Slot.it Group C – Race #1

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The Difference in One Volt – The First Slot.it Group C Race

The Austin Slot Car Club has run the Slot.it Group C series every year since the club was formed back in 2009.  Along the way we have tried different formats and power settings but have settled on running the series at 11 volts.  This has been good for the past ten years but as the skill level of the drivers and car preparation have improved it became obvious that running the series at 11 volts makes it more of a motor series than a car series.  Meaning – everyone was running the same 9T pinion and a 23T crown with relative ease.  This meant if you wanted to gain an advantage you had to have a stronger motor making the series more about a motor and less about driving.  The solution – raise the voltage to 12 so racers would have to adjust their gearing and their driving style.  With the higher voltage if you had a motor that was slightly down on power you could adjust the gearing to make up for it.

The increase in power would mean that most racers would have to adjust their gearing, controllers, and the way they would drive their cars.

What exactly is the effect of raising the voltage from 11 to 12?

At 11 volts:

A Slot.it MX16 motor (rated at 23K) will run at around 21K.

A motor running 21K combined with a 9T pinion and 23T crown would have a wheel RPM of around 8,217.

A wheel with a diameter of 20.4mm and a rollout of around 64.06mm would push a car forward at 28.782 feet per second.

A projected time to cover the track length of 54 feet would be 1.876 seconds.

 

At 12 volts:

A Slot.it MX16 motor rated at 23K will run at around 23K.

A motor running 23K combined with a 9T pinion and 23T crown would have a wheel RPM of around 9,000.

A wheel with a diameter of 20.4mm and a rollout of around 64.06mm would push a car forward at 31.524 feet per second.

A projected time to cover the track length of 54 feet would be 1.713 seconds.

 

The differences:

Motor RPM increases by 2K

Wheel RPM increases by 783 RPM

Feet per second increase by 2.742 feet

Projected time to cover the track length of 54 feet improves by 0.163 seconds

Now all you have to do is have super human car control skills that would allow you to keep a car with rear wheels turning at 9K in the slot and on the track.  Simple enough.

Let’s see how the racers were able to deal with the increased track voltage.

Let’s first look at the racers and what they were running for a car and gearing.

Marty M.                    Porsche 956KH                    9T x 23T

Ary B.                         Lancia LC2 ’83                     9T x 23T

David C.                     Lancia LC2 ’86                     9T x 23T with a 21K motor

John B.                      Lancia LC2 ’86                     9T x 24T

Erik K.                        Mercedes C9                        9T x 23T

Russell M.                 IMSA Porsche 962               9T x 24T

Mark L.                       Porsche 962KH                    9T x 24T

The first heat proved challenging as the racers were coming to terms with the higher voltage.  Driving the cars was so different as the acceleration points were different, how quick you pull the trigger, and your braking points were different if not that they just came up quicker.

The driving got better as the heats continued but no one was able to set quick times compared to what they were when we were running at 11 volts.  It looks like there was a  another learning curve we would all have to go through.

After all eight heats were complete the results looked similar to past Slot.it Group C races albit slower than past series, even with the increase in power.

The next round of the series on February 5th will be fun to watch and see how the racers adjust their cars and their driving styles to the 12 volt series.

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