dadof2 Posted July 17, 2016 Report Share Posted July 17, 2016 Yes electric motors may have only one (once assembled) major rotating part, but that part in made up of many components. High power to weight ratio electric motors have the same disadvantage as gas turbines, they have to run at very high RPM. High torque / high amp / low RPM electric have to have complex cooling systems if they are to be lightly built. The present problem with electric vehicles is not the motor, it is the weight of the fuel store. Hydrocarbon fuels are still way, way ahead in terms of energy stored per kg. None of the present batteries comes anywhere near and there is nothing even at the research stage that will significantly close the gap. Quote Link to comment Share on other sites More sharing options...
gwhy Posted July 18, 2016 Report Share Posted July 18, 2016 Yes electric motors may have only one (once assembled) major rotating part, but that part in made up of many components. High power to weight ratio electric motors have the same disadvantage as gas turbines, they have to run at very high RPM. High torque / high amp / low RPM electric have to have complex cooling systems if they are to be lightly built. The present problem with electric vehicles is not the motor, it is the weight of the fuel store. Hydrocarbon fuels are still way, way ahead in terms of energy stored per kg. None of the present batteries comes anywhere near and there is nothing even at the research stage that will significantly close the gap. The armature ( rotating part ) are magnets on a shaft, and the stator is copper wire and laminates in a shell... hardly a lot of components ( unless you are talking about brushed motors ) There is very little restriction to the speed that a electric motor can run at unlike ICE so why not run them at 10krpm to produce the torque ( its what I do ) then the motor can remain small and light . and if designed right cooling them is not a problem ( if needed ). Yes batterys ( and controllers ) are the bottle neck as regards EV's but in real terms if you can recharge a battery in 10mins ( if you had the facility's ) then whats the problem . The weight of current batterys that will allow approx 1-2 hours of typical trials weighs around the same weight as a gallon of fuel and takes up about the same amount of room and a typical trials ICE weighs around 15-20kg , So you are saving weigh on the power plant with electric ( some electric motors that only weigh 4kg can peak at the same power that a trials bike can produce ) . If you what speed, power and range this is where things get a little more complicated as you need to fit more battery capacity to the vehicle and on a bike this becomes a problem with space, But battery tech is getting better, smaller and lighter and most of all cheaper, maybe fuel cells will be the brake through that is needed but at least the power plant will not need changing. 1 Quote Link to comment Share on other sites More sharing options...
dan williams Posted July 30, 2016 Report Share Posted July 30, 2016 (edited) Well there are limits to the speed a rotor will go without tearing itself apart. Also at very high speeds balance of the stator becomes an issue. For the stator there is a fundamental limitation of the inductance of the coils. You simply cannot go above a certain frequency and get enough current into the coils to develop a rotating magnetic field. That is why higher speed motors have fewer stator poles. Torque is highly dependent on the magnetic coupling between the rotor and stator magnetic field so fewer poles means less efficient coupling and less torque. If you ditch the permanent magnets and go with a squirrel cage rotor you are also limited by the inductance of the rotor and the need to have a slip to keep current flowing in the rotor. Fun stuff to think about for an engineering geek (me). I'm curious GWHY how many rotor/stator poles are you running and do you change the number of energized poles to compensate for bandwidth limitations for high speed operation? Imagine what you could do with a room temp superconductor. You could build a stator with single wires instead of coils. Ooh even better, thin film graphene. Print the rotor on the inside of a ceramic cylinder. Ok I'm geeking out badly now. I'll stop. How well does a rotor spinning at 10k RPM handle the normal jolts of trials riding? Oh and understand that as someone who respects doers above all I ask with honest curiosity as you've actually built electric bikes and that impresses me no end. Edited July 30, 2016 by dan williams Quote Link to comment Share on other sites More sharing options...
