The next meeting, at Castle Combe, is coming up so I thought I’d write a quick missive to get up to speed with this increasingly out of date site. In fact, it’s quite likely that by the time I finish this it’ll be after Combe. Of well…
To be honest, most of my time recently has been spent doing non motor racing things. Since the last post we’ve been cycling in the Peak District, done the Way of the Roses coast to coast cycle path on our tandem, driven to Italy and back—mostly with the car roof down—and done a couple of motor race meetings. That’s one of them above, at the imperious Anglesey Coastal circuit. We’ll start with that race…
The main thing I did before Anglesey was to make a larger rear spoiler out of carbon fibre. This was made by the resin infusion technique (essentially, you stick everything in a sealed plastic bag and suck the resin through the moulding). I had some trouble making a mould of the shape that I wanted that would stand up to the vacuum so I ended up with just a flat spoiler. At some point later I’ll make this again in a more curvetastic form. However, for now it’ll do. It’s also a bit large, although interesting that it’s half a kg lighter than the previous smaller aluminium spoiler.
It is clear, from the increasing bodywork damage in various places, that the bodywork is starting to generate some downforce. I’ll have to look at supporting things a bit better at some point. What I really need to do is to start logging the suspension position, using something like some string pots on the dampers, so that I can really see what’s happening. Colin’s got some strain gauges on his pushrods to do this job, but I’m not at all sure that it works well enough to consider. The problem is that the string pots are not exactly cheap.
With this done we went up to Anglesey for a weekend in sunny, we hoped vainly, Wales. As it turned out it was sunny, which is great. Trac Mon, as it’s called, is a superb circuit but it can be ruined by torrential rain. The problem was, though, that there was a horrific wind the whole weekend. It really started to get a bit wearing when you couldn’t walk around without thinking that you were going to take off. A number of us were looking at the wind turbine that’s in the paddock and wondering if it really was supposed to make that noise…
I had booked the test day although, as it turned out, there was way too much traffic and it was very hard to get a lap. Come qualifying and it was pretty busy but I managed to get 8th place on the grid for each race. At least I’d be able to see the front.
The first race wasn’t too wonderful to be honest. I made my customary not-so-bad-but-not-good start and had to make sure Mark didn’t get in front of me at the banking. Just after that, Scott ran wide onto the grass in front. In regaining the track he threw up a whole load of mud, one clod of which completely deranged one of mirrors. Luckily, I could just about reach it to put it right. After that it was a bit of a lonely race. You can see the video here, look out for the flying mud…
I finished in 8th place; 8 seconds behind David and 5 in front of Colin. So, not exactly a busy race.
Overnight it threw down with rain but, amazingly Sunday looked like a nice day again, apart from the ever present wind. As before, I started in 8th place and this time made a rather better start. Out the back of the circuit I was side by side with Tony into Rocket. However, I managed to stay ahead of him. Unfortunately, you can’t see much on the video as I’ve not got a rearwards facing camera, yet, but Tony spent much of the race just behind me. I was quicker through the twisty bits than him but repeatedly made up ground on the back straight. I managed to get a bit away from him when we had to pass a back marker but he closed up again when there was an incident at Rocket that we had to pick our way around. However, I managed, unusually for me, to not make any horrible errors and I was still in front at the flag. I finished in 6th place, just ahead of Tony. Here’s the video for your delectation:
After the Anglesey meeting, we beetled off home as fast as we could and packed up the tandem and went off and did the Way of the Roses coast-to-coast cycle route which goes from Morecambe to Bridlington. It was supposed to be 171 miles but we managed to make it 195 by going the wrong way a couple of times… It was a great trip though. I could show you some of the video of that, but it’s really rather boring…
Rather than string pots which are indeed horrendously expensive (albeit cheaper than LVDTs) and give way too much information to be of great use, unless you’re doing damper tuning, I’d use some of those nice Sharp IR distance sensors.
They only work at 40 Hz max, so ditch a lot of the road noise and panel resonances out, provided there’s a suitable LP filter in there to stop aliasing. Because you’re looking a very low frequency events, taking forty samples (or even 80) and then median filtering them will be about your best option, perhaps with a nice exponential filter on top to finish the whole thing off…
Definitely a job for a microcontroller with ADC and a UART (they all do), rather than doing all the analysis offline after the event. Chucking it down the serial line into a DL-1 makes a lot of sense.
Dave,
Thanks.
To be honest, I do have two other schemes. One of them is, as you suggest, using those Sharp IR sensors. The other one is to actually use a rotary pot (and the thought is to use some throttle pots as they’re cheap on eBay and robust enough for the automotive environment) and mount them on the suspension bellcranks. Admittedly the rotation is not linear wrt suspension movement but that’s easily processed.
If RT would hurry up and produce the oft-promised serial-8 unit it’d make life a lot easier…
T