This is me with my motorcycle on the third floor of the Engineering building at USU on the day of the presentation. I won Best Senior Design Project from USU so that was pretty awesome! The head of the design program actually asked if I wanted to donate the motorcycle to the University and come back as a senior project adviser to coach students on an electric build each year so that was pretty cool, but like I would ever donate my baby especially after I just barely got the thing running!
Driving it on campus, through the building and on to an elevator was almost as much fun as building it in the first place. The look on peoples faces is quite priceless when the elevator dings and you drive a motorcycle out of it into a group of studying students.
December in Logan Utah is not the ideal time to ride a motorcycle but unfortunately I had no other choice but the freeze to the bone. Luckily I was able to get a few clear days where there was no snow on the streets.
The 1st test drive went really well I did not go very far at all, I did not know what to expect and get stuck and have to push it home. I pretty much stayed within a mile or less of the house and just kept making circles.
First Ride Results | |
Amp-hour | 5.77 |
Distance | 10.08 |
Watt-hours | 412.72 |
Watt-hours/mile | 39.6 |
Max speed (MPH) | 47 |
Avg. Speed (MPH) | 16.7 |
Total Amp-hours | 7 |
Total miles | 11 |
Cycles | 0 |
The 2nd test ride a doubled the distance with no problem.
Second Ride Results | |
Amp-hour | 5.657 |
Distance | 21.72 |
Watt-hours | 393.33 |
Watt-hours/mile | 18.3 |
Max speed (MPH) | 46.8 |
Avg. Speed (MPH) | 23.3 |
Total Amp-hours | 13 |
Total miles | 32 |
Cycles | 1 |
The 3rd test drive I pushed it to the limits to see how far I could go and ended up with almost 35 miles! Although the power dropped off dramatically at the end I barely made it home at about 10-15 MPH. With the batteries at their lowest after the 3rd test ride it took about 3 1/2 hours to fully charge them again so that's not bad at all.
Third Ride Results | |
Amp-hour | 8.662 |
Distance | 34.49 |
Watt-hours | 597.59 |
Watt-hours/mile | 17.3 |
Max speed (MPH) | 42.8 |
Avg. Speed (MPH) | 22 |
Total Amp-hours | 21 |
Total miles | 67 |
Cycles | 2 |
The fourth test ride I swapped out the gear on my motor to get a better ratio for speed and I was able to get a top speed of 54 MPH which I was quite pleased with since I set out with a goal of getting a 35 mile distance and a top speed of 50 MPH. I'm sure if I could loose all the fat of the AGM batteries I could do a lot better.
Fourth Ride Results | |
Amp-hour | 4.045 |
Distance (miles) | 10.94 |
Watt-hours | 280.15 |
Watt-hours/mile | 25.6 |
Max speed (MPH) | 54.4 |
Avg. Speed (MPH) | 26.3 |
Total Amp-hours | 29 |
Total miles | 78 |
Cycles | 3 |
For the number crunchers, these are some of the data points and formulas that I used to see if I would be close to my range and speed goals.
Approx values for 72 Volts | |
Max RPM approx | 3528 |
Max torque approx | 250 in-lbs at 3028 RPM |
Torque ft-lbs | 20.833 |
Max RPM - min RPM | 3528 - 3028 = 500 |
RPM/torque | 500/20.833 |
Formulas | ||||
Motor Torque (Ft-LB) = Amps * (Amps/Torque ratio)/ 12 = Amps * 1.75/12 | ||||
Motor RPM = peak RPM- (min RPM/(RPM/torque curve) * motor torque 3528- 500 /20.833 * motor torque | ||||
Wheel Torque = Motor Torque * Rear teeth/Front teeth | ||||
Force Required = Cr * Wt + Cd * A * V^2 /391 | ||||
Required torque = force required * wheel Radius | ||||
ft/rev = pi * wheel O.D./12 | ||||
Rev/mile = 5280 feet/mile / (3.14 * 25-inch wheel diameter / 12 inches/ft) | ||||
Speed (mph) = 60 * Motor RPM * (# front teeth / # of back teeth) / (rev/mile) | ||||
Constants | ||
Cr rolling resistance factor | 0.015 | |
Wt weight in lbs (motorcycle and rider) | 617 | |
Cd coefficient of drag | 0.6 | |
Area in square feet | 4 | |
Gear Ratios | ||||
Rear Sprocket | 71 | 71 | 71 | 71 |
Front Sprocket | 16 | 15 | 14 | 13 |
Ratio | 4.44:1 | 4.73:1 | 5.07:1 | 5.46:1 |
Table for 15 tooth sprocket.
Motor Current (Amps) | Motor Torque (Ft LBS) | Motor Speed (RPM) | Vehicle Speed (MPH) | Force Required | Wheel Torque Avail (Ft-LBS) | Required Torque Reqd (Ft-LBS) |
25 | 3.65 | 3440.50 | 50.79 | 15.86 | 17.26 | 15.53 |
50 | 7.29 | 3353.00 | 49.50 | 15.06 | 34.51 | 14.75 |
75 | 10.94 | 3265.50 | 48.21 | 14.29 | 51.77 | 13.99 |
100 | 14.58 | 3177.99 | 46.92 | 13.53 | 69.03 | 13.25 |
125 | 18.23 | 3090.49 | 45.62 | 12.80 | 86.28 | 12.53 |
150 | 21.88 | 3002.99 | 44.33 | 12.09 | 103.54 | 11.84 |
175 | 25.52 | 2915.49 | 43.04 | 11.39 | 120.80 | 11.16 |
200 | 29.17 | 2827.99 | 41.75 | 10.72 | 138.06 | 10.50 |
225 | 32.81 | 2740.49 | 40.46 | 10.07 | 155.31 | 9.86 |
250 | 36.46 | 2652.99 | 39.17 | 9.44 | 172.57 | 9.24 |
275 | 40.10 | 2565.48 | 37.87 | 8.83 | 189.83 | 8.64 |
300 | 43.75 | 2477.98 | 36.58 | 8.24 | 207.08 | 8.07 |
Driving Range | |
volts * Amp-hours / 1000 = 72-volts * 55 Amp-hours / 1000 = | 3.96 kilowatt-hours |
Best range @ steady 30 MPH = kilowatt-hours * 9.8 = | 38.81 miles |
Stop-and-go range = kilowatt-hours * 7.0 = | 27.72 miles |
**Based on flat terrain and 500 lbs | |
Speed MPH | |
3528 RPM | |
Sprocket teeth | |
13 | 44.01898 |
14 | 47.40506 |
15 | 50.79113 |
16 | 54.17721 |
Another one of my main goals was to maintain the same look of the original motorcycle so you wouldn't know that it was an electric just seeing it at a glance. Here is a side by side of the original and the finished project.
The only problem that I have had with the motorcycle, is I have a hard time keeping enough tension on the chain. With the large back sprocket and the small front one, the chain gets quite loose and I think I loose a lot of my power with it not being as tight as it normally would on a motorcycle. Even with the tire adjusted all the way out the chain is still loose. I've tried to take a link out but 1 link would be too much, I would need to take out a half a link and I think that would be perfect. I've seem a couple of spring loaded chain tensioners, but I no longer have my welder to install it for me.
Looking back there is not a whole lot that I would have done different. If I could have afforded the lithium batteries I would have went that route, but I think that is just about everyone's main hiccup with an electric build is getting the batteries you can afford and not the batteries that you want.
