Thursday, December 3, 2009
by: Seamus Dolly
Since Murphy or whoever it was, took credit for the round wheel, rolling technology has changed somewhat.
Today, friction whether static or dynamic, is reliant on bearings to reduce motor or engine load. What is sometimes overlooked is the inherent features and design of a bearings to reduce temperature where it is not necessary.
The basic requirement is to reduce contacting surface areas.
More extreme requirements are to reduce vibration, reduce allotted space required to house such a bearing, and extend their life.
Needle roller bearings are used where the load is spread length ways, and a typical or common application would be the “big end” bearings of motorcycles.
Plain bearings are still used in the big ends, of cars and most other crankshaft scenarios. The principle behind a plain bearing is that the thinner a material is, the harder it is to compress or displace it.
Plain bearings, often called bushings, can be “steel backed” with a relatively thin coating of white metal applied to the bearing contact surface. This would be the common type in the automotive big end applications, and should a piece of offensive hard material contaminate the oil, it can be safely embedded within the white metal. Should it be small enough then it is not an issue.
More plain bearings can be of a bronze base with impurities cast or sintered into them. The purpose is to absorb oil or lubricant before application, and become “self-lubricating, for a limited time anyway.
Many years before the industrial revolution, bearings were made from anything available that was considered appropriate. Timber, sometimes from apple trees but not in any way exclusive to them, have been used in windmills and water mills.
Indeed, stone bushings were not unusual.
You’ve heard of the more expensive watches been said to contain “X number of Jewels”? The purpose of such jewels was to reduce friction and associated loads. This would be a loose example of metal to stone contact.
Thrust bearings are designed to work through a different axis, and may be ball-type, cylindrical roller type or a combination of both. Taper roller bearings are an example.
High temperature bearings have in-built allowance for expansion, or to put it another way; they have more clearance.
High-speed bearings often have “cages” made from non-metallic materials. Typically, this material is tufnol or plastic.
Incidentally, in low-speed, combustion-risk situations, the cages can be made from brass as well. This is to help reduce any incidence of “sparking” between the balls/rollers and the cage itself. The reason for a cage in the first place, is to maintain distance between rollers/balls, because it is only in the cases of high low to space ratios, where no space is needed that cages are unnecessary and these are low speed applications.
Other low speed bearing/plain bushings are also “steel backed” with a coating of P.T.F.E. or other plastic on them. Again, this is to give some self lubrication properties, as well as to reduce friction.
P.T.F.E. happens to be excellent, as it has a low coefficient of friction.
Bearing failure is primarily due to misalignment and contamination. Of course, there are many variables, such as instances where undue load/other mechanical failure happens to be the case.
A common cause of failure in the case of automotives, is lack of oil or insufficient oil pressure.
Absence of proper cooling, generally, will bring excessive loads.
Bearing failure is all too often due to improper installation or fitting practices. Indeed, bearings can be “on the way out” almost immediately.
Induction coil heaters are readily available from manufacturers to ease the fitting operation, and spare the bearings undue trauma.
Mechanical shock from abuse with a hammer has destroyed many new bearings and they are destined to fail, as little actual work will verify. Indeed, I’ve seen a case where a six-year old machine was overdue some maintenance, and got new bearing fitted six times in six months. It would have been best to leave it overdue; such was the fitting skill of the men involved.
Even without the hammer, contamination while fitting, poses massive problems. Allowing foreign bodies to migrate into the bearing will have a detrimental effect.
Once fitted even, contaminants from its oil/grease/air supply can make running conditions unbearable. Clean lubricants and environments are the answer, and in the specific case of oil; clean filters, lines and the oil itself, will provide an up-time saving.
Cleaning and Lubricating Motorcycle Chain
By Yogesh Sarkar
Chain is an essential part of a motorcycle and keeping it clean and lubricated ensures that you have a trouble free smooth ride, at the same time it helps increase the life of the chain as well.
Cleaning the Chain
While there are various ways of cleaning your motorcycles chain as well lubricating it, I prefer to use the good old kerosene (if not available then petrol) to clean the chain. A small brush dipped in kerosene cleans out most of the sludge. Although it is a bit time consuming, but it usually does the trick and leaves a thoroughly cleaned chain.
However if you wish to clean the chain even more thoroughly then the best option is to remove the chain, dip it in a pot filled with kerosene and then clean it with the help of a brush. After the chain is cleaned, wipe it with a clean lint free cloth and let it hang for half an hour to dry up properly.
Lubricating the Chain
For lubricating the chain I prefer to use 90w gear oil, it is thick enough to stick to the chain properly and usually is good enough to keep the chain lubricated for roughly 1500-2000kms if the chain cover is on.
