Electric Track Racer

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Laerson   1 mW

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Electric Track Racer

Post by Laerson » Mar 16 2018 7:52am

As a self-study project, to learn about electric transport, I decided to build a small 10-inch track racer. I thought it might be fun to share this with the community.

Specs:
Propulsion: Hub motor, 4kW, BLDC
Battery: Custom lithium-ion, 72v 1kWh, 18650 cells
Wheelbase: 1000mm
Seat height: 600mm
Wheels: 10 Inch
Suspension: None
Frame: Custom stainless steel laser cut tubes, hinged at the top to remove the battery pack in an ergonomic fashion.
Seat: Woven string ''hammock''

Designs:
All the designs were done in Solidworks, after 16 evolutions I ended with this final concept.
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The load carriering frame can be opened to remove the battery pack from the top.
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Seat test:
First I 3D printed a 1:3 model of the subframe to pratice weaving patterns.
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The final pattern in the 1:1 model were the seat will be woven in between.
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Assembly of the Frame:
The frame is made from laser cut stainless steel tubes and sheet. I don't have access to grinding or milling machines so I found a company which could cut the shapes from my 3D STEP files. I choose stainless steel to save the need for paint and because it's just so lovely to weld.
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The hinge in action
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Calibrating the frame
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SlowCo   10 kW

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Re: Electric Track Racer

Post by SlowCo » Mar 16 2018 8:06am

Wow, nice project! 8)
Although the hinge system is beautifully crafted it seems you have enough room to remove the battery from underneath the frame? Or will there be bodywork preventing that?
Keep us updated, it's great to see projects like this!

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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Mar 16 2018 8:29am

Thank you SlowCo, I'm happy to hear you like it! I will probably have an update by the end of next week.

You are absolutely right, this model will be naked without any bodywork. There should be more than enough room to remove the battery from underneath the frame. But I wanted to test the hinge for any future motorcycles which will be bigger and with bodywork. Besides that, do we really need a good reason to do something awesome? :wink:

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garolittle   100 W

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Re: Electric Track Racer

Post by garolittle » Mar 18 2018 7:57pm

Really nice project. Are you going to spot weld the 18650 battery pack?

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zro-1   1 kW

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Re: Electric Track Racer

Post by zro-1 » Mar 18 2018 8:30pm

This is super-cool. I'll be watching this!
~01~

John in CR   100 GW

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Re: Electric Track Racer

Post by John in CR » Mar 18 2018 9:57pm

If you've got smooth roads a little 10" wheeled scooter is a blast to ride. I pump 16kw peak into mine with a 3kw high efficiency hubbie using the smallest 10" scooter tire I could find. My only complaint is that even with about 2" of rear suspension travel those 16" OD wheels are only a nice ride on the smoothest roads. I love going motorcycle hunting with it. :mrgreen:

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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Mar 19 2018 6:26am

garolittle wrote:
Mar 18 2018 7:57pm
Really nice project. Are you going to spot weld the 18650 battery pack?
Yes, I heard that soldering should be really really bad for the cells, so spot welding it is. But I will save this for last. My knowledge about batteries limited, I only build some RC battery packs back in the day.
John in CR wrote:
Mar 18 2018 9:57pm
If you've got smooth roads a little 10" wheeled scooter is a blast to ride. I pump 16kw peak into mine with a 3kw high efficiency hubbie using the smallest 10" scooter tire I could find. My only complaint is that even with about 2" of rear suspension travel those 16" OD wheels are only a nice ride on the smoothest roads. I love going motorcycle hunting with it. :mrgreen:
Tell me more master?! :lol: 16kW, that's insane, what kind of controller did you use? Any more tips for overrunning these hub motors?

John in CR   100 GW

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Re: Electric Track Racer

Post by John in CR » Mar 19 2018 9:56pm

My motors are 6 phase, so I run them with 2 controllers, and splitting the current between controllers makes selection much easier. The Kv of mine is 14.3rpm/volt, so I'm using a 31s pack to reach the top speed I need, since much of my commute is highway. 75A battery side from each of my 18fet Zombiess high voltage controllers does the trick nicely. It's got a top speed of 110kph or so on a fresh charge, but it's the 0-90 or so that makes it so fun.

