48volt brushless 3000watt scooter motor repurposed

[jvmiller95]

So I want to repurpose a Escoter motor to power a wood working multi shop tool. The Shop Smith to be exact. They have been around since the 40's and use mechanical gearing to change speeds with a 1 1/8 motor that is a bit under powered. They do have a $1800 upgrade kit to a 2hp Nova DVR type motor. But I thought a small compact 3000k 48 vote scooter motor would bring it up to over 3 hp. And I would be able to run on battery power if needed as as 48 volt 3k power supply packs are around 100 bucks as they are often found used and are the backbone to our telecommunication networks. So I am wanting to use a 48 volt 2k to 3k scooter motor with heat sink on it and a couple cooling fans as it is going to be encased in the head stock of the shopSmith. I am going to gear it up just a bit so my main shaft on the toll can make 10K rpm for shaping and routing.

I love the idea of this as it will have the ability to have a E Brake as well. I do not want the throttle cable so my question is what sizes potentiometer does these motors like a vevor scooter motor use. Do these motors have a good torque at lower speeds as well as higher. I am doing with or a2hp 3 phase electric motor and a vfr. But I love this 48 volt idea for many. Plus it is very hard to get shocked using 48 volts.


Any thought's or concerns and mostly tell me what size pot I need to run the motor rull rpm around 5400 rpm Also I have a nice 2x72 knife grinder powered by a treadmill motor that I want to rebuild using the same motor. So hit me with best advice and ideas

 

[Papa]

Not long after I purchased my 16" machinist drill press, I replaced the OEM AC motor with a 2 HP DC treadmill beast. I don't remember the brand of controller I used, but the electronic variable speed is a blessing. The replacement has dramatically more torque, and I can now run it off my solar battery bank if I wish.

 

[amberwolf]

Without knowing which specific motor and controller you have, I couldn't tell you what specific throttle replacement to use, or what kind of torque or speed it would have.

The throttle input on the controller will require a certain voltage range, and if it's well-designed, anything outside that range will either cause it to not start the motor, or shutdown the motor, but many are not well-designed and their behavior isn't always predictable.

Most common brushless controllers use a throttle input range of around 1-4v, but the specific range, and the response they have to that, varies. You may not be able to use just a pot to control it, but may have to add resistors between ground and one side of the pot, and the other side of the pot and 5v, to keep the actual output range of the pot within the controller's allowed range. Or add mechanical stops to your pot's knob so it can't go below or above the limits. A 5kohm-10kohm pot run on 5vdc from the controller would normally work, given these caveats.


The torque and speed are dependent on the motor's kV (rpm/volt) and rated Nm output, and whatever gearing you use between it and the driven device. Most motors have zero data on them for either one of those. You can guess what the kV is by dividing the RPM it is claimed to spin at for the voltage it's claimed to run at.

If you gear it up to go faster, you lose torque proportionally. If you gear it down to get the torque, you lose speed, proportionally.

A higher current controller will generally create more torque with the motor, but if you have no airflow past or thru the motor, and it's sealed up, you'll probably want to derate it's power by quite a lot (half, or much less), and so get a motor that is claimed to handle many times more power than you actually require, and use it with a controller that only produces as much power as you require.

If you have specific torque and speed requirements, I'd recommend getting motors that are already rated to handle those, with actual Nm and kV (RPM/Volt) ratings; it's likely cheap kits will not have any realistic or trustworthy such info. If it has a dyno sheet available (few do) even better so you can see how it performs over a range of usage.


Some controllers (VESC, Phaserunner, etc) are programmable for all sorts of things including throttle input ranges, phase (motor) currents, etc., so once you have them setup for your specific motor, battery, etc., you can tune them for best behavior with your specific usage, as long as all the parts you get can handle what you need from them.



If youre looking at brushed motors / controllers, things can be much simpler, if less efficient (more heat generated in the motor via brush/commutator, etc), and low-end torque can be higher than the "same" rated brushless system because of the way controllers for each may be designed. Both types are just as mis-rated, with higher claims than they really support, or inadequate info to judge them by, etc.

