# DC forklift motor max speed



## EVBike (May 8, 2020)

Hi I’m new to the forum. I’m looking at picking up the motor for my project. Now I want to use a used crown forklift motor as I’m able to get hold of them for free or next to nothing. I also want to use DC power. 

Now I have a few questions and I am hoping that you guys or someone you will be ale to answer/help me. 

1. Can a forklift motor rest the speeds I am looking for...80mph minimum. Or is it very much dependant on the specific of the motor? 

2. What’s better 36v, 48v or 72v?

3. Can I link two motors and drive them from one controller? 

4. I’ve been told the more volts I push into a motor the more speed. But if my motor is only rated to 36, 48 or 72 volts do I need to stick to what is specified or can I put more volts into the motor?

Thanks in advance


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## Duncan (Dec 8, 2008)

EVBike said:


> Hi I’m new to the forum. I’m looking at picking up the motor for my project. Now I want to use a used crown forklift motor as I’m able to get hold of them for free or next to nothing. I also want to use DC power.
> 
> Now I have a few questions and I am hoping that you guys or someone you will be ale to answer/help me.
> 
> ...


(1) Yes as long as its big enough and you feed it enough volts and amps

(2) They are usually the same motors!

(3) Yes but its rarely done - if you want more oomph so you fit two motors you usually need two controllers

(4) Most people use about 150 volts - those motors will be fine
I'm feeding my motor with 340 volts - but that is a bit radical

There is a long thread on choosing a forklift motor in the motors section - I know its a bit tedious but it's worth just fighting your way through it


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## brian_ (Feb 7, 2017)

EVBike said:


> 1. Can a forklift motor rest the speeds I am looking for...80mph minimum. Or is it very much dependant on the specific of the motor?


It depends on the motor and the gearing.

The road speed (80 mph) means nothing unless you also specify the ratio of motor speed to wheel speed, and the diameter of the tires. For instance, if you have 27 inch tall tires 80 mph will be about 1,000 rpm at the wheels, and if you think 12:1 gearing must be right because Tesla does that, the motor will turn 12,000 rpm at that speed... and even if you can provide enough voltage to make it work at that speed it will presumably self-destruct (unlike the very different Tesla motor, which is fine at that speed). On the other hand, if you have 1:1 gearing the motor will be fine but performance will be unacceptably poor. If you don't put any thought into it at all and just connect the motor to the input of a common final drive (diff, axle) with (for instance) a 4:1 ratio, then that 80 mph road speed will result in 4,000 rpm motor speed, which will probably work... entirely accidentally. Sometimes there are happy accidents.


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## EVBike (May 8, 2020)

Duncan said:


> EVBike said:
> 
> 
> > Hi I’m new to the forum. I’m looking at picking up the motor for my project. Now I want to use a used crown forklift motor as I’m able to get hold of them for free or next to nothing. I also want to use DC power.
> ...




Thanks for your post. 
I don’t suppose there is a link to this choosing a forklift motor thread? 

Also if I use 2 motors and 2 controllers won’t that cause tuning issues? Getting the motors to spin at the some time at the same speed etc? 

The motors I am looking at all have different voltages. Hence the question about 36, 48 or 72 volts. Oddly the one with the highest volts has the lowest rpm. 

😩 It’s a mind field. least this is keeping me busy during lockdown.


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## Duncan (Dec 8, 2008)

EVBike said:


> Thanks for your post.
> I don’t suppose there is a link to this choosing a forklift motor thread?
> 
> Also if I use 2 motors and 2 controllers won’t that cause tuning issues? Getting the motors to spin at the some time at the same speed etc?
> ...


Its a sticky at the top of the page this post is on

Two motors are usually used siamesed together to get more power - if you use one to drive each wheel then you need two reduction gearboxes!

Forklift motors with some judicious overvolting operate at about the right rpm to feed directly into a gearbox or if beefy enough directly into a diff


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## EVBike (May 8, 2020)

Thanks. It looks like for the purpose of what I am doing I won’t need 2 motors to reach to speed I want. What I need to do figure out what voltage I’m going to push through the motor and more importantly what the limitations of the motor are. 

I’m not pushing a lot of weight in total around 300-400kg or 650 - 850lb (that’s a very rough conversation). 

This project is to help my 15 year old son through his depression and anxiety through this lockdown period we find ourselves in. He Was inspired by this a YouTube series https://www.youtube.com/user/BenjaminNelson

And because the person who made these videos said he had no experience, my son thinks I should be able to do this. 🤨
So I’m trying to Do my best Not to disappoint and trying to help him build this bike. 

We were just going to build a combustion engine bobber but he has changed is mind thanks to this YouTube video. Now bare in mind that I am I pharmaceutical science and work in a lab lol.


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## MattsAwesomeStuff (Aug 10, 2017)

Ballpark, most DC motors from forklifts can spin around 5,000 RPM before they start to be dangerous to themselves.

Bike engines often redline around ~12,000-ish RPM. But their top speeds are often double highway speed.

So, ballpwark, DC motors can spin about as fast as a bike engine would've spun at highway speed, in top gear.

Keep in mind that Ben Nelson's series is hugely outdated.

