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moto-klasika Avatar
moto-klasika Zoran R. P.
Bern, Bern, Switzerland   CHE
Hello John,
It seems to me that you figured everything about the construction of rolling chassis and just need advice for electric propulsion.

I am not expert for that (and, experts presented here are silent), but I was searching the internet during a few previous years for my possibly built electric-powered quadricycle for roar-legal use.
I think that you need a manufacturer that could make and sell you complete kit just to be installed in your cart:

~ electric-motor;
~ controller;
~ throttle-pedal;
~ battery and charger;
~ connections;
~ schemes and instructions for installation;

There could be a few of them around, but I was interested in this one:

https://www.goldenmotor.com/

It seems to me that they have everything for you, for various powers. Most of the controllers could be programmed and give you much more power than nominal for chosen motor, with a possibility for regenerative braking and reverse... I am sure that at your request, they could afford you good complete. With modest planned speed, I think that power between 1 and 2 Kilowatts should be enough for cruising and something more for starting at traffic lights and climbing over smaller hills. For leisurely cruising, most of the gasoline propelled vehicles use less then nominal HP and electric motors are good with torque on lower revolutions - good pulling power. Also, they could run all day at full power (if there is still some energy in batteries), with proper cooling if they are of bigger power. Any one of them could work shortly at its peak, which is good in some circumstances...

As I could see, your vehicle should look as RED-BUG, electric version of Smith (Briggs & Stratton Flyer) - simple buckboard cart!
All of their variants had wooden-strips for chassis, making it flexible in all directions, replacing the non-existent suspension.

Ciao,
Zoran



Zoran R. Pualić
(mostly living in Bern, Swiss & happy in my Belgrade, Serbia)

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15UqoEcl Avatar
15UqoEcl John Smith
Bay City, Michigan, USA   USA
Yes, my design is a bit like the Red Bug... just not as graceful! winking smiley

Here's a question that I probably should've asked sooner: Let's say that a golf cart motor and controller are designed to work optimally with a one-foot-diameter wheel. If I wanted to drive a wheel twice as large, could I just gear it down further by that ratio, or would that place some kind of stress on the electrical system?

If most any electric motor system can be adapted just by fiddling with the gear ratios, then it becomes much easier to find a "plug and play" solution. In that case, the 3kW brushless one from Golden Motor might be the way to go.



Edited 1 time(s). Last edit at 2017-08-12 11:32 AM by 15UqoEcl.

chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
You've hit the nail on the head there, I've got no direct experience with electric motors in cyclekarts, but you can use any motor with the right gearing. Choosing which motor is another matter, but you can certainly go down the plug and play route.

A search on the forum for "electric" gave this: http://www.cyclekartclub.com/search/?forum=6#gsc.tab=0&gsc.q=electric&gsc.sort=;

A couple of the results look promising: http://www.cyclekartclub.com/phorum/read.php?6,13469; http://www.cyclekartclub.com/phorum/read.php?2,2130

Chris

In reply to # 25935 by 15UqoEcl Yes, my design is a bit like the Red Bug... just not as graceful! winking smiley

Here's a question that I probably should've asked sooner: Let's say that a golf cart motor and controller are designed to work optimally with a one-foot-diameter wheel. If I wanted to drive a wheel twice as large, could I just gear it down further by that ratio, or would that place some kind of stress on the electrical system?

If most any electric motor system can be adapted just by fiddling with the gear ratios, then it becomes much easier to find a "plug and play" solution. In that case, the 3kW brushless one from Golden Motor might be the way to go.

