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Thread: CMAX Guide

  1. #1
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    Default CMAX Guide

    CONTENTS
    1. Overview

    2. Transmission, Transfer Case and Gearing
    3. Adjustable C-Channel Chassis
    4. Suspension
    5. Axles
    6. Body Mounting
    7. Setups for Specific Bodies


    1. OVERVIEW

    GCM’s all-new CMAX platform is one of the most eagerly anticipated new products in the tiny trucking world, and for very good reason. CMAX delivers a unique combination of an incredibly scale driveline and suspension, unparalleled flexibility to create setups for almost any readily available 1/10th scale truck body as well as custom builds, and performance/durability that you have come to expect from all GCM products. CMAX’s highlights include:


    • ultra-realistic GCM Low Range Transmission paired with LRT2 transfer case
    • overdrive gearing to front axle through LRT2 transfer case for improved climbing and steering
    • 10 sets of powertrain mounting points allowing over 35mm range for transmission/transfer case mounting locations
    • 6 sets of servo mounting points allowing over 22mm range for optimizing servo position
    • choice of linked or leaf-sprung suspension front and rear
    • multiple suspension mounting points to accommodate wheelbases from under 10” to over 15”
    • TM8 left- or right-offset pumpkins for front axle with ability to install transfer case as left-drop or right-drop to match axle
    • innovative narrow chassis minimizes wasted space and offers more options for locating electronics and battery packs with full-depth interiors and truck beds
    • ability to service nearly all major drivetrain and electronics components from underneath the chassis without having to remove the body

    We are putting together this guide to help you understand how to make the most out of the CMAX platform and plan your build. We’ll start with detailed specs and information about each of the major platform components (transmission and transfer case, adjustable c-channel chassis, and suspension), followed by specific setup recommendations for many of the most popular hard bodies currently on the market.

    Last edited by imthatguy; 11-05-2016 at 03:52 PM.
    BowHouse RC, GCM #tinytruck Team, Team Helios RC

  2. #2
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    Default

    2. Transmission, Transfer Case and Gearing

    The CMAX platform is designed around the all-new, ultra-scale GCM Low Range transmission mated to a Low Range-specific version of the LRT2 transfer case.
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    This transmission provides a 14.33:1 gear reduction ratio with all hardened steel gears. The LRT2 transfer case in turn provides overdrive gearing to the front axle (11% taller than the rear output) and can be installed in left-drop or right-drop orientation using the same hardware.
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    The transmission mates to the transfer case using a pin drive output, which virtually eliminates drivetrain slop between the transmission and transfer case compared to a traditional universal shaft connection.

    The Low Range Transmission comes with a 12 tooth 48p pinion gear and can support pinions as large as 16 tooth. The chart below shows how the Low Range gearing with the stock 12T pinion compares to some common transmissions:

    Vaterra Ascender (single-speed with stock spur/pinion)
    24.88:1
    GCM Low Range/LRT2 with 12T pinion
    14.33:1
    SCX10 with 5:1 spur/pinion
    13:1
    RC4WD R3 single-speed with Hammer t-case with stock 64T spur and 14T pinion
    (TF2 and Gelande 2)
    11.95:1
    SCX10 with 4:1 spur/pinion
    10.4:1
    RC4WD R4/GCM LRT2 with 12T pinion
    10.1:1



    Note that the ratios in this chart reflect gear reduction from the motor to the rear output only. Total drivetrain gear reduction includes gearing in the axles you choose to run with your CMAX. Axle gear reduction can range from 1.85:1 with the GCM TM8 axles up to 3.75:1 with SCX10 II axles (see chart in the axle section below). Because of the wide range of gear reduction at the axle depending on which axle you run, as well as the impact of tire size on rollout, you’ll want to factor your axle and tire selection into your choice of motor and gearing for your build. A 35T brushed motor on 3S works well as a baseline setup with the Low Range/LRT2 combo paired with TM8 axles and class 1 tires (under 4.2” OD). This combination delivers an excellent combination of low-end control and power with plenty of top-end wheelspeed for most applications.
    BowHouse RC, GCM #tinytruck Team, Team Helios RC

  3. #3
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    3. Adjustable C-Channel Chassis

    The innovative design of the CMAX chassis gives builders unprecedented flexibility for mounting the drivetrain and suspension components as well as electronics and battery packs. Here’s how it works:


    • The transmission and transfer case are mounted using a transfer case bracket that bolts to the underside of the chassis rails. The rails include 10 pre-drilled mounting holes for this bracket spanning a range of over 35mm, allowing you to move the drivetrain fore or aft to fit your particular build.

