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February 13, 2021



Ever wondered why some bikes are equipped with conventional telescopic forks while the others get upside down forks? First and foremost, let's get the differences out the way. A fork comprises of a spring and a damping unit inside. Here, the springs act as a compression unit while the dampers, with the help of oil, control its velocity. In essence, both telescopic forks and USD forks have almost similar working components. Despite this, the latter receives more preference over the former. The origin of USD forks dates back to the late 1980s when race teams turned the fork upside down to improve handling.

In a telescopic fork, the chrome part (stanchion) is positioned at the top and held together by a triple clamp while the slider (female portion) sits at the bottom. Turn the entire assembly over and you have an upside-down fork, where the slider sits up top, braced by the triple clamp, and the stanchion is positioned below. Needless to say, the section which undergoes the most amount of stress needs to be strong, and a fatter diameter fork is the best solution. A USD fork works perfectly well in this scenario. Since the fork assembly is essentially turned upside down, the slider now connects to the triple clamp. It’s also longer compared to conventional telescopic forks. As a result, it provides more support. It’s also less likely to flex under hard braking or turning speeds. Thanks to this, bikes with USD forks handle better and provide better feedback.

Additionally, damping cartridges on USDs are slightly better than the damping rod seen on telescopic forks as the damping or spring action is less progressive. The difference extends even further in terms of a fully adjustable USD fork which uses more complex internal parts. This enables the rider to adjust compression, rebound and damping by tinkering with the adjuster placed on top to suit his/her riding style. However, it does have its drawbacks as USD forks are a lot more tricky to work with and disassembling them is a task. On the contrary, conventional telescopic forks are easier to work with due to their basic architecture, be it changing the oil seals or just taking it all apart.

Telescopic Front Suspension

  • The telescopic suspension is cheaper to design and manufacture.
  • This conventional suspension is easy to repair if anything goes south with it.

So, Usually, the commuter motorcycle uses a telescopic suspension as they are not meant to be driven hard. Nor they have to suddenly change direction at high speed. Also, due to the lower cost telescopic suspension makes more sense at a low price. This suspension hampers the performance of high-end motorcycles.

Up-Side Down Suspension

This type of suspension is restricted to only high end and performance motorcycles. In the end, fast motorcycles are all about cornering speeds and lightning-fast direction changes. So, it is the USD fork that allows the rider to extract the most out of the motorcycle without any compromise in performance. This comes at a cost.

  • Exactly COST. USD front forks are way more expensive than conventional telescopic suspension.
  • However, these more advanced USD forks allow more bump absorption that makes the suspension more prone to damage.
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February 11, 2021
Crankshafts:

The crankshaft is an engine component that converts the linear (reciprocating) motion of the piston into rotary motion. The crankshaft is the main rotating component of an engine and is commonly made of ductile iron.




All major components of the engine like piston,connecting rod etc. are supported by this shaft.
Construction Of Crankshaft:

A crankshaft is simply the same as an eccentric, except the eccentric is a much smaller diameter than the shaft itself Crankshaft length mainly depends on number of cylinders are present in engine .Firing order also considered while designing the Crankshaft .





Location :  

Crankshaft is located in crank case . On Crankshaft, Connecting rods and pistons are mounted. The crankshaft rides on bearings which can wear down over time. The bearings support the crankshaft and also the rods which connect the pistons to the crankshaft.

Applications :

It actually part of an engine where the power is available , and this power is transferred in the form of torque to clutch and thereby  gearbox and wheels.The main function is to convert liner motion of the piston to useful rotary motion.


Camshafts:

Camshaft is a part of engine which is responsible for opening and closing of exhaust and inlet valves.As the engines work they need to breathe out exhaust gases and take in fresh air ( charge) for the next cycle to take place . All these processes need to take place at a designated time with respect to each other. These processes are timed through opening and closing of valves and actuation of fuel pumps through a actuating mechanism which is triggered by movement of the crankshaft. The camshaft comes into picture here. The Crankshaft drives through a belt or chain drive the camshaft on which the inlet,exhaust, fuel pump cams are fitted for each unit when the crankshaft rotates it in turn rotates the camshaft which precisely actuate the valve and fuel pumps.




Construction Of Camshafts:

 A camshaft is a long bar with egg-shaped eccentric lobes, one lobe for each valve and fuel injector.

