I need some outside-the-box ideas for platen wheels

[Ken H>]

Just what rpm (or belt speed in SFPM) is your "high speed" wheels running? It's hard for me to imagine a 2" wheel bearing burning out that fast under the mounted conditions you describe - unless you're really blazing fast high rpm!

With a sleeve between bearings that has the exact same ID as the bearing ID I can see why it's hard to knock out the old bearing. That special collet puller mentioned above might be the answer. If you do get the bearing out be sure to put a notch in one end of the sleeve to have a place for a drift punch to catch for knocking bearings out in future.

 

[P.Brewster]

A slip fitted bearing will just destroy the wheel when the bearing locks up. You need to change something else with your setup. Why aren't your motor bearings constantly blowing out? Why is the tracking wheel holding up but the platen wheels lock up in a month? If you're running high sfpm(above 6000) you should consider building a custom d-plate and/or platen to accept 4" wheels.

First I should be clear that this isn't a black and white problem - it was explained in my original post - the bearing drags, the bearing wears, which causes the wheel to run untrue, which causes the wheel to wear unevenly, which causes the belt to track poorly/unreliably. It's a gradual decline in performance, not a sudden seizure.

With that said, I already have the problem of wheels being destroyed when the bearing starts dragging. The idea is that I'll be able to tell when the bearing starts to drag and replace just the bearing at that time. I am experiencing a short lifespan on the the tracking wheel, but it's not as bad as the 2" wheels. I assume it lasts a bit longer because (a) it's rotating at a slower RPM, (b) it's a stock TW90 wheel which apparently uses really high quality bearings, and (c) it's not directly in the water spray like the 2" wheels are. The motor bearing also lasts longer (a few years), I'm guessing for the same reasons that the tracking wheel lasts longer. The water spray allows me to work at twice the pace as no spray, so wheels/bearings IS the thing we are changing in my setup. If I have to put on new bearings every week, it's worth it - the water spray is non-negotiable.

Just what rpm (or belt speed in SFPM) is your "high speed" wheels running? It's hard for me to imagine a 2" wheel bearing burning out that fast under the mounted conditions you describe - unless you're really blazing fast high rpm! With a sleeve between bearings that has the exact same ID as the bearing ID I can see why it's hard to knock out the old bearing. That special collet puller mentioned above might be the answer. If you do get the bearing out be sure to put a notch in one end of the sleeve to have a place for a drift punch to catch for knocking bearings out in future.

It's a standard TW90, so whatever SFPM that runs at. Clearly it's the water that is making the bearings die. Thanks

 

[Ken H>]

................
It's a standard TW90, so whatever SFPM that runs at. Clearly it's the water that is making the bearings die. Thanks

OK, now I understand better - BUT, it sure seems a "sealed" bearing should hold up better than that.

If the spacer between bearings is the correct length and diameter, and your washer on the outside will only press on the bearing race, you should be able to tighten bearing as tight as desired putting pressure ONLY on the race, not the bearing itself and not add any drag on bearing. As a test take a sleeve from an old set of wheels, put on wheel axle and tighten nut - you should be able to spin bearings with no problem.

 

[P.Brewster]

OK, now I understand better - BUT, it sure seems a "sealed" bearing should hold up better than that.

If the spacer between bearings is the correct length and diameter, and your washer on the outside will only press on the bearing race, you should be able to tighten bearing as tight as desired putting pressure ONLY on the race, not the bearing itself and not add any drag on bearing. As a test take a sleeve from an old set of wheels, put on wheel axle and tighten nut - you should be able to spin bearings with no problem.

I agree, a sealed bearing should hold up well - but that knowledge isn't useful unless I have a wheel with sealed bearings, and/or the means to replace bearings, which brings us full circle to my initial question. The stock wheels on the popular grinders appear to use shielded (not sealed) bearings. As I explained in my original post, the original TW90 wheels lasted a long time (perhaps they are sealed; the point is moot because I don't want to be reliant on any one manufacturer, and I don't want to replace the entire wheel because the bearing dies). The wheels that are dying in a month are made by other popular manufacturers.

