Roller Pillow Block

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The summer is almost over, vacations are pretty much done, and time to get back to the grind.

What if I told you there was a way to reduce the applied forward/reverse torque to the roller block. When using linear ball bearings this is what causes galling to the shaft and lots of wear to the bearing, any bearing. If your carriage does not have the load centrally located you end up with applied forces which can place force on the edge of the linear bearing. Sometimes this exceeds the self aligning function of the bearing and then tries to gall the shaft, leaving marks in the shaft surface. Maybe this application was retrofitted and parts needed to mount where they did without an option of balancing the load. Under slow speed it functions properly, but when you try to ramp it up, you hear a funny grinding noise. The load has caused the bearings to exceed their self aligning capability and are now metal on metal without movement as the bearing is compressing on one end and in pull off on the opposite side causing the bearings to just use the edges and sometimes locking up. If there was a way to somehow exert load onto the bearing, but always keep the bearing with the forces applied throughout the entire length of the bearing and not edge loading.

We developed a way to transfer the self alignment feature to the center of any pillow block so it could never have edge load. We came up with the design option on the Double Roller Pillow Block to make sure the load stayed on both top rollers. The Double Roller Pillow Block load carrying capacity is based on both center rollers to be in contact with the shaft. This design would ensure that.

The design involves a saddle that mounts to the carriage plate with only the center of the pillow block mounted to the saddle. The pillow blocks are adapted with pins coming out of the sides and mounted in radial bearings in the saddle. I provided a rough sketch.

I hope this gives you ideas of problem solving. I would be happy to discuss further should you have questions.

It is time to talk about the coefficient of friction. The Roller Pillow Block is really the lowest coefficient in any contact linear bearing. In the testing stages Bob Magnuson tested these against the self aligning recirculating ball bearings and the Roller Pillow Block with sealed rollers rolled further with less effort. Not only did the rollers move freely, it would well surpass the misalignment factor of the linear ball type. The design goal of the Roller Pillow Block was to replace the linear ball bearings, but it was learned early on that each linear bearing has their own nitch. After which the goal was to show the shortcomings of the ball unit and how the Roller Pillow Block had key benefits.

During testing and design we did not even consider the PTEF linear bearings. They were not the market we were after and they really were not the answer to the automation on the horizon. Specifically the PTFE had such a high coefficient, there was no competition for ease of movement with accuracy.

During the design at LEE the testing verified of coefficient of .004 with sealed rollers. I have no idea of the specifications or accuracies the current manufacture is using. At LEE we started with McGill, Emerson, and then moved that business to off shore.

Thomson Pillow Block testing for ease of movement.
https://www.youtube.com/watch?v=IMBRvWtva2M

And Lee Control Roller Pillow Block.
https://www.youtube.com/watch?v=IRtNuaWFjoI

and PTFE
https://www.youtube.com/watch?v=Fz_ltWlZ2Vc

What do you think is the smoothest and moves the easiest?

LinearBallBushing This slide is using linear ball bushings.

SUPPORT ROLLER

While I was driving to a customer the other day and reviewing their application in my mind. It dawned on me some information that should be discussed here regarding the main support roller(s).

The Roller Pillow Block has a distinct benefit over the othe other linear bearings and that is it is rebuildable. We use to say at a reasonable cost, but those parts are no longer reasonable. However, the replacement of rollers will be less than a new pillow block.

How will you know if the top roller is worn out? First off, if it is broken or the outer race is very lose, it is shot. There are other things which can happen to this roller. I think a little knowledge on the original design should come first.

The top roller is a yoke roller which uses needle bearings. This yoke roller has been customized with a .002” deep radius in the center of the outer race. This machined radius is a very important part of the design! Never replace with a standard yoke roller as failure will be short coming. This radius is there for three reasons. The first is to start any wear pattern to the center of the roller face, secondly it takes point contact and changes it to line contact for better loading, and the third is it is the key factor to keep the roller in the center of the opening and not rubbing against the sides of the housing. The roller rolling height is 1/32” outside the housing. If your support roller becomes worn out, the aluminum pillow block housing will be sliding on the shaft.

