Wednesday, April 20, 2016

The Tamiya Carbon Front End and the TRF102

Ahh yes, the TRF102.  Pretty dang good on asphalt.  On carpet, hit or miss.  The thing is, the chassis is thin compared to the rest of the Tamya line up, at 2.5mm.  If the traction is up on carpet, it can get hard to drive.

I had brought the 102 with me to the TCS race at Access Hobbies in Springfield, Ohio in addition to the ever reliable F104WGP.  I bounced back and forth between the cars during practice the day before the race.  Towards the middle of the afternoon, temperature and humidity increased in the building and traction began to rise quickly.  This brought out the wild nature of the TRF102, which can be a handful in these sorts of conditions.  The car became very sensitive on the straight, and it did not put the power down very well out of the corners.  The temptation of this car is, of course, the easy steering feel it has.  If it can be tamed, the car should be faster than just about any of the other cars in the Tamiya line up as it steers far better throughout the corner.  The problem is that much of this steering comes from  the flex in the front of the chassis, which is a headache in high traction.

This is where the carbon front end comes in.  Without the camber gain from the moving upper arm on the standard front end, and being made of much stiffer materials, the bite should be reduced overall.

I ran one pack with the standard front end.  Traction was good on the track, and the car was a bit ill mannered.  I switched out front ends, and started with silver springs not knowing what kind of bite I would get.  I also went to the higher of the 2 camber settings, which I think is 2*.

The car was pretty good, but would lift the inside rear going into high speed turns.  The front springs were too soft, so I went to the black spring, the heaviest.  This made a big difference, and I also added a shim under the front knuckle to take a little droop out.

 Both changes helped to flatten the car out.  The car was much better, but it required a lot of steering throw to get around.  I had an Xray servo saver on the car, so I added an Exotek ackermann extension to it.  This part usually adds more bite to the front end, especially mid corner.  I tried both settings available, and the most forward was a bit too much.  The rear setting seemed a little better, not as hard to drive.  Both the rear setting and the stock Xray servo saver produced similar lap times, and the plain Xray part may have actually been a little more consistent.  It's the sort of thing that may take a little more testing to sort out, but I think ackermann changes will probably be an important part of the tuning arsenal for this front end.

On a carpet track, the front end made the car a lot better to drive, and got the lap times to a competitive level.  On asphalt, I'm not sure if it would better subjectively, or just as a matter of taste in driving feel.  I'm definitely going to find out, as I have seen  the combination be on point outdoors.  In any case, it's probably the front end to run for carpet if you want to use the TRF102.

Tuesday, April 19, 2016

Revisiting the TRF101

The TRF101 has been languishing on the shelf for a while now.  I did have an initial good impression of the car, but it became apparent that the car just did not steer enough on carpet to be really fast.  One thing I did notice was that it seemed to have better acceleration than most of the other Tamiya cars I had.  That seems like a crazy thing to say, but maybe there is something to it.

One thing I noticed from Fred Medel's quote in an early post about the car was the mention in passing of the rear end and the car's stability: "With the TRF101 the car enters the turn with immense stability and there is no sign of the car wanting to continue to turn after applying throttle after the 180. It's just that stable. I believe this is the case because you now have a solid front end like the F103 on top of having the side links further apart."

That may be the key here - the width of the side links.  The Xray style setup does have the battery sideways, but also ultra wide links compared to most of the Tamiya cars.  Even more intriguing to me is the similarity to the SpeedPassion Sp-1.  The rear end is almost identical, and I can say that the SP-1 made a lot of traction.  The first time I ran it on asphalt, I was able to run the exact same laps and time I did as I did with the F104WGP I had been working on for quite some time.  It was also very good on the not so good Pardus tires.

So maybe that stability helps the car put the power down.  I was never a huge fan of the way the Version II F104 cars accelerated, but the 101 was good.  Looking back, the thing that held the car back for me was the lack of steering .  A simple change of the upper arms makes the front end the standard F104 spec, so it was worth a little investment of time to see  if the TFR101 could be brought to life.

At the track, I first ran my F104WGP to baseline things, since I had just run it at the Access Hobbies TCS race.  It was good there, so I figured the comparison would be good, especially since I planned to simply transfer the tires to the TRF car.