 

[jvmiller95]

Not long after I purchased my 16" machinist drill press, I replaced the OEM AC motor with a 2 HP DC treadmill beast. I don't remember the brand of controller I used, but the electronic variable speed is a blessing. The replacement has dramatically more torque, and I can now run it on DC if I wish.

I have one in one of my 3 shopSmith and it does not have much torque at low speed. My 2 x 72 grinder also has one and I never run it real slow sow it works very well. I Put a jack shaft on it and cut the motor speed in half because it is around 7K. It is a 3.5hp and I have no real complaints. I just thought the scooter motors might work a bit better. I used the control board out of the treadmills on those two. They are a brushed motor. I am not sure but I think the scooter motors are controlled more like a VFD and have more torque at lower rpm. As where the treadmill motors are PWM.

 

[amberwolf]

If you're not getting good torque out of a brushed motor, your controller is probably not able to provide enough current.

If the scooter motors are brushless (both types exist) then the controllers are still PWMed; the only difference is the commutation is done inside the controller instead of inside the motor.

Speed control is still done by PWMing the voltage.

You can get FOC controllers that modulate the current to the motor instead of the voltage, so you have better control over the motor, but the ultimate control is still done via PWM.

 

[neptronix]

Look into RC motors. If the output of the shaft needs to be 1000's of RPM, they'd be very ideal and it's hard to beat the power density/price of them.

 

[jvmiller95]

Without knowing which specific motor and controller you have, I couldn't tell you what specific throttle replacement to use, or what kind of torque or speed it would have.

The throttle input on the controller will require a certain voltage range, and if it's well-designed, anything outside that range will either cause it to not start the motor, or shutdown the motor, but many are not well-designed and their behavior isn't always predictable.

Most common brushless controllers use a throttle input range of around 1-4v, but the specific range, and the response they have to that, varies. You may not be able to use just a pot to control it, but may have to add resistors between ground and one side of the pot, and the other side of the pot and 5v, to keep the actual output range of the pot within the controller's allowed range. Or add mechanical stops to your pot's knob so it can't go below or above the limits. A 5kohm-10kohm pot run on 5vdc from the controller would normally work, given these caveats.


The torque and speed are dependent on the motor's kV (rpm/volt) and rated Nm output, and whatever gearing you use between it and the driven device. Most motors have zero data on them for either one of those. You can guess what the kV is by dividing the RPM it is claimed to spin at for the voltage it's claimed to run at.

If you gear it up to go faster, you lose torque proportionally. If you gear it down to get the torque, you lose speed, proportionally.

A higher current controller will generally create more torque with the motor, but if you have no airflow past or thru the motor, and it's sealed up, you'll probably want to derate it's power by quite a lot (half, or much less), and so get a motor that is claimed to handle many times more power than you actually require, and use it with a controller that only produces as much power as you require.

If you have specific torque and speed requirements, I'd recommend getting motors that are already rated to handle those, with actual Nm and kV (RPM/Volt) ratings; it's likely cheap kits will not have any realistic or trustworthy such info. If it has a dyno sheet available (few do) even better so you can see how it performs over a range of usage.


Some controllers (VESC, Phaserunner, etc) are programmable for all sorts of things including throttle input ranges, phase (motor) currents, etc., so once you have them setup for your specific motor, battery, etc., you can tune them for best behavior with your specific usage, as long as all the parts you get can handle what you need from them.



If youre looking at brushed motors / controllers, things can be much simpler, if less efficient (more heat generated in the motor via brush/commutator, etc), and low-end torque can be higher than the "same" rated brushless system because of the way controllers for each may be designed. Both types are just as mis-rated, with higher claims than they really support, or inadequate info to judge them by, etc.

Looking at brushless. I am wanting to use the entire kit motor and controller. I am Assuming the throttle that goes on the handle bar is just a pot. From What I have read that is the case. All circuits needed are in the controller and it just has 3 wires in from a standard pot. I just not for sure the sizes I need. I do have a father that is a pretty good whiz kid with electronics. He has not played around but a little with brushless motors but I know he understands them very well. I pretty much intend on dumping it in his lap. Lol he use to do TV repair back when it was a thing and has scopes and all the gear and knowledge to use them. he has a really cool model railroad he built the entire electronics from scratch and has a computer program that can run up to 100 trains at one time if he wished that he wrote. himself. He built all of the power packs himself. No DCC plug n play here. His layout is HO and has over 250 switches in it. But he is pushing 80 now and is not always going to be around to solve my problems Lol.

