A Twisting Moment
If you’re like me you’ll have an interest in electric motors. Electric motors are beautiful, they are quiet, have a ‘flat’ torque ‘curve’ and are highly efficient. I read recently an article on the web where a gent converted a petrol engined car into electric power. Where the original engine sat now we only saw the firewalls and a small little motor plonked right down at the bottom. In driving pleasure and terms of efficiency what is better than having possibly no gearbox and clutch. We think this is a new idea, something which has been with us for the last decade but we are wrong. Diesel electric locomotives have been around since time began. Steam locomotives don’t need a clutch either. It’s all to do with torque. Look at the size of a large ship’s engine or engines. All to turn a propeller. A ship doesn’t have a clutch either – there is a direct drive between crank and propeller. My first trip at sea on a steam turbine vessel had me in awe – it was quiet, it was damned fast and as the chief said “why make something go up and down to make something go round and round”. Never a truer word be spoke. In fact, modern times dictate that there should be no demand for internal combustion engines. Agreed, all technical people love internal combustion engines, they have their place and who wants to see a electric motor driven racing car – they have no character and definitely aren’t the life and soul at the drag strip. But yet!
Yes, the car has a gearbox. It’s also pretty potent compared to the smoking version.
A steam engine can develop a huge amount of torque onto the driving wheels without moving the locomotive forward. Like an electric motor. An internal combustion engine cannot – it needs a gearbox/clutch arrangement. Torque is king not horsepower. What is torque? Ummm, best described (for me in any event) as being the force acting on a shaft to rotate it. Diesel motors known for their low end grunt still need to be running before the motor can place a force on a shaft to rotate it. Yes, the force is noticeably higher than that of a petrol engine at low revs but it comes nowhere close to that of an electric motor. (or steam engine). Whereas a steam engine requires steam to push a piston through the pressure created in a boiler, an electric motor requires current through a field the tried and trusted diesel needs an internal combustion process to complete and to cycle before enough energy is obtained to provide a force to a shaft to rotate it. Electric motors are simple beasts – they have one moving part, the armature or rotor. If one had to lock the moving part or for instance the rotor of an electric motor and then power it up the motor will make a growling sound and there will be a huge amount of torque applied to the locking mechanism. Not so with an internal combustion engine. So what is the merit?
Below is a video showing the merit, the Tesla versus the R8. New versus old. batteries are soon going to be even more efficient, lighter and reliable under heavy load cycles than what they are today. Batteries won’t have to be charged through conventional means, they will need a refill of electrolyte (fuel), the spent fuel will be recharged. Quick and painless.
Many years ago we had a big problem when it came to electric motors: control circuitry. Even in the 70’s and 80’s the control circuity used to power electric motors was very expensive and cumbersome. Not only that, often they were engineered in such a fashion that the protection circuitry was often more involved than in the actual motor drive circuitry. A common way to increase the speed of a DC electric motor is through voltage control – while this may be ideal for small electric motors which have very little load it’s certainly not practical for a large motor – large motors have phase control for instance, one where the trigger point is at the leading part of a sine wave, moving over to the peak of a sine wave (this is often used in drilling machines with a commutator). Nowadays the power is derived from a DC source, possibly a few hundred volts which is chopped (square wave), the larger the on pulse the more power the electric motor will produce. So for a motor vehicle the acceleration of the car or drive from the motor is increased by increasing the pulsewidth of the controller. Want some more information then try these great links:
- 144V Motor Controller
- Brilliant Resource site (EVSource)
- Rebirth Auto
- The electric Beetle
- The HTS Motor – US Naval High Temperature Superconductor electric motor. Put this in your pipe and smoke it!
I found the links above really interesting reading although there are many great websites out there with even better information. One thing I like about electric power is the fact that you really don’t have to get your hands dirty. Electric power is clean in more ways than one. Also the components are not heavy except the batteries. It’s not cheap but hey, nothing like a re-birth.
If you’d like to add some amusing stories, some tips and general advice please be my guest.
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