Electronic kart

[laurent helfer]

Hi everybody,
I'm building a electric kart with a 220ac engine for my son. I have two main problem right now could you please help me.

First i wanted to know if exists a switch than can be controled externally by a smaller voltage or simple contact. i would prefere not to make a direct "contact switch" and see the main voltage source going so close to my son feets so i would like to command the 220v by another way...

I'll come soon with my second question
Thank you

 

[laurent helfer]

Hi everybody,

If we want an alternate 220v motor to spin twice faster or with twice his torque is this the only way to make it run 440v (supposed he can handle it!). If i get twice the amp I think it will change nothing because reached a certain amp your motor will not go faster/stronger (if you take a 15amp or 30amp source it will change nothing!). Why with amp it will change nothing but will voltage yes (both contribute to total voltage so i cant get it!)?

So how can i make an engine faster without changing voltage?

Thank you

 

[davenn]

and tell me
how are you going to power this 220VAC motor ?
a long power cord back to a mains power outlet ?
Do you see any obvious problems with that ?

 

[jmolivieri]

Hi everybody,
I'm building a electric kart with a 220ac engine for my son. I have two main problem right now could you please help me.

First i wanted to know if exists a switch than can be controled externally by a smaller voltage or simple contact. i would prefere not to make a direct "contact switch" and see the main voltage source going so close to my son feets so i would like to command the 220v by another way...

I'll come soon with my second question
Thank you

If the only purpose is to turn on or off you could use a relay.
In a relay the most important feature is the current to cut and the voltage to isolate.

About the output power of an engine, it depends on the technology of the engine.
If it is a brush engine.
The spin speed is proportional to applied voltage. And the torque to the current.

The only electric power that will be converted to mechanical power is the active power.

Electric active power : P = U * I * cos(phi)
phi : is the phase between current and voltage.
U : RMS V
I : RMS A

Mechanical : P = C * omega
C : Torque (SI units)
omega : pulsation idem spin speed but in radian per second.

 

[Alec_t]

I'm building a electric kart with a 220ac engine for my son.

That sounds highly dangerous . Children's electric vehicles are usually powered by a 6V or 12V sealed battery, for safety's sake..

 

[Cannonball]

Hello.

I would recommend an electric golf cart. It is much safer for your son to operate and you can charge the batteries safely with the charger that comes with the golf cart.

 

[laurent helfer]

Hi every body.
No it will not be a long cord for the 220v but a 12v-220v 3000w transformer....

I understand that some of you are vorried about security concerns but all the kids (i mean not these toys for 3years old for sure) are 36 or 48v powered. It s dc current there so no way to escape and in my knowledge i think that the amp will be higher to feed the motor so i just have to be cautious (am i really wrong there?). I dont minimize the risk and dont want a high voltage near my son leg (that s why my question).

As soon as my circuits are not in contact with my son i cant see the danger (i ll seal every contact).

 

[laurent helfer]

Ps 6v kids car are not even capable of 2mph i'm looking to spin a gokart metalic axle with tyres and would like a 20mph min top speed.

 

[laurent helfer]

Thank you jmolivieri i didnt saw your message it s very helpfull

 

[Audioguru]

A 12V to 220V 3000W transformer is huge, heavy and expensive. Its 12V input is AC, not the DC from a battery. If the transformer is 90% efficient then its 12V input is 277.5A AC!

 

[laurent helfer]

A 12V to 220V 3000W transformer is huge, heavy and expensive. Its 12V input is AC, not the DC from a battery. If the transformer is 90% efficient then its 12V input is 277.5A AC!

No sir i'm sorry it s a 12dc to 220ac. As used on the car to chrge laptop or other (mine could handle some more heavy loads)

 

[Alec_t]

So you plan to use a battery-powered 12V to 220V inverter. That still means you would have a motor powered at a lethal 220v. Not recommended where children are concerned. They're inquisitive by nature and could easily poke fingers where they shouldn't.

