Thread: Electrathon - A Different Kind of "Hotrod"

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If I correctly understand, you are saying that gearing is a trial and error attempt to get the highest speed at the lowest current draw? Do you change gears during a race or do you fix the gearing for each race track and essentially run a single speed vehicle? I didn't notice a gear change lever in the car being built even though I think Jim used a derailier unit.

Originally Posted by RestoRod

If I correctly understand, you are saying that gearing is a trial and error attempt to get the highest speed at the lowest current draw? Do you change gears during a race or do you fix the gearing for each race track and essentially run a single speed vehicle? I didn't notice a gear change lever in the car being built even though I think Jim used a derailier unit.

That is essentially correct. With the limited battery power we are allowed in a race, we need to make the batteries last for the entire hour while still running fast enough to outdistance everyone else. After a few races we begin to get a "feel" for what gearing is necessary for a certain type and length of course. It's a trade-off between speed and longevity; we have to find that happy medium.

My orange car had a 6-speed derailleur in it, but I never found the right primary gear reduction to make it work effectively. Dana ("The Bat") put a 6-speed derailleur in his car and it seems to work very nicely. My team's cars now all have single-speed drive including the one I just built in this thread. I try to make an educated guess on gear ratio before a race and select the sprockets accordingly. It ain't high tech, but it's reliable.

Thanks BAT for your reply. I had the pleasure of meeting Jim and checking out his cars today. A great guy and very helpful. After seeing the his electrathon cars I am syked about building one.

I hope to see this class of racing gain some traction (pun intended) It looks like a lot of fun and could be a great event, bringing the racing to the people. Thanks
Jim for the tour of the cars!

When I start to build one I'll post some pics!

As for 5 or 6 speed gearing,having the chain come off in a race will make you fail badly,or a flat tire or any kind of brake down mostly just takes too long to fix,so if your not super up on how to control chains,it's a bad idea to used 5 or 6 speed derailers and bike sprockets that are designed and made to jump chain so they can shift.
Yes I use this set up,but take note,I'm taking a risk doing so,even though I have super know how on bike racing over many years. One gear is better if it is the right one!
For those that think they'd like to look at some of my bike racing;
http://www.wisil.recumbents.com/wisi...ge/default.htm
I think any one would also call these bikes ac kind of hot rod.

I stopped by Jim's place yesterday and checked out his electrathon cars, I was impressed! By both Jim and his cars. He seems to be dedicated to the sport his kids and racing in general. I look forward to building a car and getting out to the track/parking lot or were where ever the next venue is held. Thanks Again Jim!

Thanks BAT for the reply about gearing. Wouldn't it be more competitive on some tracks to run multiple gears. Racing all out on a speed way versus a tighter course in a parking lot. It would seem you would peak less, maintaining a constant draw with gearing.

Originally Posted by J. Robinson

I try to make an educated guess on gear ratio before a race and select the sprockets accordingly. It ain't high tech, but it's reliable.

If it's not a racing 'secret,' what ball park are you in with regard to gearing? I would guess you make changes by swapping the front or motor sprocket as it would be much easier than changing the one on the drive wheel.

What RPM are these motors designed to run at most efficiently?

Jim
I posted this under a different thread, but wondered if you've heard or seen this


The Hot Rod Hybrid, crafted by Braille Battery to compete in the Hybrid and Electric Class of the Redline Time Attack Series, also features a roof-mounted solar panel, according to the report. The owner plans to compete in the One Lap of America race series with the car, which is claimed to be making 440 hp and can supposedly tick off quarter-mile runs in 12.9 seconds at almost 110 mph.

Roc8Ray - Dana (The Bat) can correct me if I'm wrong... Using multiple gears (derailleur or some type of transmission) can be an advantage on a twisty track where the car speed changes dramatically from one part of the track to another. Keeping the motor in its most efficient rpm range is the goal as long as the gear change is accomplished smoothly and without a huge change in gear ratio. A sudden big change in gear ratio equates to a big change in motor speed and could cause power spikes on the current draw.

