Saturday, June 15, 2019

Access Hobbies 2019 TCS Race

Finals video

So the thing about Access Hobbies this year was the tight, 1/12 style layout they presented the Tamiya TCS racers with.  Before the closing of my local track, I was running my TRF103 with a peg diff tightened into a spool, and the battery lengthwise in the chassis.  This worked really well at home.

Despite the number of cars on the track, traction was not overwhelming.  The spool was hard to drive, especially off the corner.  Reverting to a slowed down ball diff was the way back to stability.  I am beginning to find that the spool must have a massive amount of traction to really be effective.  When the condition is correct, it is unbelievable, but I would say that most track conditions favor a combination peg/ball diff, or even a slightly loose peg only diff (non-TCS races you could use a gear diff as well).

The lengthwise battery did not work as well as a transverse battery, period. I have always favored the transverse battery in almost all situations, but the TRF103 really seems to like the battery lengthwise most of the time.  Not here, the car seemed a bit more planted and rotated better with a transverse set up.  I have to say it was just the tight nature of the layout.

The other factor was the track surface itself.  The traction peaked off on Saturday evening.  Leading up to this, I had shortened the wheelbase on the car, and steering was plentiful.  The last qualifier on Saturday was the fastest for me, and my car did the  fast lap of the weekend as far as I know.  Unfortunately, I had an accident that zipped off most of the spur gear, so the best time to qualify was wasted.  Sunday morning, the track had reverted to a state where the short wheelbase hurt more than it helped, and I returned to the long wheelbase.  I lost some steering, and to be honest, I think that the link setup might have been better at this point, as the link 103 cars looked to have a bit more steering in the lower traction.  Odd, in that most times T bar setups have more traction, and would be better when traction is down.  It may just be that the T bar in high traction allows the short wheelbase to work, and the improvement in corner speed is only available with the T bar's superior traction.  In any case, the car worked well enough on Sunday.  I feel like the other cars might have been a little better in the main, but I had a very good start and built up enough of a lead that I didn't have to push too much.

Other than those big changes, I was able to raise the upper arms at the kingpin, which tells me traction was not too great.  Normally, I run the upper arm pretty flat to avoid traction roll, but I was able to get away with maxing out the spacers under the arm.  I also ran 0.5 or 1 mm under the rear ballstud of the upper arm, just to take away any chance of lifting a tire.  Sometimes in the tight turns, if I had to get on the brakes, it could be hairy without the spacer.

Friday, May 3, 2019

TRF 103 short shock vs. long shock

Just a quick post on the shock length option on the TRF 103.  The local track was closing up shop for good, unfortunately, and they had one last race day.  I brought out the Tamiya as this would be my last chance to race there, and to try a few things out for the up coming May TCS race in Ohio.

I had changed the car around a bit to use the Gravity RC tires for a Motiv RC series race.  I tried the longer shock as part of the package, as the Gravity tires don't produce as much traction as the TCS/Pit Shimizu tire.  The longer shock tends to help rear bite.

Anyway, I was more or less changing everything back to the previous setup for TCS tires as the day went on.  I changed the shock back to a short set up.   It took a run or two to figure out what was going on, but the light bulb went on, and I changed the shock back to the extended configuration.  With the short shock, the car had sort of an abrupt  steering feel.  Going back to the longer shock smoothed the car out, and seemed to make it rotate better.  Most of the time I have felt a longer shock plants the car too much, but this was a perfect feel, and on high traction, too. 

Again, this car surprises me.  It does a lot of things I don't expect, and behaves much differently than most of the other cars I have tried.  The long shock working even in high traction makes some sense in light of the car's abundance of steering.  There seems to be as much front bite as you need, even with a totally planted car.  Locking the rear down just makes the car better to drive.  Worth a try!!

Sunday, February 24, 2019

TRF 103 First Weekend on Carpet

This weekend I had the chance to go racing for the first time in a long time.  My local track was having a leg of the USVTA Series traveling around the middle of the country.  They are also going to have a Tamiya TCS regional in about a month, so I figured this would be  the perfect time to get the TRF 103 set up for carpet.

Not really having too much of an idea beyond a "typical" carpet set up, I initially had the car in a transverse battery configuration.  I was also using the T bar instead of the links, and the short wheelbase, which are both not typical, but worked very well on asphalt.  This is not to say it would be right for high traction carpet as well, but I wanted to give it a go.

Right off the bat, the car got around fairly well.  The main problem became lifting of tires, and a tendency to over rotate out of the corner on power.  The over rotation stems from the tires getting light, since I had pegs in the diff to lock it into a spool.  As a tire comes up, it just rotates the car off the outside wheel.