I intend to put a heat sink on the motor and install fans inside the case. Lots as room going from a 110 size 54 frame inductance cap start motor to a motor about 4 inches around. It will be geared up but about the same as old motor was when on the highest setting. The standard motor in it is only 3450 rpm and 1 1/8hp and it has mechanical sheaves that adjust like a torque converter on a gocart. So at top speed it is way less than one HP more like 1/3rd (or rather has 1/3rd the torque to be more accurate) and reaches about 10000 rpm on the lower drive shaft in the machine but that is then is then reduced x 1.6:1 to bring the top drive shaft in at 6400rpm. I am aiming for 10,000 on final drive top shaft with a motor turning 5400 rpm at max. so 2.8:1 gives me 15120rpm on the lower shaft divided by 1.6 for the upper shaft running at 9450rpm. So a 3HP motor divided by 2.8 is still far more than a full HP left. Where my original motor is only 1.125 HP in a 3:1 ratio. (so only 13rd the torque) but 90% of the time in most operations it will never crack 40% of that speed I just want it for router options. This brings it into the same speed and abilities as the new machines that are about $4k or $2k to upgrade mine too. All the bearings are rate for this type of speed and I intend on refreshing them with new ones too.
.

 

[jvmiller95]

If you're not getting good torque out of a brushed motor, your controller is probably not able to provide enough current.

If the scooter motors are brushless (both types exist) then the controllers are still PWMed; the only difference is the commutation is done inside the controller instead of inside the motor.

Speed control is still done by PWMing the voltage.

You can get FOC controllers that modulate the current to the motor instead of the voltage, so you have better control over the motor, but the ultimate control is still done via PWM.

so on my brushed motor it is 120 volt pulse DC correct? Then at top speed it has all the power in the world. So How do I increase the amps at low speed with out speeding up the motor. Do I need a different motor driver that can give more amps at the lower speeds

 

[amberwolf]

Looking at brushless. I am wanting to use the entire kit motor and controller. I am Assuming the throttle that goes on the handle bar is just a pot.From What I have read that is the case. All circuits needed are in the controller and it just has 3 wires in from a standard pot. I just not for sure the sizes I need.

As noted previously, they're usually hall sensor throttles, with a more limited output signal range, and the workarounds noted are usually required to use a pot, and typical values were also given.

You'd have to check the actual controller manual / specifications for it's throttle signal input voltage requirements.

I intend to put a heat sink on the motor and install fans inside the case.

Heatsink on the motor may not do much good, depending on design. If it's intended to have airflow thru *and* around it, you'll need to set your system up to do that.

If it's an outrunner, you'll have to cool the stator itself that's inside it.

If it's an inrunner, cooling the stator may be easier, as long as it's fixed to the casing thermally, not insulated from it, but then the magnets on the rotor inside the motor may require airflow to cool those.

Depends on the power usage, motor efficiency, etc., as to what temperatures are actually reached inside the motor in various places.

 

[jvmiller95]

so on my brushed motor it is 120 volt pulse DC correct? Then at top speed it has all the power in the world. So How do I increase the amps at low speed with out speeding up the motor. Do I need a different motor driver that can give more amps at the lower speeds

If I could get a motor driver that give me the power I need at the lower speed on the treadmill motor I would be happy. I already have it built inside the machine. It looks good to as old speed control to adjust the shelves is hooked to the pot to control it.

 

[jvmiller95]

As noted previously, they're usually hall sensor throttles, with a more limited output signal range, and the workarounds noted are usually required to use a pot, and typical values were also given.

You'd have to check the actual controller manual / specifications for it's throttle signal input voltage requirements.



Heatsink on the motor may not do much good, depending on design. If it's intended to have airflow thru *and* around it, you'll need to set your system up to do that.
entolmen t
If it's an outrunner, you'll have to cool the stator itself that's inside it.

If it's an inrunner, cooling the stator may be easier, as long as it's fixed to the casing thermally, not insulated from it, but then the magnets on the rotor inside the motor may require airflow to cool those.

Depends on the power usage, motor efficiency, etc., as to what temperatures are actually reached inside the motor in various places.

it is a in runner. I seen another man pull the end cap off and enlarge the holes to breath more. I was planning on doing this and putting a large fan at the back. blowing air in.
Oh it is hall sensor I seen that.

But if someone could point me into what is needed to get more torque from the lower speeds on my treadmill motors I am interested greatly

 

[amberwolf]

so on my brushed motor it is 120 volt pulse DC correct?

I have no way of knowing what voltages are there, as you haven't given any details of the system. You would have to provide us with the specifics on the voltage source, the controller, etc., and probably do some measurements of actual voltages to find out.

Normally the controller will "slice up" the battery voltage, using PWM to turn the FETs on and off in whatever proportion is needed to provide the average voltage to the motor that is commanded by the throttle. Non-FOC controllers are almost always "speed" throttle, which really means "voltage control", which means the throttle is a proportional control of the voltage fed to the motor.

(FOC controllers are usually a proportional control of the *current* fed to the motor, but the actual mechanics of creating that current are via PWM of the voltage across the windings, just like the other method, but more complex in how it does it so the effect to the user is different.)

Then at top speed it has all the power in the world. So How do I increase the amps at low speed with out speeding up the motor. Do I need a different motor driver that can give more amps at the lower speeds

The motor can't go any faster than the voltage fed to it.

If the controller being used is feeding more voltage to it it will increase the speed, but:

If the load on the motor is high, it's speed will not be as high as if the load were low.

if you need more torque from a specific motor, you have to increase the current to it*** and that means increasing the voltage across it's windings. If the load isn't high enough to demand that current and keep the speed down the speed will increase too.


***or you have to gear down the output to change speed into torque, like with my drill press that has a conical belt drive where you select one of several torque/speed ratios by moving the belt to a different pulley pair, or a bicycle where you shift gears in front or rear or both.

If the motor in your system has plenty of torque when at higher speeds (meaning it will do whatever job without slowing down) then it is geared wrong for the low speed usage. You'd need to change the gearing between motor and load for that usage.


The treadmills that I have disassembled to recover motors, bearings, etc., from have all been geared down to output low speed but high torque; this is how those motors were intended to be used. If you gear them high, speeding up their output, you take away the torque. That's how gearing works--increase speed, decrease torque proportionally, and vice-versa.

 

[amberwolf]

it is a in runner. I seen another man pull the end cap off and enlarge the holes to breath more. I was planning on doing this and putting a large fan at the back. blowing air in.

I recommend pulling air thru it, rather than pushing air in. Install the fan some distance away from the actual motor, with a smooth tube of the fan diameter between the fan and the motor outlet. It works better in most cases, and is also quieter.

If you ever do this to cool a brushed motor, be sure the brushes are on the outlet end, so you can suck the brush dust out and not end up with it building up inside the rotor area of the motor.

If you enlarge holes at one end, you'll have to make identical area changes to the holes at the other, or the airflow won't change.

Be sure that you don't leave any shavings/etc in there, or they may end up in the motor and damage things over time.

 

[jvmiller95]

Doing a bit more research I think I am going to talk to my dad for some help. It appears from my hours of research that a simple rpm sensor and to create a pid controller can can see the RPM I want to keep turning t and add more or less power as needed from my supply. Instead of having a set PWM signal from my pot like I have now on my treadmill set up. This little bit of adreno software can smash the gas up and down to keep the torque I need. I would love to here your thoughts on this.


If this works it gives me a RPM readout I was going to do anyway and lets me use the set up I already have built. We will see soon enough.

 

[amberwolf]

It's likely that this will help; tuning the feedback loop is usually the hardest part.

If you make it completely analog (op-amps, etc) then you can use simple pots to tune it.

If you make it using an MCU (arduino, etc) you can use either knobs (digital or analog) to tune it, or onscreen controls or buttons.

This general search may have useful links:

PID loop for RPM control - Google Search