The temperature distribution in the weldment is therefore nonuniform. Normally, the weld metal and the heat affected zone (HAZ) are at temperatures substantially above that of the unaffected base metal. Upon cooling, the weld pool solidifies and shrinks, exerting stresses on the surrounding weld metal and HAZ.

If the stresses produced from thermal expansion and contraction exceed the yield strength of the parent metal, localized plastic deformation of the metal occurs. Plastic deformation results in lasting change in the component dimensions and distorts the structure. This causes distortion of weldments.

Several types of distortion are listed below:
* Longitudinal shrinkage
* Transverse shrinkage
* Angular distortion
* Bowing
* Buckling
* Twisting

Some of the factors affecting the distortion are listed below:
* Amount of restraint
* Welding procedure
* Parent metal properties
* Weld joint design
* Part fit up

Restraint can be used to minimize distortion. Components welded without any external restraint are free to move or distort in response to stresses from welding. It is not unusual for many shops to clamp or restrain components to be welded in some manner to prevent movement and distortion. This restraint does result in higher residual stresses in the components.

Welding procedure impacts the amount of distortion primarily due to the amount of the heat input produced. The welder has little control on the heat input specified in a welding procedure. This does not prevent the welder from trying to minimize distortion. While the welder needs to provide adequate weld metal, the welder should not needlessly increase the total weld metal volume added to a weldment.

Parent metal properties, which have an effect on distortion, are coefficient of thermal expansion and specific heat of the material. The coefficient of thermal expansion of the metal affects the degree of thermal expansion and contraction and the associated stresses that result from the welding process. This in turn determines the amount of distortion in a component.

Weld joint design will effect the amount of distortion in a weldment. Both butt and fillet joints may experience distortion. However, distortion is easier to minimize in butt joints.

Part fit up should be consistent to fabricate foreseeable and uniform shrinkage. Weld joints should be adequately and consistently tacked to minimize movement between the parts being joined by welding.

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Things to Check Regularly

Tip: There are dozens of parts on a motorcycle that could be checked on a regular basis and there is nothing wrong with check all those parts. But try to slim the list down to the most important items so you still have time to ride.

Here is a basic list of some of the most important things to check on a motorcycle. Even doing a little can make a big difference. Battery, Oil, Tires (tyres), Brakes, Chain and sprocket (Shaft Drive, Belt Drive) and Fuel (Gas, Petrol).


Tires, Tyres.

Tip: Keep a low pressure tire gauge (0psi - 80psi) in your bike tool bag at all times. Try to remember to check your tire pressure everytime you fill up for gas.

Keep your tires correctly inflated. A tire that is very under-inflated generates a lot of heat which can lead to a blow out. Tires that run too hot also wear out more quickly. The most common motorcycle breakdown is for tire damage.

Purchase a pencil-type tyre gauge and use it regularly until you instinctively 'know' what your tyres feel like correctly inflated. Use of the gauge and visual inspections must become second nature.

Replace your tires sooner rather than later. If tread depth is 1-2mm it is time to replace your tires. Take a tip from the mad sportbikers and the canyon racers - they never skimp on their tyres as they are often all that stands between them and the pearly gates.



Brakes

Tip: Brake fluid absorbs moisture over time and becomes less effective. Replace brake fluid every one to two years and your brakes will preform the best they can.

Motorcycles have up to two brake fluid reservoirs, one for the front, usually found on the handlebars and one for the back. Both should be checked regularly. Topping up should only be done from a new, sealed bottle as brake fluid tends to absorb moisture over time. If your brake pads are thin and due for replacement. Beware - brake fluid, if spilt on paintwork eats right through to the bare metal.

Also check the thickness of the brake pads. If you allow them to go right down to the metal your brake disc will be damaged resulting in an unnecessary and expensive replacement. Fitting braided steel brake lines will increase the performance of your brakes by roughly 50%



Chain and sprockets, Shaft Drives, Belts

Tip: Lube your chain after each ride when the chain is warm so the oil can easily soak in and get into all the tight spots of the chain.

These items that are essential to the well being of your bike. If not well maintained you will end up spending a lot of money all too often to have them replaced.

Chains: Lubricate them often with a commercial chain spray everytime you fill up for gas. (or at the end of each ride). Spray liberally on the side of the chain that comes into contact with the sprockets. Ensure that you spray both left and the right hand side of the chain. Position a piece of newspaper so that you do not dirty the rear wheel rim as you spray. Use a second piece on the floor to catch any drips. Wait five or ten minutes before you wipe all excess oil off the chain. This whole process is a lot easier if your motorbike has a centre stand. Spinning the back tyre will ensure that the rest of the chain is lubricated when it comes into contact with the sprocket and pinion. This is a task that is best done when you return home from your ride while the chain is still warm.

Bike chains are never taut but must be able to sag between 3/4" to 1 1/4" at the mid-point between the two sprockets. The sag is used when the bike suspension moves up and down over uneven surfaces.

Shaft Drives: Even though shaft drives on motorcycles require little maintenance we would suggest replacing the shaft drive oil every time you change the oil on your motorcycle. This will lead to a very long and happy life for the shaft drive.

Belt Drives: As with shaft drives, belts do not require a lot of maintenance. Everytime you change the oil on your motorcycle check the belt tension and adjust if necessary. Make sure your belt is always clean.



Fuel

Tip: Check your fuel filter on a regular basis and replace every 2 years.

Fuel is quite an often overlooked as a form of preventative maintenance on a motorcycle.

Check the fuel filter (if you have one) to make sure it is not clogged and looks clean and clear. Replace fuel filters every 2 years.

