I came across Electrathon when I was doing research to help my nephews build a go-cart. Seeing as how I am an 'electric' guy, I drive a Prius and work on robot propulsion systems, Electrathon seems much more interesting than a stock go-Kart :)
After my initial round of research my biggest open ended question is design priorities. Where should we spend our time and money (in terms of research, design, and testing) to get the greatest return? We are looking more towards the short track format.
1. Reliability --
2. Rolling Resistance --
3. Handling
4. Drive train efficiency --
5. Maintaining momentum through turn --
6. Aerodynamics --
Our initial approach is going to be to follow the excellent HowTo at http://www.clubhotrod.com/hot-rod-talk/41183-electrathon-different-kind-hotrod.html and tweak it to meet our needs.
Thanks in advance for any pointers or references!
David
mhodgertt said
Oct 21, 2014
David,
My suggestion is to keep it simple and basic. Less stuff to break and go wrong and usually lighter car.
-I don't know where you are from but if there is a team or more in your area go talk to them. No need to reinvent the wheel. Take there ideas and improve on them. Go to several events, involved schools/adults, etc. and see what you are building and get ideas. Many of those that don't do this put in lots of time and money for a car that has no way of being competitive.
-Decide on car/body style. Tricycle, Tri-car, etc. This is the first major decision. Most of our cars (we build 15 to 20 new cars each year) are tri-cars with 2 wheels in front.
-Work on great wheels and brakes. We use Tomos Moped wheels for the front but I heard supply is tight right now. These are aluminum mags with drum brakes and 12 mm bearings included. Very tough and hard to break on tight corners and easy to set up and dependable. 20" BMX wheels for the back with a free wheel system. I would advice double wall and as many spokes as possible to hold the side loads on tight corners.
-Look at steering options. I like the 2 handled steering but we also use go-cart style, rack and pinion, tiller steering with our tri-cars and with tri-cycle variations of bike forks work well with either handle bars or with the steering attached to the forks and then tiller, two handed, etc.
-Next is propulsion. I like original eTek motors but those are getting hard to get. You might contact Dave Cloud to see if he has any. Or a little more expensive but better are the Lynch motors. I like Alltrax controllers but most are good.
-Batteries are the next item on my list. We use Yellow top Optima 25/75 series. These have dual post so hook up in a couple of ways, are right at the weight limit but don't need to be weighed since are on the OK list. There or many other options, just be sure they make weight and you want the longest Amp Hour rating you can get at a 20-30 amp draw. Which is hard to find specks on. Also must follow the rules. If you go exotic batteries it often means you will be racing against yourself unless there are others in the area.
-For short track I like the wheel base (front axle to rear axle) to be between 45" and 55" Too short and too unstable..too long and it is like a cadi on a tight slalom course.
-Try to keep the weight fairly light. Most of our student cars weigh about 100 pounds not counting the batteries and driver. Mine is heavy cause I got tired of repairs so mine is about 130 pounds and I am a way over the 180 pound driver requirement. But we still do OK and usually in the top 3 cars at a race.
If you have any specific questions. Please let me know and I will do my best to answer them for you. My school and I have been building cars for over 20 years and so have built well over 300 cars of various types and styles. We have found a number of great ides on paper that just did not work well for us....as well as basic items that need to be there to make them work well.
Good luck and mostly just have fun!!!!
Mike
dfarning said
Oct 21, 2014
Thanks for the comprehensive response!
I live in Western Wisconsin and have contacted the Wisconsin group about participating in the open category next season.
It looks like I am heading in the right direction. So far I have read all the discussion on this site and studied most of the pictures for hints about what works and what doesn't work. From there, I have reviewed Jim Robinson's tutorial at clubhotrod.com... and tried to figure out why he made the choices he did.
My initial plan is to build a test chassis similar to his design to so I can get a few hours behind the wheel before finalizing a design.
