Research has focused on weight of the final car and performance of the motors. The materials for the frame/shell and the components are an issue. Here is what we have found out so far.
| Batteries | Motors | Controllers |
| Wheels | Tires | Need for Speed |
| Steering | Caster/camber | Amp Rage |
The standard 22nf deep cycle has performed well for us. However, new options are hopeful. The deep cycle works well with our amp hungry Etek motors. If we choose to go with a smaller 1 horse motor we can change these batteries to something lighter weight. We are looking at the Interstate 58 Mega-tron battery. It has the cracking amps to do the job and it seems to be in the right weight class.
| MTP-58 Battery Specifications | MT-58 Battery Specs | Combined Battery Specs |
| Weight: 34.00 pounds |
Weight: 30.00 pounds |
Weight: 64.00 pounds |
| Length: 9 1/2 inches |
Length: 9 1/2 inches |
Length: 9 1/2 inches |
| Width: 7 1/4 inches |
Width: 7 1/4 inches |
Width: 7 1/4 inches |
| Height: 6 7/8 inches |
Height: 6 7/8 inches |
Height: 6 7/8 inches |
| Cranking Amps: 765.00 |
Cranking Amps: 675.00 |
Cranking Amps: 720.00 |
| Cold Cranking Amps: 610.00 |
Cold Cranking Amps: 540.00 |
Cold Cranking Amps: 575.00 |
| Voltage: 12.00 |
Voltage: 12.00 |
Voltage: 24.00 |
We started with Scott 1 hp and 1.6 hp motors. The 1 hp motor got hot quickly and efficiency went out the window. We liked what we saw with the pancake style motor. We looked at Lynch motors and the Briggs Etek motor. The Etek was our choice. It runs cool and has plenty of hp on demand. The problem we see is that you will draw heavy amps at the end of the race when the batteries are lower voltage. Clearly, these motors are superiour to the Scott motors. They don't have the low voltage chucking that Scott motors have. They are smooth and clean running right through the race at all voltages. We are now looking at the Lynch 130 pancake. It is only 1 hp but it will do the job at much less amp draw with our car weight down to 92 lbs. We can trim some more weight which should make this motor a winner.
Efficiency of the controller has always been an issue. The Curtis 1204 has been on all of our cars until this year. We have tried the 300 amp Alltrax controller. Fully programmable this controller has possiblities. Software issues at Alltrax has been an issue however. The debugging of the programming software for our laptop has not come at this point. We are still running stock setting at the current time.
Rolling friction and curb weight in turns have been issues over the years. With 15" 32 spoke wheels we found we blew out spokes in the sharp turn 4 of Lime Rock. Located at the bottom of the hill and being a sharp right hand corner took its toll on the outside wheel. We looked at 48 spoke 15" wheels, and reducing the wheel size. We have gone to 16" wheels. This reduces the rolling friction on the car and also lets us enclose the wheel in the fairing. We found these wheels to be best for our car. No spoke issues have been found with our 32 spoke 16" wheels. We did decide to modify the wheel before the race. We put an extra outter wheel bearing in each wheel. We found absolutely no bearing problems with this configuration. Warning!!!! If you machine too much metal off the outer wheel the bearing could collapse the wheel and cause a roll-over. One of our cars a couple of years ago hit a pothole in turn 3 causing the outter wheel bearing surface to collapse and fold. This caused the car to roll twice out of the curve. Frame design and safety systems let out driver walk away from the crash.
We have found the higher the pressure the better. We like the 120 psi tires. We do toast a set per race however. We have examined the option of the solid foam tires. During the May race at Lime Rock, the temperature can climb. This is when we see all cars with tire failure. If the back tire goes you have a spin-out on your hands. Front tires have just as much danger with oversteering and the possiblility of flippling the car.
We have found that a speed of mid thiry miles per hour will win the race if you finish. Make these cars go that speed has never be a big issue, but making them finish the hour is quit a challenge. Efficiency of the motors is higher when they are running near top speed. Since we run an autocross circuit which has the standard "B" formation and steep hills a geared read hub has helped us keep the rpms up while grinding up the hills. We use a Shimano Nexus 7 speed hub. We have had good success this year but the shifting linkage needs modification. As for the built in brake, forget about it. It is not made for these speeds or weights. If you use it during a race it should only be used for emergency brakes.
Driver training is a must do for these cars. Beyond the different steering option, the training of a good driver requires time and a cool header driver. To see other cars do hole shots off the starting line and not chase after them takes seasoning. Watching the amps is good but going up and down hills, passing, running under a yellow all take cockpit calculations on how many amps they can spend now to garner momentum and lower amps later.
Steering wheels seem to be the most natural option but space doesn't always allow for this. Tiller style steering offers great control and small control sticks. This does take time to get use to as a driver.
Front end alignment is key here. Take the time to align the front properly to reduce tire scuff and friction.
