Nylon ballbearing problem

Remember the steering head bearings on your bicycle as a kid... When you tightened them too tight (even with just a strong hand) it deformed the bearing and got lumpy.

Just out of curiosity, why did you use nylon bearings with a SS shaft? Nylon probably has some great properties, but withstanding compression from a preload nut while still acting like a bearing is probably not one of them.

(If completely out in left field, I applogize, this is just from my unsophisticated, sales side perspective.)

Sounds logical to me, but I also have no bearing experience ;)

Tim

-- In the immortal words of Ned Flanders: "No foot longs!" Website @

Your experience has no bearing on the subject!!!

: )

Davrodiver

ballbearings.

There's a really good reason why very hard materials are used to make bearings. In most cases the harder the better. As you have discovered nylon ball bearings are only low friction at very low loads. You preload very likely exceeds the bearing rating without the applied load.

A ball bearing only has a single point of contact at worst, and a short line of contact at the very best. It takes very little load to deform the ball creating a flat on one side. Nylon when deformed like that also has a tendency to take a set where it is. So you bearing may feel nice and smooth when you first pre-load it. A day later it could be really rough.

Gary H. Lucas

"Gary H. Lucas" wrote in news:03IRa.5326$ snipped-for-privacy@nwrdny02.gnilink.net:

This is one of the reasons they recommend sleeve bearings usually if you need plastic in linear guide systems. These will have more contact/load bearing area for the same LxWxD

Dear Alex:

And lest you think you can reverse the problem, and use metal bearings on a nylon race, don't. You have been discussing polymer-metal systems here for a couple of weeks. No one had any idea you were going to try ball or roller bearings for this.

Understand that bearings *don't slide* if they are doing their job correctly. Having a low coefficient of friction for a roller system is a bad idea. The point of contact is supposed to propagate linearly and smoothly around the face of the roller. The grease in roller bearings, more than anything else, is carrying heat and contaminants *away* from the point of contact (and some very small amount of load when it is really moving).

David A. Smith

I am so ashamed I used Nylon bearings. :)

was there a specific design reason for using Nylon - ie because of corrosion aspects or something ??

if corrosion is a problem then ceramic bearings are possibly a viable option..?

ss

I was looking for a cheap solution.

Alex, Isn't it amazing how much cheap solutions can cost? The question is, are you trying to build something that will do something you need done? Or are you trying to design a prototype of something that you want to sell? If it is for something you want for your own use and you don't need lots of them then you shouldn't waste too much time trying to make it cheap, it'll only cost you more. On the other hand if you are building a prototype it is often more important that it work and prove the concept is feasible than to truly represent how it will ultimately be manufactured. Picking a manufacturing method is one of the things you do AFTER you have working prototype, AND a marketing plan that establishes the potential market size and price point. What is cheap at one level of production may not be nearly as cheap at some other level of production.

An example that always amazed me. A guy showed me a little slide switch they used in a product. The samples were purchased at Radio Shack for 79 cents a piece. They priced everything out at the 10,000 piece level and got that switch for 1/2 cent! The company closed up though. There wasn't nearly enough market for the 10,000 units they started making.

Gary H. Lucas

Don't be ashamed. Just don't do it again :-)

Note the previous comment. I corrosion is a problem then maybe a ceramic system would do the job

Mark Rand RTFM

It's a prototype, pay more later. So do you have constant velocity grease? Like the front wheel drive of a car. This grease is not wheel bearing grease. CV joint grease is not really a lubricant, in that it breaks down due to contacting forces that grind up with enough pressure like a wheel bearing grease. A single point on all contacting area, rather then the area itself, the ball bearing should get the least moment to make contact to the joining surfaces. You want it to ride the guide instead, right instead of distributing contact areas that absorb heat.

John

Do you know if anyone manufactures ball bearings with the groove on outer surface, so it can roll on the rod?

Thanks, Alex

wrote

What diameter and how many do you need? (Sorry if I missed that on an earlier post). I used to work for a company that molded a grooved roller around a bearing and I may still have a few samples around. If they work, they are already tooled up for it.

Something like: inner diameter : 5mm outer diameter : 12mm width : 5mm

Sizes doesn't have to be exactly as above. Anything close to that we'll work for me.

BTW I am >

Alex:

Nylon is pretty damned hard as plastics go, unless you get into the more exotic ones. Fiberglass is stronger.

Don

Dear Alex:

Glass-filled anything will be harder. PEEK is pretty resistant to lots of things, but is not really "moldable". The problem is that plastic makes a very poor roller-type bearing. If you can't use it as a slide bearing, you might try something else. Say a scissors array, to achieve your linear-and-parallel motion.

David A. Smith

I recommend that Gary, the OP, and people with a similar desire (like myself) to search the Google archives of misc.business.entrepreneur and misc.business.marketing for relevant articles. I also recommend the book _Bringing Your Product to Market_ by Don Debelak (Amazon link below). Engineers and inventors tend to go about things in the opposite order than an experienced business person would, e.g., we patent and design it then try to find out what the market really wants. One of the main thrusts of this book is to conserve your cash, going step by step to find out if there is a market for the product, what the distribution channel would be, what kind of markup the channel would require, packaging, etc. Of course, there are always exceptions; someone always strikes it rich. But they do in Vegas, too.

Bringing Your Product to Market on Amazon:

Rob Campbell