Knowledge Base:  
Electrathon Information - All information about Electrathons.
Last Updated: 01/31/2013
"Electrathon America" organizes races thoughout the U.S.  This class of racing is designed to demonstrate the range and speed capability of Electric Cars.  These cars carry up to 67 lbs of sealed "lead acid batteries" and run for one hour.  The car that travels the furthest distance is the winner. There are two major classes of Electrathons - High school and a Open Class.
 
Electrathon Configurations:
A few years ago a "Electrathon" participant published an article in a national news letter stating that a three wheeled vehicle with two wheels in front and one in back (Cycle Car) was more stable and a better "Electrathon" design than one with one wheel in front and two in back (Tri-Cycle).
 
This is still in dispute!
 
The Tri-Cycle configuration could be better because:
1.... It allows for a uni-body design.
This design of an Electrathon vehicle can be constructed using Light-Weight Kevlar honeycomb fiber board for a lighter more aerodynamic vehicle.  The single rear wheel design requires a much heavier structure to keep the body from flexing because of the added weight and turning forces on the rear wheel.

2.... Front Wheel drive.
 The front wheel is pulling the vehicle in the direction that you want to go.  Which reduces friction in cornering.  When the drive wheel turns in the direction of travel there is less friction between the road and tires.  When using a rear wheel drive, it is trying to push you in a straight line instead of turning the vehicle.

3....  Reduced braking in the corner.
 If the rear of the vehicle starts to swing out in a corner, you apply power to the front wheel to pull you out.  Instead of having to use the brakes in front, which will only slow you down, and then you need to accelerate more which uses much more energy.

4.... Better balance and center of gravity.
a)  Weight is more evenly distributed over each wheel, which increases stability. There is less stress on drive components, wheel bearing friction and tire wear.  In a single back wheel design you are putting more weight over the back wheel than over the front wheels.
b)  There is a myth that 2 wheels in front is more stable. That may be true when the center of gravity (COG) is above the center of the wheel axles, but is not when the COG is below the center of the wheels.  In fact a Cycle car is even less stable if the vehicle should spin 180 degrees and could even flip, do to the weight distribution.  The Tri-Cycle would be very difficult to flip in any situation and can turn just as tight a corner.

5.... Rolling resistance is greater with two wheels that are trying to steer around a turn. The geometry of the wheels is very difficult to maintain because the inside wheel wants to turn at a different speed than the outside wheel. This causes an increase in tire to road fiction and the wheel bearing friction. These two wheels must maintain a parallel configuration and is very difficult to do when used for turning. The two wheels in back configuration always stays true to parallel.

6....Rear Brake Advantages.
a)  When using the two fixed rear wheel design you don't need to use heavy, expensive and less aerodynamic Drum or Disc Brakes.  A simple light-weight custom built caliper brake that is more aerodynamic can be used.
b)  While applying rear brakes in a turn,  they don't need to work together.  In fact when turning left, if you apply just the left brake it actually helps you turn.  If you use 2 brakes on front wheels, they must be matched evenly or you could spin-out or even break a wheel or support structure.

7....Seat positioning.
a)  The driver can lay down more and move further back because he has two wheels in the rear to support this position.  This allows for lower Center of Gravity (COG) and a more aerodynamic vehicle body.
If you try this with only one rear wheel, you put to much stress on the single wheel and it could break or have excessive tire wear.

8...Cooler Motor and Hotter Batteries
The motor is much more efficient at the coolest temperature possible.  The batteries are much more efficient at the warmest temperature possible.  When the motor is mounted in the front, fresh air can be better directed around and through the motor, keeping it cool.  With the batteries in the rear of a two rear wheel "Electrathon" it is easier to keep them out of the air flow and can be better insulated to keep them warm.  On a two wheel in front vehicle you need to mount the batteries in the front because they would be adding too much weight over the rear.

95% of all Electrathons are Cycle-Cars but the Tri-Cycle Electrathons tend to prove they may be better. 
 
In conclusion you can design and build your Electrathon with the One drive and Steering wheel in front and Two Braking wheels in the back or Two Braking-Steering wheels in front and one drive wheel in the rear.  
 
 
 
Electrathon Design and Racing Tips:
The following Electrathon Design and Racing tips are listed from most important to least important but may overlap and change positions due to the race course being used.
 
1) Vehicle Weight -  Design your vehicle to use the lightest construction materials possible.  A uni-shell design using Light Weight Kevlar Fiber Board provides the best weight to strength ratio that we know of and also reduces the aerodynamic resistance.
 
2) Vehicle Rolling and power Resistance
....a)  Use the best wheel bearings and drive train system possible.  Using a chain drive system has proven to use less energy to transfer power from the motor to the drive wheel than either a belt, gear or friction drive system.
....b)  Use a three wheeled vehicle design with a powered single front steering wheel versus a double front steering and rear wheel drive system. (See the information in the previous article).  It is best not to use a rear steering system or a four wheeled vehicle design.
....c)  Use the thinnest (1.5 to 2 inch) highest pressure tires possible.
....d)  Design and construct your vehicle to be as low to the ground as possible.
....E)  Properly place the weight of vehicle components to reduce resistance and weight distribution over each wheel.
 
