Electric Gokart for thesis

[Flurky123]

Hello,

I'm a last year student at Industrial Sciences and I'll make an electic gokart for my thesis. I know how to start but I will need some help.

Starting off with the motor. I was thinking of a motor below €100.
http://www.robotmarketplace.com/products/BP639521-00.html
Do you think this would be ideal to get to a descent speed with approximately 150-200kg? Only using one gear.

If you would know some good motors, you can let me know asswell. I'll be working at 36-48V and I'd like to keep a low current.

I might have more questions in future, but this will do for now.
Thank you in advance

Flurky123

 

[itsid]

Hello,

I'm a last year student at Industrial Sciences and I'll make an electic gokart for my thesis. I know how to start but I will need some help.

Starting off with the motor. I was thinking of a motor below €100.
http://www.robotmarketplace.com/products/BP639521-00.html
Do you think this would be ideal to get to a descent speed with approximately 150-200kg? Only using one gear.

If you would know some good motors, you can let me know asswell. I'll be working at 36-48V and I'd like to keep a low current.

I might have more questions in future, but this will do for now.
Thank you in advance

Flurky123

Welcome

I don't think you won't be very happy with a ~750 Watts motor,
especially not if it's "decent speed" you're after;
it'll work, but it's not fast and not really powerfull enough for a quick takeoff.
And more important:
it has a 5mm shaft... that's nowhere near big enough for the 200kg you wnat to move, it'll snap within a week.

Take a look around for a my1020, that's pretty much the smallest thing you want to consider (The 1000W version)
and it's still below 100€.

If you want to make it cheap and powerfull, get a big a$$ truck starter (4-6kW @24V) and run it on lower currents maybe 2.5kW.. that should last long enough for some seriious fun
you'll have to mess with it though but industrial science tells me you should have the tools and skills to do so

'sid

 

[firemanjim]

Welcome

I don't think you won't be very happy with a ~750 Watts motor,
especially not if it's "decent speed" you're after;
it'll work, but it's not fast and not really powerfull enough for a quick takeoff.
And more important:
it has a 5mm shaft... that's nowhere near big enough for the 200kg you wnat to move, it'll snap within a week.

Take a look around for a my1020, that's pretty much the smallest thing you want to consider (The 1000W version)
and it's still below 100€.

If you want to make it cheap and powerfull, get a big a$$ truck starter (4-6kW @24V) and run it on lower currents maybe 2.5kW.. that should last long enough for some seriious fun
you'll have to mess with it though but industrial science tells me you should have the tools and skills to do so

'sid

Man i was just mentioning your smarts in another thread.... (go see intros)
To the O.P, Welcome to DIYGK!

 

[itsid]

I've seen it ...

I'm starting to blush again;
what am I, a twelve year old girl? Dammit...


'sid

 

[Scout]

Automotive starters aren't made for continuous run.

A guy I work with built an electric trike using a motor and drive setup from a mobility scooter. (hoveround thing). I'm not 100% sure on his setup, but I know while it doesn't have a lot of get up and go, top speed is decent.

 

[itsid]

Automotive starters aren't made for continuous run.

I fully agree, they're rated for a use of about 10sec and no more than 1min within in five.

But that's why I said, lower current,
there are two problems with starter motors.

the first (and always true) is they get too hot very fast and if, they fail very soon; (dirt protection an reliability is more important than continous power for a truck starter)

but that's why I said run it at a lower current...
Then you can control the temperature more easily and @50% it should be good enough for about 30min continous running time.

the second and less obvious, most of them don't have bearings, but the shaft runs in bushings,
that's quite a drawback, but AFAIK there are some (especially heavy duty starters) that do come with bearings.
(more likely in a truck than in a car)

And if you find a used truck starter for ~20€ to play with it for a while..
why not?

And as mentioned, it needs to be messed with anyways; one way clutch, solenoid etc. out maybe even some case mods here and there, and a way to attach the sprocket of course.
One could add a cooling fan, even add bearings if one has the tools....

And with a University in his back I think it's fair to assume he has the tools; so I'm sure he can make it work.

'sid

PS No, that isn't exactly a suggestion I would want to make to a 12yo beginner without a toolshed

 

[Flurky123]

Thanks a lot, I think I might use this motor. What I'd like to do in my thesis asswell is to use a regenerative brake. I can't find any datasheets about this motor. Do you think I might be able to use this motor as a generator?

 

[itsid]

Oh.. NO I don't think you can use this motor AT ALL! (as mentioned above)
Nevermind the power, the shaft WILL FAIL (Not a question if, just a matter of when)

motor controllers generally cut off the power generated by the motor, you can either pick it up and route it around the controller back into the batteries, or you might find a controller that does that for you.

'sid

 

[Flurky123]

Ok, I understand. So I have to look for a descent shaft (wich I might find by calculation) and at least a 1000W.

My teacher told me this might be an interesting project if I could keep the price limited. So I'd like to start keeping the motor at low cost, I've still got the batteries and other components to pay for. According to this, do you have a motor in mind? I really don't know where to look. Keeping tension at 24V-36V-48V.

To use the regenerative brake I thought about using a kind of H-bridge (including diodes) to get the energy back in the batteries. I guess you mean this can't be done because the motor itself, cuts of the power.

At last, I want to use adjustable resistors to adjust the tension on the motor. This would be necessary to limit current-peaks and adjust the speed. Could this be an option?

Flurky123

 

[itsid]

Well basically, do not try to use any robotics or RC motor, they all come with rather flimsy shafts, even if they can provide some serious wattage, they are nowhere near intended to carry the load you apply with all the weight of a kart and a person.

