Noobs first micro kart

[ambientvoid]

*couldn't find an e-kart subsection, sorry if this is in the wrong place.

I want to build a micro kart using some spare longboard wheels (90mm), iv tried reading through the forums for ideas but my grasp of motor/battery/ESC knowledge is dismally lacking, so if someone could tell me what combination of parts I need that would be awesome.
I have no interest in super high speeds, I want to spend the majority of the time travelling at around 5mph with a top speed of about 15 to 20mph. I will be on almost totally flat surfaces with very occasional slopes not exceeding wheelchair access steepness. I need a range of 10 miles.
Initial estimate of the likely weight of both me and the kart is 95kg (210lbs)
Thanks.

 

[Nobuo]

If you want to make the whole thing from scratch, you will find some specially difficult problems like vibrations or steer system.
The better it to use anything to start like a 50cc kart.

About the electric system is something near like a mid drive motor ebike.

you need a motor, then when you will know about your gear relation, choose a controller and a battery. All should be working >48V

this could be the standard motor to start

http://www.ebay.com/itm/800W-36V-DC...181?pt=LH_DefaultDomain_0&hash=item259e24ce45

 

[ambientvoid]

I'll pretty much have to make it from scratch, i need an almost recumbent seating position and a 50cc kart steering column would probably be too tall...

 

[chuttney1]

I salute for doing cause I priorities will lead to doing what you are going to do. So you want to build a chibi kart. Saw a youtube video of a guy using custom made hub motors and it works as intended. Doesn't seem to go fast. Nobuo suggestion for an electrical motor is not bad, but I wish there were torque specification for evaluation even though it's DC.

I have a suggestion is to take a look on the sections relating to e-skateboards and stuff. There is much info as part of this community has been using brushless outrunners for rc airplanes with car ESCs and works as intended, but not without issues. The main one you should look at is the "10S custom skate ESC: testers wanted!" section. The ESC is called VESC, is still in development, but the creator of the ESC has done a marvelous job it is worth a try for this application and he made it open source. The controller has a max voltage of 60V which Nobuo has specified for a system greater than 48V. Many have built it by hand or had the option to go with a bulk order since pricing is cheaper in bulk. The motors used in the e-boards have Kv value of less than 200 because of the torque created is sufficient to hill climb which you can find at hobbyking, namely the Turnigy SK3 6374 motors. The lower the Kv the more toque you will get.

What route you choose for a motor is up to you. If it is just a proof of concept project, I believe you can forgo the suspension, but a plus to have. I understand that it is best a a light setup. You'll have plenty of space to mount a bunch of lithium batteries in parallel after picking the appropriate voltage. Do you have a set budget because this project will get expensive fast. Not trying to deter you. What it the material for the frame?

 

[SlowCo]

http://www.etotheipiplusone.net/?page_id=2036

http://www.etotheipiplusone.net/?page_id=1987

 

[ambientvoid]

I accidentally found that chibikart page a while ago and it's why I even considered a micro kart as a doable thing, I intend to use aluminium extrusion for my chassis but I'll be modifying the steering and changing the layout a bit.

I've been looking at Alien Power System motors because I heard that lower kv would be more suitable for a low speed vehicle (i don't know if that's correct) and they do a 130kv 6374 motor.

I haven't thought about a budget exactly, im just trying to spend as little as I can sensibly get away with.

 

[ambientvoid]

ok so if i want to move at low speeds from a standing start (no push), what motor should i go for? iv been looking at the Turnigy outrunner motors which seem to be a popular choice for skateboards, 5065 and 6374 motors seem to be the main sizes used, is the larger motor more powerful or simply bigger? do i need two for extra grunt or would one be adequate?

 

[chuttney1]

ok so if i want to move at low speeds from a standing start (no push), what motor should i go for? iv been looking at the Turnigy outrunner motors which seem to be a popular choice for skateboards, 5065 and 6374 motors seem to be the main sizes used, is the larger motor more powerful or simply bigger? do i need two for extra grunt or would one be adequate?

