Converting AC to DC motor

[xhdskip]

Hi guys, this is my first post on the forum.
The reason I joined the forum is because I need help.
I have a single phase 3.5 hp AC motor that I want to convert to a 12 Volt for a project.
I realize DC motors have brushes and seem to spin at a slower rate than an AC motor.
For example my 3.5 motor spins at 3,450 rpm and most DC's seem to spin at 1,750.
That, is a secondary problem, right now I just want to know IF converting it is possible,
and if so, what besides changing the cord out for cables would have to be done.
I'm no electronics guy, but if the instructions are simple enough and it's possible,
I'd sure like to give it a try.
Thanks for any advice, pros, cons, etc
xhdskip

 

[Bluejets]

No.
Appears you have a split phase ac motor.(guessing either 220v or 110v)
Your assumption that "most" dc motors run at 1750 rpm also incorrect.

Best idea would be to get a motor that suits the application.
So, what is the application?

 

[xhdskip]

don't know if it's split phase or not,
I do know it's original intent was for a compressor,
yes it's 110 Volt.
Been trying to see if I can build a go cart with it.
So your NO in the opening was No it's not possible to convert it?
Why I don't get one , a (dc motor) made for it, is because I already have this one
and I can't find a DC that fits the size requirements.
Just wanting to "try" to make it functional,
but I've watched numerous youtube vids on converting
an AC motor to DC and everybody seems to have their own ideas and way of doing it,
so I figured I'd ask this forum to get the "real" truth with some advice on "how to".
Thanks

 

[duke37]

A car starter motor is 12V DC and runs fairly slowly, I think they are series connected so speed will be determined by the load. They are not intended for long term use but you could try to replace the brushes with standard carbon ones.

A car dynamo is 12V and you may still be able to find one at a breakers. I think the speed will be about 3000RPM but I have not measured it. The speed can be increased by reducing the field voltage. 10000RPM should not be exceeded or the armature may fly apart.

 

[xhdskip]

a car dynamo is what we here in the states call an alternator I'm guessing?
How could a total novice reduce the field voltage,
and are we still talking about the dynamo,
or are we talking about reducing the field voltage on (in) the AC motor?
Like I said earlier, speed is secondary right now.
My main concern at this point is HOW would I convert the AC motor into a DC motor.
I appreciate the advice guys

 

[Bluejets]

No again.
Alternator produces (alternating) ac which is then rectified and regulated to charge the battery.

A dynamo ( easy to google how the terminology works) is a dc generator which can, by modification become a dc motor , albeit low power.

A starter motor from the 70 to 80's era will be a fairly hefty dc motor you can drive via a starter solenoid from a car battery. Speed of these can be selected by using extra switching solenoids and strips of various size stainless steel as resistors. The latter works well as an RC glider winch.

Anything of the current era will tend to be piddley little motors driving through a gearbox so perhaps not enough top end speed.

You cannot convert what you have, period.

There are available electric motor/ speed controllers from the electric scooters but cost becomes an issue.

Perhaps a little pocket rocket 50cc would suit much better.

 

[Kiwi]

An old style car generator/dynamo, eg Lucas C40, will run as a motor if connected to a car battery, but pretty sure it would not have enough power for a go-cart.

Car starter motor will power a go-cart, but would draw a lot of current and flatten the battery fairly quickly.

A motor of an old battery lawnmower might be better?

 

[Bluejets]

An old style car generator/dynamo, eg Lucas C40, will run as a motor if connected to a car battery, but pretty sure it would not have enough power for a go-cart.

Car starter motor will power a go-cart, but would draw a lot of current and flatten the battery fairly quickly.

A motor of an old battery lawnmower might be better?

Power out = power in minus losses....relative here I'd say.

 

[Minder]

For high HP a auto starter motor would give you plenty of torque, many of the later types are P.M. but the older style are wound field and being a series motor operates in a run away condition and should not be powered without load.
But very high torque. Or there is a 12v bumper winch motor.
Another alternative, but higher voltage is a treadmill motor, which are fairly plentiful.
M.

 

[Bluejets]

Winch motor no good for a go kart. High torque comes from worm drive and motor is slow reving.

 

[duke37]

The way to use your existing motor is to get or build a 12V DC to 110V AC drive. I expect that this would cost more than you wish to spend.

You have not said what this motor is driving. If the load is about 3kW then 250A at 12V would be necessary. A car battery could give 30A for an hour or two.

