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December 2013 Archive for In the Shop

RSS By: Dan Anderson, Farm Journal

As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Along with his In the Shop blog, Dan writes a column by the same name as well as the Shop Series for Farm Journal magazine. Always providing practical information, he is a master at tackling technical topics and making them easy for all of our readers to understand. He and his wife, Becky, live near Bouton, Iowa.

Lock Collars--Again

Dec 28, 2013

 I don't mean to beat a dead horse, but the topic of eccentric lock collars on bearings just keeps raising questions. This time the question was about removing lock collars from bearings. It should be a simple process, but it can be one of the more aggravating steps in bearing replacement because the darn things are often rusted and frozen in place after being installed by somebody who did or didn't know the proper way to install them.

In a perfect world--which I hope to visit some day--a lock collar is installed in the same direction the shaft and bearing rotates. That lock collar is removed simply by tapping it in the opposite direction of shaft/bearing rotation.

In the real world I begin removal of lock collars by gently feeling with my fingertip the "hole" in the rim of the lock collar, trying to see if the guy who installed it left a punch or chisel mark that tells me which way it was installed. If I feel a mark on the edge of the lock collar's setting hole, I tap the lock collar in the opposite direction to loosen it. IF it loosens, the lock collar is often full of dust or rust or debris so that, even when it rotates and releases from the eccentric, it won't slide off the bearing and shaft.

In that case, I generally hose down the divide between the bearing and lock collar with penetrating oil, then grab a pair of slip-jaw pliers, clamp them on the lock collar, and try to wiggle and rotate it back and forth on the bearing. I rotate it till it re-clamps in one direction, twist it in the opposite direction till it re-clamps, then use those two "limits" to determine halfway between those locking points--which should be the place where the eccentrics are dis-engaged and the lock collar will slide off the bearing.

If, after a couple tries with penetrating oil and slip-jaw pliers, the lock collar still refuses to come off, some mechanics use a die grinder with a cut-off wheel to cut off the stubborn lock collar. Me? I grab a torch and melt the sucker. I'm probably going to have to eventually burn the bearing off, so I just cut to the chase and start melting metal.

Reverse-locked lock collar?

Dec 25, 2013

 The blog I wrote several weeks ago about installing lock collars generated the question, "What if a lock collar is locked in the wrong direction during assembly?

At worst, the lock collar will come loose and allow the bearing to spin on the shaft. In many cases the lock collar will stay in place, thanks to the "insurance" against rotation provided by the set screw in the lock collar.

Another question that came up was, "Why don't they make lock collars so they can only lock in the correct direction? The answer is, "Because the lock collars on bearings on the opposite ends of shafts always lock in opposite directions." If you lock them correctly, in the direction the shaft will turn, then one lock collar will lock clockwise (as you face the end of the shaft) and the other will lock in the counterclockwise direction as you face the other end of the shaft.

A third thing that came up, while I was talking with a customer about bearings, lock collars and repairs, was a comment I made that, in general, all shafts, pulleys and sprockets on a combine turn in the same direction as the tires (unless there is a belt arrangement or gearcase specifically designed to reverse directon of a shaft's rotation.) Knowing that most shafts, belts, pulleys, chains and sprockets on a combine turn the same direction as the tires helps determine which way to rotate lock collars, position the idler pulleys on belt drives (always on the "slack" side), and is generally handy knowledge to have.

 

What More Could A Farmer Ask For?

Dec 21, 2013

 A neighbor, Howard, died recently. He lived a couple miles south of me. I went to school with his kids, waved when I met him on the road, and always enjoyed chatting with him whenever our paths crossed.

He never farmed "big," but he farmed well enough to raise a family and live comfortablyl. Corn, beans, hogs and cattle. If you wanted a storybook example of a traditional family farm through the '60s and '70s, you could have taken a picture of his operation. He overhauled his own tractors in an unheated machine shed where an old, tinny-sounding radio played country music 24 hours a day, fed cattle and hogs with a 5-gallon bucket, and told his best stories after pausing to tuck a wad of tobacco behind his lower lip.