1. Configuration -- Tri-car. It seems like a toss up between tri-car and tricycle. Tri-car enables a nearly fool-proof drive train with an interesting engineering problem designing the steering.
2. Chassis materials -- 3/4 inch round tubing 0.060 wall thickness. I can get the tubing for about 50 cents a foot. So I an go though a couple of chassis iterations without breaking the bank. I can use heavier tube if things start breaking.
3. Steering -- Steering wheel.
4. Battery Placement -- It seem the primary choices tend to be behind the seat of along the side in pods. The trade off appears to be length vs width. I need to figure out the physics before making a decision.
This will enable me to focus on a chassis geometry, steering geometry, and rolling resistance.
5. Body -- Little emphasis on aerodynamics for this iteration.
Expensive/Interchangeable parts.
6. Wheels -- As long as I settle on 20 inch wheel I can postpone this decision for a while.
7. Batteries -- As long as I settle on lead acid I can post pone this decision for a while.
8 Motor / Motor controller -- I can postpone this decision for a while.
For a specif question... Could you point me towards a introductory reference where can I learn more about handling and energy loses due to cornering. As I understand it...
1. Better handling allows a vehicle to carry more speed through a corner which mean less energy is required to accelerate back up to speed.
2. Turning a corner, lateral acceleration, results in a loose of energy due to hysteresis and tire scrub.
Thanks
David
ProEV said
Oct 21, 2014
David,
Mike has suggested start basic and simple and go from there. I would agree and take it one step farther. if you can find a used electrathon vehicle, buy it and run it. You get right to running and learning. Ever time the vehicle runs, you will learn more and modify it. And when you are ready, strip out the motor and batteries and build your own chassis.
Here would be my priorities:
1) Reliability. Put some cones in a parking lot and run it until something breaks. Fix and repeat. Fix and repeat.
2) Instrumentation. To improve the vehicle, you need to know both speed and power usage. If you do not have accurate track of Watt hour usage then you have no way to know if your design changes are improvements. And how can you run the right race pace if you do not know how much power you are using?
3) Learning how to get the most from your batteries. What is their capacity? What is the best charge cycle? What temperature do they work best at?
4) Repeatability. There are a lot of common sense basic things that contribute to a fast vehicle. Building tools and creating procedures to make these easy and repeatable keeps these basic things right. Example are aligning the wheels (front and rear, left and right and to the chassis) before every outing. Tire pressures set before each session. Wheel bearing nut tension set and checked consistently. Chain alignment and tension set and checked.
5) Understanding your motor/controller. Where is it most efficient-gearing?
Beyond those five, is the great unknown. Here are some specific ideas but it would be hard to say which might give the best return:
Higher voltage is more efficient-we went well with 48 volts.
AC and brushless DC offer high efficiency and regen-check out electric bicycle controllers and big R/C motors for good value- we found regen braking made passing safer and easier.
We haven't tried multiple motors or castor free steering yet but want to!
mhodgertt said
Oct 21, 2014
David,
I agree with most of your idea. But no the battery placement for a tri-car----I feel the best in one battery in the back and one in front of the front axle. I have had both in front and both in back and I know my car (and most of my student's) corner much better with the weight centered more in the center of the car rather than a heavy back end. Think of a sports car, you usually want the center of gravity in the middle of the car for best handling.
I agree that Cliff is also right in buy/drive a used car for a race or two and then you will figure out so much before you make your own. I just have never bought a car and so we learned over the years what was easy and worked well if done right since we make so many and have so many students in the program. I also agree 'Dependability" is huge. The biggest factor is the driver. We have had state champion cars driven by a poor driver do poorly and a 'bad' car come in near the top with a good driver.....This speaks to "getting the most out of you batteries and knowing how to gear. Learning to take corners with out loosing power is a requirement on the short tracks as tight as some of the ones we race on. Those that vary from 28 to 20 miles and hour a time or two on each lap will be dead before the 60 min. Knowing when and how to accelerate if you get caught in traffic and have to speed back up etc. is a must and only comes from experience.
