Well, the race has been and gone.
(Scroll down for final build pics, video and blurb!)
Unfortunately, I only managed one run, but it certainly could have been a lot worse… As I thought, the brakes didnt have a lot of power but that wasn’t a massive problem in and of itself. At the finish line i got out and had a look at the back and and the brake blocks were worn right down. No problem I thought – I have plenty spares, so just bolt a new set on and away we go. However, on the way back up the hill (being towed) something jammed on the rear right wheel and it stopped turning. As i was being towed I couldn’t stop, and the wheel and brake disc were worn right down leaving a massive flat spot on the wheel and disc. As I had no spare wheels and more importantly no extra brake discs, my day was done.
I was gutted, but in the end the car did prove a lot of people wrong, and a lot of my theories right, if only marginally…
- The urethane wheels DID grip. I was taking it steady on my run, but I could feel that there was more in the tank.
- The bearings in the wheels didn’t collapse, wear out or explode… People knew they would be spinning very fast due to the small wheel size, but they held up fine.
- Sure, they weren’t super fast wheels, but i also think they perhaps weren’t as slow as some thought they might be! My time was 2min taking it fairly steady. Looking at other’s first runs, I was behind many, but certainly not the slowest on the day.
Ultimately though, one way or another, the braking force required at speed was just putting too much energy into discs and blocks that were too small to take the force and dissipate the heat. The discs were smoking at the end, and to be fair the amount of stopping power available didn’t inspire much confidence, with a very strong leg required to have much effect at all. Ultimately, when pushing, I also think that the amount of grip available (while not that bad) would not have been up to the levels of the tyres used by others. That’s an aside, but I think it’s worth admitting 🙂
Having said all that, regardless of relative success or otherwise at Harewood, the wheels were always going to be replaced anyway. I knew they would have a chance on the smooth track there, but many tracks are nowhere near as smooth – I’m already on with the search for better wheels and brakes, as you might imagine…
Other plus points were the chassis, seating position and steering – all worked really well and I’m super pleased with the results there. Of course, I will be able to keep most of the car as it is too so it’s not like I’m going to have to start from scratch. The journey continues I guess!
The event itself was fantastic and very well organised, and it was awesome to party the night before. I’ve never seen people have so much fun in an empty room with a few beers and a small karaoke machine with no songs on it… There were some great cars and it was incredibly interesting to look at all the different engineering solutions to what is essentially the same problem – going downhill fast… I met some truly great people too. Gravity racers are certainly a different bunch.
Finally, I’d like to apologise to anyone that cares for fucking off home early. After we’d chucked everything in the van my teammate and driver said he’d quite like to get off seeing as we were out as he had some stuff he could be doing at home. As I was mightily pissed off and feeling like a right dickhead I didn’t really argue, so away we slunk. Sorry guys.
Now you know what happened, I’ll go through the final stages of the build. You can read the last part HERE to see how we got this far, or start at the beginning by reading from HERE. As I had to really ramp up the effort at this point to get the car finished, this is by far the longest of the blog articles so far…
First up were the brake discs. These were to be essentially bolted to the inside face of the wheel to act as a durable braking surface. Mental, I know.
The front steering bits were almost done in the last blog, but I’d forgotten to weld on the steering arms… This meant I had to remove the bearings which to be quite honest I thought would be nigh on impossible as they took so much force to press in. However, Andy Ash said “just tap them out with a hammer” and whaddya know – out they came.
Next up the steering arms were made from 3mm steel bar. I drilled a hole in one end to take the rose joint, and shaped the other end so that I could weld it to the bearing carrier more neatly.
No I had to calculate the Ackermann angle (it worked out at 16 degrees) and weld both steering arms on in some kind of accurate fashion. I made up a jig to hold the pieces in place, and fired up the TIG.
Now the discs were on the wheel, I could put the wheels on the back axle and think about the mechanism. This was essentially a bit more inch box with a bolt pivot and a brake block bolted to one end. Nylon washers kept it relatively smooth. Hey look, I took a video of the initial fit up:
With that almost sorted I needed to move onto the frame. I wouldn’t know exactly how to link up the brakes until the axle was mounted in the finished (ish) frame, so I left the brakes for now and moved on.
Finishing The Frame
Up to now, I had two large rectangles so I needed to join them together. I essentially welded in some uprights on all 4 corners.
Next was the construction of the cross member that would form the “dashboard” – basically the past that would hold the business end of the steering wheel. I did this with a length of box section and some pie cut/bend shenanigans.
Next onto the steering column. The cross member at the top already had the bolt holes drilled for the pillow block bearing (20mm ID) so I could easily put this one in place.
And hey look, a video!
Back to the Brakes
Now I went back to the brakes and looked at how I could hook them up. The upright levers on each back wheel needed to be linked together with a cable, which would be anchored at one of the sides. When the cable was pulled, this would pull the tops of the uprights together, forcing the pads onto the discs. Most of this gap was made up with a piece of half inch bar, cut away at one end and with a flap folded over, welded and drilled to make a cable anchor.
I didn’t get any more good pics at this point, but chose to move onto making the seat anyway. I knew the seat would need to be in place so the seating position was final. This would mean I could see where I had room to run the brake cable, and also where to position the brake pedal…. Which I had yet to make.
I stared blankly at the gap where a seat would be and realised that I had no idea how to make something that would a) fit, b) be comfortable, and c) wouldn’t look shit. I messed about with bits of plywood with the idea of sticking foam to it, but wasn’t really happy with anything I could come up with. Just not good enough. The next day I went to the tip and happened to see an old office chair and I thought “AHAAA”, dragged it out of the skip and bundled it in the back of the car. Once back in the workshop I took it to pieces and was left with a nice seat base and back, all ready with bolt mounting points. Lovely job.
Finishing the Brakes
Now the car was nearing completion and it was a case of fabricating a brake pedal and plumbing everything in. I was desperately running out of time at this point so didn’t take as many photos as I should have, but there you go.
Bodywork and Graphics
At this point it was literally the day before I would need to set off for the race, so photos are slim on the ground as you can imagine. The body panels were made from 3mm aluminium composite (commonly called Dibond), and the “bonnet” section was made from 1mm PVC as it needed to bend to fit the contours of the steering column crossmember. The graphics are cut or printed vinyl, courtesy of my employer Ad Bell in Harrogate. And yes, it’s meant to be a replica of a late 80s, early 90s Benetton F1 car.