Howard wasn't perfect, but he was a good neighbor. People spoke well of him not only at his funeral, but in local coffee shops and whenever two pickups stopped on a gravel road to exchange valuable information related to farming and the community (farmers don't "gossip"). 

I'm thinking that's a pretty good thing to have farm folks say about you after you're gone. "He was a good neighbor" says a lot in a short sentence. 

Torque Wrench Tips

Dec 18, 2013

 There's no need to use a torque wrench to tighten 99 percent of the nuts and bolts on farm equipment. But if you work on engines, transmissions, final drives or other assemblies that require or benefit from fasteners being torqued precisely, here are a couple tips;

-Always grip a torque wrench in the middle of its handgrip when pushing or pulling to tighten a fastener. Torque is calculated based on the distance from the pivot point of a torque wrench to the center of the handgrip. Pulling or pushing from anywhere on the handle except for the handgrip gives a distorted torque value.

-Don't jerk or lunge against the handle of a torque wrench during a "pull." Torque wrenches give their most accurate readings if the wrench is pulled smoothly and steadily. 

-Try to arrange so the torque wrench clicks or beeps (indicating desired torque value has been reached) in the middle or toward the end of a slow, steady pull of the handle. It takes more torque to start a bolt turning than it does to keep that bolt turning. So if you have limited room in which to swing the torque wrench handle, and have to reset the wrench, be suspicious if the wrench clicks or beeps in the first few inches of the fresh pull. In that case, the wrench is probably signaling the "breakaway torque" of the bolt rather than it's actual turning torque. Most common bolts can be safely loosened then re-snugged, with the goal of getting the wrench to click in mid- or late-pull. The exception is when tightening "torque to yield" bolts, which are special, one-time-use bolts that should never be loosened and re-used after they've been tightened to full torque value.

 

Fussy Facts About Torquing Fasteners

Dec 15, 2013

Some of you who rebuild engines already know this, but even if you don't build engines, it never hurts to "know more than you can use."

In a perfect world, bolt manufacturers would prefer that nuts and bolts be installed with their thread lubricated unless specifically directed that the fasteners be installed "dry." If lubrication is recommended, use ONLY the type of lubrication recommended. Different lubricants have different coefficients of friction. A bolt lubed with WD-40 will produce incrementally different torque values than a bolt lubed with 30-weight engine oil. 

That's no big deal if you're tightening the bolts that hold disk ripper points in place, but if you're assembling the connecting rod caps in an engine, it's a BIG deal. Connecting rod manufacturers assemble and precisely torque the big ends of connecting rods BEFORE final machining, so that the finished bore is absolutely round. When the connecting rod cap is removed for shipping, the metal relaxes and goes microscopically out of round. When an engine builder installs the rod in an engine and bolts on the rod cap, it is critical that the rod cap bolts be installed using the same lubricant so the same exact torque will pull the components back into "round."

Few nuts and bolts in farming are as fussy as those in engine building, but the connecting rod example highlights the possible variances that could distort torque readings when installing nuts and bolts. It's up to the individual mechanic or farmer to decide if the particular repair requires the precision of torquing every nut and bolt to exact value, but...if never hurts to understand mechanical theory so you can make an educated decision about how to make repairs on your farm.

More About Bearings and Lock Collars

Dec 12, 2013

I don't know why, but in recent years I've seen a rash of bearings with cracked inner races. Sometimes the damage was on relatively new machines with very few hours on them. Symptoms related to a cracked inner bearing race vary. Sometimes the bearing obviously failed in a dramatic and expensive way. Sometimes there was just an odd, once-per-revolution click or knock when the bearing/shaft was turned by hand. Either way, when the bearing was disassembled the inner race was cracked or broken in a half-moon shape. Sometimes that half moon-shaped segment stayed with the bearing after disassembly. Sometimes it came off with the lock collar.