He is also right on about the instruments. Since we have ~20 cars racing each year I do not buy fancy instrumentation. We use cheap Harbor Freight multi-meters and small shunts to read Volts and Amps and give us a ballpark of where we are. With this my kids and I do OK. In the NW there are several teams with amp/hour--watt/hour--etc. meters and yes it is very important information but you can survive without it. I would like one for my car so I could be a little more competitive and have a chance to beat the Cloud cars in our area but I feel if I had one I would also need to buy all of my kids one which I can not afford. The meters will make the learning curve at becoming a good driver go much faster.
Again let me know if I can help in any way,
Mike
dfarning said
Oct 21, 2014
I am not quite ready to buy a full vehicle. The fun for me is playing....
Yes, I think instrumentation might be my niche :) I am a software and embedded computer guy. This evening I was going to mock up a monitoring system which monitors and records:
1. Battery Voltage.
2. Amperage out of Battery.
3. Speed.
4. Direction.
5. Distance covered
6. Steering wheel angle.
7. Accelerometer
8. Anything else you might thing of add ....
I was thinking that being able to download and analyze that information after a training session or race could be useful for evaluating if a modification helped or hurt.
Do you have any suggestions for good AC motors? I have a couple of AC inverters I can use for testing.
Thanks
David
mhodgertt said
Oct 22, 2014
No we tried one several years ago but with little success. I know some others are doing well with them.
Good luck
Mike
dfarning said
Oct 23, 2014
To answer my own question....
If anyone else is feeling overwhelmed about vehicle handling there is a great introductory book called "Race Car Vehicle Dynamics" available at http://www.amazon.com/Race-Car-Vehicle-Dynamics-Experiments/dp/0768011272 . The math towards the end of each chapter might get a little hairy for high school students, but one can read the first 3/4 of each chapter and get a pretty go understanding of why things work the way they do and how to do back of the envelop calculations to make sure your design is in the correct ball park.
David
ProEV said
Oct 23, 2014
David,
"Do you have any suggestions for good AC motors? I have a couple of AC inverters I can use for testing. "
The Super Coupe's AC motor does not have any markings and we have never fiquired out what it is out of.
I would suggest researching on endless sphere and seeing what the latest favorites are from the electric bicycle and scooter crowd. The Turnigy sounds like an excellent option. Here is a link, go to the fifth comment.
An AC motor is going to have to go on the back burner. This project has a pretty steep learning curve. As mike suggested, I think I'll stick with standard components for my first iteration.
I came across Electrathon when I was doing research to help my nephews build a go-cart. Seeing as how I am an 'electric' guy, I drive a Prius and work on robot propulsion systems, Electrathon seems much more interesting than a stock go-Kart :)
After my initial round of research my biggest open ended question is design priorities. Where should we spend our time and money (in terms of research, design, and testing) to get the greatest return? We are looking more towards the short track format.
1. Reliability --
2. Rolling Resistance --
3. Handling
4. Drive train efficiency --
5. Maintaining momentum through turn --
6. Aerodynamics --
Our initial approach is going to be to follow the excellent HowTo at http://www.clubhotrod.com/hot-rod-talk/41183-electrathon-different-kind-hotrod.html and tweak it to meet our needs.
Thanks in advance for any pointers or references!
David
My suggestion is to keep it simple and basic. Less stuff to break and go wrong and usually lighter car.
-I don't know where you are from but if there is a team or more in your area go talk to them. No need to reinvent the wheel. Take there ideas and improve on them. Go to several events, involved schools/adults, etc. and see what you are building and get ideas. Many of those that don't do this put in lots of time and money for a car that has no way of being competitive.
-Decide on car/body style. Tricycle, Tri-car, etc. This is the first major decision. Most of our cars (we build 15 to 20 new cars each year) are tri-cars with 2 wheels in front.
