Your eBay L298N motor driver and 4.5V power supply match each other.
Meccano 4.5V motors for road racers are usually heavy duty and take huge current.
If you have only one big Meccano motor, then I would recommend to get four small ones like those from Adafruit. Or you might like to show us a picture of your Meccano motor, just to make sure.
eBay L298N x2 Dual H Bridge DC Stepper Motor Driver Controller Board Arduino US$5.49
eBay 4.5V Power Supply 3 x AAA Battery Holder Enclosed Case Box Switch Wire Lead 2pcs -US$3.80
Meccano Off-Road Racer 25-in-1 Motorized Building Set
Adafruit DC Gearbox Motor - "TT Motor" - 200RPM - 3 to 6VDC US$2.95
AdaFruit DC Toy/Hobby Motor 130 Size US$1.95
These are standard '130 size' DC hobby motors. They come with a wider
operating range than most toy motors: from 4.5 to 9VDC instead of 1.5-4.5V.
Rated Voltage: 6.0VDC
No-load Current: 70 mA max
No-load Speed: 9100 ±1800 rpm
Loaded Current: 250 mA max
Loaded Speed: 4500 ±1500 rpm
Starting Torque: 20 g*cm
Starting Voltage: 2.0
Stall Current: 500mA max
Adafruit TT Motor Description and technical data
Rated Voltage: 3~6V
Continuous No-Load Current: 150mA +/- 10%
Min. Operating Speed (3V): 90+/- 10% RPM
Min. Operating Speed (6V): 200+/- 10% RPM
Torque: 0.15Nm ~0.60Nm
Stall Torque (6V): 0.8kg.cm
Gear Ratio: 1:48
Body Dmensions: 70 x 22 x 18mm
Wires Length: 200mm & 28 AWG
3VDC ~150mA 120 RPM no-load, 1.1A stall
4.5VDC ~155mA 185 RPM no-load, 1.2A stall
6VDC ~160mA 250 RPM no-load, 1.5A stall
tlfong01's L298N testing notes
Motor Driver and Motor Compatibility Check
I checked the TT Motor at 4V5, and no load and stalled current to make sure the driver L298N DC current limit of 2A is not exceeded. The geared output shaft stalled (but non gear shaft still moving with slipped gear chain) shoots to over 250mA, but immediately returned to a stable value of about 130mA.
So far so good.
I checked the stall current of the 130 motor without gearing, and found the stall current around 700mA. So a newbie like me should play with geared motor first, because the "stalled" current (when gear out stalled, but shaft still moving, with the gear chain slipping) is only around 140mA.
eBay AAA x3 = 4.5V Batteries Case with Switch Lead
The eBay Battery holder says "holder switch wire lead", but I don't see any switch on the holder. I usually use battery holders with a switch.
The manual switch is very useful when during testing you smell plastic burning, smoke coming out, motor finger burning hot etc, you can immediately switch off the battery. For the cheapy motors I am testing, I found them from time to time gets stalled because gears locked, and you need to start by turning it by hand. The stall current is many times than the steady current, so it is important to switch off the battery first.
I also googled that Duracell 1.5V AAA battery can last about 1,000 mAh at 100mA load. So it should be OK to test the TT geared motors which consume of the order 100mA.
1.5V AAA Duracell Alkaline Battery Tests - RightBattery.com
– 970 mAh at 0.1A load
– 777 mAh at 0.2A load
– 553 mAh at 0.3A load
– 336 mAh at 0.5A load
The Meccano motor looks like a big guy. Its shaft looks like 5mm diameter. Let me find a similar motor and measure the current.
I searched my junk box and found a big motor looking similar to the Meccanno motor. I has a 5mm diameter shaft. I measured its current with different voltages and summarized the results in the following picture.