainless steel was typically at least double and in some cases triple.
My question is, is it not practical to produce ceramic bearings such as the roller bearings in a lower shock linkage where loads are very high and lubrication seems to diminish quickly? Does someone already do this and can we purchase them? Or, is there a reason besides cost that steel would be better? What about carbide?
Thanks, and I apologize if this has been asked before although I could not find it.
XD
Posted by: Rich Rohrich
Our shifter kart friends at RCE Racing certainly seem to think there is value in using silicon nitride ceramic ball bearings for the crank mains 
http://www.rceracing.com/lowfriccerbe.html
It would certainly be interesting to see if they would provide an advantage in an environment as harsh as the shock linkage.
Posted by: Jaybird
There are basically two methods of mfging roller bearings. Full Ball Compliment bearings have the race almost completely full of balls, probably one ball short of a full race, in other words. Retainer type bearings have a cage that holds a lesser amount of balls symmetrically in the same race. Typically in industry, full ball compliment bearings are preffered because they have more ball surfaces distributing the load. From what I can gather, ceramic bearings are all caged in a U.H.M.W. plastic cage. I assume this type of retaining helps the "load" factor of the ceramic.
I'd sure like to hear an engineers take on this.
Posted by: xenasdaddy
Hmmm,
As a chemical engineer I am definitely NOT up to date on the latest materials engineering standards. I did do a little internet research though and found the following: (None of the following quoted material is my own information)
"Silicon Nitride Balls are a relatively new material suitable for applications where high loads, high speeds and extreme temperatures are factors. Long life and the need for no lubrication makes this material very suitable for aviation applications. Silicon Nitride is anti-magnetic and resistant to corrosion by most substances."
"Silicon nitride is one of the new structural ceramics developed for its high mechanical strength at room temperature and elevated temperatures, and high fracture toughness."
"Silicon nitride is stable in air to 1650°C. It is inert to mineral acids, aluminum, lead, tin, zinc, silver and gold."
"Major development effort is taking place in the use of silicon nitride in gas turbine engines to achieve a more efficient, less troublesome engine. Examples of such applications are combustion liners, rotors and stators, and glow plugs for diesel engines. Other uses that take advantage of its high mechanical strength and wear resistance are represented by wear resistant seals, metal forming dies, cutting tools, gasifier turbine tips, and rocket nozzles where critical orifice dimensions are maintained despite high velocity abrasive particles."
Hence, it seems to me that these types of rollers would be incredibly durable in our shock linkages and wherever else we experience high loads, etc. I must be missing something because as I said earlier, the price is usually only double or so that of steel balls.
Hmmm, perhaps it is possible to purchase a sealed race with ceramic balls installed that has the same OD as the ID of the outer part of the linkage holes (where the seals press in) and press fit them into the linkage? Probably too many tolerance problems there though I guess? You could still use the stock roller pins on the inside of the linkage also. the ID of the ceramic race bearings would be the same as the ID of the stock linkage with roller bearings installed.
I do not know. I guess I am just thinking out loud about how to make this weak link a little more troublefree.
XD
Posted by: marcusgunby
Seems like you are ready for a KTM.
Posted by: dirt bike dave
KTM doesn't have a shock linkage, so no need for linkage bearings. No linkage may mean better quality on the Austrian bikes, but I'll bet it is cheaper, too. :D
Seriously, dirt bikes seem like a great application for these bearings if the cost is at all competitive. Maybe we'll first see them in the aftermarket.
Posted by: RoadRunner
When I split the cases on my KTM today I did notice that instead of roller bearings on the crank it has a sort of plastic cage bearing housing some sort of non-magnetic rollers....Said made in england? Also, I've never seen a KTM tranny open before, and let me tell you.....KTM likes cage bearings! Every shaft, gear, shift drum, gear selector...all of them have cage bearings like little wrist pin bearings on them. Looked alot more impresive than my KDX tranny. I was also surprised at the large size of the shift drum, which appeared to be investment cast. Wierd stuff.
Posted by: EricGorr
I've installed RCE Racing's ceramic main bearings in several CR bike and shifter kart engines. The intened benefit is that the there will be less heat transfer from the bearings into the cases, cool cases enable a denser charge. The bearings are sealed from the outside too so it gives extra protection from crankshaft seal failure. So far the lower ends are lasting longer than usual.
I got a letter from CBR bearing company and they're testing a ceramic needle bearing for the connecting rod. No word yet on that potential new product.
Posted by: cr-man
In general Eric how much longer are these bearings lasting?
My YZ 125 will probably need main bearings this winter and I'm thinking of
going with these. Is RCE the only company selling these bearings? I ask this
because they don't make them for 250 and larger bikes.
Thanks, Joe
Posted by: EricGorr
The RCE bearings are made by NTN a popular manufacturer. I don't know how long they last but considering they don't require oil I'd venture to say that they'd last longer than you'd wanna ride a 125. I'm sure they make them for 250s too.
Posted by: freakystyley
I would hope they last longer than "conventional" bearings...seeing as how full ceramics can push upwards of $100 each unless there is a lower $$ supplier somewhere! hxxp://www.vxb.com/page/bearings/CTGY/FullCeramicBearings
~I think the biggest benefit would be as Eric stated in a race situation with lower case temps, etc. where every edge counts.
The only thing I would worry about is the HDPE (plastic) cages found in some bearings-side to side movement may increase with use seeing as how you have a very hard surface (ceramic), hard outer race and softer plastic cage. Something will give sooner or later.
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