Titanium in ball bearings?

Hi,
I am a recent graduate of mech eng. (2 and a bit years) and an very
experienced inline-skater. Occassionally these two worlds colide
(engineering and skating) and people look to me for
engineering/science answers to their inline-skating problems.
Anyway, I came across something that I had to question myself, using
Titanium in (minature?) ball bearings. It seems that some companies
are trying to sell 608 designation ball bearing (8mm ID, 22mm OD, 7mm
breadth) with balls that are either made of titanium or titanium
coated.
Does anyone know of any reason you would use titanium as a ball
material for a bearing application such as an inline skate/roller
skate or skateboard wheel? Is this just a shifty marketing ploy
because these days everyone knows that the strength to weight of Ti is
superior to chrome/stainless steel? The justifications I have come
accross are the strength to weight and lower thermal expansion, but is
this really that advantages where the many of the apparently good
bearings for skating have plenty of clearance from ball to races for
expansion?
Are there other applications where a ball bearing with Ti/Ti coated
balls would be used? What are the pro's and con's of titanium balls
for ball bearings?
Thanks in anticipation,
Corey
Reply to
Corey Gibson
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I'd be willing to be money that the biggest advantage is that they get to put the word "titanium" on the packaging... Even if it meant lower life overall.. how many would get sold before people caught on?
I've never though of Titanium as a bearing material.. maybe someone has thought of something new? (Besides the carpet baggers I mean =)
Al...
Reply to
Alan Adrian
A TiN coat is accessible, cheap technology that may help wear resistance to infiltrated grit? (I'm reaching here)
Brian W
Reply to
Brian Whatcott
The problem with Ti alloy is that it can't be made hard. It's stretching to reach a hardness or Rc 35 with Ti. One advantage would be corrosion resistance as most hardenable metallic materials corrode rather easily. Ceramic balls are possibility but are not tough and would probably break on the fist bump.
Coating a steel ball with TiN will give a ball a thin hard surface that will be gold colored. The coating is very thin and probably would do little for performance. It would however, allow a hook for advertisement.
A few years back I tested 60-Nitinol ball bearings. Rc-64 and highly corrosion resistant. These are still a few years away from large scale production.
Dan

Corey Gibs>
Reply to
Dan
As I recall, Ti is TOUGHER than steel--better impact resistance. I could be wrong, but if not, that's a good reason to use it. Roger
Dan wrote:
Reply to
roger
Tough isn't enough... it needs to be hard as well... if it is deforming (like an underinflated tire) it will get pretty warm... and if it wears faster...
Al...
Reply to
Alan Adrian
A couple of questions... What about the interaction between the ball bearings and the races that they rotate in? If your balls are hard/tough enough will the (probably more expensive) races wear out while the cheaper balls survive?
You are able to identify that your ball bearings are becomming worn and than replace them? When I skated (before I got tired of falling on my ass so much) I replaced bearings as sealed, lubricated, units- not as individual balls.
Why not put these Ti bearings in one skate and conventional bearings in the other and compare performance?
Richard
Reply to
Richard
Since you mention this, I thought this interaction was reasonably well documented (such as in Rolling Bearing Analysis by Tedris Harris formerly of SKF).
No, no one ever replaces balls only. But 608 bearings are available in many 'flavours', including chrome steel balls, stainless steel balls, ceramic balls, 'titanium' balls (which I now understand to be TiN coated), steel sheild, rubber coated non-contact sheild, rubber contact sealed, steel cage, delrin cage, one or two sheild, servicable and non-servicable and probably more. Also, you can now use a 688 (8mm ID, 16mm OD, 4mm breadth). You can also get the standard 7 balls, 8 balls and now 6 larger balls.
The only thing that remains the same fom bearing to bearing is steel races, and in 25 years of skating, this is often the weakest link. The outer race pitting is the main thing that casues failures in this application.
That would probably be like weighing two almost identical items in each hand. There's is to much 'phsycological interference' for performance evaluation and it would take ages to yield results relating to failure modes.
Corey
Reply to
Corey Gibson
Clearly, the TiN coating contributes 'zoom factor', color, and not much else, save maybe a little corrosion resistance.
Outer race pitting rings several bells for me:
- Skate bearings seem to be mostly shielded, but not sealed, leaving them accessible to any water that comes along.
- Open and shielded bearings are normally sold with a thin coating of flushing/ preservative oil, that is neither water- resistant, nor a particularly good lubricant.
- Common ball bearings are intended for applications where the outer race is inserted into, and supported by, a machined cavity in a rigid material. Plastic skate wheel hubs are not rigid relative to a bearing race, so the loading conditions on the race are not the conditions built into the bearing life equations. Every time a ball rolls over a given point on the outer race, the race is subjected to a bending moment, greater than it would see in a proper housing, and a bit less than it would see if the bearing were being used as a cam follower.
-Mike-
Reply to
Mike Halloran
[snip]
[snip]
Perhaps there is a mis-statement going on. Ceramics are often used for the rolling elements so perhaps they are using a titanium ceramic such as titanium diboride. I did a quick search and only found it used in armor and for wear surfaces. However that does not mean that someone hasn't used it for rolling elements on bearings.
Reply to
Anthony Garcia

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