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John Grikes (Engage1000)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 23, 2005 - 10:53 pm: | 
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Hi Guys,
I just recently had the idea of buying an old Argo from the early eighties for cheap and then removing the engine and tranny and fitting two decently powerful electric motors into the machine. One for each side, which would be easily controlled. Or I could run 6 smaller motors to drive each axle independantly. That would also be more reliable because I could suffer multiple drive failures and still be able to get home.
I was thinking maybe I could somehow attach the motors onto the idler chains where the tranny used to be, making use of gear reduction systems for some extreme power. In place of the engine I would have battery packs in the front and a few in the rear to balance out the weight (My Bigfoot sucks and handles poorly without weight in the back).
Actually, I might just put the battery packs in the back and leave the engine where it is as a generator, with the ability to turn it on and off at will when I want. Variable throttle too, easily accomplished for lower noise. That would be sweet!!
Not only would this be really quiet, it would be powerful and very environmentally friendly.
Anyone have any ideas? I would LOVE to hear them.
Best regards,
John |
Eugene Kochnieff
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 23, 2005 - 10:53 pm: |
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Hi John,
Great idea in principle, but hard to implement as you would need high voltage motors to keep cct curents low and minimize I^2 R losses.
So you would probably go with variable frequency drives and synchronous motors, all using Pulse width modulation to minimise losses again.
You could use Dc motors but good ones are very costly.
I think the electronics to do it well would be too costly, the same issues as electric cars, your idea of a hybrid design has most merit but i think weight would become an issue real fast.
What about a fuel cell design now that would keep the weight down but is costly again.
just my thoughts
bye Eugene. |
John Grikes (Engage1000)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 23, 2005 - 10:53 pm: |
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Hi Eugene,
Thank you for the input (I look forward to more). I appreciate it greatly. My intention for this project was not for anything professional or something that would go into production, rather that it be a fun experimental design. I can always improve upon it at a later date.
I understand what you are saying about the high voltage motors. My intention was to use decent quality AC motors and power them with an array of 12 volt high capacity battery cells using an inverter.
Since I am not an engineer, can you kindly explain to me what I^2 (I know that is squared) R losses are? I have no idea ;-).
Variable frequency drives, synchronous motors, pulse width modulation. Hmmmm... why can't i just regulate the voltage supplied to the AC motors? I know it is crude and won't be as good as a variable frequency drive but this isn't professional. I can always change it later.
I think I can handle the electronics and it won't cost me much. I have a friend who is a technologist and I have access to about a million and a half electronic components (exaggeration), old and new. I also have the resources to make my own printed circuit boards. To me the electronics side of it won't be any problem (I hope).
I don't see how an array of batteries can add much to the vehicle's weight. If you consider that I have removed the tranny and motor, that would account for at least a 200 pound weight reduction. I would set up the array in the front engine compartment and in the rear to balance it out. It wouldn't weigh much more than the engine and transmission. Maybe 300 pounds or so? I think it could work with a bit of fiddling.
Let's say for instance I hooked up a total of six 12 volt 1000 CCA Batteries as my power source... how long could I run the machine before the batteries depleted to... let's say 30%. If i can get 3 or 4 hours out of those, then that is quite fine. I would just plug it in to charge overnight and take my bigfoot out ;-).
I also wanted to ask you how much power I would need. I am looking for at least as much power as I had with the original engine. Since I am going to use gear reduction systems, I was thinking I could get by with 3hp AC's on each side. What do you think?
Anyways, I appologize for the long post. I can get overzealous sometimes.
Best regards,
John
PS Maybe if this works out alright I can market it??? (There I go again counting my chickens before they hatch). |
Eugene kochnieff.
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 23, 2005 - 10:53 pm: |
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Hi John,
I^2 R for any given amount of power say 750 watts (approx 1 HP) power is voltage X Current.
So you could have 750volts x 1 amp or 750 amps x 1 volt or any combination that gives a product of 750 in this case.