The secret to getting the highest performance out of any hubbie is to run the smallest diameter tire you can live with, because that lowest gearing gives you the most thrust. Then increase the voltage to get the top speed you want. I'm fortunate in that my high efficiency hubmotors have very low iron core losses, so they can handle any rpm without much heat from the iron side of the heat equation. eg at 1600rpm the motor's no load current is only 1.8A . Unfortunately these motors are out of production due to too high build costs.

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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Mar 23 2018 3:30am

Yesterday was another lovely day in the workshop. I completed the frame (I had to do some more welding, calibrating and finishing) and started working on the bearing cups which will be pressed into the head tube of the frame. I bought a big aluminium rod at the location hardware store and started working it on the lathe.

The triple clamp I will be using.
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Turning the bearing cups on the lathe, the old gal was probably used during W.W. 2, yes it's really that old :lol:
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Pressing the bearing into the cup.
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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Apr 12 2018 2:43am

At the moment I'm doing some research on the battery pack. The controller I have is rated at 72V, 65A (battery current), 180A (phase current), but in the future, I might want to switch it for a higher current controller. I guess my question is: is it safe to do so, and what would be an acceptable percentage for surpassing the maximum motor current?

At the moment I was thinking of taking 80x 18650 cells (Sony US18650VTC6 30A 3120mAh) and creating a 72V (20 in series), 120A (4 in parallel) to give some headroom for a future controller. Any recommendations for a BMS?

SlowCo   10 kW

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Re: Electric Track Racer

Post by SlowCo » Apr 12 2018 9:30am

What is the exact brand and type of hub motor you have?

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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Apr 13 2018 1:15am

It's a 10 inch QS Motor with the following specs:

Rated voltage: 48-72V
Continuous current: 45A
Maximum current: 65A
Max. phase current: 180A
RPM without load: 650~750

SlowCo   10 kW

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Re: Electric Track Racer

Post by SlowCo » Apr 13 2018 5:10pm

https://endless-sphere.com/forums/viewt ... 5#p1352776

From that thread:
litespeed wrote:
Jan 22 2018 12:57am
As far as current draw I'm running a QS205 and MaxE combo dumping 14kw in which ends up being about 200 amps peak.
You might need cooling in the form of ferrofluid or an internal fan. More on that in this thread:
https://endless-sphere.com/forums/viewt ... &p=1371246

Beware that when using ferrofluid that the stator heat will be transferred to the rotor. And in your scooter wheel also directly to the rim heating the air in the tire.

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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Apr 14 2018 5:43am

SlowCo, thanks for the source!

I decided to use the stock controller of 65A for now and build a 150A battery to leave some headroom. Once everything works I will buy a more powerful controller of around 130A and do some test runs were I keep increasing the current and check the temperature of the motor. It might be cool to put a thermistor on the stator so I can check the temperature in real time while riding.

Next week I will be in the workshop again, I will keep you posted.

litespeed   100 kW

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Re: Electric Track Racer

Post by litespeed » Apr 15 2018 11:11pm

VTC6 cells are not 30 amp in reality, they are move of a 20 amp cell. 30 amps they over heat big time. I’d recommend figuring them at 15 amp and going a minimum of 10p. At 4 or 5p they will sag big time. At 30 amps they sag .8 volts on a fully charged cell. At 15 amps peak it will live a long, long life.

Tom
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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Apr 16 2018 5:33am

That's good to know, thanks! Since I'm not building a drag racer where the heat can dissipate after a short burst, I think running a 130A controller might be overkill anyway, not just for the battery, but also the motor. I gave it some more thought and found a nice 110A controller which I could try after the stock 65A controller. With a 6p battery, this would come down to an individual cell draw of 11A (for stock controller) and 18A (for aftermarket controller). Do you think this is acceptable?

Sidenote: My plan for the battery enclosure is sewing a bag out of PVC cloth which will be suspended with straps within the frame. I want to add two flaps (front and back) with a zipper which can be opened when riding on hot dry days to improve cooling.

litespeed   100 kW

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Re: Electric Track Racer

Post by litespeed » Apr 16 2018 6:44am

11 amps would be fine and 18 amps doable but again, I think we should always plan for a maximum of 15 amps. By going to 8p you would drop your overall draw from the aforementioned 11 and 18 to 8 and 13.75. That would keep your voltage up, heat down, battery stress down and over all wattage much, much higher in racing conditions.

Letting the batteries get ventilation would only help but by adding just a couple more cells, as I wrote you will dramatically lower the batteries core temperature. Have you used this battery configurator program? Really good stuff. http://lygte-info.dk/review/batteries20 ... arator.php Compare different cells at different amperages.

