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Simon Peaty, GSC Regional Sales Manager discusses how vital the GSlevel and GSpositionsensors installed in the Bloodhound SSC are throughout testing and in the final land speed record attempt.
Simon: What made the Gill capacitive level sensors suitable for tanks on the car?
Kev: The capacitive aspect of the sensor design was very attractive to us; it means that they are fully sealed sensors and operating on a dried lake bed, things will get very dusty. Having all the sensors as sealed units means they are going to be more reliable. The moving part aspect means we can fit the sensors without worrying about dust ingress and getting into moving parts, so should be very good for that side of things.
Where we have the HTP sensors mounted into bulk head of the car, to get access to these we actually have to split the car at the bulk head and open it up to get into the HTP tank.
Simon: So you need sensors that will be super reliable that you can just fit?
Kev: It’s major, major maintenance getting into there and it will effectively mean packing everything up and coming back to the UK and into the workshop. Because of the dusty environment out there we just wouldn’t be able to do that kind of work.
Simon: …so these sensors can’t be accessed on location?
Kevin: That’s right, we would have to pack everything up and come back to the UK. It would mean delaying the project by another year, so it’s massively important that these are reliable level sensors.
Simon: Absolutely. So how important are sensors to the performance of the car?
Kevin: One of the main points of a land speed record has obviously got to be safety, so we’ve got to know that the data we’re receiving from the sensors is accurate. We compare the data after each and every run and if there are any areas of concern then we stop the run and we find the route of the problem. So every time we see an anomalous or mysterious reading we will stop the run for the day and analyse the data to find the reason why. We need to be confident that the sensors are going to be reliable.
Simon: Right, so the sensors give you a vision into what is happening throughout the whole car. Why is measuring the suspension deflection important?
Kevin: Well as I mentioned the surface of the desert is an alkali plate so it will have almost like a crust on top of the mud. The wheels have been designed to sit in the crust to give us some lateral traction. If we have too much downforce on the car we will be putting too much pressure on that crust and may break through it and end up on the softer mud underneath…
Simon: …which will cause extra drag and slow you down…
Kevin: …exactly, so we need to monitor the amount that the suspension is moving and how much the car is pushing down on those wheels, which is where the 25mm Position sensors play a key part.
Simon: So we are still working through the exact specification and design but we are also looking at a brake stand-off sensor application as well to make sure that the brake disc isn’t engaged with the pad in any way. How is that going to affect the performance of the car?
Kevin: We need to be 100% certain that there is no contact between the brake pad and the disc as the car increases in speed over 200mph. When it gets over 800mph, if there’s any contact at all the brakes will overheat and Andy will lose those brakes when it comes to slowing back down and stopping before the end of the 12 mile straight…
Simon: …and Andy has a mile overrun, how many miles is it to brake?
Kevin: It’s a 12 mile strip; we are using the centre 11 miles, so he has 5 miles to get up to speed, do the measured mile and then 5 miles to stop so we have about half a mile overrun at the end. We have to have the measured mile done in the centre because he’s got to turn around and do another run in the opposite direction within an hour. So he will have the same amount of overrun at each end. So if those brakes overheat then he’s got to rely on the parachutes and the air brakes to stop…
Simon: …and those are going to be less effective below the 200mph speeds, so the sensors are pretty key ensure that 200mph to 0mph is achieved.
Kevin: Yes exactly.
To learn more about GSC’s involvement with the Bloodhound project at gillsc.com/bloodhound