TFX Comparison Testing

[gmcullan]

Today I decided to test to see how the TFX chassis might fit into the grand scheme of things with HOCOC's various chassis classes.

I used my standard test method of running a timed round robin on my Banzai BuckTrax running 3 minutes per lane with 1.5 minutes in between heats. All servicing was completed in the off periods. The Lambda power supply was set to 18.5 VDC. A Medanic M-Magic-S controller was used. Data is reported as total laps/segments.

First up was a full blown Fray car based on a Dash chassis and running a 12 tooth pinion and a 15 tooth crown. This car features sili-foam rear tires and an OS3 Anchor front end. It indicates mid-180 on the VRP dyno @ 18.0 VDC. The long wheelbase was used and the body was a cast resin Fray type body. This combination yielded 107/9. Handling was pretty much spot-on.

Next up was an AW chassis setup similar to the Dash Fray chassis with the exception of using slip-on Super Tire SE silicone rear tires. This chassis was run with the same body as the aforementioned Dash chassis. Also indicating mid-180 on the VRP dyno, this car turned in 96/9. The limiting factor of this chassis was the rear traction. Excessive throttle on corner exit resulted in considerable fish-tailing.

The first TFX chassis was run as received but in the short wheelbase position. The body was a Fray type cast resin short wheelbase Lola GT. Dynoing at ~190, this chassis turned in 92/2. Again, the limiting factor was the rear tires. This car just begs for better rear tires.

The second TFX chassis was run in the long wheelbase configuration as received. A Dash Camaro body, typical of what we would use on an ASRL car, was used. Indicating ~200 on the VRP dyno, this chassis yielded 93/19. Again, the limiting factor was the rear tires. This car just begs for better rear tires.

While more testing is certainly in order, I'm starting to think that this chassis would nicely fit in with our AW/JL classes, especially with better rear tires and possibly in independent rotating front end . This is certainly something to think about for next racing season.

I did find one disconcerting issue. My Banzai BuckTrax features power rails that stand 0.015" proud of the racing surface. The chassis is low enough that with the stock pickup shoe configuration, spinning the chassis 90^o to the slot and applying power creates a short circuit that is guaranteed to pop your electronic controller fuses. I popped three fuses before I realized what was going on. Silly me.

With the proper sized better tires, I would anticipate the performance of the TFX chassis to approximate that of the AW/JL chassis as used in some of our racing series/classes.

[Austin]

I found the same short out on my Viper track in a few places. I was thinking it was just my track.

[RichD]

I had no problem with shorts on my track.
I got some tire testing with my OS3 TFX car today. I had a Vonco Porsche Carrera GT Fray style body on the chassis. The Lamborghini body that I used for my initial testing actually works better with the car.
The stock tires are perfectly satisfactory for casual running, but on my track they tend to go off very quickly. I can do a couple of quick laps before the car starts to slide a lot. Before I begin tire testing I wipe the track down with a special dusting cloth, then run a magnet car with sponge tires with a little traction compound on them for about 25 laps, then another car with slip on silicone tires until the grip does not change much as the laps pile up. I run a couple of air purifiers while the testing is going on. I used the tire cleaner that Ed Bianchi makes.
With the stock 0.352” OD tires I was able to get down to 5.783 seconds on my ~50 foot MaxTrax road course, but within five laps the car was sliding a lot. It became difficult to do a lap where the car did not slide out enough to lose time and the lap times after that were over 6 seconds. At the limit the car would spin out.
With 344RF tires (0.354” mounted OD) the best lap time was 5.642 seconds and the drop off as the laps piled up was only one or two tenths of a second. There were few spinouts those tires. With 344RSE tires the best time was 5.716 seconds, that was a surprise because they are usually good for another 0.1 to 0.2 seconds less than regular silicone slip-on tires. The car did not get loose as the laps went by, but the front end would come out of the slot at the limit. With 340RF tires (0.350” mounted diameter) the best lap time was 5.675 seconds, as with the other aftermarket tires the lap times did not fall off by much and the car was only slightly loose at the limit. With 340RSE tires the best lap time was 5.621, the times did not increase by much after 30 laps or so and there was not the front end understeer problem that I got with the 344RSE tires. I am guessing that the car has a smidge more magnetic downforce with the 0.004” smaller diameter tires. That would tend to increase cornering speeds while the top speed would go down slightly.
Note that the aftermarket tires were a little loose on the stock wheels and those wheels were a little too narrow for the tires. A fanatic would probably want to switch to the appropriate CNC machined double flange wheels.
Finally, I finished up with the stock tires, the lap times did not change from what they were at the beginning of the test session.
If the stock tires had been able to maintain their best lap time the difference would seem to be slight, but it would in fact be significant to a hardcore racer. During a 12 minute race the stock tires would do 124.5 laps and the best (at least for me) aftermarket tires would be good for 128.09 laps, a 3.5 lap advantage.
Note that my track favors cars with a lot of top speed and it has few joints to upset a car. On a twisty track, and especially if it was a little bumpy, the SE tires would probably have a greater advantage.