One bigger challenge of a motorbike is getting enough voltage. Your battery pack is going to be small, your cells are going to be large, and with the size of pack you have you might not make a significant enough voltage to spin the motor fast enough. You'll have enough power, but not enough voltage.

Electrifying an already-existing motorbike is pretty simple. Could be a weekend project. There's not a lot going on.


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## EVBike (May 8, 2020)

MattsAwesomeStuff said:


> Ballpark, most DC motors from forklifts can spin around 5,000 RPM before they start to be dangerous to themselves.
> 
> Bike engines often redline around ~12,000-ish RPM. But their top speeds are often double highway speed.
> 
> ...



Ok would that change if I change the motor I use? Say to this https://www.ebay.co.uk/itm/273356341511
Would it be easier work with? 

I was thinking because the frame I have has enough space for me to get the battery packs in that I thought I would need I would be ok with the forklift motor. 

I planned on making these battery packs myself with 18650 cells. Each pack 72V 28Ah and I should have enough space for 4 packs. 

Would that be enough?


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## MattsAwesomeStuff (Aug 10, 2017)

> Ok would that change if I change the motor I use? Say to this


Smaller diameter motors are going to be able to spin faster (edge speed is lower). But this is just linearly proportional.

Depends what you're feeling for your project, but, I wouldn't waste $500 on a motor like that for almost any project.

One thing that is slightly better with that motor is that it's permanent magnet. Permanent magnet motors will spin to a known RPM per volt that you give them (minus some sag). On a chain-drive motorbike, the forklift motor you were planning to use would almost certainly be series-wound. Series-wound motors have no top speed. With no load, they accelerate almost instantly and tear themselves apart. In normal condition this is irrelevant. But it means if the chain breaks and he doesn't almost immediately react and release the throttle, he might grenade the motor. It's probably fine, except for the motor which'll be wrecked internally. Pretty low odds of it mattering, you'd have to have a comedy of errors.

The motor is smaller though, which might be more appropriate. Though I don't know how big your forklift motor was. Even the smaller pump motors from a forklift might be a bit overkill for a motorbike.



> I planned on making these battery packs myself with 18650 cells. Each pack 72V 28Ah and I should have enough space for 4 packs. Would that be enough?


72v * 28ah = 2000 watt-hours.

Four of those is 8000 watt-hours.

I punched it into a calculator: http://www.enginuitysystems.com/EVCalculator.htm

I was too lazy to fill in all the aero properly (and tires, which are among the worst because they're usually softer and grippier), but it came out to around 100 watthours per mile. I think that's low, maybe by half.

But ballpark, you might get 40-80 miles of highway range out of that battery pack. Whether that's enough or not is up to you and your kid. You'll get a lot longer range zipping around the town at lower speed.

Where are you getting 18650s? That's almost surely not cost effective to do.

That said, I (mostly) built a motorbike with a forklift motor and 18650s for batteries. A lot of it was figuring out how to reassemble a bike I never disassembled, but, if it's of interest to you here you go: https://www.diyelectriccar.com/forums/showthread.php?t=195073


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## EVBike (May 8, 2020)

Ok so I’m having a few different people inform me of different things in relation to the motor I should go for. 

Repurposing a forklift motor was the route I intended of going. However, I now have a been told that should use a smaller motor like https://www.ebay.co.uk/itm/271111809926

I’ve even been told that an AC motor is the route that I should go. Can please have some help with what the best route for us to go would be. 

I have a oil cooled AC motor I could use but it’s 70kw
Input voltage 400V
Type 3 Phase synchronous perm magnet brushless 
RPM 14000rpm max

I have a dc to ac controller but not sure it’s right for this motor as it’s from a Nissan Leaf. 

I also don’t think I can meet the voltage requirements.


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## piotrsko (Dec 9, 2007)

my $0.02 YMMV:
Ac motors are the "NEW" thing, mostly because they easily regen spin fast, and controllers are now quite common.

Series DC is still the cheapest to buy and install /control for torque vs price. Rule of thumb when I started here 10 years ago was a 9" would power a bike respectfully. 9" was a used hydraulic pump motor out of a forklift.

A forklift motor shouldn't explode on it's rated voltage unloaded. however very few things running on 36 volts.

Metal jacketed cells in boxes is considered risky mostly from an assembly point keeping the cells connected and isolated while cooling them and shorted or open circuit cell issues.

I dont show up much anymore, too many Google trained aexperts for my taste


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## EVBike (May 8, 2020)

So you’re saying that a AC motor is the way for me to go???🤔

I’m happy to use my AC motor and from what a few people have been saying to me recently I’m leaning towards doing so. 

I’m concerned that I don’t enough space to fit the quantity of batteries that I need to get the 400 volts needed for the motor


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## EVBike (May 8, 2020)

Can if this motor will be good enough for my needs

https://www.ebay.co.uk/itm/183943032200


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## MattsAwesomeStuff (Aug 10, 2017)

I would not spend $125 + $80 shipping on that motor.

You get free forklift motors, I'd go with one of those.


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## EVBike (May 8, 2020)

MattsAwesomeStuff said:


> I would not spend $125 + $80 shipping on that motor.
> 
> You get free forklift motors, I'd go with one of those.


No not in the UK you don’t. I’m still looking though.


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