gwhy Posted July 31, 2016 Report Share Posted July 31, 2016 Yes there are limits but they are well byond that of a ICE motor and this also depends on design and construction of the electric motor, Physically and electrically. Eddy currents play a major part in the max that a motor can spin and is one of the main considerations when using a motor at high speed. the smaller motors that I have run at 8-10krpm are 12 pole motors, but have used many motor types and configurations, the controllers I mainly use are basic 16khz and these drive my motors very well. Yes room temp superconductors would be the the ulimate! and can lead to 100%+ efficiency , this can then solve all power production problems as it will lead to overunity. The motors run at a max of 10krpm but this is a restriction of the bearings but have run them upto 14-16krpm not for perlonged periods as It starts to get a bit scary when motors are spun upto those sort of speeds unless they are specifically designed to do so.. 10krpm is the max rpm for full geared speed and is very rearly hit for trials but i have used them for small race bikes that are run flat out on a circuit and have coped very well with all the knocks,bumps and crashes. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted August 7, 2016 Report Share Posted August 7, 2016 "Yes room temp superconductors would be the the ulimate! and can lead to 100%+ efficiency , " That would be a perpetual motion machine and that is about as likely as me maintaining perpetual motion in the Scott! 1 Quote Link to comment Share on other sites More sharing options...
dan williams Posted September 30, 2016 Report Share Posted September 30, 2016 So where is the Mecatechno already? Quote Link to comment Share on other sites More sharing options...
masso Posted December 1, 2016 Report Share Posted December 1, 2016 Well, I'm glad to see so many highly technical ,smart type people involved.... Maybe someone could explain to me why the loud howl of the electric motor....i'm still wanting a quieter motor for neighbours I've been around electronic cars. a..and they are soundless......... is there a way of quieting the motor ?......masso Quote Link to comment Share on other sites More sharing options...
stan wellback Posted December 1, 2016 Report Share Posted December 1, 2016 Well, I'm glad to see so many highly technical ,smart type people involved.... Maybe someone could explain to me why the loud howl of the electric motor....i'm still wanting a quieter motor for neighbours I've been around electronic cars. a..and they are soundless......... is there a way of quieting the motor ?......masso easy, wrap a ton of bodywork around it. Quote Link to comment Share on other sites More sharing options...
gwhy Posted December 10, 2016 Report Share Posted December 10, 2016 (edited) its the type of controller that makes the noise in the motor... trapeziodal controllers are much louder than sinusoidal controllers. Edited December 10, 2016 by gwhy Quote Link to comment Share on other sites More sharing options...
masso Posted December 10, 2016 Report Share Posted December 10, 2016 well, thank you there GWH Y ...I'm impressed .I know nothing of electronics ..but ride rear humans and the EM is still a bit noisy . so, why do you think the EM people used the trapezoid instead of the sinus ? also...I notice an E sherco...whats that about ?? Quote Link to comment Share on other sites More sharing options...
gwhy Posted December 10, 2016 Report Share Posted December 10, 2016 cost :-).. but sine controllers are coming down in price all the time and some are acually cheaper now than the trap controllers.. some also say that trap controllers are able to give a better instant hit than the sine contollers but in my experience I can not tell any difference between them as regards power delivery, as long as the sine controller is setup well. I have (used to have ) a self converted sherco . :-), well i still have it but its gone through many configurations/motors and controllers but at the moment its just a rolling chassis again. Quote Link to comment Share on other sites More sharing options...
guys Posted February 3, 2017 Report Share Posted February 3, 2017 Here's one based on a GasGas. Extra batteries can be added to increase the action radius. Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 26, 2017 Report Share Posted June 26, 2017 Hmmm the competition has finally shown itself. http://www.trial-club.com/webzine-trial/actualites/2017/mecatecno-lourdes/ Interesting. Looks like an Ossa swingarm but where is the shock? I think I see one but there's not much space. Frame looks almost like a trials bicycle. Quote Link to comment Share on other sites More sharing options...
breagh Posted June 26, 2017 Report Share Posted June 26, 2017 For sure it's an Ossa swingarm most of the frame too and plastics. Quote Link to comment Share on other sites More sharing options...
dan williams Posted June 26, 2017 Report Share Posted June 26, 2017 I wonder if they just sopped up the leftover stock of Ossa parts to use as a development platform. Kind of a serendipitous opportunity as it saves a lot of development time. Quote Link to comment Share on other sites More sharing options...
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