So, take a look around in motors for e bikes, karts, ATVs and such, those come with a more reasonable shaftsize, that indeed IS meant to carry a more serious load

And yes, i you keep the weight as low as possible, a 1000W motor is a nice thing to have, it should provide some fun.

A my1020 should be available for about 80-90 € (I've seen one for 85 on amazon, but it can be had cheaper I assume )
the controller from a mach1 scooter can be had for about 30€ new (also amazon)
(the 36V 1000W my1020 is used in said "Mach1 scooter")

so apart from batteries you should get away with about 150€ incl a throttle and some fuses and switches.
But carefully take a look around, sometimes you find cheaper sources maybe even used parts on ebay, to push the price as low as possible.

For the regenertive brake..
No, I meant it can be done rather easily
Since it's the controller that prevents that from happening more or less automatically
yes an H-bridge for example, but you should add a charging circuit of some sort to level the amount of current to charge the batteries I think. maybe with or without capacitors as a buffer, that way it'll be an even supply of power; batteries love that

No need for resistors to adjust speed or limit peaks, the controller will take care of that.
And the throttle is basically the one variable resistor you need (well... very basically).

You can of course make your own controller this had been done before, and I think you might even find the plans and pcb layouts here on diygk,
But you cannot simply hook a variable resistor inline with the motor to control it's speed,
that must be a very expensive resistor (think about all the wattage) and it will consume the power to limit the speed. That's simply a bad idea.

'sid

 

[Flurky123]

I have to thank you a lot for all this information. I think I'm finding a kind of way to make this gokart.

Right now I'm thinking about using the my1020 1000W motor either the 36V or 48V. I hope the shaft can hold the weight. I didn't know to use a controller, I might asswell use the one you told me (from the mach1 scooter), although I still have to learn a lot about internal operating, what it exactly does, ...

I hope this will work, I still have to speak to my teacher electricity to ask for more information .

As for now, I'd like to thank you big time.
Hope I'll be soon

Flurky123

 

[landuse]

As for now, I'd like to thank you big time.
Hope I'll be soon

Flurky123

I am glad itsid could help

 

[Flurky123]

I've done a bit of research about the motor controller. As far as I know this is actually a device wich adjusts the max. current you can put on your motor.

I found a basic drawing with just the purpose of the controller:
http://www.howstuffworks.com/electric-car2.htm (no wiring). This tells me to use a potentiometer to adjust the controller.

Am I thinking in the right direction, or just thinking stuff that doesn't have anything to do with controllers? Sorry for basic questions, I have limited knowledge about electricity and electronics. Wich I have a total of 6 hours in a week

Flurky123

 

[itsid]

I am glad itsid could help

Not as glad as I am

I have to thank you a lot for all this information. I think I'm finding a kind of way to make this gokart.

Right now I'm thinking about using the my1020 1000W motor either the 36V or 48V. I hope the shaft can hold the weight. I didn't know to use a controller, I might asswell use the one you told me (from the mach1 scooter), although I still have to learn a lot about internal operating, what it exactly does, ...

I hope this will work, I still have to speak to my teacher electricity to ask for more information .

As for now, I'd like to thank you big time.
Hope I'll be soon

Flurky123

you're welcome

Now, using a controller is pretty straight forward, attach two cables to the batteries, two to the motor, two to a throttle and off you go,
all the regulation is done by the controller, no
fancy resistor layouts, no mosfets no triacs no relais needed to control the power output...
everything's packed inside the controller

Am I thinking in the right direction...?

Absolutely!

check out this post for controller internals and this thread on building it
his controller is actually very nice; so be sure to read through.. maybe you want to built it yourself

'sid

 

[Flurky123]

Thank you,

I get it now, building it might be an option. But just buying it and explaining the internal working of it might be as good.

Well, I have do do an integrated exercise (thesis) throughout the year. There's a part practical and a theoretical part. So we have to make something, and then write a book about it. I think I'll include some information about electric cars in general (since it has to be 30+ pages for sure ).

Luckily enough we had to choose our project, so there's a value of interest from me , since I really want to make something that does a decent job.

We'll see

Flurky123

 

[landuse]

There have been many members who have logged onto this forum asking questions relating to projects they have to do at school, and none of them ever stay to show us what happened, or if they ever build the thing. It looks like you might be one of the first. I hope so.

 

[Flurky123]

Haha,

Well, I think this might become a hobby of mine. So when I finished this project I will post photos and a video for sure. I'm even thinking of making a buggy when this is done. Just a buggy to mess around .

You will hear from me

Flurky123

 

[mckutzy]

There have been many members who have logged onto this forum asking questions relating to projects they have to do at school, and none of them ever stay to show us what happened, or if they ever build the thing. It looks like you might be one of the first. I hope so.

I would think it has to do with the skill/effort/money required and/or time ran out, so after that not much interest in continuing the project. Thus we don't hear back from the guy(s).

 

[landuse]

Haha,

Well, I think this might become a hobby of mine. So when I finished this project I will post photos and a video for sure. I'm even thinking of making a buggy when this is done. Just a buggy to mess around .

You will hear from me

Flurky123

No....we will get pictures and video from you during the build process, not just after. We are interested in how you got to the end (while you were doing it) and not just the end product itself.

 

[Flurky123]

No....we will get pictures and video from you during the build process, not just after. We are interested in how you got to the end (while you were doing it) and not just the end product itself.

Well... This is actually what I meant. I'll start off showing the plans (electic circuit, components,...). In January I should start the building proces, this will come with a lot of pictures. I hope to get finished with a decent project around February, then I'll do the testing asswell. Afterwards comes all the schoolwork (making a book ) Then I will try to improve

Note: There will be no pics around building the chassis. I start off using an old, tiny gokart .

Flurky123