 

[hevans1944]

No sir i'm sorry it s a 12dc to 220ac. As used on the car to chrge laptop or other (mine could handle some more heavy loads)

If the device accepts 12 V DC and outputs 220 V AC at 3000 watts, it is called an inverter, NOT a transformer. And 3000 watts delivered by 12 V requires 3000 / 12 = 250 A of current from the 12 V battery at 100% inverter efficiency, which is impossible to achieve.

The @Audioguru was being optimistic quoting 90% efficiency. That doesn't include the losses (inefficiencies) of the motor, the drive train, and where the rubber meets the road at 20+ mph. You will be lucky to reach 50% efficiency from battery to wheels-on-the-road. And how will you control the speed of your AC motor? Variable frequency drive? What kind of AC motor are you planning to use? How will you control its speed and torque?

Methinks you don't know WTF you are doing. A 3 kW inverter provides about 4 HP, adequate for a "go kart" type vehicle, but it will very quickly drain any 12 V battery that is sufficiently small to carry on board. Show us your engineering design calculations, specifications and model number for the motor you intend to use, gear-ratio from motor output shaft to driven-wheel axle, estimated weight of vehicle and weight of driver.

Please, no rectal extractions or hand waving for design specifications! Building a vehicle that safely carries a child (or anyone) close to the ground at 20 mph is not something you do on the spur of the moment, nor "on the fly" with a "let's try this" approach. Steering and braking alone are major design considerations, before even attempting to add a motor with acceleration and speed control. What are your qualifications to proceed with this project?

Inverter technology is popular for use in emergency power supplies, but getting a good sinusoidal wave form out of them is problematical. Many so-called sinusoidal inverters do no such thing, instead providing a triangular wave output, full of harmonics, that does not play well with AC motors. Check inverter specs and output wave forms carefully to make sure the inverter will work with your particular AC motor.

You might want to consider building your son's kart around a commercial, portable, gasoline engine-motor generator set that does produce a reasonable sinusoidal output at constant frequency. At the very least, you could use the MG set to re-charge the battery on your son's go-kart if you are determined to build an all-electric vehicle.

 

[laurent helfer]

If the device accepts 12 V DC and outputs 220 V AC at 3000 watts, it is called an inverter, NOT a transformer. And 3000 watts delivered by 12 V requires 3000 / 12 = 250 A of current from the 12 V battery at 100% inverter efficiency, which is impossible to achieve.

The @AnalogKid was being optimistic quoting 90% efficiency. That doesn't include the losses (inefficiencies) of the motor, the drive train, and where the rubber meets the road at 20+ mph. You will be lucky to reach 50% efficiency from battery to wheels-on-the-road. And how will you control the speed of your AC motor? Variable frequency drive? What kind of AC motor are you planning to use? How will you control its speed and torque?

Methinks you don't know WTF you are doing. A 3 kW inverter provides about 4 HP, adequate for a "go kart" type vehicle, but it will very quickly drain any 12 V battery that is sufficiently small to carry on board. Show us your engineering design calculations, specifications and model number for the motor you intend to use, gear-ratio from motor output shaft to driven-wheel axle, estimated weight of vehicle and weight of driver.

Please, no rectal extractions or hand waving for design specifications! Building a vehicle that safely carries a child (or anyone) close to the ground at 20 mph is not something you do on the spur of the moment, nor "on the fly" with a "let's try this" approach. Steering and braking alone are major design considerations, before even attempting to add a motor with acceleration and speed control. What are your qualifications to proceed with this project?

Inverter technology is popular for use in emergency power supplies, but getting a good sinusoidal wave form out of them is problematical. Many so-called sinusoidal inverters do no such thing, instead providing a triangular wave output, full of harmonics, that does not play well with AC motors. Check inverter specs and output wave forms carefully to make sure the inverter will work with your particular AC motor.

You might want to consider building your son's kart around a commercial, portable, gasoline engine-motor generator set that does produce a reasonable sinusoidal output at constant frequency. At the very least, you could use the MG set to re-charge the battery on your son's go-kart if you are determined to build an all-electric vehicle.

