Youre right, bobcat. Maybe I need to go back and show my work. Here is Mike's specs from previous posts:
Motor: Etek Motor Voltage: 48V = max RPM 3500 (using posted info from electricmotorsport.com) Max Motor Amperage: 330 amps @ 1 min Continuous HP: 8 hp = 48V * 124.3 A / 746 (barring the efficiency of the motor, I think I had it written down as 6 hp = 48V * 93.25 A / 746 so taht is why the green line is lower.) Torque: 1.14 lb-in/amp (0.13 nm/amp) Gear Ratio: 1:4.2352941176 Rear Tire: 170/60 Bike Weight: 377 Mike Weight: 165 I used an excell spreadsheet to do most of the math so that it could be copied onto the graph. Doing the math for the y-axis was easy, I used the HP conversion and multiplied 48V to each amp value and divided by 746. Then multiplied taht by the gear ratio to get the HP @ gear. HP= 48V * Amps / 746 Torque was available from the listed specs so I found the values at each amp value again and multiplied by the gear ratio to find the Torque @ gear. [EMAIL PROTECTED] (1.14 * Amps) * Gear ratio The x-axis to find the max speed is probably where I messed up. I figured I would start with the RPM of the motor so I took that and divided it by the gear ratio to find the RPM @ wheel. [EMAIL PROTECTED] = [EMAIL PROTECTED] / gear ratio Then took 170 which I believe is the circumference and divided that into 63360 in/mi to find the revolutions per mile 372.70. Finally, I took the [EMAIL PROTECTED] and divided by revolutions per mile and converted the minutes to hours by multiplying by 60. In summary, MPH = ([EMAIL PROTECTED] / Gear Ratio) / (63360 in. / Circumference) * 60min per hr MPH = (3500 rpm / 4.24) / (63360 in. / 170 in.) * 60 min per hr MPH = (825.47 rpm) / (372.71 in.) * 60 min per hr MPH = 132 So double check my math and see if I messed up for setting the max speed per the gearing and motor rpm. --- Bob Martin wrote: > Right on! We're all working toward the same thing, > Electric Motorcycle > Excellence! When figuring drive wheel circumference > you can use the mark, > roll and measure technique or, I think Dia x Pi = > Cir ( that's off the top > of my pointy head) Double check me. Later, Bob > ----- Original Message ----- > From: "lyle sloan" > > To: "ElectricMotorcycles" > <[email protected]> > Sent: Tuesday, September 04, 2007 7:34 PM > Subject: Re: [ElectricMotorcycles] Zee science of EM > was (Throw another > Etekon the barbie) > > > > Repeating what I had said earlier in another post, > I > > find taht alot of the times I witness ppl using > the ev > > calculators but not "see"ing the math and how it > > interrelates. So I have been working on a couple > of > > graphs trying to illustrate the max performance > ranges > > or limits for the newbies. I wanted to keep it > simple > > enough by FOCUSING on single gear performance > range at > > a set voltage (and not delve into battery/voltage > > switching and/or transmissions, yet). As the > > following graph is intended to show, the max > amperage > > of the circuit will determine the max Torque at > the > > wheel at a set gear ratio. Also, the max voltage > of > > the circuit is the max RPM at the wheel at the set > > gear ratio. Then the cycle's and rider's weight > and > > all the other aspects are plotted for > > amps/torque/force needed to MAINTAINING each given > > speed. (Acceleration is intended to be a > different > > discussion and graph with times squared. not shown > nor > > ready for discussion at this time) > > > http://electricmotorcycles.net/uploads/wordpress/2007/09/4-to-1-gear-ratio-to-torque-to-mph.JPG > > > > So after Mike's post, I though it would be > interesting > > to throw in the ETEK heat performance as a sort of > > graduated color scale on top of the graph with my > best > > "guess"-timation for the ETEK. Which I say is the > > green zone from the continuous HP @ 93 amps to > stall > > and anything above that is a yellow and red zones. > > The yels and reds are gonna have to be found out > how > > long we can stay in each zone. I basically took > the > > guess taht 180 is the red zone. > > > http://electricmotorcycles.net/uploads/wordpress/2007/09/mikes-amp-torq-gear-to-mph-graph.JPG > > > > Unfortunately, when I tried calculating Mike's max > > speed range for the circumference, I came up with > a > > max speed of 132mph. But I am willing to bet that > the > > plotted/actual force to maintain speed is gonna be > > greater than the etek can sustain at Mike's given > > weight and gearing. (Or I messed up his > circumference) > > > > I would like the rest of the EM list to check my > math > > to see where I messed up (if I did) and if > possible > > the pro and cons of theses illustrations to be > used > > for the site. > > > > Thanks in advance. I am pretty sure the fur is > gonna > > fly, but I am willing to stand with my > illustrations > > unless of course I see a suitable counter argument > to > > refine a point or two. > > > > Lyle > > > > --- lyle sloan wrote: > > > >> Man, this parallels what I was thinking. Except > I > >> wanted to show it in a graph. I will post as > soon > >> as > >> I get mike's info > >> > >> ----Andrew Wowk wrote: > >> > Say you are pulling 200 amps with one etek > running > >> > at any voltage: > >> > > >> > 200 * .033 ohms (terminal resistance) = 6.6v * > 200 > >> = > >> > 1320 watts in heat that > >> > one etek must dissipate without frying. > >> > >> > >> > >> > >> > >> > >> > > > ____________________________________________________________________________________ > >> Luggage? GPS? Comic books? > >> Check out fitting gifts for grads at Yahoo! > Search > >> > > > http://search.yahoo.com/search?fr=oni_on_mail&p=graduation+gifts&cs=bz > >> > >> > > > > > > > > > > > > > ____________________________________________________________________________________ > > Looking for a deal? Find great prices on flights > and hotels with Yahoo! > > FareChase. > > http://farechase.yahoo.com/ > > > > > ____________________________________________________________________________________ Luggage? GPS? Comic books? Check out fitting gifts for grads at Yahoo! Search http://search.yahoo.com/search?fr=oni_on_mail&p=graduation+gifts&cs=bz
