Sunday, July 24, 2011

Exo104 and 104X1

The weather has been weird around here lately.  Hot, crazy thunderstorms, everything changing every 15 minutes.  With that being the case, it was time for a trip to the carpet track.

I wanted to shake down the 104X1, and also fool around with my Exotek car.  I got a hold of some of the Pit tires last week (R-1 and F3-S), so it would be a nice time to try them out on carpet.  Luckily, the layout has been down a couple months since its summer.  There are at least a few guys practicing every week, so the traction was ok.

The Exotek car was pretty good to start with, but it didn't quite rotate enough, and had a bit of a mid corner push.  I changed the ballstud on the rear of the upper arm from a short Tamiya to the standard Tamiya, which is about 1mm higher.  That helped to get the car turning mid corner, but it picked up a traction roll if I cranked the wheel too hard in the sweeper.  Reducing camber to 1.5* helped  a little, but I wound up changing the 3.5 mm offset steering arms for the stock parts.  This helped since I was able to take throw out of the radio, and the car transitioned side to side way better.  Basically, the car had more steering with less throw, so it wasn't diving onto the outside tire so hard and traction rolling.

At this point I threw the Pit tires onto the 104X1 just to make sure it went in a straight line, steered ok, and just to see what it drove like.  I was actually surprised at how good it was.  It wrapped the corners a little better than the Exotek car, and had quite a bit of off power steering.  At the same time, it pushed if you got on the throttle too quick, and it didn't have the overall front grip of the Exotek, nor was it as easy to drive.

I took one of the 1.5mm washers out from under the rear shock ball stud, making the shock a bit flatter.  That made the car better on power, but also took away a bit of rear grip.

After all that, I looked at my Exotek car and made a few changes to get it closer to some of the things I liked on the X1.  I went from 50wt in the side damper to 35wt oil, and from  red CRC side springs to whites,  one step down.  I measured the front caster on the X1, and put the Exotek car at about 7*, or as close as I could eyeball with my camber gauge.   I also lowered the front ride height 1mm.

This really helped the car wrap the corners much better.  It was fast but really easy to drive.  The only thing you had to be aware of was not totally sawing the wheel hard in the sweeper.  Some of that may just be the nature of the beast, in that the car is so narrow.  I also noticed the car was only making a few small chirps in a couple corners, so it was using the tires without sliding them.  That was one thing about the X1, it was making a lot of tire noise.

Another small but significant change was the servo saver.  I was using a small Kimbrough, but it had a crack on the edge of one of the ballstud holes.  It broke when I got into a tube, so I replaced it with a Kimbrough Medium (they are black, and come with inserts for different servos).  The ball stud holes are are further apart, and a little farther away from the center of rotation.  This repair was the only change before I went back out on the track, and I noticed the car had more steering without upsetting any other part of the setup.  I had tested out all 3 sizes of Kimbroughs, and the big Tamiya horn last summer with the servo positioned per the manual.  I hadn't gone through that test again once I started to run the servo with the output shaft facing up.  Last summer the Kimbrough Medium had the most steering, and also produced better lap times (I had a hard time believing there was a difference, but there it was).  Once again, the Kimbrough Medium was an improvement. 

I ran the X1 one more time, just to compare the two cars.  The X1 was definitely fast, but a little more on edge.  As I  said above, it made a lot of tire noise, and with the shock a little more level, you could tell it was sliding a bit in the sweepers.  I think some of that could be remedied by playing with the o rings on the T bar, maybe running only one o ring vs. the inner and outer o rings.  The car did have a very good feel, and was shockingly close on setup.  With a few changes, it will be really good.  I'm going to try to get it out on asphalt ASAP with the Tamiya tires to see where it really stands, but so far, so good.

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