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RE: (ET) Chipper conversion, ET motor power evaluation
Pieter,
thanks for your thoughts. I may have to put a larger pulley on the
E15 motor to compensate for this phaenomena. With full field the
E15 motor would still turn at about 800 rpm if a braking force
of 25 ft-lb is applied according to the curves. If I assume we h
eave to have 1500 rpm to be useful (I guess the ICE was running 2000-2500
rpm) then with full fueld the E15 would still develop 15 ft-lb
which is about the same as the ICE. If the RPM of the chipper
wheel is not high enough I could always put a larger pulley on the
motor to comensate for the different torque characteristics. I have
to watch out though not to overspeed the chipper when there is no
load applied. Maybe I need to do more tests while the ICE is still
mounted with different load scenarios. Unfortunately with the bad
carburator its kinda tough to say if the motor is running at its
typical speed.
A question: What would happen if I applied more than 36V to the field,
then more than the rated 1.9A would flow though the field and make it
stronger. Would it also mean that the motor starts out with a smaller
max. rpm in no-load situation has less of an rpm cave-in under load -
i.e. the RPM curve would be more flattened. This might alleviate the
overspeed concerns in light-load situations.
Well back home we have a saying "to try it out is better than to study it",
so I think I'll just try it out and see how it works out .... back to work
Markus
> Another thing to consider in re-powering is the speed at
> which the engines
> develop maximum powr. Electric engine develop maximum torque
> at stall (0
> RPM). Gas engines don't - I suspect the chipper gas engine
> might develop
> maximum torque between 1500-2500 RPM (??). In any case, this
> difference
> will cause them to perform quite differently in an application like
> chipping even though the two power sources might have the same HP and
> torque ratings. A chipper developing maximum torque at 0 RPM
> isn't very
> useful.
>
> At 08:55 PM 9/29/2004, Markus Lorch wrote:
> >All,
> >
> >I know some of you have done this and I just
> >wanted to share my findings. I just "acquired"
> >an older, large chipper/shredder with an 8 HP
> >B&S combustion engine. A neighbor of my friend
> >wanted to toss it out but I couldn't stand by
> >and watch him do it. None of us had a way
> >to move it though and it was about 1 mile from
> >where my house is. So I strapped an emergency
> >car light (one of those that flash red, it was
> >already dark) to the back of my E20 and drove
> >through the neighborhood (the mower deck still
> >on, as I was too lazy to take it off) ... it was
> >great going down that 0.5 mile hill with
> >the cruise control on and full regenerative
> >breaking. I didn't dare to take it out of
> >gear (something I had done with larger
> >tractors when I was a foolish teenager)
> >but rather enjoyed the smooth ride on
> >asphalt.
> >Ok, long story, I got there hooked the
> >chipper up and drove it back. It was a nice
> >ride, even though driving on asphalt the
> >tractor feels much slower than in my bumpy yard.
> >The information i got with the chipper was
> >that it needs carburator work and was
> >missing an exhaust.
> >
> >Tonight I did fire the chipper up with the
> >combustion engine. Poured a bit of gas in
> >there (still got stinky fingers), fiddled with
> >the carb. and took the air filter off.
> >About 10 good pulls and it ran. Its flooding
> >the carb but with the gas valve almost closed
> >it sort of works. However it has no muffler
> >(other than an old pineapple can) and is really
> >loud. Its not spinning too high, i would guess
> >2000-3000 rpm. I wanted to do this test to see
> >how/if it worked in general and would chip
> >wood. I was happy with the results.
> >
> >Now I thought I buy an AC motor and have it
> >hooked up to the grid. Mike Wallace suggested
> >to look at an E15 drive motor or similar. So I
> >looked at the motor performance curves that Mike
> >has (posted on http://www.econogics.com/ev/etsites.htm)
> >
> >This is great information. I didn't expect the
> >E20 motor to deliver 35 lb-ft (at 400A!). And the
> >E15 motor goes up to 25 lb-ft. pretty cool.Even
> >the largest B&S engine (18HP) that jackssmallengines
> >has specs for doesn't go above 30 lb-ft. Now I
> >see how they could claim that the E20 has the torque
> >of a 20HP gas.
> >
> >I wanted to see if an E15 motor would do for the
> >chipper so I checked jackssmallengines for the
> >recommended B&S replacement ICE for the chipper
> >and they propose a 10.5 HP that delivers 16 lb-ft
> >peak at 2700 rpm. The E15 motor just about maxes
> >out at 2700 rpm with full field and would provide
> >its maximum torque of 25lb-ft. (and draw about
> >280 A under full load which is equivalent to
> >about 10kw or 14HP of input, prob. around 11HP output)
> >... so the point being the E15 motor could provide
> approximately twice
> >the torque than the 8HP engine the chipper has right now. I
> think thats
> >gonna be beefy!
> >
> >Well - I am pretty hyped about it so I just thought
> >I share it with y'all.
> >
> >Markus
> >
> >
> >
> >
> >----------------------------------------------------------------
> >Markus Lorch
> >Department of Computer Science Phone: +1 540 231 5914
> >Virginia Tech, m/c 106
> >http://www.econogics.com/ev/etsites.htm Fax: +1
> 540 231 6075
> >Blacksburg, VA 24061, U.S.A. http://people.cs.vt.edu/~mlorch
> >
> >
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