High Thrust Clutch

Invention: a little change that makes big difference.

A good clutch should transmit engine torque to wheel torque efficiently. However, power loss always exists, for ALL clutches.

  So, we invented something new, a patented HiT system that can borrow engine torque directly, and then add this extra power to the clutch shoes. In this way, you get at least 35% higher force to grab the bell, the clutch pads won’t over slip, and the clutch bell won’t be overheated. We shorten the pad slipping time to exactly what your clutch needs. Never overdo nor waste effort.

  The patented HiT design is a true design, not just adding a screw to change springs for fun. Therefore, HiT clutch performs smoothly at the time of engagement, as well as disengagement. Get your vehicle “HiT clutch inside.”


HiT Clutch, US Patent No. 8,025,139 B2.

Chapter Mechanism

The Uniqueness of HiT Clutch

  Compared to the clutches we commonly see on the market, Dr.Pulley HiT Clutch contains more components and is more complicated in terms of structure. For easier understanding, we simplified the structure in the figures below.

So, there are mainly three portions of the whole clutch, including:

  • Base 1    -HiT Special.
  • Base 2    -Function as traditional clutch.
  • Pillow Spring -Bridge, only in HiT Clutch.

  You may see several designs of HiT clutches, including various types of Dry clutches and Wet clutches. Even though they are not completely the same in terms of the mechanism, the principle behind the design is the same.

Base 1

  Base 1 is one of the parts that specially created for HiT Clutch; that is, you will not see this part in other clutches on the market.

  Among the parts onto Base 1, Push Pins play a critical role, accounting for the transportation and transmission of force in the system. When the engine works, Base 1 is the first to be driven.

Base 2

  Base 2 contains Clutch Weights and Clutch Springs.

  Clutch Weight is the one to touch (connect to, or grab) the clutch bell when driven by the centrifugal force;

  Clutch Spring is the one that controls the timing Clutch Weight activates. Yep, you are right. It is basically the conventional clutch we know.

Base 1 + Base 2

  Now we are going to combine Base 1 and Base 2. For easier understanding, we color Base 1 red and Base 2 blue.

  Base 1 can rotate freely in a certain range (*the range appeals wider here for easy understanding);

  When Base 1 rotates to the extent that Push Pins touch Clutch Weights, a force is therefore generated.

Pillow Spring

  Pillow Spring is one of the most crucial parts of HiT Clutch. There will be 2 to 4 Pillow Springs in a HiT clutch, located between Base 1 and Base 2.

  Once the engine starts, the force is transited from Base 1, through Pillow Springs, and then to Base 2. Therefore we can see Pillow Springs as a bridge.

  Moreover, given it’s a spring, we can adjust its strength so as to manipulate the timing that Push Pins touch the Clutch Weights.

The stronger Pillow Springs are, the later Push Pins activate.
On the contrary, the weaker Pillow Springs are, the earlier Push Pins activate.

How does a HiT Clutch work?

For a vehicle to start to move, generally we know there are a few procedures, such as:

  • engine start.
  • throttle open.
  • revolution speed-up.

  Afterwards the Clutch (or, more specifically, clutch weights) can firmly connect to (or engage with) the Clutch Bell and the vehicle starts to move. In fact, people often forget that there is a so-called “slippery contact” stage right before the engagement of clutch weights and the Clutch Bell. For easier understanding, we will see from the BACK VIEW and explain the following three phases:

  1. Not Engaged
  2. Slippery Contact
  3. Fully Engaged

  In Phase I, HiT Clutch works the same as a conventional centrifugal clutch does. In Phase II, a RESISTANCE FORCE starts to generate. And then in Phase III, a FORCE (from Push Pin) works on Clutch Weights and onto Clutch Bell.

(It is recommended to see BACK VIEW as Push Pins do not show in the FRONT VIEW.)


  Phase I : NOT ENGAGED represents the period from the very beginning when the engine starts (and clutch rpm is zero) to the moment that Clutch Weight touches Clutch Bell. During this phase, HiT Clutch works the same as a conventional clutch. Also, the key point here is that the Clutch is in a rotating state while the Clutch Bell is in a stationary one.


  Clutch rpm keeps going up. The centrifugal force of Clutch Weight becomes strong enough to overcome the resistance of Clutch Spring, Clutch Weights touch Clutch Bell, and then both Clutch and Clutch Bell are rotating. Initially these two parts are rotating at their own rotational speed, respectively, and they will then gradually synchronize to the same speed. The period existing after Phase I and before both Clutch and Clutch Bell synchronously rotate, is what we call Slippery Contact.

Starting from here, HiT Clutch works differently from the conventional clutches.

  A resistance force is generated once Clutch Weights touched Clutch Bell, and it is opposite to the direction Clutch rotates. Since this force is not very strong at this stage, it can only slightly stretch Pillow Springs; thus Push Pins have not touched Clutch Weights yet.


  Clutch rpm keeps moving up. The centrifugal force gets stronger, and Clutch Weights gain sufficient force to conquer the strength of Clutch Springs to connect Clutch Bell and rotate at the same speeds. This whole process brings to FULLY ENGAGED.

Thrust Force

  While the resistance force gets stronger, Pillow Springs are pulled longer. Once Push Pins touched Clutch Weights, a thrust force is generated onto Clutch Weights, make them moving outward to firmly connect (or say, engaged with) Clutch Bell.


The stronger Pillow Springs are, the weaker the thrust force is.
On the contrary, the weaker Pillow Springs are, the stronger the thrust force is.

Conclusively speaking, Pillow Springs have three important functions:

  1. Transfer the rotation from Base 1 to Base 2.
  2. Determine when Push Pins touch Clutch Weights.
  3. Control the strength of the thrust force, i.e., the firmness of the engagement.

  How, then, does a HiT Clutch work? Conclusively speaking, during Phase II (Slippery Contact) and Phase III (Fully Engaged), a resistance force is generated. This resistance force, opposite to the direction that HiT Clutch rotates, will extend Pillow Springs and therefore make Push Pins touch Clutch Weights, where a force is produced. The force is what we call “thrust force”, i.e., a special force which only exists in HiT Clutch, that enables much solid engagement between Clutch Weights and Clutch Bell.


Less Slippage Features

What is ADAMS?


  ADAMS (Automatic Dynamic Analysis of Mechanical System) or MD ADAMS (Adams for Multibody Dynamics) is a simulation application software for developers and engineers to build and test virtual mechanical prototypes. It is one of the most popular software for mechanical module analysis.


What data do we have?

  We used three different Clutch Springs with k-value of 30, 50 and 74, respectively. The larger k-value Clutch Spring (or, say, the stronger it is), the later Clutch engagement happens. By observing the spring rpm at different phases, including Not Engaged, Slippery Contact, and Fully Engaged, we will see the difference between HiT Clutch and stock clutch (i.e., conventional clutch).


  • Not Engaged: The Clutch hasn’t touched the Bell yet.
  • Slippery Contact: The Clutch touches the Bell in slippery contact situation.
  • Fully Engaged: The Clutch rotates synchronously with the Bell.

Stock clutch (Conventional clutch)