I was able to do a 9.7 hotlap, but that was sort of a freak lap.  The rest of the laps were closer to a 10.0 average.

Putting the TRF car down, what I noticed right away was that it was really consistent.  While I was a couple tenths off of the WGP car on average, I could knock out the same lap over and over.  What the car was missing was quick transitioning in a couple S sections on the track.  At first I had the car set up with the #2 plastic camber adjuster (.5* camber) and copper side springs, the softest.  I had good success with the WGP car set to 2.5 camber, so I changed the TRF to 2.5 as well, and changed the side spring to gold, the second stiffest.

Now the car had the ability to transition quickly in the S sections.  I was able to consistently do 9.9 and 10.0 second laps, and it still retained it's stability.  I added a bit more front and rear droop as well which helped the car get a little more into the track.  The best part was that I could stand on the brakes, which was important for the short chute in front of the driver's stand, and the end of the sweeper.  I really enjoyed driving the car, as it was a dragster point to point.

In the next few runs, I tried some slight adjustments to the droop settings, to fine tune things.  I also tried some of the other side springs, but settled again on gold.  One thing that did make a difference was the center spring.  I had tried a few, from the ultra heavy purple to a red sedan spring.  What seemed to be best was a white sedan spring.  The softer springs actually made the car a little unstable, and the really heavy one slowed it in the S turns.

One other option was the steel axle.  For my style, I usually go a little faster with a steel axle, and it helped me as the car was now completely locked yet turned hard.  Overall, I was surprised at how good this car was with a little time tuning it.

In the end, I feel like the results were unexpectedly good.  The car was so enjoyable and worked so well, I just wanted to keep putting runs on it.  My WGP car was really good at the TCS race I had attended, but I think my results might have been even better if I had run the TRF101. The consistency and corner speed were excellent. Really, this car just needed the standard F104 front end to come to life.  I had been considering selling this car, but I think I may just hold onto it a bit longer....

Tuesday, April 12, 2016

Xray Aluminum Chassis Feedback

So after several races with the aluminum chassis on the new black CRC carpet, it's time for some thoughts...

Oddly enough, I sort of felt better about how the car set up with this chassis on the older gray CRC carpet.  The first time it put it down, it was awesome.  On the black carpet, it was a bit harder to nail the setup.  However, this could also be partly due to the high bite at both the races I attended, especially the ROAR nationals in St. Louis.

 Part of the problem at the ROAR race was a lack of mid corner steering.  Going too aggressive with the front end would only result in a traction roll anyway, so my mistake may have been going with the least flexible front end parts on the aluminum chassis.  I used the cross brace for the lower arms, and a pair of Xtreme racing lower arms which have extra bracing.  I feel like that may have been what was limiting the car in the middle of the corner.  Upon returning to my home track, which has the gray carpet, I went back to the standard lower arms and removed the brace.  I felt like the car was a little more forgiving to get around the track.  It was hard to tell how much this affected the mid corner steering, since the grip level was different, but at my track mid corner was good.   I will return to the Ft. Wayne track in the next few weeks, so it will give a chance for me to revisit that issue.

I would like to point out that the eventual champion at the ROAR race and the rest of the local racers ran the graphite chassis on the car, and did not seem to have a big problem with traction roll.  Sometimes the cars looked edgy at the start but they were able to manage that for the most part.  Part of this may also have been the tire dope strategy.  I noticed some guys doping their tires 15-20 minutes early, so that the compound would dry on the tires.  I tried this as well and the car finished the race better.  It also didn't seem to make the car any harder to drive.  Letting the compound dry might have helped alleviate some of the initial oversteer/tire lifting that occurs when the tires are wiped just before the race.

In general, I think that the aluminum chassis makes the car very consistent, and reduces a lot of the tendency to traction roll.  I probably went a little overboard on the stiffer components for the front end.  I would imagine that the cross brace for the front end is not necessary in most cases with the aluminum chassis.  The stiffer lower arms might be helpful depending on the level of traction.  Being aware of how these parts affect the car, I'd like to test again on the black carpet.  I should have a little more knowledge in a few weeks.