Instructables

Electric Microkart with Independent Suspension

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This Instructable provides an overview of the design and construction of a small electric go-kart or microkart with brushless motors, lithium batteries, independent suspension and a composite deck chassis, built from new components for under $1500. By keeping the design as light as possible, this microkart maximises performance from 6.5hp and its tiny size exaggerates the 40mph top speed.

SKIP TO BUILD STEP 1 - DRIVE TRAIN or continue reading below for more background info about the project.

The Goal

My overall goal was to produce an electric go kart for under $1500 that showcases current motor and battery technology, is suited to on or off road use, great to drive and challenges a few of the standard approaches to kart design along the way.

Approach

Some friends are building electric gokarts by taking a sprint kart (fixed gear racing gokart) and replacing the 2 stroke engine with an electric drive train. This is a quick way to make an electric kart, but unless you already have a racing kart you need to first buy a kart which would blow my price goal. I also wanted to further develop the go kart concept in a few other areas including size, chassis, suspension and independently driven wheels.

Size - to keep weight as low as possible, provide greater options for racing in carparks and indoors and make for easy transport in the boot of a car rather than a trailer, this design miniaturises the already miniature, hence the name microkart. This will extract maximum performance from the small electric drivetrain.

Chassis - structurally racing gokarts are flexible enough to lift or at least reduce the pressure on the inside rear wheel when cornering to counter the effect of a solid rear axel. In this design the rear wheels are driven independently with a motor for each wheel so the chassis will not need to flex for cornering and all four wheels can remain on the road. In addition the electrics are mounted inside the chassis instead of on top for protection and a cleaner look.

Suspension - go karts don't usually have suspension which is fine on a smooth kart track, parking lot or in a warehouse, but to find more places to drive it, improve performance and to provide a smoother ride off road, the microkart is designed with suspension. While it does appear to go against one of the principals of the go-kart which is keeping the design as simple as possible, the challenge is to do it cheaply and simply using easily available components.

Independent drive - ultimately I want to produce a 4wd gokart to maximise acceleration on and off road with each wheel independently powered by its own electric motor. To reduce costs and complexity (avoiding CV/universal joints at the front) I will be driving the rear wheels. Independent drive should extract more grip than a solid axel as well as saving the weight of the axel. It also opens opportunities for the future for developing a traction control system.

So on with the build....

 
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tlaselle1 month ago

very impressive!

atroiano22 months ago

re: Suspension, Skis make pretty good transverse leaf springs. You can use the portion of the ski which gives you the desired spring rate. You would cut the part you're going to use off each ski and lay them over the UCAs and fasten them to the chassis. You can even replace the upper arms with them like I did on my kid's power wheel. I reccoment cross country skis as they're pretty much the same width throughout the length and are made of fiberglass = super light and strong.

Ganhaar (author)  atroiano22 months ago
Thanks great idea sounds perfect. Just need to work out where to find skis. Nearest snow to us is 3000km away.

Thrift stores are a good option to consider. The ones in my area regularly have ski's and other winter sporting items.

Ganhaar (author) 2 months ago

Got an amp meter on the kart today and it was only running at about 40Amps max, so was able to increase the power by about 50% by adjusting the settings on the controller program. Kart was noticeably quicker and was getting wheel spin on corners and bumps on the gravel driveway. The young fella was having great fun for a couple of minutes until one of the rear wheels came off. The garden trolley wheels just weren't up to over 3kW and the rim sheared off the hub.

Ganhaar (author) 2 months ago
(removed by author or community request)
Ganhaar (author)  Ganhaar2 months ago

Here are some clips of the Microkart in action, still fine tuning controller program and gear ratios. Have it turned down so I don't blow anything up until I get an amp meter to measure what it is drawing, so will get it going a lot faster than this.

HoldOnTight2 months ago

I enjoyed this. Thanks!

Ganhaar (author) 2 months ago
The headways are much bigger capacity, 15ah versus 2.6ah for the 18650's but at a tenth of the price per cell, the 18650's are cheaper per Ah. The challenge with the 18650's is you need 5 sets of them in parallel for a similar capacity and also the cheap ones typically do not have high discharge rates. Maybe there is a need for an instruct able on building 18650 battery packs.
Regards Wayne
Errfadi2 months ago

it looks unfit for youth .. suitable for children

bell an2 months ago

good job forgot to say

I-Klondike2 months ago

Would be interested to see info on range and weight limitations (or even suggestions on how you would calculate that for this)? Would be a great base for a small art car.

Ganhaar (author) 2 months ago

Video planned for this weekend.

Also no bind in rear suspension. Can place the kart on a stand and rear suspension moves freely with springs removed.

Wayne

pmelnikov2 months ago

Good Job, Ganhaar!

Interesting project.

Only one advise -- DO NOT locate Li batteries under the seat. They may flame up or even explode. Consider another location for the battery pack far away from a driver.

Good driving ;)

Ganhaar (author)  pmelnikov2 months ago

Thanks all for the support and good feedback.

Also note that headway cells are lithium iron phosphate which is much safer / not prone to explosion like lithium polymer and with a battery management system and batteries enclosed in a chassis box, do not need to be concerned about them under the seat.

industriald2 months ago

Thank you for sharing. I have voted for you. Good luck with the contests.

hazmat4562 months ago

looks like the rear suspension might have some bind in it? can you show a video of the motion?

samern2 months ago

This is a very nice design. If at all possible can you please provide a close-up photo of the rear suspension from several angles: side (to see how you are allowing the rear wheel to move up and down with the chain) and top (to see how the tie rods are attached to the frame and axles). Having built several go karts myself and working on a 6x6 ATV, I am debating adding suspension to my design instead of relying on partially deflated balloon tires for some cushioning.

kloder12 months ago
That's a fantastic design, could you upload a video of it in full
Motion.
shazni2 months ago

Wow that is amazing! My son is in love with it :)

wow awesome please upload video .

Ganhaar (author) 2 months ago

Hey thanks Honus and JRF.

I have an old Moulton Bike with full suspension (pre-dates mountain bikes) and Moulton (mini hydrolastic suspension fame) used rubber in combined shear and compression for the bike rear suspension. I'm sure there would be a great solution using Moulton inspiration plus modern elastomers.

Wayne

jessyratfink2 months ago

Fantastic documentation - thanks for sharing your kart! :D

Honus2 months ago

Very cool project! Looking forward to the updates!

The biggest problem with rubber bump stops is that once it starts compressing the spring rate goes to infinity very quickly. You could try using an elastomer bump stop instead as they're a bit more progressive and they come in a huge range of sizes.