I spent a day getting the suspension set up for asphalt and parking lots. Right out the gates, the initial setup was a bit too low while the camber and toe combination was giving me a bit too much oversteer for my liking. I suppose the initial setup was designed around a prepared track. So I raised the chassis about 1.5mm and ended up with the front at 0 toe and 0 camber and the rear at +1 toe in and -1.5 camber. With these settings, I was able to track nice and straight and the car was well balanced at both low and high speeds. The location of the battery along the centerline of the car (along the length of the chassis) was something I had never felt before on an RC car and I definitely prefer it over all the previous RC cars I’ve owned in the past. I like it because it makes tuning the suspension much easier since there is perfect left to right and front to back weight balance. Previous chassis I’ve owned had the battery on one side or the other, or in one case, perpendicular to the long axis of the chassis.
While tuning the suspension, I was able to work out a couple of problems in my build. Oil was leaking out of the front differential. This was entirely my fault – the screws keeping the differential together was not tight enough. I also noticed the servo saver screw kept coming loose. I fixed it with a dab of Loctite on the screw. I had to jimmy jack around with the ESC location so that the cables didn’t touch the drive belt. I also ran into a meshing problem with the spur gear and pinion gear. This was not my fault – the machining on the pinion was pretty poor. I had to remove some flashing off the pinion to get a good mesh with the spur gear. After a few runs, the spur and pinion “broke-in” pretty nicely.
After a day of tuning and shaking the car down, it was time to tune the ESC and motor. I bought the PC interface for the ESC which allows me to do deeper programming of the ESC. I can set throttle profiles, braking profiles, boost, response, etc. In the end, I left the throttle profile linear. I also set braking to be a little softer. This interface allows me to store two custom profiles in the ESC. So I programmed one of them to be mildly aggressive with a little motor boost and another to be ultra aggressive with maximum motor boost. Why don’t I just keep it at ultra aggressive? Well, those settings are well beyond the maximum spec of the motor – so I can use it, but it can potentially destroy the motor!
Here is the PC interface that attaches to the ESC on one end and to a PC via USB on the other end:
Some screen shots of the software:
Unfortunately, the software doesn’t work on OSX nor does it seem to work on Windows 7 (even though they claim it to work on Windows 7). So I had to install a Windows XP virtualized on my iMac – the software worked perfectly with Windows XP.
So why did I go with a 21.5T motor when I could have spent the same exact amount of money on a 10.5T or 13.5T motor? Well, I’ve been down that path before and found that being able to achieve straight line top speed was absolutely boring. I hated having ultra quick motors only to flip the car every time I made a high speed turn. Suspension settings were almost pointless once the car was hitting 50+ mph. I wanted to build a car where I could actually feel the differences from making an adjustment of half a degree here or a quarter of a millimeter there. I want to feel like I am in complete control over the grip of the car. I like being able to make these minor adjustments and see the impact on the street. I may get a more powerful motor down the road, but probably not on this chassis.
Now time to play! The best part of any build is it’s first run to get the suspension tuned. Once that is all set up nicely, I look forward to programming the speed controller! I bought a programmable interface for the ESC which allows me to plug it in to a PC. I can’t wait for them to come out with an iPad app – that would be awesome!
…let’s see how long before I build another RC car!
My electronics arrived today! While waiting for all of it to arrive, I finished up the lexan body…
I used a body reamer to cut out the holes for the body posts.
This body required a two step paint process. I had to mask the windows, then mask everything else except the black areas, spray the black, remove the mask, and then spray the violet.
Once the paint was complete, I had to remove the protective outer film and start applying the decals.
The kit came with LED light buckets. You can build them out or use a decal. Building them out truly adds realism, so I decided to use them but without working LEDs in them. I filled the headlights with dummy LEDs to complete the look.
The rear wing and exhaust.
Here is the completed body along side the power plant I picked out for it!
I like how you can see the inboard front suspension through the windows.
I have been working in a workspace with crappy lighting, so I apologize for the poor quality of my progress pictures. Overall, the body took about 10 hours to complete. Working on the lexan body is my favorite part of any build! I am obsessed with making the car look the best it possibly can! I will work on the electronics between now and the weekend. Don’t worry, I will cut down those body posts as soon as I’m ready to run it!