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    • The steering servo mount is adjustable and includes 7 mounting positions spanning a range of 22mm for locating the steering servo.

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    • The chassis rails include multiple mounting holes for shock hoops and leaf mounts/shackles in both front and rear, allowing for wheelbases ranging from under 10” to over 14.5” whether using leafs or links.

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    • GCM will be offering sliders with integrated electronics trays and an electronics tray that sits between the rails. These trays provide plenty of space to mount all of your electronics and battery packs (3500 mAh 3S or larger) while maintaining full-depth interiors and full-drop beds.

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    BowHouse RC, GCM #tinytruck Team, Team Helios RC

  4. #4
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    4. Suspension

    CMAX is designed to support fully leaf-sprung, fully coil-sprung, or combination setups with one axle leaf sprung and the other coil-sprung. One of the biggest innovations in the CMAX suspension architecture is the placement of the shock mounting positions closer to the center line of the axle than on most 1/10th scale trucks. Mounting the shocks closer to the center of the axle has significant benefits and will require adjusting some of what you’ve come to know about suspension setups. The biggest benefit of moving the shocks inboard is that it allows (in fact requires) the use of much shorter shocks while still maintaining plenty of suspension travel. The smaller shocks work great and are much closer to the proportions of their 1:1 counterparts. So get used to running 55-60mm shocks on your trucks! CMAX Ultimate Kits include all of the chassis mounting hardware for your desired setup, and you will need to supply the leafs and/or coils, as well as dampers. Here’s what you’ll need to know to provide the rest.

    (A) Leaf springs

    CMAX uses fixed mounts and hangers attached to the outside of the rails, not underneath the rails as is the case with popular leaf-sprung platforms from RC4WD, Tamiya, Gmade and others.
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    This makes adjusting leaf packs much easier than with many other truck platforms. With leaf springs, you can set up full leaf suspensions with wheelbases ranging from under 10” up to 15.5” with the shorter Tamiya leafs (up to 14.5” with longer RC4WD leafs). As with any other leaf-sprung truck, choosing the right leaf spring combination is critical to maximizing the performance of your truck. Because the leaf springs are located in the same position on the axles with CMAX as they would be on other platforms, you can use similar leaf spring arrangements to what you’re used to on other leaf-sprung trucks. For a main leaf spring on moderately heavy to heavy trucks, choose a stiffer spring like the Tamiya leafs or black RC4WD leafs with more than one helper under each leaf. For lighter trucks, the RC4WD red leafs with full-length black helpers underneath provide nice compliance and flexibility. If you prefer Gmade leafs, you will need to supply u-bolts to mount them to your axles (or drill mounting holes into the leafs) because the Gmade leafs do not include axle mounting holes.

    Here are a few other tips that will help you get the most out of your leaf spring setup:
    -- Install a full-length helper underneath the main leaf and/or a small helper above the main leaf to help reduce axle wrap.
    -- The Chino mod helps improve suspension travel by allowing the main leafs to pivot more freely as the suspension cycles.
    -- To allow the leaf springs to do their job, remove the springs from whichever dampers you are using.
    -- Use a thicker oil in your dampers than you would otherwise use with a coil-sprung setup to help slow the suspension cycling.

    For dampers, we recommend choosing a narrow-bodied, oil-filled shock in the 55-70mm range, with coil springs removed. The ECX shocks made for the 1/18th trucks (part no. ECX 213000) work very well, and CMAX combos including specific hardware for mounting these shocks.
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    The 60mm RC4WD Ultimate Scale Shocks are another excellent, scale looking option.


    Finally, it’s worth noting that the RC4WD Z-Boxes and Revolver Shackles will not work on the CMAX chassis without modification.

    (B) Linked suspension with coil buckets and dampers

    CMAX’s stock linked suspension uses a 3-link setup with panhard in front and a 4-link setup in the rear. Both front and rear were designed to work with coils separated from the dampers.
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    The coil version of the GCM TM8 axles include integrated coil buckets next to damper mounts, along with upper and lower link mounts and a panhard bar mount on the front axle.
    The coil buckets are designed to accept Axial SCX10 springs or any other 12.5x60mm spring. Axial offers 5 different spring rates in this size. Because the springs sit closer to the center of the axle than the shocks would sit on an SCX10 axle, for example, you’ll end up using stiffer spring rates than you may be used to on other trucks.

