We found an error in the tests of maximum speed. Well, not so much an error as a misunderstanding. These emails explain.

Yes. Here’s a weird thing: it goes faster in reverse than forwards. Might that be a factor?

Canberra

Definitely weird. I have read somewhere that forward and reverse have different speeds. I will see if I can find it. How fast would you say it went?

Sydney

Fully charged: reverse feels 50% faster, especially from standstill. [The] Lower the battery’s state of charge, the faster reverse feels compared with forward.

Canberra:    

I found details of a speed controller that said ‘forward 60A reverse 30A’. Have you somehow got a reversed connection somewhere?

Sydney

Great. I’m just recharging the battery then I will dismantle the car and examine the speed controller connections.

Canberra

Ok. So I switched the leads that connect the speed controller to the motor, so it’s yellow-yellow and blue-green. This accords with the instruction book. And it goes twice as fast forwards as backwards now. But to get it to go forwards I have to indicate backwards on the transmitter and vice versa to get it to go backwards.

Canberra

Solved! There is a switch on the transmitter that can reverse the direction of the trigger input. I’m feeling rather clever right now.

Canberra

I’m off to the car park now with measuring tape and stopwatch.

Canberra

On the analogue stopwatch I’m getting 1.8 sec consistently at top speed over 10m. Now for the digital.

Canberra

Phone stopwatch is coming out closer to 1.9

Canberra

I make that [1.8s] 20km/h. That degree of agreement is a fluke , but we might be in the right car park.

Sydney

Digital keeps coming up with 1.9 and I back your calculations.

Canberra

1.9s gives 18.9km/h

19 to 20km/h sounds reasonable.

Next we’ll go back to the theory and incorporate the gearing.