Tom
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coleasterling   100 W

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Re: Electric Track Racer

Post by coleasterling » Apr 19 2018 11:55am

I just saw this and love what you're doing here. Would you be willing to let me pay you for your design when you're done? That, or I could sponsor you some CNC work in exchange. I own a small CNC manufacturing facility. Feel free to PM me. I'm starting an electric pocket bike racing league and we're using modified Razor mx and rsf350's right now.

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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Apr 26 2018 2:07pm

Hey peoples,

I've been preoccupied with a career change so I didn't have much time lately. So for now, it's just a small update.

I installed the brake caliper bracket, fitted the hub motor and did some more finishing on the frame (pickling and brushing).
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Next up is the front fork tube and brackets for the front wheel and brake caliper. After that, I will start building the battery.

Thanks for all your help and support so far!

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macribs   1 GW

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Re: Electric Track Racer

Post by macribs » Apr 29 2018 11:57am

Nice work. And cool design. This I got to follow.

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Dui, ni shuo de dui   100 W

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Re: Electric Track Racer

Post by Dui, ni shuo de dui » May 16 2018 10:43pm

Amazing frame work, bravo!

Regarding controller, motor and battery, I'd put at least a 150A continuous controller in that thing if I were you.
I'd use the sabvoton controller since it is both cheap, programmable, reliable, easy to install and very, very nice to ride.

I can't see the exact reference of your motor. If it is a 2000W version then a 150A controller will work fine with it. I'm using a 2000W QS motor with this very controller for more than 3 years and never had any issue, running every single day.
If less than 2000W then it might heat too much, but since this controller is programmable you can tweak the Amps down, which will leave you some room for changing your motor to a more powerful one later.

But all of this depends of what battery you plan to use, of course. I think you have enough space to put a lot of cells here so it shouldn't really be a problem...

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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Jul 02 2018 12:34pm

I'm sorry it took this long people. My proffesional life took over for a while and I had absolutely no time to spare. Also, my workshop is 3 hours from where I live..

Progress so far - Last week I ordered parts for the battery pack and a battery spot welder, an update will follow soon!

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Laerson   1 mW

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Re: Electric Track Racer

Post by Laerson » Oct 07 2018 1:54pm

Hi guys,

I finally finished the battery, needles to say it wasn’t as easy as I hoped for.

After some research I ordered all the parts I needed, battery spot welder included. After a couple weeks of waiting patiently for the parts to arrive, I started thinking about how to go about building the battery pack. Soon, I discovered that the the welder was not up to the task. First, the switch to start welding was inside the machine and worked by pushing the welding electrodes and the whole battery upwards. Second, the arms holding the electrodes were to short to reach the middle of my 5-row battery.

So I started rebuilding the spot welder to my requirements. I replaced the switch with a manual one so I could set up the welding position and battery leads so I could weld stationary without having to move the battery upwards. After that I ordered and machined some hexagon brass bar and build extensions for the arms. Because the arms were longer I also needed to replace the springs for stronger ones. Finally I mounted a foot plate so that I didn’t need to strap the spot welder to the table because of the pressure from the arms.

As I getting ready to finally start building the battery I discovered that the welder wouldn’t go over 30% without blowing the fuse the 16A fuse of my house, dang. Luckily the main fuse was 40A and changing the group fuse for a 25A fuse did the trick.

What I found out is that building the battery itself was one of the easiest things and it took me just one afternoon.


Once upon a time,my phone fell into the toilet, and this is the only picture I have left of building the spot welder.

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I didn't want to solder the BMS leads on top of the cells because of heat getting into the cell and damaging it. That's why I left these small attachments.

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13S 8)

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Splicing and extending the BMS wires.

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Finally charging..

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All that's left now is to cut some soft shock protection material for around the battery and heat shrink it.

I hope you guys enjoyed it :D
Last edited by Laerson on Oct 07 2018 2:30pm, edited 1 time in total.

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garolittle   100 W

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Re: Electric Track Racer

Post by garolittle » Oct 07 2018 2:07pm

Really nice pack. Great work. :D

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Re: Electric Track Racer

Post by Voltron » Oct 07 2018 4:36pm

Maybe needs some insulation between the balance tabs and the sides of the cans, in case it chafes or melts thru the shrink wrap then contacting the negative of the can sides?

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