RestoRod - It depends on the motor and its efficient rpm range. Motor manufacurers provide info at what rpm range their motors run most efficiently. The challenge then is to figure out what ratio is necessary to keep the motor in its efficient range on the track you are running. The Scott 1hp motor is most efficient at 2800 rpm. If we are running on a tight course like the parking lot course at USF Tampa, the average speed is about 22 mph. If I calculate the rpm's of the rear wheel, it needs to turn 370 rpm to go 22 mph. Now divide 370 wheel rpm into 2800 motor rpm and I come up with a target ratio of 7.56:1. Just to keep a little extra speed available for the long backstretch, I would probably go with something in the range of 7:1.

For sprockets I try to determine what may be the lowest and highest ratios I might need, get a big enough wheel sprocket to achieve it, and buy a selection of motor sprockets to give me a selection in between.

Steve - I saw that car in your other thread. It's amazing what electric power is capable of these days and I believe that industry has only scratched the surface of future potential. The down side right now is the expense of converting a vehicle to electric, but those costs are coming down as more stuff becomes available...

I been thinking about building a small trailer to hull our Electrathon racer on[ I don't have a pickup truck or my van any more] So going to find a jetski trailer to make one out of or just make one. I do see some small kits for lite trailers at Northen Tool and Harber F. that could work.
Getting racer and all batterys plus spairs to the race sites. Geees we missed 3 races cus couldn't get there

Bat, I bet you could find a nice used trailer that is a lot more heavy duty the the Northern tool ones for less on craigslist. Trailers seem to go for pretty cheap, after sitting on the side yard for 10 years! Just a thought. I've heard the wheel diameter and speed limitations on some of the small Northern Tools, and Harbor freight trailers, can be a problem if your highway bound. Course you could hotrod a trailer from them!

I, too, have looked at the trailers at Harbor Frieght and Northern tool. They look like they would be plenty substantial for hauling these lightweight little cars and all their attending equipment. I would definitely opt for one that has the 13" wheels. That way, if you have tire problems on the road, tires are readily available just about anywhere. It would also be an easy job to enclose one of those little trailers to make it lockable and weather-proof for those overnight trips to some of the races.

Originally Posted by The Bat

I been thinking about building a small trailer to hull our Electrathon racer on[ I don't have a pickup truck or my van any more] So going to find a jetski trailer to make one out of or just make one. I do see some small kits for lite trailers at Northen Tool and Harber F. that could work.
Getting racer and all batterys plus spairs to the race sites. Geees we missed 3 races cus couldn't get there

Hey bat I don't know if you built a trailer yet, if not this seems like a great trailer on sale at Northern tools
http://www.northerntool.com/webapp/w...e=&marketcode=

Thanks for input all;
Well I found a old jetski trailer that about the right size for free,so think I'm going to play with it some,may need a deck and tie downs etc, and maybe some aero wind cuter out of house door skin[1/8in. ply that cheep and can bend EZ.
I'm wishing it had bigger wheels but there no real lbs. here anyway.
There's a race coming up 12/5/09 up near Tampa Fl.,could be if all goes well we'd make that one?.

Hi Bat,
I'm planning on being at that one, too. I got one of those dual-cable brake handles that you told me about and have it installed on the car. I also put the boots in the front rims so maybe I can make more than 8 laps... I need to test my batteries, but otherwise I guess I'm ready.

Originally Posted by J. Robinson

Hi Bat,
I'm planning on being at that one, too. I got one of those dual-cable brake handles that you told me about and have it installed on the car. I also put the boots in the front rims so maybe I can make more than 8 laps... I need to test my batteries, but otherwise I guess I'm ready.

Nuts,my new to me as of less then two months,2001 Ford Focus DOHC auto tranny just blow up,so now thats the big fix needed,no racing for now,need to fine another tranny for it. This was the car I got to replace my old van tow car for racer.
One good thing,is we're getting stuff done on my son's 23T bucket frame and should have a roller in a week or two.
Dana