    [PLACEHOLDER FOR SPRING RATE RECOMMENDATIONS BY WEIGHT OF TRUCK]

    Damper recommendations for coil bucket and damper setup are similar to those for leaf spring setups. Narrow-bodied shocks in the 55-60mm range work best.

    (C) Linked suspension with coil-over shocks

    It’s also possible to set up a linked suspension with coil-over shocks. To do this, you’ll need to supply front shock hoops and either rear shock hoops or a rear axle that will allow shocks to be mounted at the cross brace between the chassis rails. Standard SCX10 rear shock hoops are a close enough fit that they can be mounted to the front and rear of the CMAX with a slight re-drill of the mount holes, or bending of the legs. Because SCX10 hoops are significantly taller than the CMAX hoops, you will need a longer shock when using SCX10 hoops. An 85mm shock on SCX10 hoops will provide a similar ride height to the stock CMAX coil bucket/damper setup.
    BowHouse RC, GCM #tinytruck Team, Team Helios RC

  5. #5
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    5. Axles

    (A) GCM TM8 Axles

    In conjunction with the release of the CMAX, GCM has also released the all-new TM8 axle family that offers unparalleled flexibility for your build.

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    Key features of the TM8 axles include:

    -- front axles available with left or right drop
    -- centered rear pumpkin
    -- your choice of leaf-spring, or link mounts with coils/dampers
    -- proven ring/pinion/locker from the Vaterra Ascender
    -- GCM-spec front CVDs and rear straight axles
    -- integrated carriers that accept Ascender knuckles on front axle
    -- rear axles accept Ascender bearing caps

    This range of TM8 options allows you to choose the configuration that best suits your build.
    Here is a comparison of the gear reduction for the TM8 axles and several of the more popular axle offerings on the market:
    Axial SCX10 II stock
    3.75:1
    Axial OG SCX10 underdrive
    3.31:1
    RC4WD K44 axles
    3:1
    Axial OG SCX10 stock
    2.92:1
    RC4WD Yota/Yota II axles
    2.67:1
    Axial OG SCX10 overdrive
    2.57:1
    GCM TM8 axles
    1.85:1
    Vaterra Ascender axles
    1.85:1

    (B) Other axle options for leaf-sprung builds

    The CMAX platform is fully compatible with all RC4WD leaf-compatible axles (Yota, Yota II, K44, etc.). The spacing of the CMAX leaf mounts allows these axles to bolt onto the CMAX chassis with no modification to the chassis or axle housings. GCM also is planning to release a conversion kit for SCX10 II axles that will allow you to bolt those into a leaf-sprung CMAX, or a coil/damper CMAX setup.

    (C) Other axle options for linked suspension builds

    If you want to use other axles for your linked suspension CMAX builds, you’ll first need to decide whether you want to keep the separate coil/damper setup or use coil-over shocks instead. GCM will be offering a bolt-on coil bucket/lower link mount for the SCX10 II axle. To keep the separate coil/damper with other axles, you will need to make coil buckets to install on your axle (which is relatively easy to do). If you prefer a coil-over shock setup (or internally sprung shocks), you can use just about any 1/10th scale axle (OG SCX10, Ascender, etc.) by adding a standard height shock tower. Stock Axial SCX10 shock towers will bolt onto the CMAX with a slight bend at the legs to accommodate CMAX’s slightly wider hole spacing. When using other axles with coil-over shocks, keep in mind that you will probably need to add spacers between the shocks and shock hoops to account for the narrower rail location of the CMAX chassis.
    BowHouse RC, GCM #tinytruck Team, Team Helios RC

  6. #6
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    6. Body Mounting
    GCM is developing bolt-on body mount kits for many of the most popular hard bodies currently available, including these:
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    We will update this section as the body mount kits become available.
    BowHouse RC, GCM #tinytruck Team, Team Helios RC

  7. #7
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    7. Setups for Specific Bodies
    BowHouse RC, GCM #tinytruck Team, Team Helios RC

  8. #8
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    CUSTOM BUILDS
    We will be adding pictures and links to some of our favorite custom CMAX builds. Here are a few to get you started:

    GCM's CMF Ford F-150
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    http://scalebuildersguild.com/forum/...highlight=cmax
    (Note this truck started out on a Cross Canyon chassis and was later converted to a CMAX)

    GCM 49 Chevy 3100 Panel Truck
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    http://scalebuildersguild.com/forum/...highlight=cmax

    LoneRanger's D90
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    http://scalebuildersguild.com/forum/...highlight=cmax
    BowHouse RC, GCM #tinytruck Team, Team Helios RC

  9. #9
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  10. #10
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    Reserved 2
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