Your responses make me reconsider the use of 220v and maybe i'll turn for a 36 or 48v setup(my son born in brasil where poeuple take shower heated directly by a 220v source on top of there head - and as brazilian use to tell me ,taking shower is the less dangerous thing in theyre country).

Thank for you tips for the frame setup and handling issues but the frame is a 100cc gokart FIA regulated and i could setup it as good as it possible because it was my karting when i was a kid and spent countless time to setup it....

Internet sell very good regulator but as you said i go on the fly and take one problem after one...

 

[laurent helfer]

If the device accepts 12 V DC and outputs 220 V AC at 3000 watts, it is called an inverter, NOT a transformer. And 3000 watts delivered by 12 V requires 3000 / 12 = 250 A of current from the 12 V battery at 100% inverter efficiency, which is impossible to achieve.

The @AnalogKid was being optimistic quoting 90% efficiency. That doesn't include the losses (inefficiencies) of the motor, the drive train, and where the rubber meets the road at 20+ mph. You will be lucky to reach 50% efficiency from battery to wheels-on-the-road. And how will you control the speed of your AC motor? Variable frequency drive? What kind of AC motor are you planning to use? How will you control its speed and torque?

Methinks you don't know WTF you are doing. A 3 kW inverter provides about 4 HP, adequate for a "go kart" type vehicle, but it will very quickly drain any 12 V battery that is sufficiently small to carry on board. Show us your engineering design calculations, specifications and model number for the motor you intend to use, gear-ratio from motor output shaft to driven-wheel axle, estimated weight of vehicle and weight of driver.

Please, no rectal extractions or hand waving for design specifications! Building a vehicle that safely carries a child (or anyone) close to the ground at 20 mph is not something you do on the spur of the moment, nor "on the fly" with a "let's try this" approach. Steering and braking alone are major design considerations, before even attempting to add a motor with acceleration and speed control. What are your qualifications to proceed with this project?

Inverter technology is popular for use in emergency power supplies, but getting a good sinusoidal wave form out of them is problematical. Many so-called sinusoidal inverters do no such thing, instead providing a triangular wave output, full of harmonics, that does not play well with AC motors. Check inverter specs and output wave forms carefully to make sure the inverter will work with your particular AC motor.

You might want to consider building your son's kart around a commercial, portable, gasoline engine-motor generator set that does produce a reasonable sinusoidal output at constant frequency. At the very least, you could use the MG set to re-charge the battery on your son's go-kart if you are determined to build an all-electric vehicle.

I thank you to warn me about the fact it could drain the battery very quickly i m not looking for a long range vehicule (5-10minute max) but it surely needs some calculations. The fact that the list is so huge with the inverter make me think i ll go for 48dc... thank you

 

[hevans1944]

Back in the last century, around 1980 of thereabouts, I was going to build a go-kart for my two boys, based on two reel motors from a scrapped 9-track computer tape drive. These two reel-drive motors were salvaged from a commercial tape drive. The two huge DC motors were used to move the tape reels at high speed while the tape was inserted in two vacuum columns and the tape itself moved with a separate pinch-roller drive. I also had salvaged a very large brand-new, never before placed in service, 24 V DC lead-acid battery. I think it was originally intended for installation on an aircraft and was purchased as a spare. Years later, the company I worked for decided it didn't need its own private airplane, nor the pilot who flew it, so both departed. The spare battery stayed behind, ignored and forgotten in the basement until I found it. No one objected to me "salvaging" either the reel motors or the battery.

Starting with a known-good go-kart frame is an excellent idea. I didn't, and that explains why I never finished the project and both sons are now adults who never experienced the thrill of riding a go-kart... unless they rented one.