The car was driveable, but touchy in areas and not stable enough to attack.  I tried changing side dampening and t bar settings at first.  5000, 7000, and 10,000 in the damper tubes provided enough feed back to see that lighter would be better, and really the T bar needed to be tightened.  I settled on 5K in the tubes and moved on to the t plate.

There are a few ways to change the t plate characteristics even without changing the t plate.  I started with an orange o-ring, which is fairly soft.  Going to a stiffer black o-ring, and then even the outer o-ring in combination with the black o-ring, as was used on the F104 T bar cars still was not quite enough.  The t bar needed less tension so it could pivot, but the overall travel was a bit too much.  In this case, I replaced the smaller black o-ring with a similar thickness nylon washer.  The larger o-ring was retained.  Now the t bar could be set with less tension, but the washer reduced the overall travel as it pivoted.  This made the car feel more stable and reduced the tire lifting.

The first qualifying run I made was not bad, but as the race wore on and the tires heated up, the tire lifting came back into play.  There was some time to practice, so I was able to try a longer wheelbase on the car.  Surprisingly, the car did not lose much steering at all, and the tires stayed in contact with the carpet much more consistently.  I tried a few other things, including raising the rear ball stud on the upper arms of the front end.  This usually helps to quell a bit of the tendency to traction roll while taking a little steering away, and indeed, it did help. This car seems to have plenty of steering, so it was  a worthwhile trade off.

By this time, the track was about to close for the night, so any more experimentation would have to wait until morning.  Reflecting on the car's main problems, it seemed an overabundance of weight transfer was happening at the pivot point of the t bar.  There is really no forward/aft movement of the battery in a transverse setup on this car.  This left me with an inline setup as the only alternative to change the weight bias.  I have not been a big fan of the inline battery over the transverse on carpet, though there has been quite a few racers using an inline battery on high traction very successfully over a range of different cars.  On day 2, I decided to test it out.

Arriving at the track the next morning, I ran through a couple quick changes before reconfiguring the battery.  Mostly front and rear width, which was maxed out close to 190mm at the end.

After fighting the wiring and electronics onto into a suitable  configuration, I dropped the battery into the car inline and went out onto the track to test.  In the past, I have found inline cars to be overly aggressive off center, even a bit jittery, so I was apprehensive.  Imagine my surprise as the car was very docile and had to be thrown around to make it want to pick up a tire.  The over rotation problem was gone as well,  and I could drive it hard through the chicane leading onto the straight with fear of having to make a correction and upsetting the car.  A miscue was met with a smooth response instead of a jerky reaction when corrected. My car was now a good .3 seconds a lap better, being able to drive it confidently at all points on the track.

For the final qualifier, I was able to move into P2 for the mains, and lap times were much closer to the TQ driver.  The car handled in traffic very well.

What really capped off all the progress I made was a small change to my tire dope strategy.  I began applying more tire sauce, but wiping it off about 5-6 minutes before the race, as opposed immediately before setting the car down.  The front tires were more or less dry, though they had been sauced for about 10 minutes wet time.  This really settled the car, but still provided enough steering throughout the race.  Starting second in the main, I was also able to be ready to fight and apply pressure immediately, and twice I made a pass on the first or second lap to get into first place at the start of a race. I had one first place and two seconds, for a second place final position.  In the second main, I actually had first place for a bit, but I crashed when a marshall screened my view of a chicane.  I probably should have gave myself a little more room there, but I was going for the win.  For the third race, I did not have quite as good of a start, and made a mistake on the left side of the track, costing a little time.  Ultimately, I was able to close down on the lead car, but never get close enough to try to pass.  The winning car and driver were very good, so congratulations are in order.

Overall, I was really happy with how quickly the car setup came together, and even more, how easy it was to drive the car at race pace.  It's also encouraging as this was outside of the body, a TCS legal setup.  For typical races, you could use an aftermarket spool or gear diff, and also front end pieces that could offer more caster and camber settings than the stock parts.  There are more tenths to be had out of the car, but this was a good weekend.  I plan to also try the link setup as well for comparison, but I have always liked the solid feel of a t bar car.  Don't be afraid to try it if you own the TRF 103.

EDIT: Turns out I also managed hot lap of the weekend!!  Not bad.

Inline car

 Please excuse the somewhat disheveled

 Note the short shock configuration.  Also, 42 g of lead was added to the car to make weight with a standard short pack.  Lead was distributed close to midship.

Electronics were directly in front of the battery.  The lead was tried at more forward positions (on the side of the servo, under the lower arms).  No bueno, mucho oversteer.

Sunday, January 20, 2019

Some stuff I have been working on

It's been a long time since I have posted.  I bought a house, so my rc time has been much limited.   Lately, i have had a bit more time, so here's a few new things I'm goofing around with.

