MINIATURE-ART - M1A2 ABRAMS

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Simple DIY ideas and solutions

abrams-underrepair.jpg
Major repairs in progress

Owning a Tokyo Marui tank can be fun, but like all mechanical objects, eventually it will break down. As of 2004, there are no official Tokyo Marui R/C tank importers in the US, as most stores that sell them purchase the tanks directly from Japan themselves. Thus obtaining spare parts in the US is difficult at best.

 

There are a few options should you suffer a mechanical problem, assuming you have identified the cause:

 

1)  Post a message asking for help or advice on the Yahoo Marui Tank Group (see links page) Members can offer repair tips or perhaps trade or sell you the parts you need.

2)  Contact the vendor who sold you the tank. They often have returned stock or store demonstration models that can be cannibalized for spare parts.

3)   ***Never purchase a pirated copy of Tokyo Marui tanks manufactured by Hen Long (commonly found on E-Bay) for spare parts.***

 

Options #1 and #2 are the best choices because in general Hen Long Airsoft tanks are inferior in fit, finish and quality to Tokyo Marui products, and should be avoided if possible.

 

 Recently Hen Long released their illegal copy of Tokyo Marui's M1A2 Abrams. Avoid it at all costs! This knock-off can be identified by:

 

1)     the lack of Tokyo Marui label on the box

2)     Rechargeable batteries (Genuine Marui tanks use AA Batteries)

3)     Type 90 style tall transmitter

4)     The tank has only 6 road wheels (not counting the idler or drive sprocket)

5)     The smoke grenade launcher boxes are upside down

6)     Oversized LED on the coaxial machinegun and headlights

abrams-henlongabrams.jpg

Genuine Tokyo Marui Tanks retail for approximately $135USD. Some unscrupulous dealers (especially on E-Bay) inflate the $40USD price tag of a Hen Long Abrams; or feature a Tokyo Marui tank on their advertisement then send you an inferior Hen Long product after they receive payment. Buyer Beware!

As of writing, I have experienced 2 problems with the Airsoft gun,  I will describe each in turn:
 
1) The 6mm Airsoft Gun stops firing
 
Approximately 6 months after purchase, I began to experience problems with the gun firing mechanism. The Abrams tank eventually stopped shooting BBs all together. Instead of trouble shooting, I continued depressing the gun firing buttons which resulted in the gun motor drawing extra current from the batteries. This resulted in a burned out circuit board. In retrospect, this is what I should have done:
 
1) Shut off the tank and transmitter before checking for the problem.
2) Disassemble the upper and lower hull of the tank. Check the contacts and wiring leading to the gun motor and circuit board. Occasionally roadside debris and dirt will work its way into the hull, and interfere with the current flow between the circuit board and gun motor.
3) Depress the firing buttons on the transmitter. If the red warming LED is on and the motor sputters or does not run, this indicates the current is flowing, and the problem is the motor itself.
 
Carefully remove and disassemble the turret. Remove the 6mm airsoft mechanism from the turret. Check to see if the gun motor bracket is cracked. If it is cracked, the motor will slip out of place, causing a jam with the Airsoft cocking gears. (Continuously depressing the firing buttons at this time will cause extra current drawn to clear the jam, and burn out the circuit board instead!)

abrams-brokengunmotor.jpg

If the gun motor bracket is cracked, the repair work is simple. Find a thick sheet of plastic or thin metal strip, and use CA glue to reinforce the cracked bracket. Push the gun motor firmly back into place before securing the reinforced bracket. Be sure to test the 6mm Airsoft gun prior to screwing the entire gun assembly together. It is important not to over tighten the screws which can crack the gun motor casing.  Also, I was able to solder in a new circuit board with a donated replacement from a fellow member of the Yahoo Marui Tank Group!

2) The 6mm Airsoft Gun fires but with difficulty

 

If you have gun motor problems, such as sputtering, or surging when the motor rotates, disassemble the hull and turret, and remove the Mabuchi 130 size gun motor.

 

1) Disassemble it by prying open the metal tabs on the body of the motor and pull the white plastic cap off.

2) Inspect the gold contacts and black carbon brushes inside the plastic cap. It is not uncommon to have broken contacts, causing motor problems.

3) Inspect the inside of the plastic cap to see if there are any tiny black specks. These specks are carbon "dust" broken off from the motor's brushes. The purpose of the carbon brushes is to prevent excessive wear on the gold contacts inside the motor. Cheaper toy 130 size motor do not have carbon brushes. The excessive carbon dust interferes with the flow of electrical current, causing the motor to  perform poorly.

 

 

abrams-130motor.jpg

To remedy this problem, simply use a stiff paintbrush and alcohol, and clean out the carbon dust. When finished, I added a tiny drop of R/C car motor oil to the motor's axles. This will work its way into the motor and reduce friction without affecting its performance.
 
At this point, my Airsoft M1A2 Abrams shoots like it was new out of the box!

Finding the right replacement motors can be difficult. Most 130 size motors are the cheap variety (brushless, uses only gold contacts), commonly found in toys.  If you are in need of new motors, Tamiya's Jr. Mini 4WD Torque Tuned Motor (#15130) has similar specs to the original Tokyo Marui gun motor. This is a heavy duty motor designed for slot car racing and uses carbon brushes as well.  If you need only replacement plastic motor caps with carbon brushes, check you local automobile salvage yard. Mabuchi 130 size motors are used in the side view mirrors in cars, and I obtained several free of charge from my auto mechanic.

3) The Drive Sprocket Teeth are Broken
 
On Marui tanks, the drive sprockets are composed of a cylinder with a cutout in the middle. In the cutout space are bar shaped "teeth" that are evenly spaced to permit the center guide teeth on the tracks to fit inside. Unlike actual tanks, the center guide of the tracks provide the actual contact point to the drive sprocket, permitting locomotion.
 
Over time (especially in Hen Long tanks that are made of lower grade plastics), the center bars can break off, causing the drive sprocket to spin freely, and not making contact with the center guide teeth of the tracks.

abrams-drivesprocketfix.jpg

Replacing the center drive sprocket bars is an easy repair job. You will need to purchase 2-3 mm brass rod. Brass is easier to cut then steel wire, and the brass can be filed to provide a key for CA glue. Follow the steps below:
 
1) Roll the brass rod under a #11 hobby blade with light pressure, and it will cut cleanly. The piece you remove should be 7-8 mm long.
 
2) With a pin vise (small hand drill) drill a hole perpendicular to the drive sprocket directly over the placement of the broken drive bars. Then cut and widen the hole into a "U" shaped channel with the tip of a hobby knife.
 
3) Insert the brass rod first into the aperature opposite the "U" shaped channel. Then push the other end of the brass rod gently down into the channel to seat it properly.
 
4) Use gap filling CA glue to secure the brass rod into the aperature and channel.

abrams-sprocketrepair.jpg

Take care to insert the brass rod at the correct depth to ensure the track center guide teeth fits into the space between each drive sprocket bar. The brass rods should be perfectly parallel to each other. Precise placement will prevent problems such as the track not fitting or binding.  Your Airsoft tank should now run like new with no problems.

 
 
 
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