The 220 V electric shower heaters are a popular up-scale bathroom fixture in the United States, but waaay too expensive for my taste. I do like the idea of never running out of hot water while showering, and this would be especially important in large households, but paying a large premium for the privilege doesn't make any sense to me. Geez... it's just electricity, and hot-water-on-demand systems have been around for awhile. Putting the heating element at the point-of-use in the shower head makes a lot of sense, but gouging the customer who wants one is just plain greed.

Going with DC has some advantages. I would choose a 48 V DC distribution system, and perhaps brush-less variable reluctance motors, You can also use less expensive brushed DC motors, but changing brushes is a PITA that probably should be done every month until you get some idea of how fast they wear. DC motor control is quite sophisticated today. There are "chips" that do everything for you, from controlling the ramp up and ramp down rates to monitoring the motor current and then using high-speed chopper techniques to pulse-width modulate the motor current. These systems shine for their efficiency and ease of implementation. Motor current-sensing can be performed with inexpensive, low-ohm resistors or Hall Effect devices. If you don't want to "roll your own" circuits, there are plenty of commercial units available for sale on the Internet.

 

[kellys_eye]

Using any motor other than a 12V one will introduce problems you could do without.

An old car starter motor will provide more torque than you will ever need, can be controlled/regulated with a relatively simple MOSFET arrangement, won't require much (any?) gear reduction, is cheap and commonly available, uses a simple car battery, will run for 1/2 hour or more etc etc.

Don't over-think the solution or you'll end up complicating beyond the point at which your son will think it'll never happen.....

 

[Minder]

Hi everybody,

If we want an alternate 220v motor to spin twice faster
So how can i make an engine faster without changing voltage?
Thank you

An AC induction motor rpm is controlled by the frequency of the supply, not voltage..
If using an automotive starter, you should look at the later type that uses a P.M. field, the old style is a series motor and operates in a runaway condition, it depends on a high load to control the rpm, this is why you should not run it on a bench unloaded.
M.

 

[laurent helfer]

An AC induction motor rpm is controlled by the frequency of the supply, not voltage..
If using an automotive starter, you should look at the later type that uses a P.M. field, the old style is a series motor and operates in a runaway condition, it depends on a high load to control the rpm, this is why you should not run it on a bench unloaded.
M.

Ok thank it s help a lot my understanding of the thing the frequence us the key there and no way to get something else than the 50hz with a basic setup i pretty sure!

 

[hevans1944]

If I recall correctly, a world-class manufacturer in Switzerland makes and sells very reliable variable frequency motor drives. Can't seem to recall the name, but we used them for lubricant test stands where a motor ran for weeks at a time, driving a heavily loaded shaft spinning in steel ball bearings infused with heated lubricant. This was to simulate, on a time-accelerated basis, the bearing wear and lubricant degradation experienced by jet engines used by the U.S. Air Force. We had some forty-odd test stands set up in a lab at Wright Patterson Air Force Base and two test stands in a lab at our company main campus. The two motors at the on-campus lab ran for years with nary a problem. I was most impressed with this European engineering, and I do not impress easily. It simply worked from Day One and kept right on working. As far as I know, it's still working.

The point is, variable frequency motor drives are not new, are readily available, and would probably be a reasonable DIY project for an engineer with mechatronic skills. The ones we used were energized using 408 VAC, 60 Hz, 3-phase power, but the VFD controllers would also operate on 50 Hz. Three-phase AC is pretty much standard for motors greater than one horsepower, but a DIY version could operate from a 12, 24, or 48 V DC (or greater) power supply and the choice of motors would be great, including DC as well as AC motors.

Nice thing about DC motors is the ability to control output torque and speed using pulse-width modulation (PWM) of the DC supply. Applied to stepper motors (for example), it is not unusual for the DC supply voltage to be several times the name-plate steady-state voltage, so a motor with 2 V windings could be safely driven from a 48 V DC power supply using PWM. Not that I would necessarily recommend using a stepper motor for a go-kart application, but often large steppers are available inexpensively as surplus equipment. When it comes to building go-karts, you have to use what is available and affordable, which means some compromises will be necessary. Good luck on your project! Have you found a suitable electric motor yet?