We took our lessons from the Model T here. We tried a 15 degree angle on the kingpin to help keep the camber in the curves. We set our camber slightly in to make our cornering more aggressive. We have about a - 1 degree. Our suspension gains camber during deflection and compensate for body roll. Our caster is about 4 degrees to help steering in the straight-aways. We run zero toe for efficiency.
If you want to catch up on caster/camber/toe, click on this link to learn more (excellent webpage!)
Amp Rage
We have ampere meters and voltage meters in our cars. We have our drivers monitor this as we drive the circuit. We place a red line around 30 amps. When the batteries wear down in voltage, the amperage goes up to keep the same amount of energy flowing. We fould that overbuilding the circuit breakers from 100 amps to 200 amps helped latter on in the race and up the hills. Matching the new meters and shunts for higher amps are important details as well.
Connecticut Electrathon runs at Lime Rock track on the Skip Barker Autocross track. We have the upper track with the start/stop line right at the pits and turn 5. Cars climb the hill from start to turn 1. The grade levels off between turns 1 and 2. A quick drop makes the straight between turn 2 and turn 3 the fastest place on the track. The right angle turn in 3 has made the lower part of the track the most dangerous. Cars have spun out here with blown tires and caught drafts that have blown their fairing right off the car between turns 3 and 4. The climb starts as you enter turn 4 and quickly climbs to turn five to make it heart break hill. Many a car never make it up to turn 5 to get the final lap in.
During the 2003-2004 year we have started using the full butterfly track. This makes the race even more challenging as the quick turn after turn 2 drops down and crashes into a level grade. Many cars were ramming their noses in this turn.
Rules for the Connecticut Electrathon requires a driver change between 20-40 minutes in the race. This makes the pits a hot spot to watch for driver and ballast changes during the race. Racing on this track is challenging and exciting. While we are racing our two to three heats on our track someone is racing on the big track.
The design and construction process is a two year process. The new designs of the Electrathon vehicles are created by the Designing Minds class during the fourth quarter of one year and the designs are passed onto the next year's Alternative Energy Vehicular Design class. This collaboration between two classes gives our students authentic design and custom production experience. As you may imagine, the designers make some challenging issues for the production class. The details of front end geometry, gear ratios, fiberglass body techniques, and frame refinements are done during the construction phase of the vehicles. Engineering and design processes taught during the two classes have helped create innovative and effective vehicle designs. This is our fourth year of this process and the melding of classes has really installed a high student satisfaction and pride level for all participants.
Over the past four years we have trimmed 100 pounds off the car. "Granddaddy" 526 was built for safety. The newer cars have used lighter materials, newer fabrication processes, and better designs to cut extra weight off the car while still creating a safe vehicle. We use Rhinoceros for the design work. This company has been great to work with over the years. This lets us put our Poser created drivers into various vehicles. We will be adding Solidworks software and the material anaylsis software to test breaking points on the aluminum superframe and crashbars assemblies.
The Frame The frame of the car has been shrinking over the years as me have constructed more of a monocoupe design. The motor and wheel mounts still are machined and created from aluminum or steel tubing. All members are wither MIG or TIG welded. We are toying with the thinnest and strongest metals are reasonable prices. 6061, 6063 Aluminum Mild, 4130 Alloy Steel have been our choices so far. Our latest car design has 26" height and we are trimming it dow to 22" by rearranging motor placement. A lower meaner car should help us with air flow.
The Body Construction of the car body starts with the designs in Rhinoceros. We select the most promising design and we create 2" sectional of the fairing. We plot out 1:1 prints and cut out 2" styrene foam to the exact size. We number and assemble the cut-out in order creating a step pyramid-like car body. We then surform the body to the rough shape. That is when the fun starts. We now have to seal the foam, use bondo to create the line and smooth out the surface. We prime the finished body and block sand it to a smooth surface. Now we have the mold in which to create the fairing. Once the mold has been created we then lay up our resin and fiberglass, carbon fiber, or kevlar weaving and try to smooth out the body as little as possible to provide the lightest body possible. Warning, working with kevlar was a real pain. It warped wildly in the various temperatures. It would react to sun light on one side of the car over the other to cause crazy distortions. Technical problems like this has eliminated it as one of our weaving choices.
We have gone to a monocoupe design for this year's car. The entire drive train is modular. Below are the male and female molds we are using for the pan and the top sections which include the rear mechanical compartment, the central roll cage and battery box, and the driver cockpit.
When designing the cars on a computer some slight misreadings or design problems are always presented to the Alternative Energy Vehicular Design class. Some of the designs for steering have been modified during the actual construction. This is where working with metal and bodies in position clarifies design issues. All of the alterations are made by the Alternative Energy Vehicular Design class with Dr. Michaud. This year we added rack and pinion steering to the mix to facilitate easier turning in these small vehicles and less driver fatigue. We retrofit the last year's car with a rack and pinion as well.
The bodies are created with positive molds. They need sanding and paint to finish them off. One of our cars was left without paint to show off the carbon fiber body. Much work is done to sand and paint the final body.
