Electric Greyhound Conversion Motor

by Ross Wilson
(Prince Rupert, BC Canada)



I have an opportunity to buy a used electric motor from a mining operation. it is a 300-hp 460-V RMP-1800 phase 3.

From this info, can I use this on a greyhound bus? I have an opportunity to purchase 2 with the same capacity.

Hi, Ross -
What a great idea, converting a vintage greyhound bus to electric! The company in the video above is also doing this. You can get the old buses for cheap, he says, and convert them for a quarter of the price of a new electric bus.

I don't know about your motor, though. Sounds like a monster!

The bus in the video is using a 170 hp motor with 1200 ft-lbs of torque.

What sort of work was your mining operation motor doing before? I just did a little reading on mining operations and electric motors, and it sounds like there are dozens of electric motors used in mining operations for all sorts of applications. Motors used in traction applications (like a forklift traction motor, not the hydraulic lift motor) make the best EV conversion motors.

Some considerations for your motor choice:

How big is it, and does it fit well in your greyhound's engine bay? How will you secure it to the chassis? How heavy is it?

Was it designed for continuous running, or intermittent?

What kind of modifications will you have to make in order to match the motor's shaft to your transmission?

What sort of torque curve does your motor have?

How is it cooled? It looked like some of those mining motors are all enclosed with an integrated cooling system.

I'm afraid I've introduced more questions than answers, so, maybe not much help in the short term.

And that wasn't even the real Debby Downer part. Here it is:

I have spoken with many people who bought a motor (cheap, salvage) and designed an electric car conversion around it. Many (most) of them were disappointed with the final product and would do it differently next time. This is a really crucial choice and the wrong motor can make you very unhappy.

Hope this helps.

Lynne





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Torque, HP, and RPM
by: Fixx

So to help you with your final question I will provide a little background information.
- torque is a measure of the twisting force
- horsepower is simply the torque with a time element, in the case of rotating machinery RPM represents the time element.
- RPM combined with the overall gear ratio determines cruising and top speed.

From what you posted and the previous reply I would guess your 300HP motor at 1800 RPM will provide enough torque to get you moving (considering electric motor torque curves) but you may have a problem with the top speed. I am assuming the bus was diesel to begin with (can't view your post from comment dialogue) so it should be designed for a low reving engine, which is in your favour. I work in the industrial field and the rule of thumb is that you can run a motor up to 2 times the rated speed, I would add additional cooling though if this is the cruising speed vs passing speed. That would give you 3600 RPM, which is in the ballpark redline for diesel engines. This bodes well for the ability of the motor to be a drop in replacement for the original diesel engine.

Long story short (OK, not that short):
- from what I've read here your HP and torque are non-issues, you should be fine with one 300hp motor (depending on if you are going to race it or not) :)
- use an online calculator with your overall gear ratio and tire sizes on the bus to determine if you need a gearbox to cruise reliably at highway speeds (the short answer to your RPM question)
- check to see if the motor you have access to is "inverter duty", this affects the durability when using simulated AC waveforms instead of true AC waveforms. You can maybe take a chance on this since industrial motors often run 24/7 whereas motive power systems tend to be a fraction of that.
- gearboxes trade RPM (speed) for torque, so a 1:2 overdrive unit would half your torque but double your speed. There are under/over gearboxes that may help make your bus more versatile without breaking the bank.
- You can run industrial motors faster than the rated speed but I would recommend that you minimize how much through gearing. Pushing anything tends to decrease the longevity.
- If you use a two speed transmission (like the under/over) and eliminate the original transmission you will already be saving a lot of weight.
- Power to Weight ratio is not just for race cars. Electric motor vs diesel motor is likely in your favour but added weight in batteries (which will determine your range) will work against you. You should be able to do a lot of the math before you even start.



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greyhound conversion
by: Anonymous

Hi Lynne-great questions. I understand the motor was used in a lime mine and ran a conveyor (I think), and I may have access to a identical (new)motor giving me 600 hp if they are dual shaft motors. more info on the motor; 300 hp/1800 rpm/TEFC/447T frame/460 V/Phase 3/2677 lbs. this is all the details I can get a hold of. hoping someone may have some insight into my idea of installing on the bus. have lots of room for batteries (in luggage compartment) and BMS, and controller. taking out all the bus seats and motor will reduce weight a lot but still hope a 300 hp motor (or two) could push me along at a moderate speed. a newbee at this, but very keen on starting my conversion already started renoing the interior. will 1800 rpm be adequate to move my bus.

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