The relationship between the rotation of the camshaft and the rotation of the crankshaft is of critical importance. Since the valves control the flow of the air/fuel mixture intake and exhaust gases, they must be opened and closed at the appropriate time during the stroke of the piston. For this reason, the camshaft is connected to the crankshaft either directly, via a gear mechanism, or indirectly via a belt or chain called a timing belt or timing chain.





Location : 

Depending on the location of the camshaft, the cam operates the valves either directly or through a linkage of pushrods and rockers. Direct operation involves a simpler mechanism and leads to fewer failures, but requires the camshaft to be positioned at the top of the cylinders.

Applications :

This shaft receives the power from crankshaft  (1:2) and operates the engine valves through cam and follower mechanism(generally mushroom headed follower is used to reduce friction b/w cam and follower). 

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February 08, 2021


Slipper Clutch – How Does it Work?

The actual difference between the slipper clutch and normal clutch is the clutch hub. The base of clutch is on the right side and the hub of clutch is on the left side. You can see ball and ramp in the clutch base and ramp and engagement dogs in clutch hub (It may come with or without ball bearings, this one is without ball bearing). In normal operation, when the engine is trying to turn the rear wheel, the flat engagement dogs push on each other, and the clutch drives the motorcycle forward like a normal clutch operation.

During massive deceleration or hard breaking the torque forces the ramps together. To absorb engine braking force the ramps slide up on each other. This action lifts the hub up from the base, in the direction of pressure plate. It slides until the entire braking force is absorbed and then act like a normal clutch. This mechanism is called “spring loaded ball sliding up ramp”. The above process absorbs the engine braking force and partially disengages the clutch from the engine.





When you are riding at high speeds and suddenly you encounter a sharp corner – the obvious reaction would be to slow down by applying the brakes and shifting in lower gear. But what if you have lesser time and you want to shift 2-3 gears at a time? And when you do this, you do it at the cost of damaging the gear box and putting your safety at risk which arises due to engine braking force. As a mechanism to reduce these issues, Slipper Clutch (also known as back torque limiter clutch) was introduced. Slipper Clutch helps by allowing the clutch to partially slip until the engine speed matches your own speed.

In normal clutches, the engine braking force is transmitted to rear wheel via chain drive (or shaft drive) which causes rear wheel to shake, jump or lose traction. This is the main concept behind slipper clutch – to control rear wheel under hard braking and downshifting that causes the rear wheel to lose traction. It is particularly helpful especially on higher displacement bikes where the engine braking force is massive and may cause the motorcycle to go out of control, resulting in a high-speed collision/accident!

Clutch Stake height:

Clutch stack height is more critical in a slipper clutch than in a normal clutch. The slipper clutch tends to work the best with a clutch stack height that is about 1 mm more than the distance between the clutch hub base and the pressure plate.

Clutch Plate:

Clutch plate order for slipper clutches may vary from the original method due to the clutch hub lifting off of the base. Some clutch plates include special friction plate and judder spring apart from steel plate and friction plate to engage the clutch smoother. In such conditions the first plate which is closest to the engine should be a friction plate. The second plate is a steel plate after, followed by special friction and judder spring.

Slipper Clutch Advantages

The following are the advantages of slipper clutch over normal clutch…

  1. Slipper clutch reduces sudden forces on the inside of the transmission and hence, reduces wear and tear on the transmission
  2. Correctly installed slipper clutch improves performance.
  3. It can prevent disastrous rear wheel lock up in case of engine seizure or transmission failure.
  4. It also reduces work of suspension by absorbing engine braking force hence less bumpy ride while cornering.
  5. The rider does not need to concentrate on clutch operation which allows him to concentrate on other things such as body posture, braking etc while cornering.

Slipper Clutch Disadvantages

Practically there are no disadvantages of slipper clutch but hypothetically there are a few, such as…

  • It’s mechanically complex. Some slipper clutches are really complex to install and deal with (not many of them).
  • They are expensive (not against the saving they make by reducing wear and tear of transmission, less suspension movement and increased rider safety).
  • Sometimes you really need the engine braking force to slow down the bike (but how many times?) which can work against the concept and investment on slipper clutch.
  • Slipper clutch can’t give desired results if not adjusted according to requirements.
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