Tamiya M4 Sherman Project

Many Tamiya fans believe that the first Tamiya RC was the 58001 Porsche 934 Turbo RSR.  While that was indeed the first RC car, the first Tamiya RC of all was the 56001 M4 Sherman tank model two years earlier in 1974 (it was called RT-1601 at the time).  The model was designed by Dr. Fumito Taki who had recently transferred from the accounting department.  The original idea was to use the German Maus tank as the subject, but they soon learned that due to the tank geometry it wouldn't turn well and the tracks would easily get clogged with debris.  They needed something short and driven by the front sprockets which gripped the tracks at the outer edge.  This made the M4 Sherman the only viable option.  The other advantage of the Sherman was that some uncommon versions used a 105mm howitzer instead of the standard 75mm cannon, and this short barrel would be less likely to hit obstacles, making it more suitable for a running model. So Dr. Taki headed off to the garrison at Higashifuji to measure the real thing for a scale model.  After making a few mockups from wood and clay, he proceeded with the gearbox.

In these earliest days of RC, proportional controllers scarcely even existed.  For that reason, the original Sherman tank was basically a static model with a gearbox that could be built using 0-2 channels (cutaway shown at upper left).  The gearbox had two sides like a skid steer which could be connected independently to two 360 sized motors or connected in parallel sharing a single spur gear.  Each gearbox side had a clutch at the forward end which was spring loaded to grip the input gear.  However, if the front of the clutch housing were pushed forward it would gradually release the input gear and connect to ground instead.  In the simplest setup, the motors were just connected in parallel with no RC at all.  The model could simply be turned on and off and would drive forward when on.  Because the left and right sides were hard coupled together, it would drive straight.  The one channel version was intended to use the old controllers with one toggle button.  In this configuration the motors were connected to each side separately.  It would drive straight forward until the button was pushed which would simply disengage the left hand motor causing a turn.  Stopping, turning right, and going backward were not possible.  Even the most deluxe configuration was still very electronically simple (but mechanically complex).  A proportional servo was used for steering.  It was connected to a wide crank which could contact either clutch, so by rotating the servo either side was gradually disengaged and then grounded.  This allowed proportional turns all the way to stopping one track.  Pivot turning was not possible.  Incidentally, many early tanks used a similar clutch and brake turning system.  The prototype gearbox was made by Dr. Taki himself on a lathe.  It worked perfectly and even allowed him to attempt a version with a water cooled engine.  There were no speed controllers yet, not even mechanical, so there was no proportional throttle.  Instead, another servo just contacted either a forward or reverse switch.  This means the model could be stopped, full forward, or full reverse.  This was the full extent of the controllability.  No remote control of the turret or barrel was possible.  In terms of scale realism, the real 105mm didn't have powered turret traverse or elevation, so the lack of these features on the model is actually correct. 

Tamiya made three more RC tanks over the next few years (Leopard A4, Flakpanzer Gepard, and King Tiger) which each progressed a bit in terms of technology.  The Leopard used the same gearbox but switched to a single 540 motor.  The Gepard used the same thing but added a proportional mechanical speed controller and an optional 3rd channel with it's own battery that rotated the turret, elevated the guns, and rotated the search radar all at the same time.  The Tiger used a modified version of the same gearbox, a rotating turret, and a strobing light in the barrel.  This 4-channel version was the most deluxe tank of that original generation.  Then things went quiet for 18 years!

In 1998 Tamiya finally came out with a "new" tank, and for this new generation the M4 Sherman was the first choice again.  Outwardly this new 56005 Sherman was indistinguishable from the original, using all the same plastic body parts and suspension.  Inside, however, everything was different.  A pair of new gearboxes using 380 motors was introduced.  These gearboxes lasted a long time.  They were used in new tank models up until 2016 and are all still sold today.  The real revolution though was the DMD (Dual Motor Differential), a twin motor electronic speed control box.  Using this controller, power to each gearbox could be modulated separately.  The transmitter signals were mixed inside the DMD allowing the driver to use standard throttle and steering controls instead of skid steer.  It was still a 2-channel model though with no turret control.

So what does "Horizontal Volute" mean?  This refers to the springs used in the suspension.  Most suspension uses coil springs but these have some big disadvantages for tanks.  Because of the weight a very large wire diameter is needed which means the solid height of the spring is very tall and therefore the suspension has hardly any travel.  A volute spring is made in a tapered spiral out of wound rectangular bar stock.  Because it is tapered, it nests when compressed and has much more travel.  Most M4s were made with the volute springs arranged vertically, but a few later models used horizontal springs connected to pivoting bogies mounted in pairs.  The system used in the model is made to represent HVSS although it actually uses coil springs hidden inside cans to simulate volute springs.

There were also a wide range of engines used in the M4 Sherman.  The model represents a version using a 15.98 liter 9-cylinder radial engine from Wright Aeronautical.  The distinctive sound of this engine was recorded for the model.  The sound is contained in the MF-02 unit which is unique to this model.  The DMD T-05 is also unique to this model.

There were also variations of the Sherman in different combinations of cast and welded hulls.  The square sides of the model represent the welded hull version.

The kit was available in two versions, one with a radio and one without.  By the time I was looking, I could only find one so I ended up with a 27MHz AM radio I will never use.  It was still worth it.  This tank is awesome.  It turned out to be everything I hoped.  I don't know how they can make it better, so I'm betting against a fourth version.  Everything can be controlled remotely using only a 4 channel transmitter.  Remote functions include throttle, steering, turret rotation, gun elevation, main gun firing, machine gun firing, and turning lights on and off.  Most functions are accompanied by sounds which are automatic.  Speed and power is good despite the small motors.

©2021 Eric Albrecht