LocostUSA.com

Wow. Stunning work as always.

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-Keith

Time for an update! Unfortunately, I didn’t get my car out to many events last year due to covid restrictions, and a mechanical issue. I had the opportunity to give my dad a ride along at a lapping day while he was in town. Although the day was cut short after just one session, that was about all he could stomach, haha. While on track I started to smell raw fuel, and upon parking at the end of the session you could actually hear fuel pouring out from underneath the front. The RCI fuel cell had split! I found two large cracks in the welds. One was on the seam between the front and top, above the fuel level. The other was on the seam of the front and right side, in the middle of the tank. Each crack was roughly 4” long. The fuel slosh inside the un-baffled tank was enough bow the walls, and crack the welds (doesn’t look like much penetration to start with) in just a few thousand km’s.



I looked into various other fuel cells and replacement options, but ultimately decided to repair and reinforce the existing tank. To do the repairs I cut the top off the tank leaving a ½” flange all around the opening and used my spool gun to fully weld the inside of all the seams. I took the opportunity to add some diamond shaped baffling to reduce the fuel slosh and strengthen the walls. The design also allows for the reuse of my multi point pick up system and fuel level float. I bent up and added an extra angle all around the opening and then tig welded the top back on and redid all of the outside seams. Pressure testing revealed a few pinholes but those were easy to touch up.



I have some grip enhancing mods in the works for this season, and I wanted to add some extra insurance against oil starvation so I decided to install an accusump. Due to space constraints I had to opt for the 2 qt version. Most accusumps seem to be plumbed in after a sandwich plate or the filter/oil cooler, but my oil pump has a huge galley plug in it that I thought would make a perfect connection to the main oil galley. It should offer the most direct, and responsive path, and it works well with my packaging.



Another neat project I had was building a sim racing rig. I found out that the local track I do lapping days at had been modeled for Assetto Corsa and thought it would be a really cheap way to improve my lap times. I managed to transform my computer desk from something just like this:


To this:




I was able to retain the keyboard slide out, and relocate the drawers, and tower cabinet so it still functions as my computer desk all while being more compact and comfortable! The seat is from a Volvo S60 that I had previously turned into an office chair, which I then put back on the power base for the rig. I haven’t hooked up the seat heater yet but if it gets banished to the garage I might just have to do that.

Bummer about the fuel tank rupture, the baffles should cut down the oil canning due to slosh now, sensible improvement.

Brilliant work on the sim setup, looks very comfortable.

Thanks. I have to say I was immediately impressed with the feel and realism of Assetto Corsa and the modeled track. I thought the KTM X-Bow would be the closest match to my car for power, weight, and driving dynamics. Right away I noticed the braking, shift, and turn in points were all right on, and the cars vehicle dynamics felt extremely familiar. The lap times that followed were also bang on what I had been getting with my car! Within an hour of trying different things and looking at the lap telemetry I found a couple places where I could shave off some significant time.

After the fuel cell cracked I wasn't sure how long the car would be out of commission, so I immediately ordered a new set of tires for our daily driver, a 2019 Chevy Bolt EV. I had autocrossed it a few times already and it had done reasonably well, but the wider aftermarket wheels moved me in to STH class where the PAX index was not so friendly. I've always been curious just how competitive it could be in HS with the original wheels so I got some 215/45r17 Falken RT660's for them. The only other mod is a Whiteline rear sway bar, and so far in overall PAX points I've snagged four 1st place finishes, one 2nd place, and two 3rd places. It does very well, and it costs pennies to do it! It's hands down my favorite car I've ever owned. It's got nice quick steering, good pickup, great interior room for the size of it, and it's so smooth and quiet. Not to mention with the current price of gas we've saved close to $14,000 in fuel in the last 3 years compared to our old Volvo.

Everyone I know who have Bolts and Volts love them. The bad pub on account of the battery fires seems to be what those who don't own them want to talk about, but I guess that's what we get for listening to the news.

I came very close to getting a Bolt, but then I retired, and with the few miles I drive, it (and all EVs) lost much/all of the advantages.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I thought for a long while on how to make my car faster for this year. At first I was considering adding more power, either with building up the compression, or adding a turbo/supercharger. But all those options were fairly costly, and required lots of time. I wanted to make sure my car would be ready and reliable for this season as it’s the last year our local autox venue will exist. At the end of the season the track will be bulldozed and redeveloped in to an industrial park with a little bit of residential mashed in there. So instead of power, I thought focusing on grip would be better. I don’t drive the car much on the street these days, and I have access to a trailer, so it opened up the possibilities a little.

The first and easiest way to make it faster was obvious, tires. I was pretty impressed with the BFG Rivals that I first had on the car. When they wore out, I opted for some Hankook RS4’s that I got a smoking deal on. I thought I would be OK with the drop in grip, since they would last longer and they were a great deal. I loved how they drove and thought they were great tires, but in the end I just couldn’t handle intentionally making the car slower. I considered A052’s, AR1’s, NT01’s, and RT660’s, but I figured if I’m going to trailer it and I want to see what the cars full potential is, then it has got to be Hoosier A7’s. 