-Work on great wheels and brakes. We use Tomos Moped wheels for the front but I heard supply is tight right now. These are aluminum mags with drum brakes and 12 mm bearings included. Very tough and hard to break on tight corners and easy to set up and dependable. 20" BMX wheels for the back with a free wheel system. I would advice double wall and as many spokes as possible to hold the side loads on tight corners.
-Look at steering options. I like the 2 handled steering but we also use go-cart style, rack and pinion, tiller steering with our tri-cars and with tri-cycle variations of bike forks work well with either handle bars or with the steering attached to the forks and then tiller, two handed, etc.
-Next is propulsion. I like original eTek motors but those are getting hard to get. You might contact Dave Cloud to see if he has any. Or a little more expensive but better are the Lynch motors. I like Alltrax controllers but most are good.
-Batteries are the next item on my list. We use Yellow top Optima 25/75 series. These have dual post so hook up in a couple of ways, are right at the weight limit but don't need to be weighed since are on the OK list. There or many other options, just be sure they make weight and you want the longest Amp Hour rating you can get at a 20-30 amp draw. Which is hard to find specks on. Also must follow the rules. If you go exotic batteries it often means you will be racing against yourself unless there are others in the area.
-For short track I like the wheel base (front axle to rear axle) to be between 45" and 55" Too short and too unstable..too long and it is like a cadi on a tight slalom course.
-Try to keep the weight fairly light. Most of our student cars weigh about 100 pounds not counting the batteries and driver. Mine is heavy cause I got tired of repairs so mine is about 130 pounds and I am a way over the 180 pound driver requirement. But we still do OK and usually in the top 3 cars at a race.
If you have any specific questions. Please let me know and I will do my best to answer them for you. My school and I have been building cars for over 20 years and so have built well over 300 cars of various types and styles. We have found a number of great ides on paper that just did not work well for us....as well as basic items that need to be there to make them work well.
Good luck and mostly just have fun!!!!
Mike
I live in Western Wisconsin and have contacted the Wisconsin group about participating in the open category next season.
It looks like I am heading in the right direction. So far I have read all the discussion on this site and studied most of the pictures for hints about what works and what doesn't work. From there, I have reviewed Jim Robinson's tutorial at clubhotrod.com... and tried to figure out why he made the choices he did.
My initial plan is to build a test chassis similar to his design to so I can get a few hours behind the wheel before finalizing a design.
1. Configuration -- Tri-car. It seems like a toss up between tri-car and tricycle. Tri-car enables a nearly fool-proof drive train with an interesting engineering problem designing the steering.
2. Chassis materials -- 3/4 inch round tubing 0.060 wall thickness. I can get the tubing for about 50 cents a foot. So I an go though a couple of chassis iterations without breaking the bank. I can use heavier tube if things start breaking.
3. Steering -- Steering wheel.
4. Battery Placement -- It seem the primary choices tend to be behind the seat of along the side in pods. The trade off appears to be length vs width. I need to figure out the physics before making a decision.
This will enable me to focus on a chassis geometry, steering geometry, and rolling resistance.
5. Body -- Little emphasis on aerodynamics for this iteration.
Expensive/Interchangeable parts.
6. Wheels -- As long as I settle on 20 inch wheel I can postpone this decision for a while.
7. Batteries -- As long as I settle on lead acid I can post pone this decision for a while.
8 Motor / Motor controller -- I can postpone this decision for a while.
For a specif question... Could you point me towards a introductory reference where can I learn more about handling and energy loses due to cornering. As I understand it...
1. Better handling allows a vehicle to carry more speed through a corner which mean less energy is required to accelerate back up to speed.
2. Turning a corner, lateral acceleration, results in a loose of energy due to hysteresis and tire scrub.
Thanks
David
David,
Mike has suggested start basic and simple and go from there. I would agree and take it one step farther. if you can find a used electrathon vehicle, buy it and run it. You get right to running and learning. Ever time the vehicle runs, you will learn more and modify it. And when you are ready, strip out the motor and batteries and build your own chassis.
