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June 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.

Pre-Loading Wheel Bearings: As Easy As You Thought

Jun 29, 2013

 The traditional way to pre-load or adjust a simple wheel bearing on a wagon or other piece of farm equipment is to spin the wheel hub and then tighten the nut against the pre-lubricated bearing until the hub begins to drag and slows. Stop the wheel from turning, reverse the nut until it's loose, then re-tighten the nut "hand-tight" before installing a cotter key in the castle nut.

I always thought that sounded rather imprecise, but when I had opportunity to talk with Carl Bush of Wilwood Engineering, the company that makes brakes systems and wheel hubs for NASCAR teams, he said the traditional way of tightening wheel bearings is more than adequate. "You can use a torque wrench and make it more complicated, but for simple wheel bearings, the old way is just fine," he says.

There are all sort of specifications available on the internet for four-wheel-drive, front-wheel-drive and particular designs of wheel hubs. But plain ol' wheel bearings on mid-'80s Monte Carlos, Camaros and Chevelles have recommendations to be tightened to "...12 lb./ft. of torque before loosening nut, then finger-tightening the nut before installing cotter key." Those are similar to the wheel bearings used on generic farm equipment, so...

Twelve lb./ft. of torque turns out to be just enough torque to create drag when you spin the wheel hub. So if you tighten wheel bearings the way Grandpa taught you, you'll be pretty darned close to manufacturer's recommendations for preloading simple wheel bearings. Sometimes the simple way is simply sufficient.

An Electrical Wiring Diagnostic Tip

Jun 27, 2013

 Summertime is trailer time--boat trailers, camping trailers, livestock trailers, etc., etc. And anybody who pulls a trailer will eventually spend time trying to diagnose electrial problems in the trailer's wiring system. Here's a tip:

The old school way to test for voltage in a wire was to scrape the rust or paint from a nearby frame component and ground the voltmeter or test light to the frame. That test worked okay when lights were wired with one power wire to the bulb, and ground was achieved via the light's mounting bracket or a short jumper wire from the light to the frame.

But modern trailer wiring harnesses are often wired with a ground circuit that goes all the way back to the towing vehicle's negative battery post. If the mechanic tests for voltage at the light socket by grounding his voltmeter/test light to the nearby frame, it bypasses the ground circuit back to the battery. Grounding the test meter to the nearby frame only tests half of that sort of circuit.

For example, let's say that ground wire is broken. If the mechanic tests the positive wire to the light and grounds his voltmeter or test light to the frame near the light socket, it shows 12 volts. But because the ground wire back to the battery is broken, the circuit is open and the light doesn't illuminate, even though there is technically "12 volts to the light socket"--when a temporary ground is provided.

It takes a little detective work, some deductive reasoning, to figure out if an electrical problem is in the positive wires or the negative wires of a circuit that shows zero volts. But that's better than grounding to frame at the light socket, showing 12 volts, and then wondering, "If I've got 12 volts at the light socket, why doesn't the light work?"



Another Tool You Gotta Have

Jun 22, 2013

 I have complained for many years about Torx-head fasteners. Their heads look SORT OF like a Phillips-head screw, but have more "points." I carried a grudge against Torx-head fasteners because they required me to buy a new set of tools to install and remove them, because Phillips screwdrivers WILL NOT remove Torx-head fasteners without damaging those fasteners.

Believe me about that---I tried. Oh, how I tried.

I finally bit the bullet and bought a set of Torx-head screwdrivers, and eventually some larger Torx-head sockets to use on ratchet wrenches. And, though I'm reluctant to admit it, I now prefer Torx-head fasteners to Phillips-type fasteners.

That's because I'm an expert at stripping out Phillips-head screws. From the number of stripped out Phillips-head screws I see on equipment that comes into our shop, I'm not alone. That's why I've been pleasantly surprised with the durability of Torx-head fasteners. I'm not saying their un-strippable---I've repeatedly proven that ANY fastener can be stripped, mangled, marred and twisted beyond salvage. But Torx-head fasteners, if installed and removed with common sense and the approrpriate-size Torx-head screwdriver or socket tool, are pretty durable.

Torx-head tools really aren't that expensive, between $40 and $100 depending on how big of a set you get and what name is on the handle. It was tough to spend the money on my first set, but it was money well spent.

Battery Powered Impact Wrenches

Jun 01, 2013

 Battery-powered tools, especially battery-powered impact wrenches, have become commonplace on farms. They're not perfect. If you don't use them frequently it's difficult to keep their batteries charged and in good condition. Some of you were hesitant to spend big bucks on your first battery-powered impact wrench and got one that's under-powered. But I think we've all seen enough advantage and convenience to justify always having some sort of battery-powered impact on our farm. 

Enough advantage and convenience to either replace, upgrade or justify having TWO battery-powered impacts around. Whatever excuse you use to justify getting another battery-powered impact, here are a few tips to get the most from that investment.

Spend money. Yes, there are $150 battery-powered impacts on the market. They are for yuppies changing the tires on their golf carts on Saturday afternoons. Plan on spending $400 or more for a manly, battery-powered impact with two batteries and a battery charger. You get what you pay for, and as long as you buy name-brand products, it's worth it.

Buy torque. A good 1/2-inch drive battery-powered impact should now be capable of 500 lb./ft. of torque, both tightening and loosening. If you want to get picky, dig deep and research HOW LONG it produces that torque. Some companies test their tools in 1 or 2 second bursts. Others test them the way we use them--5 to 10 seconds at a time. Or longer.

Don't buy weight. Lithium ion batteries are expensive, but they're considerably lighter than nickel-cadmium batteries. When you're standing in a store comparing the weight and "feel" of two different battery-powered impact wrenches, hold them at arm's length above your head, straight out from your shoulder and maybe behind your back, to simulate real-world situations.

Consider buying smaller. If your first investment in a battery-powered 1/2-inch drive impact wrench was in a high-quality, premium-grade tool that is powerful enough and light enough so you really don't want or need to replace it, look at investing in a similar quality 3/8-inch drive battery-powered impact. The latest generation of 3/8-inch battery-powered impact wrenches produce more than 250 lb./ft. of torque and are much lighter and more compact than their bigger brothers. My 3/8-inch battery-powered impact is my go-to tool for changing sickle sections on grain tables and for working with sockets smaller than 9/16" or 13 mm.

Finally, if you decide to buy a 3/8-inch drive battery-powered impact to complement your existing 1/2-drive tool, try to match batteries. It saves money and reduces the number of battery chargers cluttering your workbench if all your battery-powered tools use a common size and voltage of battery.


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