# DC motor without controller?



## RIPPERTON (Jan 26, 2010)

I had a bicycle like this, it worked ok. I just clicked the derailer up and down. Had a small DC motor on a handlebar switch and double chain reduction. 
Basically Detroits were almost like this as they shifted their resistors.

I wouldn't do it in a road car because it would be just to unrefined.

EV conversions and budgets don't mix


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## dcb (Dec 5, 2009)

Like this? 
https://www.youtube.com/watch?v=unhXEQQk8G8#t=28


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## major (Apr 4, 2008)

rampampwobble said:


> would it be possible to power a DC motor straight off batteries using a contactor, then regulate speed with a manual transmission? 1st gear = 15mph, 2nd = 30mph, etc.
> 
> I understand the stock gears in a manual transmission may have to be changed to get useful speeds, but eliminating the controller could reduce conversion costs considerably.
> 
> ...


Ideas? Here's one. Danger. Bad idea. The controller is a safety feature. Eliminating it will put you and others at risk.


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## evmetro (Apr 9, 2012)

It would be like removing the gas pedal from your gasoline powered car and then going under the hood and propping the throttle wide open. As soon as you start the car, it would take off at full speed. When you went for the next gear, you would probably float a valve and blow your engine up, but I am not sure what an electric motor would do. I could not imagine why anybody would try this.


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## rampampwobble (Apr 15, 2014)

Ripperton, thanks for the input, I wasn't thinking refinement, but without a soft start, it might be jerky, which is not very refined at all 

As for your video DCB, I can't tell if it's like my idea, the content is a little over my head.


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## arklan (Dec 10, 2012)

youd put it in the highest gear to reduce jerkiness and control low speeds with the clutch, expect to replace the clutch a few times 

also expect to weld the acceloration pedal to the floor when ur making contact every time u give it some haha

i thought about this idea too and even thought about getting one of those big arc welder transformers that slide the secondary coil in and out of the primary coil to change the amps, and have one of those u could just slide in and out. it would be hugely inefficient tho


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## dcb (Dec 5, 2009)

In the video, the "engineer" IS the motor controller. He taps the wand to the overhead power line (hopefully not too many volts there) in short bursts to get the train moving (probably so he doesn't overheat) then holds the wand to the line once he is up to speed (which looks about 5mph).

Human as the motor controller only works at low power levels and/or where there is lots of inertia (things don't change rapidly). I've done it on a 2 stroke moped even. I can imagine pulsing a larger motor in a large vehicle by hand, but I would use a solid state switch (i.e. a large IGBT), and once you figure out how to control one of those, you might as well throw in a $10 microcontroller board to translate a gas pedal signal into a duty cycle at higher switching frequency for you (much smoother). Then realize that you are tired of frying motors so you add current feedback to your microcontroller to limit the current delivered. And then you realize that it would be much more driveable if the throttle controlled the current instead of directly changing the pwm...


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## evmetro (Apr 9, 2012)

If a motor controller controls a motor, then a motor without a controller would be out of control. I understand the use of duct tape, coat hangers, and other hoakey stuff, but I would strongly urge you to control your motor with a proper controller


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## rampampwobble (Apr 15, 2014)

thanks for the input everyone. I've no real intentions of converting a car, but the idea interests me and I follow the movement online.

I'm gonna go back to lurking mode now and hope this thread fades off the front page soon.


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## onegreenev (May 18, 2012)

Check your private message. Yes you can do this. It has been done before and could still be done but you have no amperage control and you are at the mercy of the contactors not failing. SepEx motors would be best to help prevent motor runaway in the event of a failure. The motors I have used are the old Military Starter/Generator types but I never did just use the contactor method of control with them. I knew one who did in a Buggy and it was quick and responsive. His was a 72 volt only system and he just used the clutch to smooth it out. worked out quite well. Most setup a system to put a pack in low volt mode or high volt mode by splitting the pack in two equal parts. Some even did a pack in three parts for three voltage levels and 4 speeds usable in each voltage level. Its setup to not allow the batteries in the pack to be drained in an unequal amount. The split pack was the norm. 36volts and 72 volts. Great for light weight buggies. These motors don't do well with normal controllers because of how the motors are wound. They do however work in that mode if needed. I did a little test using a standard Series Controller with one of these motors. The motors have no cooling fan and get hot so you must provide external cooling and move lots of air. 

So if you like there are more videos to watch if you want. I still have the Curtis Clone. The guy who sent it to me for testing just dropped off the face of the EV world. Not a single peep since this test. So I still have it for playing with. No, I can't sell it. Its not mine to sell. Good practical controller for a very basic system. 






Pete


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