Jerry,
For clarification, do the SS bearings have SS races and steel *****, or SS races and SS *****?

Based on all the data provided so far it looks like the best solutions would be to switch to a roller bearing if possible or to go with the factory 6303 bearing and the factory size, or larger, idler pulley with a longer belt to fit. That would keep the Idler at the acceptable rpms and make it last longer. We still need to do regular checks on all bearings to catch them when they start to fail and not after they fail. Factory bearings are cheep enough, keeping a couple factory bearings on the shelf at home sounds like a prudent thing to do.

MikeR

 

I can see that it is thicker on the belt face, its the other face that looks the same. The radius looks a little bigger, It should be as big as the WP flange allows. That radius has to support the belt face, all the flexing is acting on that radius and the side wall.
I always go by the rule that you make things as strong as possible within reason. Taking off less material saves time and you have less chips to get rid of. As my previous post states steel is a better material.

Bearing's
Roller bearings are out because of the RPM's involved. They heat up too much.

Stainless steel bearings are all stainless steel construction, using different grades of stainless for ***** and raceways. I do not think these are as good as the regular steel in this application.

The best steal bearings I can see are those that are used stock #6303Z or ZZ not RS or 2RS If two bearings can be used in a redesigned pulley that is better. Grease lubrication not oil, oil will need to be added too often as it will come out of the seals.

Ceramic Hybrids would be the other choice again using the Z type seal.

Different makers bearings are used because they are purchased by the idler manufacturer on a cost basis. It boils down, as most things, to $$$$

The bearing 6303 is a standard size (17mm ID x 47mm OD x 14mm wide) and variations of it exist, material, seals etc eg. SS6303ZZ, 6303Z, 6303RS, 63032RS etc.

 

I think the ASP-Kit uses a different WP-Pulley. I have to take a look at my car...

 

The WP pulley on my ASP 178 kit is steel and rather bulkie, not gonna fail like the 181 LET pulley did. Woody

 

This would be a custom run, using steel bearings with stainless races / retainer with rubber seals.

Finding a bearing that has a documented speed rating of 19k or higher (grease or non-bath oil) is next to impossible...in the 6303 size.

It's a slow process...

 

CERAMIC BEARING

1. RMADERMAN
2. tighed1
3. distantpulse
4. moparrbust
5. AMA FIRE
6. SRT6-Man
7.SRT6 Gang Member
8.
9.

STAINLESS BEARING

1. Bulldogger
2. Waldig - Woody
3. Bluemdsrt6
4. MDSRT6
5. Cruzinquick
6. PA/ XFIRE
7. BrianBrave
8. MikeR
9.

 

The real problem if finding a sealed bearing that can take these rpms.

The bearing I listed earlier is rated for high enough rpms but is only sheilded on one side. (allows for good cooling). When I installed the bearing I put the sheiled side facing the front to keep out the most contaminates.

 

If air can get in, then grease can get out. Use 6303ZZ nort 6303Z

 

The last 6303ZZ bearing seized. (and we are back to the start of this thread with the rpm/cooling issues with the ZZ)

 

I realize your point, but no grease means it runs hotter, at these speeds air will not cool it as it runs in an enclosed space. The seal makes it impossible for air to pass through even if it could. No air flow = no cooling.

Normal heat from bearings is taken out through the contact of the inner and outer races with the shaft and pulley. It is the surfaces of the ball and races that see the most heat and that is were the failure starts when excessive heat is generated. Oil flow cools the best but this case has to rely on grease. Lubricants keep friction down and oil is the best. The whole bearing does not see the extreme heat, just the surface. Heat and excess speed causes the lubrication to break down.

I apologise for my wordiness but it requires a reasonable explanation.

PS. Stainless steel is a poor conductor of heat and that is one of its drawbacks, the heat stays on the surface longer, allowing the temp. to rise faster.

 

BrianBrave - did you ever receive this bearing? I thought you mentioned ordering one or two of them...