As for the spacer, yes, that's correct - I'm able to tighten the bolt as I wish, and I'm able to spin the wheel freely when it's new. The issue is not drag created by mounting method.

 

[CallumRD1]

Shielded bearings usually look like this:

And sealed bearings usually look like this:

I'd be very surprised if a grinder maker was selling wheels with shielded bearings because they wouldn't last at all with all the grinding dust around them.

 

[P.Brewster]

Shielded bearings usually look like this:
And sealed bearings usually look like this:
I'd be very surprised if a grinder maker was selling wheels with shielded bearings because they wouldn't last at all with all the grinding dust around them.

Maybe you're right, but the point is moot and nothing is accomplished by debating the topic. All that matters is that I need a way to replace bearings without replacing the wheel.

 

[Ken H>]

Can you at all get the bearings removed from the wheels? If so, then it'd be fairly easy to do a mod to make the bearings easy to knock out. Getting the first set of bad bearings out is the issue.

 

[Natlek]

With a sleeve between bearings that has the exact same ID as the bearing ID I can see why it's hard to knock out the old bearing. That special collet puller mentioned above might be the answer. If you do get the bearing out be sure to put a notch in one end of the sleeve to have a place for a drift punch to catch for knocking bearings out in future.

Ken , ID of wheel behind bearing should be quite large then OD of sleeve so you can move it in side and that way you can knock out old bearing...That s how we change bearings on bike wheels...........

 

[CallumRD1]

The problem with that technique is that you walk the bearing out in a crooked way. This damages the bearing seats. You can often get away with it for a light press fit, but it's a gamble. Bearings should always be removed collinear with their axis to avoid deforming the seat.

 

[Natlek]

The problem with that technique is that you walk the bearing out in a crooked way. This damages the bearing seats. You can often get away with it for a light press fit, but it's a gamble. Bearings should always be removed collinear with their axis to avoid deforming the seat.

Whole world do just that ...light hammer strikes on bearing on different places ....I change millions bearing on motorcycles that way....never damaged bearing seats . if you want in your way/collinear with axis/ this is the tool .We use this when bearing is difficult jammed by rust...

 

[Natlek]

I think that this video makes sense to be here .............

 

[mike-E]

Ok. If you want to be able to change bearings quickly via a slip fit there's a simple solution. Order platen wheels WITHOUT bearings installed. Put a 220 grit belt on your grinder. Hold the bearings one at a time on an axle and grind the o.d. of the bearings down 1-2 thousands of an inch or until you can just slip the bearing into the pocket. This technique works best if you hold the bearing at about a 20 degree angle to the belt path and let a thumb just rub the back of the bearing as it rotates. You should be able to grind a bearing in about 5 seconds, probably less with a fresh belt. A rotary platen or slack belt should be used to do this rather than a hard-backed platen.
But be warned, the second that bearing starts to drag, it's going to destroy the pocket of the wheel.
You really need to consider 4" custom wheels and a shorter platen/d-plate. Order 4 wheels total and tell the maker to cut the bearing pockets with .0015 CLEARANCE. Install the bearings with Loctite bearing retainer. Every 10 days or so change out wheel sets and swap the bearings by heating the wheels and melting the loctite.

 

[Natlek]

Ok. If you want to be able to change bearings quickly via a slip fit there's a simple solution. Order platen wheels WITHOUT bearings installed. Put a 220 grit belt on your grinder. Hold the bearings one at a time on an axle and grind the o.d. of the bearings down 1-2 thousands of an inch or until you can just slip the bearing into the pocket. This technique works best if you hold the bearing at about a 20 degree angle to the belt path and let a thumb just rub the back of the bearing as it rotates. You should be able to grind a bearing in about 5 seconds, probably less with a fresh belt. A rotary platen or slack belt should be used to do this rather than a hard-backed platen.
But be warned, the second that bearing starts to drag, it's going to destroy the pocket of the wheel.
You really need to consider 4" custom wheels and a shorter platen/d-plate. Order 4 wheels total and tell the maker to cut the bearing pockets with .0015 CLEARANCE. Install the bearings with Loctite bearing retainer. Every 10 days or so change out wheel sets and swap the bearings by heating the wheels and melting the loctite.

mike , i was thinking on this problem a lot . Many option there ......like additional seal/packed with grease/ on both ends of wheel .I can make them totally waterproof if i want , I can use ceramic seals , but why ? If my SKF rubber sealed bearing don t last as I except i will use cheap one with rubber seal and change them often so that s why little loose tolerance is good thing .Slip fit ,will work ..... the outer surface of the bearing is large and there would be enough friction to stop bearing to turn in seats if damage occur on race...

