Machinery Chatter

Here's How to Repack Your Bearings

Bearing with grease (left). Bearing without grease (right). Get the picture? (DTN/The Progressive Farmer photo)

DTN/The Progressive Farmer's Ask The Mechanic Columnist Steve Thompson answers readers' mechanical questions. You can read Steve's columns every month in The Progressive Farmer's digital edition (click on the "Resources" tab to find the magazine and inside, Steve's Ask The Mechanic columns).

If you have any questions for him, you can contact Steve at: Write Steve Thompson at Ask The Mechanic, 2204 Lakeshore Dr., Suite 415, Birmingham, AL 35209, or email: mechanic@progressivefarmer.com.

Here are Steve's answers to two questions recently submitted by readers:

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READER QUESTION:

It's time around our place to repack the dreaded wheel bearings on all of our utility trailers. We put it off, and we put it off again, but now we must "bite the grease" and just take time to do it. The big question that I can't get answered at the coffee shop is exactly the best way to repack the bearings. Can you give me a few tips before I get grease all over me?

STEVE'S ANSWER:

We all can feel your grease on this job. Because bearings are key players on almost everything around the farm or ranch, it's important that they get a little respect because a hot bearing can cause great damage to machines and set fires. As shown in the photo, sometimes bearings can be abused. The two bearings in the photo are the exact same bearing from a piece of hay equipment. Bearings come in all shapes and styles, from wooden bearings, to sealed bearings, to cone bearings like on your trailer axles, and many more. Here are a few tips on how to successfully repack the wheel bearings on your trailers. After removing the bearings and rear seals check for dirt and debris on the bearings. Clean bearings are a must. Brake cleaner works great for that job. Flat spots or scratches on the bearings signal replacement. Never replace the cone without replacing the race—they grow up together. Pack the grease into the face of the bearings until grease is seen on the bearings. A packing cup to help pack the bearings is available at auto stores. Clean the axle before reinstalling the hub, bearings, and seal. Here is one last tip on how to finish the job. Always over tighten the castle nut so that "rolling torque" is snug. Then, back off the nut until there is no endplay and the wheel rolls freely. Sometimes when you find that exact "sweet spot," the cotter pin will not align with the hole. When this happens (which seems like always), loosen the nut until the pin fits the next hole. Finally, take off those greasy gloves.

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READER QUESTION:

I did some shop work on my disc to reinforce the area where the cylinder mounts. I made it stronger, but the problem that I now have is that the single lift cylinder will not fit the way it was made. In other words, the end coming out of the cylinder is now at the bottom instead of the top. Everything fits perfectly, but it will not raise the disc like it did before I reversed the placement of the cylinder. I am using the same tractor and cylinder on the disc, so I know there is nothing wrong with my tractor or cylinder. Do you have any suggestions as to what is going on here?

STEVE'S ANSWER:

Your problem is coming from the fact that you have decreased the lifting power of your cylinder when you reversed it. The rod end of the cylinder has more lifting power than the other end because the surface on the "donut" in the cylinder on the back side (where the pressure is applied to push out the rod) is much greater than the surface of the donut on the rod end. The more area that is available to be pushed by the pressurized oil, the more the cylinder will lift. So, in order to fix your problem, you will either need to increase the pressure on your tractor's hydraulic system, increase the size of the cylinder, or do some more work on your disc so that you can return the cylinder so that the extending end is doing the pushing to raise the disc. A bigger cylinder will probably be the easiest fix if your cylinder cannot be reversed without a new design.

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STEVE'S SAFETY TIPS

As an operator of machinery, always be sure all persons around the machine are seen or heard from before starting a piece of equipment. Harvest time is a hectic "hurry up, got-to-go" time around the farm, and it's easy to go without checking. Just yesterday, we removed the straw spreaders in order to look inside and set the chaffer sieve. As we were reinstalling the straw spreaders, the operator started the combine and turned on the separator. The rubber slingers slapped around onto the belly of the installer -- about two seconds away from disaster. The operator should have never started the machine until everyone around the machine is seen. We are lucky to be harvesting good wheat, but luckier not to have had an accident.

(DM/AG)

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