Updated: March 2008

21st Century Toys 1/9th Scale RC Main Battle Tank

 
 

Background
The 21st Century M1A2 1/9th scale Abrams MBT model was introduced in mid-2005 following success of the 1/6th scale RC M5 Stuart tanks introduced in previous years. The M1A2s retailed for $199 at stores including Wal-Mart although clearance price reductions often drove the price well below $100.



 
 

The Abrams leverages the same basic drive system and electronics (including the piston sound effects!) from the Stuart. The Abrams is a detailed model that is basically faithful to the original. The Abrams is just under 36" from front to rear (not including cannon) which makes it a tad too small for legal RC Tank Combat. With it's highly detailed exterior and large open spaces in the turret and hull, the Abrams makes a wonderful subject for all kinds of modifications by RC armor enthusiasts.

A few weak points in the design include the sprockets, roadwheels, and chassis which are made of thin ABS plastic which is easily repairable but not highly durable. The turret of the Abrams is relatively bulky while the drive system is somewhat underpowered which results in jerky turret movement when underway over rough terrain. Aside from a few detractions, overall the the 21st Century Abrams makes a great low-cost large-scale RC model.

 


 

Answers To Some Common Questions:

What's that clicking / snapping sound that I'm hearing when my Abrams is underway???
If you hear an intermittent click, pop, or snap that emanates from the tracks when running the Abrams you'd better stop and take a look at the front sprockets. The Abram's hull is thin and the front sprockets have a tendency to get pulled backwards under the track tension. This can result in sprocket misalignment with the track and that snapping sound is the teeth of the sprocket catching on the track. Watch out or you'll loose sprocket teeth or the sprocket will break! A solid axle is the best fix but pulling the sides of the hull inward in front of the independent axles will make them line up. Quick fix is to drill a couple of small holes on each side of the hull in front of the axles and use a piece of wire to pull the hull sides inward.

Why are the motors in the Abrams so loud?
Unlike the 21st Century RC 1:6 Stuart Tank, there's a gap between the lower hull and the deck of the Abrams. The gap allows sound from inside the tank to escape (from the gear trains and motors) as well as allows stuff from outside (dirt, leaves, pine needles, rocks, etc) to easily get inside the lower hull. It's best to disassemble and carefully clean out the inside of the lower hull from time to time if you've been running outside. Otherwise, the junk that gets inside the hull can get caught up in the drive motors and gearboxes and cause problems. Some simple sound shielding around the drive motors and the turret motor will help dampen the noise of the drive mechanisms.

How do you disassemble the Abrams?
There are a series of phillips screws on the bottom of the tank. The screws toward the center require an extended phillips head screwdriver to reach as the recessed holes are deeper than a standard phillips head driver. Remove the screws from the lower hull and the deck will easily separate. Be sure to remove the battery before disassembly. Be VERY careful to identify all the connectors that will unplug from the PWBs in the tank to ensure they go back in the same places upon reassembly. Plugging a connector into the wrong position will very likely damage the tank's drive electronics.

 
  Following are some links to pictures of the Abrams electronics with relevant signals identified:
 

Receiver Decoder Pinouts, Power Board Inputs, Receiver Board Outputs

 

 

 

AS OF January 2009 these MODS are no longer being produced for the RC ABRAMS.

There are no replacement parts available for the tanks.

  The Abrams stock radio is OK but a dual stick standard RC radio is even better. A skid-steer mixer can be used to implement a new radio without a lot of fuss or expense. This mod works for single speed only. Here's the schematic.
 

A digital sound module that produces actual Abrams turbine sound effects replaces the poor piston sound effects in the stock tank -- and adds remote startup. The sounds are mixed so the weapon sounds are heard over the turbine sounds. Here's a demo (8Mb Windows media file) of the module in action. Installation of the module does require soldering wires to the receiver in the tank. Speaker mounting can be as desired (for example, speakers in the turret). The module produces the following sounds; turbine spin-up, turbine idle, turbine running with track noises, turret sound, 120mm cannon, and 7.62mm coax MG sounds. Here are installation instructions. Here are some technical & interface details.

  The Abrams sound module with an integrated skid-steer mixer that allows installation of a standard RC radio system into the Abrams replacing the stock radio system completely. Single-speed operation only. The module is plug and play (plug the connectors into the servo outputs of an RC receiver (PPM), solder the four wires to the motors, mount the module, amplifier, and power board in the tank and it's done. Here are installation instructions for the mixer & sound module.