The Definitive Guide to Mini-Z / 1:28th scale Differentials: Mini－Z／1:28 比例差速器官方指导说明
The Definitive Guide to Mini-Z / 1:28th scale Differentials
The stock gear differential that comes with most Mini-Z offerings from Kyosho has a lot of friction and play making handling difficult and unpredictable.
Upgrading to an adjustable ball bearing differential, an adjustable metal gear differential or a clutch-type gear differential will provide a smoother throttle response and a much more stable rear end compared to the stock gear differentials from Kyosho. After tires, your differential is the second most important aspect of your car's handling so choosing the correct one needs some consideration.
All differentials have pros and cons; some are better suited to different classes or tire choices
- Make sure you choose the correct differential shaft length for your motor mount.
Traditionally there have been the "regular" length shafts compatible with HM (high mount), RM (rear mount) and MM (mid-mount) motor pods (motor mounts) and then there was a longer shaft for LM (low motor) motor pods.
The double-bearing pro adjustable ball differential from MC3WLS is the best of both worlds. The differential fits a "regular" motor mount but is longer by 2mm on each side. This means that instead of using +3 rims, which has lots of deflection due to their larger lips, you can use a +1 rim which has less deflection while still maintaining the same wide wheelbase.
- While upgrading your differential, you should also change your gear pitch to 64 or 126 from the stock 48.
It usually doesn’t cost you extra and will give you smoother throttle control and more power due to reduced friction. Although 126 pitch gears are very smooth, the pinion gears wear out extremely fast and can be destroyed easily if the meshing isn’t set correctly. So, it’s not just the pitch that matters, but also the material the gears are made out of.
The MC3WLS double-bearing pro adjustable ball differential features a set of precision injection molded POM (aka Delrin or Acetal) spur gears and pinions. The included spur gears range from 52 to 54 teeth and pinions range from 9 to 12 teeth. This gives you many different options for gear ratios that can be a pivotal part of setup especially in stock classes. Delrin aka POM or Acetal is a slippery material and well known to be beneficial in applications such as gearing where friction should be minimal compared to other materials like ABS or nylon which other manufacturers use for their gearing.
Here are some pros and cons of the different types of differentials on the market.
Standard Ball Differentials (Kyosho, GL Racing, Atomic R/C, Nexx Racing, 3Racing)
- Smoother operation than stock gear differentials from Kyosho
- The amount of diff action aka slippage is adjustable
- Works well with motors that have a lot of torque because it allows some slipping if you over-throttle out of a corner (although it is not recommended to set your diff that loose)
PN also makes a Limited Slip Ball Differential (LSD) gear which locks the diff at higher RPM. It works very well, has smooth operation and keeps the rear stable.
- You might have some power loss at points on the track depending on how lose you set the diff, robbing you of motor power
- Requires more cleaning and maintenance than other differentials as the diff components are exposed to the external environment
- These designs use radial bearings only which are only meant to handle centrifugal (e.g. spinning) forces only. They are not meant for lateral loads which exist when running the diff. Over time, the races wear on the outer axle radial bearing and performance suffers. Additionally, these designs can suffer inconsistency as the diff setting can tighten up just a bit through the run to change the handling characteristics of the car
- This design uses an e-clip to secure the outer wheel hub onto the shaft. To rebuild the diff requires removing this frustrating clip along with having to loosen the tension adjustment nut which means losing your diff setting. The e-clip can also become bent when taking it on and off and this can cause inconsistent differential action as the e-clip can get caught on the radial bearing.
Metal Gear Differential (PN Racing)
- Does an excellent job of transferring power to the ground all the time
- It can be set very loose and at the same time will not rob you of motor power. For this reason, it works best with stock class motors where corner entry speed and motor torque are lower
- Difficult to drive if you have a high KV motor
- Can become easily damaged if you’re not careful with the threaded adjustment collar as it can come loose while running.
