Thanks for your reply.
Here is the motor that worked:
Pololu Mini Metal Gearmotor
• DC Motor
• Nominal Voltage: 6V
• Free RPM: 140
• Stall Torque: 15 oz-in (1.0 kg-cm)
• Stall Current: 800mA
• Reduction: 100:1
• Size (mm): 1.66" x 0.46" x 0.60"
• Weight: 0.80oz / 27g
Yes - thats a much smaller motor; as you can tell its stall current is well under what the h-bridge you have can supply, which is why it works well.
Also, I couldn't find the datasheet for the 'Tamiya USA 540 Motor' as it came with the RC chasis. But it should be similar to what you posted.
From what I saw online, the Tamiya motor -is- a Mabuchi motor; but I don't have it in front of me, you do - so look on the motor and see if you can see any markings or numbers that you can google on...
And I believe you. I think the motor's pulling too much current saturating the H-bridge. (Multimeter shows 2.15 A for a sec then it goes away >> way beyond the H-bridge capability)
If you can't find a spec sheet, what you could do is hook up your multimeter to measure current using the 10A probe setting, switched to current measure mode (make sure you do this properly!), then hook it in series with the motor, and attach a small pair of vice-grips to the shaft (enough to prevent it from rotating, but not so much to damage it - you may want to put something between the shaft and the jaws as well, like a piece of rubber or leather). Apply your voltage (for less than a second!), and watch the meter, record the reading. Record the reading while free running, too. That will be your min/max range.
Any suggestions on how I can decrease the current going into the motor to about 1 A. The thing is, the '540 Motor' fits perfectly on the chassis but the Polulu is like one quarter the size of '540'. So, if possible I would like to use the "540" and avoid more assembly work. Another fact, the speed of the Polulu's revolution speed is perfect for our project but the "540" spins at an insanely high speed (due to high voltage/current ??).
Well - you could try a high-wattage sand-resistor inline with the motor, but its going to decrease the torque (and the resistor will get hot); the thing is, it would be cheaper to get the right h-bridge, rather than control the current. The reason the motor spins so quickly is due to its design and the voltage, it was just designed that way.
I am going to dedicate today to running the "540". If you have a suggestion for a better H-bridge (and available at Radioshack so that I can get it quick: I cannot wait a week so I can't order it online) please provide. Otherwise, I will have to switch to the Polulu.
Without knowing the exact specs, its difficult to say; you won't be able to buy a cheap (or expensive) h-bridge IC that will run that motor from RatShack though - they don't sell them. What you might try is to build an NPN transistor h-bridge, using 2n3055 NPN TO-3 case transistors, which I know RS sells (whether yours have them in stock is another matter). The only problem with such an h-bridge is cost (RS 2n3055s don't come cheap - they overprice them), plus you may need a heatsink (which they don't sell) for each/all transistors (plus insulators, etc).
With only a week, and from what I gather, not enough understanding to design your own high-current h-bridge, your best bet might be to stick with the Pololu motor for now...