 

It is interesting to note that the 6303Z bearing is also used on my idler pulley on my RX7. Since I'm redoing the whole car, I took a look at my idler pulley. Spinning the pulley makes a nice metallic sound? This sounds similar to the sounds you guys have experienced. Bought a new bearing for this idler and it is marked 6303BULL. This bearing superseded the orginal 6303Z. I have not been able to locate specs on this one but it might be another option.

 

No, the WP upgrade was for the LET pulley's. See pics of the difference in WP pulley in #218.

MikeR

 

On order - I'm hoping for delivery sometime this week.

 

I can't beleave that in a world of the internet or even our own two legs that this discussion has gone on for 13 pages. Get off the computor and get to a Bearing Supply House. NOT a parts store.
1) We need a bearing that can run 18,500 plus.
2) A bearing that size that can run 20,000 is only a bathed bearing.
3) using a smaller (next size Down) ZZ bearing with shims will sustain 20,000rpm all day long. Need different stud/shaft. Plus shim in pulley.
4) this is most important! You have all asked Jerry what he's going to do. Rather than having him spend all his time answering all these worthless argumentitive guestions let him get to the point at hand.
The answer is simple but it will take some effort and can anyone blame him for trying to solve EVERYONES' problem at an affordable price. So many of you make it more than obvious you have never had a true custom part made by a machine shop or you would realize how fast the costs can go right through the roof.
Now I don't need everyone sending me statements of how much they or someone else has done in the past. Just as most of the last 13 pages of this blog it just doesn't matter.
Let Jerry handle things if you are expecting him to take care of it for you.

 

Did you wake up on the wrong side of the bed?

 

I agree, my posts have only meant to point out that this is an engineering problem.

The problem: Speed and load.

My solution: A new pulley with a longer hub, fitted with two 6303Z bearings (not St. Steel) to share the load and packed with grease.

Anyone thinking of ceramic should go to
http://www.tribology-abc.com/abc/default.htm. type ceramic in the google search and read the first article on ceramic ball bearings.
this says that ceramic ***** can take 15% less load, although the speed is higher. This is not what is required.

I will say no more. Good luck.

 

Don't go away from this thread 180.
I find your posts informative. Lots of good info to consider.

I like the two bearing idea.
Makes a lot of sense.

 

Ah you think this makes good sense do you?
The single Z indicates ONE side is sealed. How much dirt do you think it takes to destroy a bearing?
Still think it is a good idea?
If a bearing will self destruct at a given RPM how do you expect 2 to take any more RPM?
But as long as YOU think it's a good idea, let's discuss it for a few more pages.
as long as you use THIS SIZE bearing you will be limited on RPM. Therefore we need a smaller bearing. NSK-6202zz (15mm I.D. X42mm O.D.) Will run 20.000+24hours a day.
How's that for good sense???
Just as many of you I am waiting for a bearing replacement from LET. I hate having to read page after page of Cr%$p just to see if they have answered the question of when we can expect it to arrive. This is why I sound as though "I got up on the wrong side of bed".
Not to mention the anger I have when people will sit and argue over things they no nothing about and I can't reach out and squeeze there little necks shut so they will stop talking.
OK, MAYBE THAT WAS FROM THE WRONG SIDE OF THE BED...Wlecome to Montana
Mike

 

I have two cermaic bearings, that are double sealed, the same size & dynamic load and are greased rated to 19,500 RPM - being shipped to me today.

To re-evaluate some of the possible solutions so far - and keep in mind that the stock idlers in a non-modified engine also tend to fail - but not at the premature rate we're seeing.

1) Re-install the stock idler pulley, torque to 15-20 ft lbs. & source a larger belt. See this link for calculated RPM rates: <link>

2) Install a 6303 bearing (un-shielded or shielded one side) and re-pack with quality PTFE grease that you can source in a small tube and re-apply without removing the bearing. - If you look at the pictures on the first post - that bearing looks real dry... but that's the major issue using an unsealed bearing.

3) Buy a double-sealed bearing (just like our factory idler) but one that's custom (Cermaic -or- Stainless) and capable of operating at RPM's beyond the speed your crank pulley will be spinning it and with the same dynamic load rating.

I'm choosing #3. Ceramic bearing on the way, stainless bearing from LET (for back up) - - Then if all else fails I'll go with #1