If alignment is off and the support roller is rubbing the side of the housing, heat and wear will severely reduce roller life. The roller should be centered in the opening.

We worked with McGill during our design and they did not think it would work, but afterwards embraced our design and even came to us for help in the use of bearings in this manner. This brought a new understanding to the use cam followers or rollers.

My last note for this post is, yes, you can machine the radius in standard yoke rollers for some of the models. The depth was the same in all rollers. Build a fixture to hold the roller, maybe machine a collet, or chuck.

The other day I received a call from someone who had been using the Roller Bearing Pillow Block and had stopped using it due to life issues. The main rollers wore out and after replacing them several times. The application is a frame moving bottles into a filling line which builds up lots of travel per day. They changed to a Super Smart bearing which worked for several weeks and eventually had a crash of a corner bearing. From this time forward they were replacing bearings every two to three weeks. They were getting longer life out of the Roller Bearing and wanted to go back, but also wanted to make sure they were correct in their setup.

To cut to the chase, this application worked fine in the beginning, so what changed? After a review of speed, forces, and general operation, the wear on the rollers seemed to be the problem and the solution was as simple of applying 600 weight cylinder oil to the shafts on the monthly maintenance and now runs fine for long periods before a roller needs replacement.

This application also needed the further ability of self aligning found in the Roller Bearing Pillow Block. At half a degree the Super Smart balls would jam which leads to failure. Pushing bottles from a pallet was not an even force and the frame could see some twisting when bottles were more to one side. The ease of roller movement in the Roller Bearing Pillow Block allows for a greater amount of misalignment without binding.

OUTCOME: TRAVEL LIFE EXTENDED DUE TO LUBRICATING THE SHAFTS.

TIP: During the design and engineering of the Roller Bearing Pillow Block all testing was done on lubricated shafting. We found 600 weight cylinder oil worked best as it stayed on the top of a round shaft longer. Thinner oils will roll to the bottom of the shaft causing the support roller to ride on a dry shaft.

Note: The bearing can run on a dry shaft, but wear will become a factor. Low travel and slow speeds are perfect for an nonlubricated shaft, but some life will still be sacrificed.

The Roller Bearing Pillow Block is a linear bearing which has some unique benefits, but if not used as intended, will certainly self destruct. I will list some benefits that come to mind as a write this post. Some of them include the speed it can attain, high load models, and the fact that it is rebuildable. Some of the negatives is when used in a pull off condition or inverted, high shock loads, contaminants which stick to the shaft, and high speeds without good lubrication.

Most people naturally assume that they have a one inch shaft and when their bearings need replacement they buy for the existing shaft size installed. This can cause you many problems going forward. You need to do your do diligence and run the numbers on life and loading.

What are your choices? RBPB, Recirculating Ball, or PTFE are the three types available in a linear bearing.

What the factors to look at? How easy will it be to move the load and how long will it last?

Things to think about.

I Think I need to setup a few things which need to be addressed about the RBPB.Things like life, how life is calculated, how to get more life, perfect applications, failure applications, and tricks the current manufacturer doesn’t know or doesn’t want to tell you.

If you have something you want to know, just drop us a line.

Roller Pillow Block updated their website address.

Roller Pillow Block updated their info in the about section.

After selling Lee Controls inc and giving the new owners a hand to understand the product and business for a couple years, they thought they knew it all and let me retire. I am here to give the information you need and want about linear bearings and how the RBPB lines up. Hoping to pass along bearing applications, life issues, and what is the best bearing for your application. Please like this page.

Welcome to the Roller Bearing Pillow Block page. I have been answering questions since I retired and figured it would be better to put up a page where viewers can find the information on this bearing. I am the last member standing of the original engineering design team and know the true capabilities the Roller Bearing Pillow Block. Follow this page for more information regarding this bearing and the other linear bearing types available.