Once again the best way to lubricate the chain is to remove the chain and dip it in a pot filled with 90w oil, this way the oil penetrates all the parts of the chain. Let the chain remain inside the oil filled pot for 10minutes and then hang it for half an hour to ensure excess oil drips out (put a pot under it else the you will be left with a lubricated floor). After the excess oil has dripped out, put the chain back on and ensure you put chain lock back on properly.
If you do not wish to go in to the trouble of lubricating the chain in the above mentioned manner, then you can simply apply the oil to the chain with the help of a brush. While applying oil ensure you put a coat of oil on each side of the chain to lubricate the chain thoroughly and ensure rusting doesn’t take place.
2 stroke oil: You can also use 2t oil to lubricate the chain in the event you are unable to find 90w gear oil. However the 2t oil is only good enough for 400-500kms if the chain cover is on.
WD 40: WD 40 can also be used to clean as well as lubricate the chain; it is usually easier then above mentioned option. However it is an expensive affair and requires quite a lot of WD 40 spray to clean and lubricate the entire chain.
Chain lubes: There are chain cleaner cum chain lube spray available in the market from Motul and cleans and lubricates the chain at the same time, also it is quite easy to apply since it is only a spray. However it is quite expensive to use it on a regular basis.
Chain Cover: Removing chain cover reduces the life of the chain drastically especially in monsoon months. If you have removed the chain cover then inspect the chain on regular intervals for signs of dirt and also keep on the look out for the chain noise as a hint that chain needs to be adjusted and/or cleaned.
How to Change a Spark Plug
By David Demetre
As befits one of the most vital parts of your vehicle's engine, your spark plugs require replacement every 24 months or 30,000 miles to maintain optimal fuel economy and engine performance. You can save some money by doing it yourself.
The interval varies depending on your vehicle’s make and model. A vehicle equipped with the newer platinum-tipped spark plugs can go as far as 100,000 miles before plugs require replacement. Replacing your own spark plugs is relatively easy, as you’ll see from the instructions listed below.
The first thing you’ll want to do is gather all the tools you'll need. Of course, you’ll start with a set of new spark plugs. Add a 3/8” drive spark plug socket, extension and ratchet driver, a spark plug gap gauge, and a brush or rag and set aside some time.
Now we’re all ready to gap your spark plugs. Correct spark plug gaps can be found on the engine specifications decal underneath the hood. It’s a good practice to stick with the brand of plugs originally installed in your car at the factory. For Ford products they are Motorcraft, in General Motors products they are AC Delco; Chrysler products use Champion. Refer to a parts guide to find the correct spark plugs, or ask the salesperson in your local auto parts store.
Okay, let's get to work.
Never change your spark plugs without the engine being cold. Wait two hours after driving to let it cool off. Grasp the plug wire by the boot, give the wire a twist and cautiously pull the spark plug wire out of the end of the spark plug. Don’t pull the wires themselves or you may damage them. TIP: changing the plugs one helps avoid mixing up the spark plug wires.
Use either a bicycle tire pump or an air compressor and pump a few bursts of air to rid the spark plug area of dirt, dust or gravel. Alternatively, clean off the old plug and the area around it with a rag or small brush. These steps help prevent any foreign material from falling down into the cylinder when the plug is removed.
Remove the plug by turning it counterclockwise with a spark plug socket and ratchet. Spark plug sockets have rubber linings that prevent damaging the plug’s ceramic case. Crack it loose, spin it out until it’s off the threads, and take it out by hand.
OK, time to set the gap of the new plug with a spark plug gap gauge (Remember the proper gap is specified on the engine specs decal underside of the hood). You can buy a gap gauge at your auto parts store. Slide the correct thickness wire or feeler between the inner and outer electrodes at the tip of the plug. The feeler will slide between the electrodes with a slight drag when the plugs are properly gapped. If the gap isn’t right, slightly bend the outer electrode until you achieve the right gap. Ensure the outer electrode is inline over the inner electrode.
Next, have a look at the cylinder head threads. Are they in good condition, clean, and free of dirt? New spark plug should freely screw into the cylinder head by hand. Any binding of the plug is an indication of debris or damage in the thread. TIP: lube the plug threads with a little grease or spray lubricant before you install them, this will make for an easier removal at your next spark plug change.
Insert the new plug into the spark plug hole by hand and turn it clockwise until it's snug. After finger tightening the plug, firmly torque it with your spark plug wrench/socket. Be careful not to over-tighten the plugs.
Reattach the correct plug wire to the new plug with a twist on the boot until it's firmly seated on top of the plug. You should feel and hear a click as the wire positively clamps onto the spark plug.
Repeat all the steps for the other plugs. Even taking your time this job will probably take you less than an hour. And that’s it for another two years or 30,000 miles!
Posted by cheri at 1:20 AM