Chassis Team Leader Andrew Dunn talks through his EV Pedal Box Design
12.03.20 · Engineering News
Rachel: So, this year with the transition to electric there are a couple of things that need changed like the pedal box. So Andrew, can you talk us through the final year project and what you’ve been doing?
Andrew: Yeah, no worries, so changing to EV means we have to do 2 very major changes straight away. First off, the clutch pedal, that is used to stop the car generally in an IC car, but we don’t need that anymore. So that can be taken out completely and we are left with just the throttle and the brake pedals.
The second big change is the throttle pedal itself. It used to be actuated by a throttle cable, which worked with the intake at the top of the roll bar, but now we can change that so it is electric, which then runs through 2 sensors, which runs electric down the wire to the inverter, and controls and send signals to the motor, which then controls the wheels.
In the past the pedal boxes tended to suffer from one big mistake or problem, and that was that it was very hard to adjust, or it was not easily adjusted. Which is a big problem because during the endurance race you have to change driver halfway through. To try and get the to pedal box to change then was always a big, big hassle as it was held in with bolts. But this year I have spent a while trying to optimise the adjustment process, making it a lot quicker. So when you are moving it forward and back it takes seconds as supposed to minutes.
The final big change that I made was that I made the pedal box shorter. So these master cylinders, I managed to choose different ones because these are linear master cylinders which stick out from the back of the pedal box a lot, whereas I have used ones that connect up here and down here, which then pivot, which allows the pedal box to be made much shorter.
Rachel: Obviously the driver has to exert a certain amount of force on the pedal without it breaking. So how have you made sure that your designs withstand the force of the driver?
Andrew: So the IMeche form the rules for Formula Student, say that the pedals have to withstand a minimum of 2,000 newtons. Through some testing that we carried over from last year to the beginning of this year, prospective drivers were told to press as hard as they could on the pedal and the force was measured. This came out with the maximum force they could press was generally about 1,600 newtons. So, if we design the pedal box to the 2,000 newtons using FEA tools, then it should give us a reasonable factor of safety and it shouldn’t break.
Rachel: And what about the future of this sort of project like regenerative breaking, is that something you are going to look into?
Andrew: Yeah, absolutely, so for my project this year I am looking into how regenerative breaking could be done. We’re not going to implement it this year, but with the aid of different sensors on the brake pedal, then regenerative breaking could be implemented to allow some of the power that is wasted during the breaking to recharge the battery which will give us a bit more range in the endurance event.
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