View Full Version : The MRCG

2008.01.14, 06:20 AM
Greyscale Racing MRCG Conversion Chassis

The MRCG project was intended from the very beginning to create the most effective chassis to ever compete in 1/28 RC car racing. Based on Kyosho’s proven Mini-Z MR02 platform, we have created a new chassis from the ground up that combines smart engineering with high-quality materials to gain an edge in the budding market of 1/28 open-class competition.

At a glance:
- Built on the race-proven Mini-Z MR02 platform; uses many MR02 parts
- Mini-Z F1 inspired side plate suspension
- Tools-free quick-release battery system designed for endurance racing
- Ultra-low center of gravity and polar moment of inertia
- 15% weight reduction over MR02
- 1.5mm woven graphite chassis
- 0.8mm FRP flex plates and small chassis parts
- Sliding, 1-piece motor mount allows easy gear mesh adjustment
- Unique tierod steering system with optimized Ackerman
- Fully adjustable suspension: spring rate, anti-roll, damping, preload, droop, ride height, roll center, rear steer, camber and toe
- 98mm or 94mm adjustable wheelbase
- Compatible with Mini-Z MR02 bodies and polycarbonate bodies


Ultra low CG, weight, and polar moment of inertia


Like any good race chassis, the MRCG is designed to be low, light, and nimble. Having a low center of gravity was of utmost concern: the battery pack and motor are mounted flush with the bottom of the chassis, the battery strap is as thin as possible to lower the electronics, and the disk damper barely even clears the top of the motor (which is already very low). The battery pack is oriented transversely and placed in the center of the car to achieve an optimal weight distribution and polar moment of inertia. Woven graphite is used extensively in the chassis for its light weight and high strength; wherever its strength is not required, super-thin G10 is substituted in to reduce weight and lower the CG even further. Thanks to this attention to detail, the MRCG has an extremely low CG and polar moment of inertia, and a huge 15% weight reduction over the MR02, making it very responsive yet naturally stable.

Improved side flex plate suspension


Derived from the Mini-Z F1, the MRCG's rear suspension uses soft and durable G10 flex plates to generate the most grip possible. Like the F1, the flex plates have unlimited droop, which keeps the rear pod planted to the ground at all times while allowing weight to shift to the front for increased turn-in. Lots of adjustability has been incorporated into the suspension's design: in addition to standard mounting points for side springs and a top shock, an all-new center spring location has been added. This center spring gives the MRCG its dynamic and responsive handling by slightly shortening the lever arm of the rear suspension and tightly controlling the rear pod like a pivot-ball suspension. This unique addition also gives the MRCG's rear end a much wider range of tuning than normal, and as a bonus, preload can be adjusted with the turn of a screw. The flex plates themselves can be moved up or down with optional shims to adjust the roll center, and rear steer can even be controlled with a combination of shims and preload.

The MRCG comes with a disk damper complete with hardened steel post, Delrin disks and a set of springs. Properly assembled, it is the smoothest system on the market and makes the MRCG faster and yet more forgiving. No top shock or center spring is included in the kit as these items should be chosen to match the individual user's tire setup.

Lightweight, user-friendly rear pod


The MRCG’s rear pod is among the lightest on the market, weighing in at a scant 5 grams. The lightweight motor mount comes ready to accept any drilled 130-can motors; it doubles as an extra standoff on the pod, stiffening its structure to further improve handling. Because the motor mount is a separate part from the rear pod bulkheads, the screws for adjusting gear mesh are on the top and bottom of the rear pod instead of near the differential. This change makes adjusting gear mesh easier and makes removing the motor easier as well – no need to completely disassemble the rear pod or take out the differential just to get to the motor. The rear axle is held by bearing carriers that allow ride height adjustments in 0.75mm increments, and the bottom plate has a center mark for ease of use on setup boards.

Refined kingpin front suspension


The traditional kingpin front end has been stiffened up and made more easily adjustable thanks to a woven graphite top brace (prototype G10 part shown) and an innovative tierod mount. By removing the top brace, ride height, droop and preload adjustments can be made without removing the kingpin, saving precious time in the pits. Camber adjustments are made using Mini-Z MR02 knuckles, and the top brace can be changed out to adjust caster (coming soon).

The MRCG is the only 1/28 pan car to offer a steering system with zero bump steer and optimized Ackerman. To do this, we utilized the servo strap as a tierod mount and created a linear steering rack like that of the Mini-Z MR02. Slots in the tierod mount allow the toe angle to be changed without having to remove any parts.

Quick-release battery system


The battery strap (which doubles as a radio tray) was designed with endurance racing in mind. The new quick-release system keeps tweak consistent from pack to pack and allows the fastest battery changes of any 1/28 RC car. All it takes is a twist of the latch and the battery strap flips up; no need to fumble with clips, screws, or nuts any longer.

Accepts both hard plastic and polycarbonate bodies

The chassis accepts both hard plastic bodies (Kyosho Auto Scale Collection, Atomic VDS and VDSII, PN Pan Car, etc.) and polycarbonate bodies. Because of its 94mm and 98mm wheelbase compatibility, the MRCG will fit any Mini-Z MR02 body and several other Mini-Z bodies as well. For polycarbonate bodies, mounting points for body posts are provided and are spaced far apart to provide extra stability to the shell. (Body posts not included.)

Compatible with most Mini-Z MR02 parts
Being based off the Mini-Z MR02, the MRCG is compatible with all sorts of MR02 option parts: kingpins, front knuckles, springs, bearing sets, motors, differentials, dampers, wheels, tires, etc. In the name of cost-effectiveness, we do not include any MR02 parts in the kit except the disk damper system. Convert your MR02 to an MRCG or build the MRCG kit from the ground up, the choice is all yours!

What You'll Need:
- CA glue
- Light threadlock
- Mini-Z MR015/02 knuckles, kingpins, springs, spring perches, C-clips, ball differential,
- Mini-Z top shock or oil damper
- Mini-Z MR01/015/02 wheels, tires, bearings
- M2 locknuts (4)
- Micro servo (no wider than 23mm), servo saver
- Thin double-sided tape for servo
- Receiver and ESC (or combo)
- Receiver-compatible transmitter (and transmitter battery pack)
- Mounting tape for receiver and ESC
- 130-size motor, Mini-Z pinion
- Battery pack
- Charger appropriate for battery pack
- Hard plastic or Lexan/polycarbonate body, 94mm or 98mm wheelbase

2008.08.03, 05:43 PM
Additional pictures: