# No controlller motor rpm



## Efiero (Feb 7, 2009)

Ok I asked this on another site but realy no one realy knew 100 precent I know that they say dont run a motor at over 12 VDC will it just rev out of site and come apart pleas tell or will it accelerate so fast it comes apart or draw so many amps it melts down. why i ask is why not run the motor at full RPM and then run a hydrostatic drive for vehicle speed


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## Guest (Mar 10, 2009)

Efiero said:


> Ok I asked this on another site but realy no one realy knew 100 precent I know that they say dont run a motor at over 12 VDC will it just rev out of site and come apart pleas tell or will it accelerate so fast it comes apart or draw so many amps it melts down. why i ask is why not run the motor at full RPM and then run a hydrostatic drive for vehicle speed


At over 12 volts you risk over reving your motor and it can over rev faster than you could shut it down. It would just come apart at the commutator. That is the weak point. There are pictures here that show a good commutator blow up. This can happen and any over rev can cause this. It is not a melt down but just spinning too fast for the commutator to hold together. As with ICE's you can over rev them. You do need to trust the gurus when they say something. It may take a while to get the how and why but trust that if they say no more than 12 volts for an unloaded motor believe them. 

There is lots of info here so go read until you see double. 

Pete : )


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## Efiero (Feb 7, 2009)

i dint know if it would spin up to fast that it would over rev so could like a 50 LB fly wheel fix it or would the whole thing just spin out of control


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## Guest (Mar 10, 2009)

Efiero said:


> i dint know if it would spin up to fast that it would over rev so could like a 50 LB fly wheel fix it or would the whole thing just spin out of control


If you had lets say 48 volts and just that 50 lb flywheel it would spin up so fast your head would spin. The motor has so much torque that that 50 lb flywheel is nothing. Just think about it. Even with a load and 120 volts of 6 volt lead acid batteries it can still propel and auto to freeway speeds with out breaking a sweat. Trust us, it will spin up real fast. If you have lets say 24 volts and that 50 lb flywheel then maybe it would not spin quite so fast but if you were not careful it could over rev. Don't assume. 

Pete : )


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## tj4fa (May 25, 2008)

Efiero said:


> ...why not run the motor at full RPM...


Like Gottdi says, the motor will spin up so fast (even with a flywheel) it will blow apart. Without a substantial load against the motor, there is nothing to limit the motor's top RPM and will self-destruct from centrifical force. 

I think some of the guys who drag race EVs use several bands of Kevlar to try to keep the motor from blowing apart from centrifical force. They also are likely to have some sort of overspeed device to limit the motor's top RPM. Sort of like a rev-limiter on an ICE race vehicle.

Just sayin'...you could take the other's advice or you can go ahead and pay the price...


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## Guest (Mar 10, 2009)

Here is what happens to a motor when you over rev it. They will puke their guts out. 

Don't over rev your motor. I can happen in the blink of an eye. Yes, Go to Jim Husted's site and have a look. He is the Guru of all Guru's on these motors. He fixed this one. Now that is a master.


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## Efiero (Feb 7, 2009)

well now i know it would take a pretty good load so some sort of controller is needed is there a way to get a motor to run at a constant speed like it has a govener on it so as load is applied more power applied to the motor with out a controler some sort of machanical device


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## tj4fa (May 25, 2008)

Efiero said:


> well now i know it would take a pretty good load so some sort of controller is needed is there a way to get a motor to run at a constant speed like it has a govener on it so as load is applied more power applied to the motor with out a controler some sort of machanical device


One of the beauties about running an electric motor off a battery pack is that when you are not "on the pedal" you're coasting saving battery power.

What are you trying to do?


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## Guest (Mar 10, 2009)

Efiero said:


> well now i know it would take a pretty good load so some sort of controller is needed is there a way to get a motor to run at a constant speed like it has a govener on it so as load is applied more power applied to the motor with out a controler some sort of machanical device


Use 12 volts to test under no load conditions and use a controller when you want to move the vehicle under load. If you have a controller on the motor and not load you still run a risk of over revs but you will have better control. Just don't open it all the way up. If you slip with the pot it will over speed unless under load. A light load would be off the ground installed in your vehicle and in gear so your rear tires will spin. It can still over speed but you have the trans and the diff and the weight of the tires to put a light load on the motor for testing. 

Pete : )


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## Efiero (Feb 7, 2009)

Ok looks like we have to run a controler not that big a deal just gota figure how much gear to rpm load speed with the hydrostatic drive


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## Guest (Mar 10, 2009)

Efiero said:


> Ok looks like we have to run a controler not that big a deal just gota figure how much gear to rpm load speed with the hydrostatic drive


What are you building?


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## Efiero (Feb 7, 2009)

I am building a fiero verey slowly you know a part hear and there i will tell you the guys on the Hydualic web site think the motors should drive the wheels direct no gear reduction i try to tell him it would not be not eficent but he thinks he knows it all i told him it would draw a ton of amps to get the torque and be slow accelerating


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## tj4fa (May 25, 2008)

Don't know about the hydrostatic drive concept, but here are some successful Fiero conversions to check out if you haven't already.

Some have webpages to look at other information.

http://www.evalbum.com/type/PONT


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## tj4fa (May 25, 2008)

Researching hydrostatic drives. Not electric but interesting and possibly within your limited price (scrounge) range for now...

http://www.motherearthnews.com/Gree...-75-Miles-on-a-Single-Gallon-of-Gasoline.aspx

Note that in the article they say: 

"If and when we couple our hydraulic motor directly to the car's wheels, we should realize a marked improvement in our car's efficiency."

Here's the other one (Vince Carman) mentioned in the MotherEarth news article:

http://www.motherearthnews.com/Gree...smission-Really-Double-Your-Cars-Mileage.aspx

http://www.rexresearch.com/carman/carman.htm

http://www.rexresearch.com/carman/4441573.htm


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## tj4fa (May 25, 2008)

Ok, (I'm a little slow) so it seems to me you are considering using a limited amount of battery power and an electric motor to spin up a (50 lb) flywheel. You're intention seems to be to never have the electric motor driving the EV in our "conventional" way.

The motor driven flywheel operates an inertia storage hydrostatic transmission system that runs the vehicle down the road. 

Interesting...(I like it).

The only thing the motor/flywheel system would be used for is to keep the hydraulic accumulator system pumped up when needed to operate the main hydraulic drive system.

I also like your option to hybrid this electric system (or not) with a very small gasoline or (better) diesel engine at a steady RPM in the engine's efficiency range.

Using the electric system, you would definitely need to limit the DC electric motors max RPM to prevent overspeed damage while taking advantage of it's high initial torque and fast RPM build up.

If you could rig it so that an accumulator hydraulic pressure switch turns the motor on and off when needed, it might save battery charge by allowing the motor to coast when not needed and having to run all the time.

And when the pressure is needed, could the flywheel be geared up to run at even higher RPMs than the electric motor if there was some way for it to have it "break free" (de-couple) the direct motor connection at the motor's max RPM so it could spin at even higher RPMs (like a whip or slingshot effect)?

In this scenario, once the flywheel spins down to a "safe" (from overspeed) motor RPM, it could re-couple and coast unpowered until the hydraulic system pressure switch starts the process over again.

The question is would it be more efficient on the batteries to operate the pump system all the time or in pulses since the hydrostatic drive system can use wasted forward momentum pressure back to the accumulator system on slowing/braking (hydraulic regen)? 

I'm thinking a pulse drive if electric.


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