3) Energy  Management
....a)  Use the available energy form the batteries to the maximum. Heat your batteries to about 110 degrees (if your rules allow) WHILE CHARGING, to increase their capacity to  30% or more, versus a 60 Degree battery temperature.  If your batteries should cool down after charging, the available stored energy will dissipate by turning into expelled heat.
....b)  Use meters to track battery pack voltage and amp draw information.
....c)  Set up the gear ratio to match the race course - You want to gear your vehicle so it can average about a 40 amp/hr draw for each lap. (See the following article)
....d)  Charge your batteries properly.  NEVER let your batteries stay dead for more that just a couple hours!  You can charge them individually with 12 volt chargers or use a 24 volt charging system with the batteries in series, but always check the batteries for an equal charge.  Charge them until you reach about 15 Volts at a 2 amp charge and then leave them at the 2 amp charge until they reach about 16 volts.  Maintain this 16 volts (each battery) at less than 2 amps, until the last minute before the race.  Make sure you heat the batteries WHILE CHARGING to about 110 degrees.
 
4) Aerodynamic Resistance - Design your vehicle to reduce the airflow over and around the vehicle, including the wheels and other protrusions.  Use a canopy to cover the driver.  This reduces the energy required to maintain a higher speed, and this becomes even more important on the longer or more banked race tracks.
 
5) Driver Ability 
....a)  Drive the best line possible.
....b)  Use the brakes the least amount as possible.
....c)  Watch your energy usage.  Adjust your speed to maintain your energy usage plan.
....d)  Be patient!  Remember, you are not RACING other cars. You are RACING for distance against time!
 
What is the most efficient motor rpm's for an Electrathon?
Scott Electric Motors are most efficient at 2500 rpm. That is, they get about a 90% efficiency power in, to power out ratio. But if you set up your motor to be most efficient in an "Electrathon Race" you may never finish or have to much energy left in the end.  This is because you should be concerned about the efficiency of your whole vehicle and not just the motor.  The motor "efficiency rpm's" don't determine the most efficient configuration for a race vehicle. (The Scott 1.6 hp, Etek and the Lemco motors have been the most efficient motors used to date.)
 
For an Electrathon race, the best way to determine the most efficient configuration is to set up the gear ratio properly for a specific race track.  The gear ratio you end up with will depend on the rolling, turning, and aerodynamic resistance of your racing vehicle and the available energy in your batteries. You need to set up your gear ratio to average about a 40 amp average (40 amp/hr) draw per  lap. (If you have really good batteries, charge and heat them up properly, you may be able to get more than 40 amp/hrs out of 67lbs of lead acid batteries)
 
To do this while using a Scott 1.6 hp motor, you need to guess at a gear ratio to start with.  Electrathon "Controllers" will work at their most efficient when you have your throttle set to full output. Otherwise you throw away electric energy into heat in the controller.  So you need to gear your vehicle to use full throttle most of the time during a race. On a 1/4 mile non banked track the gear ratio will be about 4.25 to 1 ( example: 14 tooth motor sprocket to a 60 tooth wheel sprocket) while using a 20" drive wheel.  Go out and take a few laps with your throttle set  at maximum for most of the lap and while maintaining your lap times, watch your meter. (It is very important to have an amp meter and to be able to see it while testing).  The speed that you are going is not important, the average power usage is all important.
If you see about a 40 amp draw on an average, then you are geared correctly.
If you see an average of about 50 amps (amp/hr) then you need to gear down to about 4.6 to 1 (13 tooth motor sprocket to 60 tooth wheel sprocket).
If you get about a 30 amp/hr draw then you need to gear up to about 4 to 1.
When you finally get the right gear ratio,  you will be able to get about that speed for one hour, then your batteries should be just about dead at the end of 60 minutes.
This will be the most efficient race you can run with this particular vehicle on this specific race track.  If you have low drag resistance and set up your vehicle efficiently and stick to your race plan, you should finish with the race leaders, if not the winner!
 
Get to know your Batteries!
Have you ever wondered how the top Electrathon teams are always on top?   They KNOW their batteries!
You can bench test them with a dummy load and record the voltage & current until the battery voltage goes down to 10 Volts.  A good battery will start at around 50 Amps, and last 50 minutes, or more.  Each car should get two of the best batteries in the batch.
With the test results you calculate the Amp/Hours you can get out of your battery pack.  Then you figure out the Amp/Hours you need to maintain a certain speed for a particular race track.  On a constant speed track, like an oval, you will be able to use more of the total Amp/Hours than on a variable speed road course.
 
BS Designs has developed the "BatteryManager".  This unit displays current, voltage, Amp/Hours, and elapsed time since the start of the race. These units can be used for drain testing, in addition to use during the race.
 
So how do you improve your team's performance during an Electrathon race?
Watch your Meter and plan how much energy you need to use during your race, and drive your plan.  If you are ahead of schedule, slow down!  If you haven't used enough, go faster!  Do your best to use ALL that your batteries can produce.  You may need to go slower to go farther.  One rule of thumb is that you can slow down 10% and save about 20% of energy used.


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