Now given that superconductors aside all real wires have some resistance and the power dissipated in a resistance is given by I^2R; so lets say all your cables are robust and have a total of 0.1 ohms resistance, not much.
At 10 volts and 75 amps I^2r =562.5 watts out of your planned 750!!!!!( all power lost as heat in your cables)
Now lets go 100 volts at 7.5 amps I^2R = 5.625 watts out of your planned 750 a much better solution. This is why the pwer is distributed around the grid at 330000 volts or more.
So You want 3 HP / side that will need approx 2250 watts per side with six 12 batteries that give you 72 volts that will need to draw 62.5 amps (close to our 75 amp bad example above) so your I^2R losses can be expected to be significant on the 72 volt side of your inverter. On the high voltage side un less you are using 3 phase inverters (big bucks) you will need to use universal brush motors as used in large industrial grinders (typicaly under 2 HP). Now universal motors can be regulated by varying the supply voltage but this is a problem in itself as your options are Autotransformer (variable Transformer) costly at these power levels or linear ( very inefficient) or Pulse width modulation.
Pulse width modulation PWM is best explained thus.
Using an electronic switch power is applied to the load in a short pulse followed by a short period of no power. Now if the total time of pulse and pause is fixed say 0.1 second you can vary the ratio of off to on and control the amount of power that gets to the load fom zero (pulse =0 pause=0.1s) to half power (pulse=0.05s pause=0.05s) to full power (pulse=0.1s pause=0)
or anywhere inbetween. This method uses the energy storage ability of the motors magnetic circuit
to even out the pulses and give a smooth average with little power loss (assuming a high voltage system as explained above).
Now to the bad news lets say you use on average half power, thats 1.5 hp/side or 3hp total=2250 watts.with 6 100Ah batteries at 12 volts each, you get one 100Ah battery at 72volts so this will give you 2250 watts for 100x72/2250 =3.2 hours till flat and this is assuming no losses in conversion or any where else so to be conservative i'd guess 1.5 hours!!!!!!!!!!!At Half power; so if you want to go for it and 6 Hp is not much, 45 mins might be your lot!!!!!!!!!!
boy you thought your post was long.
bye Eugene. |
David
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 23, 2005 - 10:53 pm: |
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John,
The closest thing to what you want right now would be an electric golf cart. They use special 6 volt batteries and DC motors. These batteries are bigger and heavier. Your standard deep cycle 12 volt batteries are not designed for this kind of use. Their life spans drop off drastically if you start discharging them to less then 50% capacity on a regular basis. Take a close look at the golf cart, it should give a good idea what you need to do.
David Bass
99 Max IV 600T |
John Grikes (Engage1000)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 23, 2005 - 10:53 pm: |
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Thanks David.
That's interesting. I think I will put my "project" on hold for a while. I might start again this fall when I will have some more time.
Thanks for your help.
John |
P.J.
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 23, 2005 - 10:53 pm: |
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Back in 1976 I restored a General Electric electric lawn tractor. Battery power wasn't a bad idea for this application but for an aatv application it would be too slow and too far away when you run out of juice. You would also have to reduce the weight of the unit considerably to get ANY type of performance. |
Lee Henson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 23, 2005 - 10:53 pm: |
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Dear John,
Like the Idea, I started my design a few months ago. At first I was going to attempt to run everything using electric motors. After a lot of research I decided against all electric motors.
Recently I aquired a large Printing Company, and of all the items it came with there were 2 Crown sideshifter forklifts that I did not need. I have a engineer on hand at all time in case of a press faliure. But lately I have had him assisting me with my project.
I am designing my 6X6 using one electric motor powered by a series of battery cells resulting in 36 volts. The Electric motor will power the hydraulic and or hydrostatic system.
I wont give all the details as of yet but I will send you the information on how the first test run goes. We should be finished in 2 months.
Lee |
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