TRF 103

I got the new TRF 103 last summer.  At the final TCS Nationals at the Aliso track, I was able to qualify 3rd.  I didn't get the car really good until the main, when, in the warmup, I could tell it was fantastic.  The start didn't go very well for me.  I had some racing contact that put me down to last, though I was able to make a small comeback.  The car I had in the main was excellent, and if I had it working like that in qualifying, I think I might have had a chance to maybe started one place higher.  The two guys in front of me are excellent drivers, so I would have needed a lot of luck to have started any better than I did.   

The second car will be a carpet only setup.  If it's as good as the asphalt car, good things will happen.

Mutant V2

Once again the F104V2 pops up, this time with an IRS axle turned into a spool, and a couple CRC left side hubs for good measure.  This is possible with the Exotek 1/4" axle conversion.  It's a great idea, allowing the use of 1/4" axle parts like the many spools available and the Xray gear diff.

I also have the Tamiya carbon front end lower, with an Exotek upper arm setup for adjustable camber and caster.  I tried some other setups, but this works really well.  All that it needs is a small piece of carbon to mount the upper arms to the bulkhead.  It's fairly simple.

"Speed Jam"

So I bought some random parts online from a Japanese hobby shop to make my Speed Passion SP-1 into a Street Jam SJF01.  The rear end of the car has always intrigued me due to the amount of travel it has.  I mocked up some changes to see if the would work.  The upper links and top plate are too close to the rear of the car to transversely mount the battery, so I was able to bolt them to the SP-1 upper deck to allow a short pack sideways on the car.  At some point, I need to make a one piece top deck to mount the links, as this setup is flimsy.  The suspension does move well but I'm not familiar enough with this style suspension to know how lengthening the links affects handling.  

Eventually, this will get the same front end as the Mutant V2.  It worked well when the car was 100% Speed Passion.

That's it, just a fun update of what I'm keeping myself entertained with when I have some non-remodeling time.....

Monday, March 19, 2018

TRF 103 Manual!!

Thursday, March 16, 2017

What about your tires?

I haven't posted in a while, no reason other than laziness..... Anyway, this came up at a race recently.  My car just seemed to be a pile of junk.  Nothing I did seemed to make any difference or change to how it worked.  Looking back, it reminds me of how an F103 would get when the T bar went bad.  Hind sight is 20/20 as they say.

Luckily, one of the other locals, Mark, happened to be sitting nearby and asked how old my tires were.  I hadn't thought too much of it, but I had put them on the car for the Hudy race in St. Louis, in January.  I had run the car for countless packs since that point in time.  Mark is pretty sharp, and has a lot of ideas on tires, including the idea of rotating between two sets during the day to keep the tires from getting too soft.  In any case, he got me to change tires on the car.

On a car that would barely crack a 9.8 second lap, a newer set of tires got the hot lap down to a 9.5 in the first minute of practice.  On the older tires, it was on skis, pushing all over the track.  The new set got back all the steering the car was missing.

This is not to say that your car needs to be fed a constant diet of new tires.  Far from it, new tires take 3-4 runs to get broken in, and they will last quite a long time.  They last so long, that the deterioration can be hard to notice.  2+ months of running is a long time to get out of any set of tires.

The lesson is that when nothing seems to help the car, it might be the tires.  Just like when nothing seemed to help an F103, it was usually the t bar.  Or when a new set of front and side springs brings a link car back to life.

Just keep an eye on your tires.

Sunday, November 20, 2016

V2.V2 pt.3

I probably should have posted this a long time ago, but I did finally run the V2.V2 after a Gravity RC Midwest All Star Series race.  I ran it with a 21.5 motor, as it was all I had available at the time.  The track was the new CRC black carpet, and after a day of racing, had a nice groove.

There was really only time to run one battery, but I was very surprised.  The car was actually really good for something that had a guess at the setup based on what I thought should work.  It was a bit twitchy, but generally got around well, and didn't traction roll.  I wasn't sure how it would react in the high traction, but it was fine.  Even more interesting was that it was very easy to get on the power, even with the 21.5 motor.  UF1 MIDWEST past champion/engineering genius Rick Vessel even gave it the thumbs up when he was passed the controller.  The long links do seem to be doing their job of getting the car some traction.

At some point I'll continue to work with this car.  Luckily, the new local track has now opened.  There hasn't been an opportunity to practice locally in the past several months.  I may not get to this right away, as the front end has migrated to another project, a very interesting prototype development...