Check the fuel lines for weather damage and cracking, replace immediately if any is found.

Generally untreated gas only lasts (is good for) 6 months. After this time the gas starts to break down. Dispose of untreated gas older than 6 months rather than risk running it. Treated gas can last up to 2 years.

Remember when parking your motorcycle for any length of time to turn the petcock (fuel tap) to the off position. This prevents any fuel potentially leaking out and flooding the carbs or the engine.



Oil

Tip: Check your oil level when it is cold before you go on a ride. If it is not at its high or max level top it up before going out.

Regular oil and filter changes will keep your motorbike young and healthy.

Oil level. Make sure you regularly check and keep your oil level at its HIGH or MAX level. It is best to check your oil level on the bikes centre stand or when it is in a level position. An under filled oil level can be disastrous while too much oil over the limit may flood your air cleaner with oil. (it is embarassing too).

You should also know the difference between the 'low' level and the 'high' level in ml e.g. if the difference is 300ml you cannot purchase a 500ml tin and pour the whole can in!

Here are some pointers regarding oil which are true for most motorcycles

- The bike should be level as possible.
- The oil should best inspected cold and is therefore best done before you go out on a ride.
- Becareful to not allow foreign matter and dirt to fall in during the inspection process
- With threaded dipsticks do not screw the dipstick in when taking a reading, just allow it to rest on the lowest thread.
- High temperatures, time, speed, heavy traffic, short trips and dust quickly destroy the quality of your oil. If you do ride in these conditions change your oil more frequently.
- I suggest changing your oil every 2-4000km or 3-6 months, whichever comes first. (I change mine every 2,500 km).
- It is recommended you change your oil filter everyother oil change if you are using a good quality oil filter (e.g. WIX, Your Motorcycle Manufacturer Brand). If not, every oil change!
- Always use a good oil filter (WIX brand from UAP/NAPA is a recommend one)
- Motorcycles can and do use the same oils as cars although special synthetic motorcycle oils are available. Always use the recommended oil weight for your motorcycle (e.g. 10w40 or 20w50). Older (15+ year old) motorcycles run best on regular (non-synthetic oil), while new bikes like either.



Battery

Tip: Check the fluid levels on each chamber. If any chamber is low, carefully top it up. Use only distilled or deionized water, NOT tap water. Tap water has minerals in it that will not do the battery any good.

The humble battery is a very common cause for motorcycle breakdowns! Unfortunately they are awkward to get to and therefore do not get checked as often as they should.

A battery only requires a little monthly maintenance to perform perfectly. Keep the battery charged to 100%, recharging when the lights dim, the starter sounds weak, or the battery hasn't been used in more than two weeks. Other than that, follow this simple check list every month:

- Check the electrolyte level
- Top up only with distilled or deionized water, wear gloves and protective glasses. Top up in a well ventilated area, Beware of fumes.
- Keep the top free of grime
- Check cables, clamps, and case for obvious damage or loose connections
- Clean terminals and connectors as necessary
- Check inside for excessive sediment, sulfation or mossing
- Make sure the exhaust tube is free of kinks and clogs
- Replace caps firmly
- Finish up by testing the battery with either a hydrometer or voltmeter. To extend the service life of your battery, make monthly battery maintenance part of your routine.

Use only distilled or deionized water, NOT tap water. Tap water has minerals in it that will not do the battery any good.

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Nickel and nickel-alloy weld metals do not flow and spread like steel weld metal. The operator must direct the flow of the puddle so the weld metal wets the joint sidewalls and the joint is filled appropriately. This is sometimes accomplished by weaving the electrode slightly. The amount of
weave will depend on such factors as joint design, welding position, and type of electrodes. A straight drag (stringer) bead deposited without weaving may be used for single-bead work, or in close quarters on thick sections such as in the bottom of a deep groove. However, a weave bead is generally desirable. When the weave progression is used, it should not be wider than three times the electrode core diameter. Regardless of whether the welder uses weaving or the straight stringer technique, all weld beads should be deposited such that they exhibit the recommended slightly convex surface contour.


When used properly, SMC flux covered welding electrodes should exhibit a smooth arc and no pronounced spatter. When excessive spatter occurs, it is generally an indication that the arc is too long, amperage is too high, polarity is not reversed, or that the electrode has absorbed moisture. Excessive spatter can also be caused by magnetic arc below.

When the welder is ready to break the arc, it should first be shortened slightly and the travel speed increased to reduce the puddle size. This practice reduces the possibility of crater cracking and oxidation, eliminates the rolled leading edge of the crater, and prepares the way for the restrike.

The manner in which the restrike is made will significantly influence the soundness of the weld. A
reverse or “T” restrike is recommended. The arc should be struck at the leading edge of the crater and carried back to the extreme rear of the crater at a normal drag-bead speed. The direction is then reversed, weaving started, and the weld continued. This restrike method has several advantages. It establishes the correct arc length away from the unwelded joint so any porosity resulting from the strike will not be introduced into the weld. The first drops of quenched or rapidly cooled weld metal are deposited where they will be remelted, thus, minimizing porosity.

Another commonly used restrike technique is to strike the arc on the existing bead In this manner, the weld metal likely to be porous can be readily removed by grinding. The restrike is made 1/2 to 1 in. (13 to 25 mm) behind the crater on top of the previous pass, and the restrike area is later ground level with the rest of the bead. This technique is often used for applications requiring that welds meet stringent radiographic inspection standards. It is also noteworthy that it is much easier for welders with lesser levels of skill to produce high quality welds than they can using the “T” restrike technique.

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