And that was the clue to the cause of the problem in almost every case: the lock collar had been over-tightened. When the eccentric inside a lock collar "locks" onto the eccentric on the inner bearing race it can exert incredible force. If you've ever "started" a lock collar onto a bearing with just your fingers, then tried to slide the bearing and lock collar on the shaft, you were probably surprised by how little rotation it took to tightly anchor the bearing to the shaft. 

It only takes a firm tap with hammer and punch or chisel to seat a lock collar onto a bearing. Pounding on a lock collar until it absolutely will not move another fraction of an inch is a great way to crack the eccentric edge of either the bearing race or the lock collar itself.

My personal strategy is to manually rotate the lock collar onto the bearing until I feel it "click" onto the bearing's inner race, then snug it finger tight. After that, a good, firm tap with a hammer and punch usually rotates the lock collar an additional 1/8 to 1/4 turn, and that's good enough. 

Sometimes it's hard to walk away, when it's obvious I could give the lock collar another good smack and gain another few degrees of rotation, but in the case of lock collars and bearings, more is not always better. 

Which Way To Lock A Lock Collar?

Dec 06, 2013

 Every so often even the most experienced mechanic has to pause and think for a minute to remember which way to rotate a lock collar to lock it to a bearing.

If you think about it long enough and try to understand centrifugual forces acting on the bearing, you can convince yourself it needs to lock in a clockwise direction. If you think a bit longer and harder, you can convince yourself that counterclockwise is the correct direction.

Rather than have to think and use logic every time I want to lock a lock collar, I've just memorized that I need to lock a collar in the same diretion the shaft it's being locked to will turn. Another way to look at it is, lock the collar in the direction the lock collar itself will be turning. 

Lock collars will lock in either direction, but will be more secure if locked as explained above. Some guys have a personal rule to always lock collars in a  clockwise or counterclockwise direction, but...if you use that strategy on bearings on opposite ends of a shaft, one of them will be locked in the "wrong" direction.

There IS an exception to the rule. If a shaft will stay stationary while the bearing/housing rotates around it, the lock collar should be locked in the OPPOSITE direction the bearing/housing will rotate.

But let's keep it simple. Bottom line: if a bearing is installed on a rotating shaft, the lock collar should be locked in the same direction the shaft (and hence the lock collar itself) will rotate.

 

No Tool Is A Bad Gift

Dec 04, 2013

 Sometimes we fret and stew about what tools we should give as gifts to friends or family members. As someone who considers the acquisition of tools as an ongoing quest, I can guarantee there is no such thing as a "bad" tool if it's given as a gift.

More than 40 years ago Dad gave me a 32-ounce wood-handled ball peen hammer. For years it was my main instrument for beating on things. Once Dad passed away, for some reason it felt appropriate to retire it before I broke the original handle or--even worse--lost it.

I was pretty sure when my son was a teenager that he never listened to a thing I said. Till one Christmas, when he gave me a battery terminal clamp puller as a gift. I had mentioned, "It would be nice to have a battery clamp puller," several months before Christmas when we were working on his car. It's one of my most valued tools, not for what it does (and it's a very handy and useful tool), but for what it symbolized when it was given.

My wife has for years bought me mundane, "boring" shop accessories as Christmas gifts. "Boring" to her, but I think of her every time I roll under a machine on my top-of-the-line mechanic's creeper or sit comfortably on my rolling mechanic's chair. 

So, when buying tools as a gift, don't agonize over getting the "perfect" tool. Even if they already have 5 left-handed pipe wrenches, the one YOU give to them will be the best one in their toolbox.

BUT--if you're tired of getting left-handed pipe wrenches for Christmas, be a nice guy and drop some heavy hints, maybe mark pages in a tool catalog, or even make a detailed list of tools you'd like to have. Remember--your wife feels as comfortable in the tool section at the local hardware store as you do in the dress department of her favorite clothing shop.

 

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