Wednesday, September 7, 2016

V2.V2 complete

V2.V2  is complete, this time with the Tamiya carbon front end/Exotek combination.  As it turns out, the Exotek upper arms can be used if you make a plate to mount the camber links.  Now you have a front end similar to the other high end cars, carbon fiber, and the ability to adjust ride height at the lower arms.  I found the slightly shorter CRC front springs are a little better for this front end as the lower ball does not have a recess for the spring.

I have not had a chance to run the car........ yet.  

Friday, July 1, 2016

Basic geometry

So I have been thinking about a few things after a conversation at the track.  Lately, I have been feeling like the biggest things on an F1 car outside of the tire selection are the car track widths, and the steering setup.  I was talking to someone about what really gets F1 cars working.  The steering is gigantic, but not everybody thinks much about it.

A few years ago a friend who was a long time 1/12 guy, and national level A main racer, among other things, really clued me into how steering geometry works on pan type cars. Working with the concepts he explained to me really opened up possibilities I did not know existed.  Sometimes, there were things I wanted to change on the car that I didn't know how to get without big compromises, or even how to change at all.  The steering on your car can actually affect almost all areas of set up, things that would be counter intuitive in some cases.

The big one is the bump steer settings.  Generally, in a typical servo set up with the output shaft pointing up, you will use maybe 5mm of shims on the bottom of the servo saver.  That will generally get the tie rods somewhat level.  What is this really doing?
In general, the less shims you use on the bottom of the servo saver, the more the car will want to steer on exit, from mid corner on.  I have actually seen a car do pirouettes because the driver had NO shims under the servo saver, and an extreme angle upward toward the saver.  (CAUTION: bad paint program diagrams ahead!)
 A more typical setup has some spacers underneath the servo saver to get the arms sort of level.  A level tie rod will have a minimal amount of bump steer and make the car feel pretty much the same in all phases of the corner.  Usually, this is the best approach to take at first.  It's fairly easy to add or remove spacers in small increments like 0.5 or 1mm to tune things in.  Big changes are good to familiarize yourself to the extremes, but remember to look at the tie rod length to maintain toe as close as possible!

Adding spacers to the servo saver making the tie rods run down towards the inside of the car will make the car steer more in the beginning of the turn.  Additionally, spacers on the knuckle tend to make the car more reactive at first turn in as well.  This does increase the angle of the rods as the spacers on the servo saver does, but I think that the difference in height from the axle is a little different from just adjusting the rod's angle in general.
The other factor in the steering is Ackermann.  The difference in the steering radius of the two front tires generally affects overall steering and aggressiveness.  Generally, moving the servo saver ball studs forward, whether by servo position or length of the servo saver/steering arm, will increase aggressiveness and steering.  This will also kill some mid corner roll speed, especially on carpet.   On asphalt, this can actually be a benefit, since it's almost like drag brake.
Making a straighter tie rod will promote roll speed in high bite conditions (note most 1/12 cars are fairly straight), and be less aggressive.  Rubber tires do seem to like a bit of angle to make the tires work.
The other part of the equation is the actual servo saver.  The width of the space between the ball studs makes a difference.  Narrower spacing tends to be more aggressive.  Wider less so.

The other part of the equation is the track width on both ends of the car.  

At the front, I like a wider car in general.  It promotes more on power steering, and helps the car be more stable under the brakes or on corner entry.  Narrowing the front will make the car a bit more nervous, and help turn in.  There is usually less overall steering, however.  Having on power steering is key in my estimation since the car's corner speed is important to lap time since they do not have the acceleration of a 4wd car.  I try to get the car as wide as rules allow, and the track conditions will permit.

As far as the rear I generally try to make the car narrow as conditions will permit, to gain rotation mid corner.  It will also feel like there is more side bite as well. In high bite, like carpet, this can work very well.  On asphalt, it pays to try to run as wide as you can while maintaining rotation.  A wider rear will be more stable out of the corner (launch), and will keep the tires from overheating during the run.  The overheating is less of a concern on carpet.  In the past, the 190mm width limit led some option part manufacturers to make widening kits for cars.  Enjoying some initial popularity, a lot of drivers wound up removing the kits and going back to stock width, looking for steering.  As it turns out, just removing the rear end parts and leaving the front 190mm would have been even faster.  Widening the rear of the car will lock it down and kill corner speed on a tight track, especially high traction carpet.  I like to use 0.5 mm spacers on the axle to widen 1mm at a time.  It's a change that you can feel but it's not too drastic.

To me, these are the basic settings after tires that will establish the overall feel and balance of the car, along with ride height.  Most of the rest like springs, oil, camber are finer, but still important, adjustments.  It's just that the things I have described about are more "macro" and will change the character of the car immediately.  I hope this will help get more guys into the ballpark a little faster.  Don't take my word for it, try it out!