The second part of adding grip was aero. When I first built the car I had a pair of wings for it but they were just $100 ebay specials. The wing profiles were pretty horrible, the element spacing and overlap was all wrong, and they were pretty small as well. Maybe they had a small effect on the road course, although I doubt it, but they were certainly useless for autox. I started by looking at commercially available wings, that would actually produce some decent down force, but they were way outside my budget so then I started looking into building my own. I had planned to do fiberglass over a foam core, and settled on using an Eppler E423 profile to get decent performance while not being too difficult to make. The problem with this approach was it was going to be very time and labour intensive. One day I discovered 9LivesRacing (9LR) sells “mini-wangs”, and thought this would be a really good option. Their normal “wang” (wing) is a really nice aluminum extrusion with great performance at a reasonable weight. Because they get these extrusions in huge lengths, they end up with off-cuts up to 30” long and sell them super cheap. I pulled the trigger and ordered a dozen 30” off-cuts for less than the price of one single 6’ wing. I wasn’t exactly sure how I was going to use them but now I was committed.

I had a couple wing ideas that I wanted to explore, both through modeling and real world experimentation. I wanted to use JavaFoil (a free cfd program that can handle multi element wings) to compare the performance between a single 9LR wing, a biplane configuration, and a multi element configuration. I couldn’t blindly trust the software so I wanted to build a test rig and verify the general findings. I started by cutting a thin slice of a wing section, scanning it, and tracing it in AutoCAD.



After running the numbers in JavaFoil, and taking them with a grain of salt, I built a test rig to mount to my truck and take some actual measurements. I would do a small scale test with just one 30” section in each configuration. I made some roller slides for the wing assembly to slide up and down on (or forward/backward for drag), purchased a 300lb digital luggage scale for the down force measurement, and used an old cell phone for GPS speed readout. My data acquisition unit was just a gopro camera filming both the scale and phone at the same time. Runs were made at a consistent speed, on the same stretch of road, same day, minimal wind, and averaged over both directions. After confirming the dual element was in fact the best configuration I decided to explore it a little more. I tried various gurney flaps and AoA up to the point where JavaFoil predicted stall. When it didn’t stall I drilled more adjustment holes and kept increasing it. At 12* beyond where the software said it would stall, the down force just kept increasing. At this point I figured I must be close, and needed to move on to the construction stage.

I extrapolated the results from my 30” test wing up to the ~72” final size and calculated a combined front and rear down force of ~400lbs at my test speed of 88kph (55mph). I figure 60kmh is probably a decent average speed to use for an autox, so that should result in about 180lbs of force, which is roughly 10% of the vehicle weight with me. I used the down force and drag test results to fine tune the position of the wings, and tried to match the force distribution to the weight distribution that way the vehicle balance remains consistent at all speeds.

To build it I made each wing in three separate sections that bolt together. The outer sections bolt to the middle section all around the perimeter of the airfoils, as well as the main mounting bolts. I had to do a little extra bracing in the front as the outer sections are so large, and the inner section is only a single foil. Getting the rear pylons right was a bit tricky because of the roll bar tube angles. My CAD model got me close but I had to fine tune it a bit afterwards.






The total package weighs a little less than 100lbs so it’s a bit on the heavy side, but I think the extra grip should more than make up for that. I also managed to keep the final cost under $1000cdn which I thought was very reasonable. Here’s a comparison of the original ebay wings, to the new 9LR wings which I have dubbed the “gargantuwangs”.






The Hoosiers also finally showed up. I went with the same size as I had with the RS4’s (225/45r15 & 245/40r15) and they’re definitely wider, but just fit under the fenders so it’s all good.


One thing I overlooked at first was my spring rates. It wasn’t until after I finished building the wings did I calculate how much the suspension would compress at speed. For autox I probably could have gotten away with it, but on my local track lapping days the suspension would compress over 2” at top speed. I was running 300 front and 450 rear springs, so I moved the rears to the front and got some new 650’s to start off with. If 450/650 isn’t stiff enough, I can bump it up to 650/1000 which would put the wheel frequency at ~3hz. I’ve got a test and tune day, and it’s first autox coming up next week, so hopefully the weather holds out and I finally get to see what difference these make.

The test and tune day went fairly well. I managed to get one session in before the rain started and scrubbed in the new tires. The A7's actually stick pretty darn good in the wet, provided there's no standing water. My later session was cut short as I was having intermittent electrical issues where the main power was cutting out. I found the connector for the ignition switch working it's way loose from the under dash fuse box. After clipping that back in, all seems to be good.

The autox on Sunday was great. It was a short, but fast course that flowed nicely. I ended up getting FTD by 2.5 seconds on a ~34 second course.
https://www.youtube.com/watch?v=bt9jU-mufqE