 

[xhdskip]

A little background info if I may guys.
I'm a 61 year old man and not very computer literate,
hence not thinking of "googleing" the terminology
of what a dynamo is called in America.
I'm trying to build this as a project for me and some of the grandsons,
as the law hereabouts don't like the noise of their gocart.
I figured it would be possible to get rid of the internal combustion engine
and make them a "silent" gocart with an electric motor.
When I searched on youtube before joining this group and searched for
converting an AC motor into a DC motor, I got 53,500 results.
Watched a few of them, and just got confused as the ideas were numerous and all different.
Thought I'd ask the experts, so here I am.
I appreciate the info and ideas. but so far, not many answers,
at least not many that will help in this endeavor.
I'll keep pecking away at it, as there has to be a way, considering the fact internally,
they both (the AC and DC motors) are basically the same.
Still looking for advice here guys, and I sincerely appreciate the time and trouble you guys
are going through to try to help me.
I will post pictures or a vid as soon as it happens,
and Thanks again,
skip

 

[xhdskip]

Duke37,
what exactly is a 12V DC to 110V AC drive. ???
And also, since I'm trying to convert a 110 volt motor to a 12 volt system,
would this drive still work?
Thank you

 

[duke37]

There are drives (boxes) which can take in 12V DC and put out 110V AC to drive shavers, radios, TVs, central heater controls and other low power loads.. These are used when the mains fails. There are uninterruptable power supplies for computers which charge a battery and then replace the output when the mains fails.

I am an 80 year old man, (duke37), not very computer literate but I can Google. You need to get the terminology correct or you will get the wrong end of the stick.

AC and DC motors are not the same, they are wound differently and the windings are glued into place to counter centrifugal force, they are very difficult to rewind. However, I think that you will not get the power you need from batteries. Consider what a golf buggy does.

I applaud your desire of getting rid of an infernal compustion engine. Fit some pedals, that will keep the driver fit.

 

[kellys_eye]

Winch motors are actually very suitable for go-karts. Most kiddies karts have small motors driving either a huge gear reduction or via worm drives.

Work backwards from your wheel rotation requirement - if you have a 12" diameter wheel it will move a kart 36" per revolution and at 100rpm this would be 3600" (300ft/min or 3.4mph - the legal limit for such is, I think, 4 (maybe 6) mph).

A winch motor can run at this speed quite easily and the torque available would allow the kart to drive vertically up a wall - literally!

Even a windscreen wiper motor would have sufficient torque to drive a small kart (have you seen how small the motors are on kiddy-karts?) and has the worm drive reduction necessary - a simply external gearing arrangement would give rotational multiplication if required - consider a sturmey archer 3-speed hub for a 'geared' drive system and a 'free-wheeling' ability that will conserve battery power.

Controlling a windscreen wiper motor (12V) is simplicity itself, they are readily available - new or used - fit TWO if you want - 4-wheel drive anyone?.

Build a sound system that simulates an F1 (or NASCAR - steam train even! etc) and have fun!

Loads of ways to skin this cat!

 

[Minder]

, considering the fact internally,
they both (the AC and DC motors) are basically the same.

Don't know where you got that from!
Incidentally there are quite a few version of each under the banner of "AC or DC".
The basic version of each is the AC induction motor and the DC brushed motor, they are completely different animals!.
Having worked with motors and generators of all stripes, including a session re-winding, for over 60yrs you would need to explain that further for me.
M.

 

[Bluejets]

Even a windscreen wiper motor would have sufficient torque to drive a small kart

Well, I was going by what the Op posted originally.

single phase 3.5 hp

 

[kellys_eye]

Well, I was going by what the Op posted originally.

As one should - but as the thread progressed and the facts became clearer the relevant adjustments have to be made. A 3.5hp motor could get a kart to 60mph+ but I'm not sure if this is a kiddies kart or the electrical equivalent of a standard 'adult' kart - either way there would be severe limitations due to battery pack size/weight/longevity based on a 3.5hp motor.

There IS an electric drag racing standard! which can be quite impressive to watch but that's due to short duration, high discharge situations where run-time is much less of an issue.

There's still no beating good old fossil fuel for power-to-weight ratio - essential in a karting situation - but for a 'tootling around' experiment a largish electric motor may have some merits but trying to do it with an AC motor is just added complication, energy loss and inefficiency.