[Slotmanmoss]

What brand of tire were you using, ie: 344RF, 344RSE,340RF, 340RSE? Thanks

[RichD]

With respect to the shorting problem the TFX shoes have windows like most other pancake shoes and those allow the shoes to wiggle from side to side a little. On T-Jet type cars I prefer to use Slottech shoes that have narrower windows. Wizzard shoes have narrow windows as well. The TFX shoes are like Aurora A/FX or Magnatraction shoes and those have a flatter step than T-Jet shoes. If you are having a shorting issue possibly the step of a Slottech shoe could be flattened out somewhat.

[RichD]

I got a shipment of spare TFX parts last week, that included both 15 and 19 tooth crown gears and some spare axles. I made up a couple of rear axle assemblies with CNC machined 0.170" DF wheels. I wanted to run some laps using other tires that are not a great fit on the stock TFX wheels. I did my initial TFX testing with my MaxTrax configured as a road course, but right now it is an oval. While running the car around the road course would probably tell me more I probably will do at least a little testing on the oval this week.

[RichD]

My track has gotten a great deal of use lately so now it is really in top shape. The track is now in its oval condition, which is not ideal for tire testing however. I ran some laps yesterday and the stock tires held up very well as the laps went by. Previously they went off quickly while the aftermarket tires that I tried lasted a lot longer. I made up a couple of rear axle assemblies using TFX axles and CNC 0.170" DF wheels, one has a 15 tooth crown gear and one has a 19 tooth crown gear. With the 19 tooth crown gear the car was just over 0.2 seconds slower around my 35 foot MaxMrax oval.
With the stock rear axle assembly and 0.352" OD tires the car was a bit faster than with the DF wheels and 0.354" OD tires. It looks like the folks at OS3 did some testing before they settled on the 0.352" diameter.

[TuscoTodd]

Great info! Appreciate you continuing to share your findings!

[gmcullan]

Continuing on with my testing, AW, Dash. and TFX chassis were tested as follows, with all chassis fitted with the same Dash Camaro body.

AW and Dash chassis, both with OS3 Anchors on the front measuring 0.326", Quicker Engineering 0.177" wheels with ST SE silicone tires measuring 0.340". Both cars with 12 tooth final drive pinions. The AW car measured 179 on the VRP dyno while the Dash car measured 170. The AW car had the stock magnets while the Dash car has dimpled Super II magnets. Running my typical 12 minute round robin testing and reporting as laps/segments, the AW turned in 101/2 while the Dash turned in 103/9

Testing a long wheel base TFX chassis with stock wheels and tires, fronts of 0.344" and rears of 0.350" and measuring 200 on the VRP dyno resulted in 93/13. This chassis was reconfigured with an older JW brass independent rotating front end with mounted tires measuring 0.344" and a rear axle with Quicker Engineering 0.177" rims and ST SE silicone tires with a mounted diameter of 0.354". Front and rear track is at maximum allowed width. With a 15 tooth crown gear, this combo turned in 107/2.

I had some slightly smaller ST SE tires that had a mounted diameter of 0.352". This combo did not go well on my track, dragging the rivets in the shoe hanger plates. Strange, as that did not happen with the stock 0.350" rear tires.

Going back to the 0.354" rear tires and a 19 tooth crown gear, the car turned turned in 102/9.

Of course more testing and experience with the TFX chassis is in order, but at first glance it sort of looks like it might fit in with the AW/JL/Dash cars if we specify a 19 tooth crown gear. Certainly we will have a better point of view by next season.

[gmcullan]

Here is the TFX chassis and body that I tested with the 19-tooth crown gear. As stated it pretty much runs with my AW/JL/Dash based cars that are configured the same. This chassis is slightly faster with the 15-tooth crown gear.

IMG_1400 by gcullan, on Flickr
IMG_1398 by gcullan, on Flickr

This is a TFX chassis configured with the short wheelbase and still using the stock wheels and axles. The body is a resin cast Chaparrel Couple (I believe) that nicely fits the chassis and covers the tires.

IMG_1403 by gcullan, on Flickr
IMG_1405 by gcullan, on Flickr