 

[Mike Read]

You asked for outside the box:

Bulk purchase some 50mm OD sealed bearings. A quick google shows you can get stainless 52mm bearings 10mm wide with a 20mm ID easy enough and not expensive.

Get a 20mm spindle machined with an m12 hole for a retaining screw. Thread both ends and it will bolt directly to your existing hole.

Stack 5 bearings onto the spindle and retain with m12 screw and washer.

You do not need a press fit as the securing bolt will clamp the inner races together

The bigger bearings should last longer, if you go for stainless they should last longer too. Just replace the bearings that start to fail, you might find that only the outer bearings do so.

 

[P.Brewster]

You asked for outside the box:

Bulk purchase some 50mm OD sealed bearings. A quick google shows you can get stainless 52mm bearings 10mm wide with a 20mm ID easy enough and not expensive.

Get a 20mm spindle machined with an m12 hole for a retaining screw. Thread both ends and it will bolt directly to your existing hole.

Stack 5 bearings onto the spindle and retain with m12 screw and washer.

You do not need a press fit as the securing bolt will clamp the inner races together

The bigger bearings should last longer, if you go for stainless they should last longer too. Just replace the bearings that start to fail, you might find that only the outer bearings do so.

Yes, this is exactly the idea I describe in my first bullet point in my original post. I'll probably try a few ideas over the coming months and see what works best.

 

[mike-E]

mike , i was thinking on this problem a lot . Many option there ......like additional seal/packed with grease/ on both ends of wheel .I can make them totally waterproof if i want , I can use ceramic seals , but why ? If my SKF rubber sealed bearing don t last as I except i will use cheap one with rubber seal and change them often so that s why little loose tolerance is good thing .Slip fit ,will work ..... the outer surface of the bearing is large and there would be enough friction to stop bearing to turn in seats if damage occur on race...

I believe that rubber sealed bearings are sufficient for stopping water intrusion. My outboard motor's lower unit has a single rubber seal that stops all water from entering the gear set. That unit is completely submerged while the propeller is rotating.

 

[WC53]

The seals on the cheap bearings are not that great. You can get a better seal with more drag.....

I use the cheap stainless sealed ones on a boat dolly around salt water and just accepted that I change them once a year. Moisture gets inside and stays there, they corrode and seize. I wonder if there is a shield you could use on the outside of the wheel to limit intrusion. Similar to an additional felt or shroud? Initially thought of harrows triseal but a 500rpm limit won’t work

sounds like you have a good handle on time frame. Regular maintenance of bearing replacement with a second wheel on hand?

 

[Natlek]

I believe that rubber sealed bearings are sufficient for stopping water intrusion. My outboard motor's lower unit has a single rubber seal that stops all water from entering the gear set. That unit is completely submerged while the propeller is rotating.

We'll see, I think you're right . You know what's weird ? SKF make stainless steel bearing only with metal shield not with rubber seal ? At least at catalog i have .
About outboard motor ......that seal is right one , have spring from back side ......

 

[Natlek]

Yes, this is exactly the idea I describe in my first bullet point in my original post. I'll probably try a few ideas over the coming months and see what works best.

If you have lathe this is not difficult to do .............do it once and for all ?

 

[P.Brewster]

If you have lathe this is not difficult to do .............do it once and for all ?

Yeah, for now I'm going to try a custom-made stainless wheel with permanently lubricated bearing ("A solid polymer lubricant surrounds the balls, eliminating the need for additional lubrication. Because it's solid, the lubricant blocks out water and dust, extending the life of the bearing."). I'll evaluate the performance - if I can get 2 years from the wheel and 2 months from the bearing, that will be good enough.