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moto-klasika Avatar
moto-klasika Zoran R. P.
Bern, Bern, Switzerland   CHE
... thanks to Chris, there is one more kit-complete on market:

http://www.electricmotorsport.com/ev-parts

Ciao, Zoran



Zoran R. Pualić
(mostly living in Bern, Swiss & happy in my Belgrade, Serbia)

15UqoEcl Avatar
15UqoEcl John Smith
Bay City, Michigan, USA   USA
An article about George Fortin's "Z-Kart" states, "The 300 pound (136 kg) vehicle is powered by a 72-volt DC motor via six lead-acid batteries (chosen because they are more cost effective than lithium ion). It charges from a 110-volt outlet through a retractable cord in about three hours, has a range of around 20 miles (32 km), and a top speed of 40 mph (64 kph) – although George believes it could reach 50 with different gearing."

I'm shooting for half that speed, which means e=mv^2 scales the power requirement to just a quarter of what the Z-Kart uses, right? That quadruples the running time, which, taken in conjunction with the halved speed, results in a net doubling of range. (If I'm off on this, please let me know.)

So, what does "half" mean, in electrical terms? Using a motor of 36 Volts instead of 72?



Edited 2 time(s). Last edit at 2017-08-13 03:47 PM by 15UqoEcl.

chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
John,

Half in terms of what you are trying to do means you can use lower gearing, a lower output motor, lower capacity batteries, and still achieve your speed and range requirements. A higher voltage is better, as that lowers the current which is where you get losses due to the heating effect in your wiring. You'll also gain some speed and endurance due to the lower weight of motor and batteries. It's a case of optimising the setup for what you need, while keeping a little in hand so you don't run the batteries flat short of your destination.

Chris

In reply to # 25954 by 15UqoEcl An article about George Fortin's "Z-Kart" states, "The 300 pound (136 kg) vehicle is powered by a 72-volt DC motor via six lead-acid batteries (chosen because they are more cost effective than lithium ion). It charges from a 110-volt outlet through a retractable cord in about three hours, has a range of around 20 miles (32 km), and a top speed of 40 mph (64 kph) – although George believes it could reach 50 with different gearing."

I'm shooting for half that speed, which means e=mv^2 scales the power requirement to just a quarter of what the Z-Kart uses, right? That quadruples the running time, which, taken in conjunction with the halved speed, results in a net doubling of range. (If I'm off on this, please let me know.)

So, what does "half" mean, in electrical terms? Using a motor of 36 Volts instead of 72?

moto-klasika Avatar
moto-klasika Zoran R. P.
Bern, Bern, Switzerland   CHE
Hello John,
Just some of my thoughts about electric propulsion for light motorised vehicles, including CycleKarts or something similar. Something I learned from the internet, something from my friends, real or from various forums... No personal experience, so any corrections from experienced builder are welcomed.
--- ---
General opinion, with some truth in that, is that electric motors, the same as steam engines, have the same (maximum) power from start... But, they have maximum torque from start and power is minimal – it is a mathematical calculation. Every electric-motor work the best at a nominal revolution that is mostly known from written information about performances. It is in a range from some revolutions up to maximum. Bellow that and above that – it becomes less efficient.
--- ---
For start – electric motor pulls a lot of amperages (current as often named) or above that the same. Besides using stored energy more than you should want, there are limits how many Amperes any battery complete could give. Even you could use any motor without controller (especially brush types), a controller should correct most of the problems – making a balance between Amperes and Voltage to give needed power – around nominal electric-motor power.
A power of a motor (given energy to wheels) is something lower than power (energy) that is pulled from a battery. A motor could work with much higher Volts than nominal, even something lower, but it is best if a voltage of battery and motor is the same. Of course, a controller is there at the main role to solve problems, and most of them could be programmed by a computer (for me space science).
Without an adequate controller, a motor would have problems at start and acceleration, or pulling up-hill: needing more amperes than usual – emptying battery and overheating the motor. Even with a controller, many light vehicles used some kind of mechanical speed-changing: gearbox, derailleur system, variable transmission (CVT – TAD torque converters.) A light vehicle with a proper motor, controller and battery could work with the only single-speed transmission.
--- ---
In your case, similar to mine, necessary is to calculate all parameters in advance, so to have simple and cheaper testing, without too many expensive modifications later:

1. By advice of manufacturers (if they are willing to give advice) or experienced friends and examples in magazines and internet – choose type and power of electric-motor (Volts, Amperes: meaning Watts, then optimal and maximal revolutions, brush or brush-less type, direct power or with inbuilt reduction, weight and cooling: without any, or pushed air or water;

2. Then, choose battery complete (type: lead-acid or some modern lithium or whatever appeared), with proper total voltage and amperage (connected parallel and in series);

3. Generally, it is better to have more Volts and fewer Amperes for the same Watts (for 3 Kilowatts you will need 42 Amperes with 72 Volts and with 36 Volts you will need 83 Amperes):

3.a) if you choose 36 Volts instead of 72 Volts (reduced power to ½) doing that by installing 50% fewer batteries – you will get less power for 50% in Watts and generally fewer performances: acceleration, pulling at hills, maximum speed, range...
3.b) if you choose 36 volts but keep the same quantity of batteries, now connected in a parallel way – you will get a possibility to pull more Amperes that is good in some conditions...
3.c) of course, a good controller is a necessity for all experimenting...

4. Practically, after choosing motor, you should calculate transmission ratio:

4.a) for start - decide on two fixed parameters: speed and diameter of wheels that you want...
4.b) for instance: 20 mph and 22” (outside diameter for 17” wheels?), you should calculate transmission to has that speed at a maximum revolution of motor...
4.c) as every motor could give peak power for 15-30 seconds well above nominal power (sometimes even double), you could have reserve for some prints...
4.d) if you use wheels with double diameter but correct that with “slower” transmission for 50% - speed should stay the same, but probably acceleration and pulling power should be weaker...
4.e) general opinion is that bigger wheels give less torque transferred to a road (testing?) with the same inputs...

5. With calculated Brutto weight of 500 pounds, I think that a few kilograms saved on batteries do not mean too much for performances – therefore, I would go with lead-acid batteries for start and maybe later change for lighter – if everything else goes fine;

6. I think that you could be right with your thinking:”I'm shooting for half that speed, which means e=mv^2 scales the power requirement to just a quarter of what the Z-Kart uses, right? That quadruples the running time, which, taken in conjunction with the halved speed, results in a net doubling of range.”;

Because of you and me, but other members reading this, too – I would like comments and especially corrections of my too long speech...

Ciao,
Zoran



Zoran R. Pualić
(mostly living in Bern, Swiss & happy in my Belgrade, Serbia)

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15UqoEcl Avatar
15UqoEcl John Smith
Bay City, Michigan, USA   USA
Point 3...

So then voltage is the "pressure" that drives the motor on uphill climbs, and amperage is the "volume" of electricity that drains the battery (and overheats the motor on account of the wire's resistance)? Just to be clear: higher amps = shorter range?


Point 4b...

After several years of manually calculating how wheel RPM converts to speed, I just recently realized that CycleKart wheel RPM divided by 15 is almost a perfect match for miles per hour. (About 900 revolutions per mile.)

Also, rather than picking it by maximum speed, perhaps I should select a "cruising" speed and choose gearing that allows the motor to run at peak efficiency. Or perhaps motors are only listed for peak efficiency, so the maximum is just right?

chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
John,

"Point 3...

So then voltage is the "pressure" that drives the motor on uphill climbs, and amperage is the "volume" of electricity that drains the battery (and overheats the motor on account of the wire's resistance)? Just to be clear: higher amps = shorter range?"

Yes voltage can be thought of as pressure, and amps as volume. Higher amps does = shorter range. A battery is your tank, capacity measured in amp hours, Ah/A=hours run, so you can calculate range for a given battery from mph.

It's always better to run higher voltage lower amps as that improves efficiency, you need more batteries, but they can be lower capacity for the same range.

I did a search for: electric motors most efficient at maximum rpm, and one of the results gave me the attached PDF. It's for large AC motors, but will probably be applicable to DC too.

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Attachments:
10097517.pdf    190.3 KB

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