Wednesday, March 26, 2008

118 mph - Team Novak from the 2007 WFRRRC

Team Novak headed to the 2007 World’s Fastest R/C Car Challenge (W.F.R.C.C.C.) with almost twice as much preparation as the year before. Virtually, one entire Friday was spent tightening screws and checking bearings. It’s not the epic workload you would expect to prepare fast cars. However, with just a few hours – and some off-the-shelf items – the Novak Crew was able to push their cars past the 100 mph mark several times over the day, even on repeated back to back to back runs.

So everyone is up to speed, here is a little background on the W.F.R.C.C.C. The wonderful folks at Radio Controlled Car Action magazine decided last year to start hosting the event. They rent out the quarter-mile drag strip at the California Speedway in Fontana and let us R/C nuts loose on it with whatever we can come up with. There are some basic ground rules. For example, no rockets or push cars allowed, but the main goal is to have fun at high speeds.

We kicked off Saturday morning with a brief drivers’ meeting and photo session. This year, there was an attempt to have two measuring systems. In addition to last year’s Stalker Radar System, the folks from Model Drag Racing Association (M.D.R.A.) came out to setup their timing lights. Unfortunately, some quirks prevented the system from performing, so the radar gun was used.

This year, our intention was to mainly run HV systems in our two Touring Cars. One TC is a standard XRAY T2 sedan (car No. 1) that had basically been sitting in the garage since last year. The second is an XRAY FK05 sedan (car No. 2) with a custom motor plate and a very special pinion-gear adaptor, made by Novak’s in-house machinist Dean Sowa. We also brought along our old faithful Kyosho 777 buggy with HV system installed and one Team Losi XXXBK2 off-road buggy to test some GTB/Velociti speeds.

First out was our XXX buggy, and well, it was not spectacular. We stripped a spur gear on the first run and did not have a spare with us. We shelved the car for the day.

Next, we brought out my off-the-shelf sedan and HV system using two 2S Lipoly packs from Austin and Clint over at Max Amps were very helpful getting us chargers and a selection of battery packs for the event. Max Amps sells everything we used at its Web site.

The first runs are usually “shake down” runs, and we don’t max out on anything. We just want to get the car down the track at a decent speed to make sure nothing is going to go wrong. Pass No. 1 was 93 mph. We drove the car back to the start section and clocked in at 99 mph. Not bad for the test runs. We continued to add pinions to the car and ran it some more. The most important aspect at gaining speed is the car’s initial acceleration.

There is so much power being put to the ground that smooth and precise throttle application is very crucial. It’s a balance of trigger speed and how much track is left. You would think it would be easy to drive in a straight line.

Most of the day was spent fine tuning the car. We started with the same body we ran last year to 105 mph. However, it was proving problematic this year. We tossed it for a body that had some more straight-side sections. This seemed to help stabilize the car quite a bit. We crashed all our cars numerous times throughout the day, mainly in the shutdown area of the track. The racing surface of the drag strip had been recently cleaned and sprayed with VHT and had excellent traction. But the shutdown area was left untouched and, in turn, was very dirty. This made the cars very hard to control as they slowed down.

At one stage, car No.1 was destroyed, breaking the suspension, the wheel and damaging the body very badly. Luckily, we had enough parts on hand to repair it.

Car No. 2 did not fair nearly as well. We had intended to run this car from a total of 6S Lipoly. But in the shake down runs, it hit a rock and was propelled into the wall at, what I would assume was, 70-90 mph easily. The crash damaged the custom motor plate and rendered the car unusable. However, it hit 106 mph with a 4S battery and HV 6.5 motor. This car had nearly 1:1 gearing.

The crash, though bad, helped us focus on the remaining vehicles we had left. Bob was able to get his buggy on the track, and, at the normal recommended usage, it went 54 mph with a 6.5HV setup. With the 4.5 HV setup, we saw more than 60 mph.