Clutch-type Limited Slip Gear Differential (Atomic R/C)
Atomic R/C issued this design a while back for the Kyosho MR-03 but then included it as part of their MRZ RWD chassis. This differential is a type of limited slip gear differential. It uses a centrifugal clutch that locks the rear differential at a specific RPM. When you are off-power, the clutch disengages and this allows tighter cornering as the differential can work. When you are on-power, the clutch re-engages locking the differential and causes the car to understeer or push out of a turn.
Unlike the PN LSD ball differential, you can purchase different clutch O-Rings that engage the clutch earlier or later, allowing you to fine tune the differential to the track conditions. If you have too much initial turn into the corner or are oversteering out of the corners, then you can use a softer O-Ring to keep the diff locked at lower RPMs. You can also use a harder O-Ring to get the reverse effects.
- Works best with cars that are setup with a bit of oversteer
- Spur gear is quick and easy to change; it takes less than a minute
- Makes the rear of the car more stable and allows you to take the corners tighter when compared to a regular ball diff or the stock Kyosho gear differential
- Differential gears are fully enclosed in an outer casing so you never have to worry about dirt getting into them
- Clutch system works well and provides a very smooth feel, both on and off-power.
- Design miss in that there is some play between the side gears (attached to the shaft) and spider gears (4 small gears) causing there to be some excessive friction when turning as the lateral forces cause the side gears to push into the spider gears. This makes the differential action inconsistent even when taking the corner with the same line and speed as the previous lap.
- Requires additional parts to make the diff work consistently:
- You need to put a 0.4mm washer on both sides of the spider gear assembly to ensure they stay the correct distance from the side gears.
- Use a custom cut brass bushing (cut from brass tubing) inside the centre of the spider gear plastic housing to add some strength and reduce friction
MC3WLS Dual-bearing Pro Adjustable Ball Differential
This design features two types of ball bearings: a thrust bearing controls axial loads while the outer diff half bearings controls centrifugal loads. Using a thrust bearing in place of a radial bearing allows you to fine tune the amount of pressure between the plates as the outer hub rotates freely on the thrust bearing. This combination allows more precise transfer of power which means more throttle control providing a more consistent handling car lap after lap.
- A proper thrust bearing just like 1/12th scale cars: Throughout a race, the diff maintains a very consistent feel since the axial loads from the pressure plates are managed by the thrust bearing. The thrust bearing allows for more precise differential action giving you better and more consistent grip through a corner when compared to a standard ball differential. It also allows for finer adjustments and prevents “locking” of the differential when the diff is set tighter.
- No more eclip: a threaded shaft and a specially designed nut replaces the e-clip allowing rebuilding of the diff without losing the diff setting (e.g. it is not required to loosen the tension adjustment nut in order to take apart the diff for maintenance)
- The diff right wheel nut also assists in not overtightening the actual (outside) wheel nut that holds the wheel unto the diff hub. Most racers traditionally overtighten this nut creating binding
- The kit comes with 12 ceramic balls as stock
- The kit comes with titanium coated differential rings stock; these d-cut rings can also be used to replace PN Racing rings
- The kit comes with a set of spurs and pinions
- The kit is compatible with the yellow PN spur gear that must be used in the GTLM Super Stock Class.
- Not compatible with narrow width chassis
- Not compatible with LM motor pods
- You likely cannot reuse wheels that were previously built for other diffs as the diff is 2mm wider on each side when compared to a standard Mini-Z differential. This means using a +1mm wide offset rim is equal to a +3mm offset wide rim on a standard Mini-Z differential
标准珠差（Kyosho，GL Racing， Atomic R/C， Nexx Racing，3Racing）
- 珠差的 AKA 侧移量（松紧）可调
- 即使差速调的很松，也不会损失动力，因此这种差速适合在弯处不需要更多动力的 stock 组别的马达
Atomic R/C 应用这种设计可以追溯到MR03车架中，而现在也用在MRZ 车架中。
- 套件与PN黄色大齿相配使用时需在GTLM Super Stock组别使用
- 不适用于 LM 马达座
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