E-Kart

[jkv357]

Well... it's been a while since I updated this thread...

The E-kart has taken us a bit longer to complete than we expected (like a year) - but it's done! My son was in a full leg cast for 4 months, and had rehab for another 4, so we got behind on the project. The shop that was bending the 4130 Chrome moly tubing last year screwed-up, and didn't get us the tubing on time, but I don't think there would have been any way we could have gotten it all cut and fitted in time anyway.

It took quite a while to notch and fit the cage tubing to satisfy the rules, but it should be legal. We had it professionally TIG welded, and that alone took the welder almost 4 hours.

We added another battery (behind the seat) for 48V, and picked-up another 1000 RPMs and more power. Top speed has been 48 MPH, but that was in the neighborhood. Should be faster on the track's 1mi+ straights.

Here's a picture from today -




Competition is this Monday (5/13/13) at Road America. I'll post results as soon as possible.


Jay

[sendler]

Beautiful. What are the rules for the formula you are competing in?

[jkv357]

Originally Posted by sendler

Beautiful. What are the rules for the formula you are competing in?

Thanks.

There's a bunch of safety rules that we had to comply with (tubing type, size, and wall thickness and opening size in the cage), but we will be competing in the "Exhibition" Class - hence the "E" designation in our number.

In order to actually compete in class, we would have to add 60 pounds or ballast that needs to be removable so it can be weighed with the driver. Rules say the driver needs to be 180 pounds. My son is 120. There are numerous other rules that would be impossible to comply with using our current set-up.

There's also a max battery weight that we are now over.

To really be competitive in-class we would need a "purpose-built" chassis. My son plans to do some other improvements for next year based on how we do this year, but after that they could use the motor/controller/batteries to power a purpose-built chassis if they wanted to. That would be up to the teachers/advisers. We built this one the way we wanted to in our garage (with plenty of our own money...).

We are planning to keep it at the house over the summer so he can race a few SCCA-type solo slalom races in the area with a couple mods.


Jay

[jkv357]

Here are a few photos from the Electrathon competition at Road America May 13/14 2013.

We weren't competing in a class, but we did have the unofficial fastest slalom time, fastest lap time, and fastest top speed at just under 60 mph on the GPS. Last year a team from Canada had the fastest speed at 50 mph using Li-Po batteries.

We knew we wouldn't be competitive in the endurance part of the competition, but did complete 3 full laps - about what our testing predicted. The winning team in the open class with Li-Po batteries did 7. Plenty of vehicles did 6. Coasting was nowhere near as good as some of the enclosed 3-wheelers with bicycle tires, but our cornering speeds were way up. When he was running with the lead pack at the beginning of the event he consistently had to add power to keep up while they were still coasting.

We learned quite a bit about batteries. Some of the top teams are getting 18V from their 12V batteries by deep cycling them. That's a big part of it that we didn't know about or do before the competition.

He was happy after the last heat of the day where he just wanted to open it up without concerns about efficiency. We went with our tallest gearing. He figured he would get one good hot-lap and that's it, but was able to do 2 at full speed. He lapped some of the cars before coming in. We did get a fair amount of compliments on our set-up and fabrication, and the kart was the probably one of the safest and easiest to drive vehicles there.

[sendler]

Awesome fun!
.
A hot battery is a full battery. The best electrathon class teams use battery heaters and hard charging to run to the car with the race battery still bubbling as they install it just before the race. I believe C. Michael Lewis still holds the record at 62 miles in an hour with his beautiful luge style streamliner.

[renault_megane_dci]

how about using scooters 10 or 12" wheels and tires next time ?
I can't see them being less FE friendly than go kart items ...

[jkv357]

Originally Posted by renault_megane_dci

how about using scooters 10 or 12" wheels and tires next time ?
I can't see them being less FE friendly than go kart items ...

I have seen them use wheels from a Yamaha PW50. Not sure the exact size, but pretty small.

They would require a bit of mods to the bodywork to use, but it's not a bad idea. It would reduce the scrubbing while cornering significantly and I'm sure the smaller contact patch would give better coasting. The small/wide kart slicks are definitely a big disadvantage for rolling resistance and also limit our gearing.

I don't know if he'd go for it though - he really liked the fast cornering!


Jay

[renault_megane_dci]

Not my project but more efficiency in the drivetrain = more speed ...

[Smurf]

I'll be sure to mark that event on my 2014 calendar. You have one of the best looking machines in all the pictures, that has to be worth something, right?

Are you able to put Lexan over the 'windshield' part of the cage? Maybe some underbelly sheeting?

[jkv357]

Originally Posted by Smurf

I'll be sure to mark that event on my 2014 calendar. You have one of the best looking machines in all the pictures, that has to be worth something, right?

Are you able to put Lexan over the 'windshield' part of the cage? Maybe some underbelly sheeting?

Thanks. We felt good about the performance and execution, even though we didn't really win anything with it.

We have considered a pan and windshield, with a full body pan being first on my son's list.

I'm not sure about enclosing the roll cage and adding a windshield - would it increase the frontal area and create more drag? Seems like it would punch a much larger hole and produce a larger wake - but I don't know for sure.

Thanks for the ideas everyone!


Jay