Skip the 5065 motors. Users on the eboard forum use the 6374 motors since the torque is good enough for the size of motor chosen and able to reach 20mph with the correct gear ratio. I probably believe you might be able to use Alien's 80100 motor since the kv is low enough with good torque for running from dead start with a little extra for fun. The diameter of the motor is a factor. Torque is a function of force x radius from physics.

One motor of adequate size with the torque level you require will be fine to climb a hill. Two is even better. Four if you can some how figure how to motorize the front with the steering, but that's added complexity to tackled later if you wish. Chains or timing belts can be used to transmit power from the motor to the skateboard wheel. Because of the motor size, you may be able to run a gear ratio closer to 1:1.

For a more technical, but helpful understanding about this refer to this page. http://vedder.se/2014/10/chosing-the-right-bldc-motor-and-battery-setup-for-an-electric-skateboard/ Vedder's the one who made the VESC which is why his information comes in handy with motor selection.

Do you know what the curb weight of the kart will be? Are you a college student? You can get access to cad software from Autodesk for free as a college student which comes in handy. People would recommend Solidworks for stuff like this, but its not free. Im not an mechanical engineering major so I don't know most things to take into consideration other than the basic forces at play and places vibrations may be induced.

 

[torqueboards]

One, you should probably go sensored if it's on a gocart. You can't really kick push. Unless you about to do a fred flintstone! but then you wouldn't need motor power.

There are some benefits to 63mm motors but ideally they aren't that much better (dual longboard wise). You get lower KV but that can be accomplished by custom 50mm motors. You have a bigger can which can disperse more heat. You have bigger bearings which are a bit more durable. Besides that I'm not too sure what else would benefit as far as weight to power ratio on a longboard. The added weight 1 lb or so isn't worth the added weight IMO. If your running dual motor 50, your setup won't get hot enough for the 63mm to be of any use if your gearing ratio is correct.

My dual motor 5065 200kv wouldn't be much faster if any on 6374 200kv on 12S..

On a gocart, I would run (2) 6374 and 12S or higher if you can find the controller of course (higher than 12S) also you should go sensored. Only because weight doesn't matter on a gocart. You wouldn't be carrying it.

Just my 2 cents although I'm not an EE.

 

[made_in_the_alps_legacy]

might be inspirationnal for you : a kind of "chainless - drill powered - wood made - recumbent"

 

[Slowrider]

I built this go kart for my kids, it is powered with a Q100 hub motor and now does about 30 km/h max speed.
https://www.youtube.com/watch?v=O9Gm7Raem10

Of course this is not an ultra light micro kart, but if you change the wood for alu profiles it would be quite close

I actually started with 80100 outrunner motor see here
https://www.youtube.com/watch?v=FWeCp7ZoIrI

But the problem with this type of motor is to get it started from standstill. Sometimes it did work ok, but a lot of times there were issues and I had to push start. Once I had it rolling it was fine and had lots of power.
But if you want to have a reliable and simple to use motor I would go for hub motor. There are motor kits like this http://www.diytrade.com/china/pd/8954152/500w_electric_hub_motor.html
almost ready to bolt on to a chassis. By using a kit like this it can save you a lot of time.

 

[made_in_the_alps_legacy]

@slowrider : do you suggest to make a 3 wheeled 1RWD kart ? I think that's what I would do - I just Wonder if you had to make a diffential in your 4 wheeled version -
which is lovely by the way

 

[Slowrider]

@slowrider : do you suggest to make a 3 wheeled 1RWD kart ? I think that's what I would do - I just Wonder if you had to make a diffential in your 4 wheeled version -
which is lovely by the way

Thanks, Yeah a 3 wheeled 1RWD should work fine and be simple to make.
The one I built has drive on only one wheel, but works well and is of course more stable and safe. For my kids that is quite important

 

[ambientvoid]

On a gocart, I would run (2) 6374 and 12S or higher if you can find the controller of course (higher than 12S) also you should go sensored. Only because weight doesn't matter on a gocart. You wouldn't be carrying it.

Except that in my case i would be carrying it, i don't drive so my only means of transporting something like this is by train and by foot. I have considered incorporating something like a wheely bar so i can drag it but still the less weight the better. From my experience with transporting a previous project 13 kgs (29lbs) is probably my drag/lift limit...