The day was starting to wind down. We were confident in car No.1 at this stage and started to add more gearing to the motor. We were able to surpass 100 mph and were very pleased. Unfortunately, we had taken this setup to its limit. The ESC was only designed for a 4S, which was what we were using. The pinion and spur were both giving us the tallest gearing available. So, what to do? Since we work at Novak, we decided it would be OK for us to try some things beyond the recommendations of the products. The only real option we had to go faster was to increase the voltage we were using (This is not recommended and most likely will damage your HV setup).

We did this by running a 2S battery pack and a 3S battery pack, totaling a 5S pack. The HV is designed to operate the ESC and the BEC for the RX/Servo from one of the packs. The second pack simply for powering the motor. For this setup to work, you must be very careful connecting the two different voltage packs. If done incorrectly, your ESC will not run the motor properly and can damage it very quickly.

The first test of this was done with Bob’s 1/8-Scale buggy. It pushed the heavy buggy up past 72 mph. That’s a fast 1/8-Scale! The ESC was very hot at the end of the passes. Because the ESC survived, we decided it would be safe to try it in the sedan setup as well.

With an unrecommended 5S battery pack connected to our HV powered sedan, we set out to improve our speed. If you think 101 mph is fast for an R/C car, anything above that is crazy. The car lost a lot of stability and was noticeably more difficult to keep in a straight line. The first pass with the 5S was 108 mph. The back up pass was 118 mph! We attempted a third pass, but one of the RP30 tires finally let go. These tires are designed for maybe 40-50 mph so to ask them to do twice that, well, we expected them to fail. The problem was when the tire let go. It threw the car airborne and into the concrete barrier. The crash damaged most of the parts in the front end, and we didn’t have enough replacements. Panic set in. What to do?

John from HPI came to the rescue with some foam tires to try. Our confidence in foam tires is not very high because they don’t seem to have the traction needed to get up to speed. Also, we had seen foam tires fail at much lower speeds. But it was worth a try, right? What about the damaged parts, you ask? Luckily for us, we bought some Krazy Glue at the gas station in the morning and were able to glue most the parts that broke back together with no real problems.

With time winding down, we set out to back up our 118 run or at least get close. To our surprise, the foam tires were easier to drive with and performed significantly better in the shutdown area of the track. We saw a first run of 108 mph, a second of 112 mph and a third run of 116 mph. On our fourth run, one of the tires let go and sent the car skyward again. The car was fine, so we changed tires and went back out. We mustered up a final 109 mph pass right smack dab into the foam-scoring block of the drag strip. That ended our day in a spectacular fashion. Needless to say, the parts that were glued together were no longer glued together. The day was over, and everyone had put in their best runs.

In the end, our 118 mph pass was the third fastest run of the day. Nic Case and his little orange land missiles topped the charts with a 127 mph and a 119 mph pass. Nic was one of the other drivers that was consistently in the 100 mph Club. Jim “Rainman” Schauer also showed what a real dragster can do and was able make a few 100 mph plus runs.

John Schultz from HPI was also on hand running his Nitro Savage but had his electric powered PRO4 on hand with him as well. He had a GTB/3.5R Novak Brushless System installed and wanted to kill some time with it. Well, he killed a few records, too. John’s race-prepared car (not speed-run prepared) pushed well past 85 mph. His final speed was 87.5 mph using a MaxAmps 7.4v 4,000 mah Lipoly pack. He started his runs using a simple 6 cell NiMH pack that looked fairly old and raced over 70 mph the whole time. This is not official, but I believe he was the only car not using multiple battery packs. Most drivers there ran at least 12 volt setups.

Now, we cannot express how simple and easy our setup was. To be able to walk into a hobby shop and purchase each and every item we used to build your very own 100 mph R/C car is a very impressive feat. Anyone reading this article could easily do what our team did. Even simpler is the setup that Mr. Schultz has: a standard TC with a standard Novak BL System and regular packs to go 70-80 mph. The total prep time on our fastest car was only a few hours of actual work.

We must take a few moments to thank everyone that helped us with our efforts. Thank you to Bob, Charlie and Dak for going to the event and walking up and down the drag strip all day.

Thanks also to:

Jay Kimbrough for the last minute delivery of 88-tooth spur gears!

Clint and Austin from Max Amps for providing battery packs and chargers at the last minute.

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