Here would be my priorities:
1) Reliability. Put some cones in a parking lot and run it until something breaks. Fix and repeat. Fix and repeat.
2) Instrumentation. To improve the vehicle, you need to know both speed and power usage. If you do not have accurate track of Watt hour usage then you have no way to know if your design changes are improvements. And how can you run the right race pace if you do not know how much power you are using?
I agree with most of your idea. But no the battery placement for a tri-car----I feel the best in one battery in the back and one in front of the front axle. I have had both in front and both in back and I know my car (and most of my student's) corner much better with the weight centered more in the center of the car rather than a heavy back end. Think of a sports car, you usually want the center of gravity in the middle of the car for best handling.
I agree that Cliff is also right in buy/drive a used car for a race or two and then you will figure out so much before you make your own. I just have never bought a car and so we learned over the years what was easy and worked well if done right since we make so many and have so many students in the program. I also agree 'Dependability" is huge. The biggest factor is the driver. We have had state champion cars driven by a poor driver do poorly and a 'bad' car come in near the top with a good driver.....This speaks to "getting the most out of you batteries and knowing how to gear. Learning to take corners with out loosing power is a requirement on the short tracks as tight as some of the ones we race on. Those that vary from 28 to 20 miles and hour a time or two on each lap will be dead before the 60 min. Knowing when and how to accelerate if you get caught in traffic and have to speed back up etc. is a must and only comes from experience.
He is also right on about the instruments. Since we have ~20 cars racing each year I do not buy fancy instrumentation. We use cheap Harbor Freight multi-meters and small shunts to read Volts and Amps and give us a ballpark of where we are. With this my kids and I do OK. In the NW there are several teams with amp/hour--watt/hour--etc. meters and yes it is very important information but you can survive without it. I would like one for my car so I could be a little more competitive and have a chance to beat the Cloud cars in our area but I feel if I had one I would also need to buy all of my kids one which I can not afford. The meters will make the learning curve at becoming a good driver go much faster.
Again let me know if I can help in any way,
Mike
Yes, I think instrumentation might be my niche :) I am a software and embedded computer guy. This evening I was going to mock up a monitoring system which monitors and records:
1. Battery Voltage.
2. Amperage out of Battery.
3. Speed.
4. Direction.
5. Distance covered
6. Steering wheel angle.
7. Accelerometer
8. Anything else you might thing of add ....
I was thinking that being able to download and analyze that information after a training session or race could be useful for evaluating if a modification helped or hurt.
Do you have any suggestions for good AC motors? I have a couple of AC inverters I can use for testing.
Thanks
David
Good luck
Mike
To answer my own question....
If anyone else is feeling overwhelmed about vehicle handling there is a great introductory book called "Race Car Vehicle Dynamics" available at http://www.amazon.com/Race-Car-Vehicle-Dynamics-Experiments/dp/0768011272 . The math towards the end of each chapter might get a little hairy for high school students, but one can read the first 3/4 of each chapter and get a pretty go understanding of why things work the way they do and how to do back of the envelop calculations to make sure your design is in the correct ball park.
David
David,
"Do you have any suggestions for good AC motors? I have a couple of AC inverters I can use for testing. "
The Super Coupe's AC motor does not have any markings and we have never fiquired out what it is out of.
I would suggest researching on endless sphere and seeing what the latest favorites are from the electric bicycle and scooter crowd. The Turnigy sounds like an excellent option. Here is a link, go to the fifth comment.
http://endless-sphere.com/forums/viewtopic.php?f=35&t=60996#p914144
Thanks,
An AC motor is going to have to go on the back burner. This project has a pretty steep learning curve. As mike suggested, I think I'll stick with standard components for my first iteration.
Dave