Haha. We will do a body. The kids are voting on a design direction for the body, but we have a ways to go before we get that far. I have to find a sponsor for the drive system, so it'll be a bunch of soapbox style testing until we get one.
Cycle Kar(t) now Electrathon car
- Thread starter irk miller
- Start date
sav0r
Coast to Coast
I see you are using a standard kart spindle now. That is the right move.
Run those in the lowest Ackerman setting possible (will explain). Generally that means the holes furthest from the center of the chassis. With your rack setup you will have to measure this though. Just measure the width of a point on the wheels when they are at zero toe, then turn to lock, and measure the difference (front to back on the wheel). This will tell you how much toe you gain or lose across your degree of lock.
With three wheels you have zero rear roll stiffness. The only way you can generate that is via the front. Your spindles have significant scrub radius, meaning any castor (spindle bolt top closer to rear axle) while create significant lowering of the outside front tire and a raising of inside front bolt. This helps center the steering going straight, but will create a chassis that wants to roll outward with (especially) three wheels. Ackerman would only make this worse as the inside front will turn greater and lower further. Additionally, a three wheel vehicle tends to turn very quickly as a result of zero differential action (needed). Ackerman increases turn in, meaning if you have a bunch of ackerman you are looking at a really unstable vehicle at turn in.
Run those in the lowest Ackerman setting possible (will explain). Generally that means the holes furthest from the center of the chassis. With your rack setup you will have to measure this though. Just measure the width of a point on the wheels when they are at zero toe, then turn to lock, and measure the difference (front to back on the wheel). This will tell you how much toe you gain or lose across your degree of lock.
With three wheels you have zero rear roll stiffness. The only way you can generate that is via the front. Your spindles have significant scrub radius, meaning any castor (spindle bolt top closer to rear axle) while create significant lowering of the outside front tire and a raising of inside front bolt. This helps center the steering going straight, but will create a chassis that wants to roll outward with (especially) three wheels. Ackerman would only make this worse as the inside front will turn greater and lower further. Additionally, a three wheel vehicle tends to turn very quickly as a result of zero differential action (needed). Ackerman increases turn in, meaning if you have a bunch of ackerman you are looking at a really unstable vehicle at turn in.
Sderbyshire
Into Sailing, classic Triumph cars and motorbikes.
Love this build!
Thanks for all the input. Lots of teaching points and I’m thankful.
Here is our spindle setup before mounting to the axle. The scrub radius, with neutral camber measures 2” with the spacer inboard and 1” with the spacer outboard. I hope I’m correct in wanting to set up this up positive and that 2” is not a bad number.
Turnturtle
Been Around the Block
If you haven't already, take a look at the solar car design reference material, https://www.americansolarchallenge.org/regulations/solar-car-design-reference-material/ . The math in there is way above my pay grade but it may be of use to you.
sav0r
Coast to Coast
Scrub radius is called “scrub” for exactly why you think it is. For an efficiency vehicle I doubt you really want to incorporate it. At a minimum just space the wheel in as far as it goes.
As for camber run as little you can. Camber thrust is a form of scrub.
Rider52
Over 1,000 Posts
I have been following this thread on ADVRider. The "motor wheel" is very interesting. https://advrider.com/f/threads/vespa-p125-200-project-now-gone-electric.1381662/
We have looked into hub wheels. They're aren't the way to go in this application. Not as efficient and they're not the wattage you need. We'll get a 3kW BLDC motor from Golden Motor. https://www.goldenmotor.com/
Chain drives are actually more efficient. You don’t want a CVT, because it eliminates regenerative braking. This is the same reason why you don’t want to run a freewheel. There are also more sprocket options with chain drives vs belts.
The swing arm is mounted with two linkages that allow us to raise and lower the rear end. Race rules require the vehicle to be 1.5in off the ground to prevent a slide in the event of a flat tire.
We’re now at a point where I need to convince the team that we should compete with one driver and build the rest of the car around her. At opposite ends of the spectrum, we have a female who’s 5’4” and 130lbs. She’s a champion mountain biker who isn’t unfamiliar with competing. On the other end, we have a legit D1 prospect football player who’s 6’4” 210lbs and has shoulders that don’t fit in the frame of the car as it is. He’s our best skill driver. I’m going to do my best to get this team onboard with our female driver during competition.
We pulled it off the table and tested our steering. It works pretty well. There’s room for more angle on the wheels, but I think we’re well within need for any turn we will encounter. I need to dig around to find out what the radius should be. We also tested our yoke in both directions. It’s going to stay with the bars facing up, but with a few inches removed.
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