Watts |
Vehicle Type | -10 | -8 | -6 | -4 | -3 | -2 | -1 | 0 | 1 | 2 | 3 | 4 | 6 | 8 | 10 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0 |
Upright | 42.2 |
37.4 |
31.9 |
25.2 |
21.1 |
15.9 |
7.9 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
| Recumbent | 53.8 |
47.7 |
40.7 |
32.1 |
26.8 |
20.2 |
9.9 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
| Velomobile | 126.4 |
112.0 |
95.3 |
75.0 |
62.3 |
46.7 |
20.4 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
50 |
Upright | 42.6 |
38.0 |
32.6 |
26.3 |
22.6 |
18.3 |
13.3 |
7.9 |
4.5 |
2.9 |
2.2 |
1.7 |
1.2 |
0.9 |
0.8 |
| Recumbent | 54.2 |
48.2 |
41.4 |
33.2 |
26.3 |
22.7 |
15.8 |
8.5 |
4,5 |
2.9 |
2.2 |
1.7 |
1.2 |
0.9 |
0.8 |
|
| Velomobile | 126.8 |
112.5 |
96.1 |
76.1 |
64.0 |
49.1 |
29.3 |
9.4 |
4.5 |
2.9 |
2.2 |
1.7 |
1.2 |
0.9 |
0.8 |
|
100 |
Upright | 43.0 |
38.5 |
33.3 |
27.3 |
23.9 |
20.1 |
15.9 |
11.6 |
8.0 |
5.7 |
4.3 |
3.4 |
2.4 |
1.9 |
1.5 |
| Recumbent | 54.6 |
48.7 |
42.1 |
34.3 |
29.8 |
24.7 |
18.9 |
12.9 |
8.3 |
5.7 |
4.3 |
3.4 |
2.4 |
1.9 |
1.5 |
|
| Velomobile | 127.3 |
113.1 |
96.8 |
77.2 |
65.5 |
51.6 |
34.4 |
16.6 |
8.5 |
5.7 |
4.3 |
3.4 |
2.4 |
1.9 |
1.5 |
|
200 |
Upright | 43.8 |
39.5 |
34.6 |
29.1 |
26.1 |
22.9 |
19.4 |
16.0 |
12.7 |
10.0 |
8.0 |
6.6 |
4.8 |
3.7 |
3.0 |
| Recumbent | 55.4 |
49.7 |
43.4 |
36.1 |
32.1 |
27.7 |
23.0 |
18.2 |
13.8 |
10.5 |
8.2 |
6.6 |
4.8 |
3.7 |
3.0 |
|
| Velomobile | 128..1 |
114.1 |
98.1 |
79.3 |
68.3 |
55.7 |
41.2 |
26.3 |
16.0 |
10.8 |
8.2 |
6.6 |
4.8 |
3.7 |
3.0 |
|
300 |
Upright | 44.6 |
40.4 |
35.8 |
30.6 |
27.9 |
25.0 |
22.0 |
18.9 |
16.0 |
13.4 |
11.2 |
9.4 |
7.0 |
5.5 |
4.5 |
| Recumbent | 56.2 |
50.7 |
44.6 |
37.8 |
34.0 |
30.1 |
25.9 |
21.7 |
17.7 |
14.3 |
11.6 |
9.6 |
7.0 |
5.5 |
4.5 |
|
| Velomobile | 128.9 |
115.1 |
99.5 |
81.3 |
70.8 |
59.2 |
46.2 |
33.0 |
22.4 |
15.8 |
12.0 |
9.6 |
7.0 |
5.5 |
4.5 |
|
500 |
Upright | 46.0 |
42.1 |
37.8 |
33.2 |
30.8 |
28.3 |
25.7 |
23.2 |
20.7 |
18.3 |
16.1 |
14.1 |
11.1 |
8.9 |
7.4 |
| Recumbent | 57.6 |
52.4 |
46.8 |
40.6 |
37.2 |
33.8 |
30.3 |
26.7 |
23.3 |
20.0 |
17.2 |
14.8 |
11.2 |
8.9 |
7.4 |
|
| Velomobile | 130.4 |
117.0 |
102.0 |
84.8 |
75.2 |
64.9 |
53.8 |
42.5 |
32.4 |
24.7 |
19.3 |
15.7 |
11.3 |
8.9 |
7.4 |
|
750 |
Upright | 47.6 |
43.9 |
40.0 |
35.9 |
33.7 |
31.5 |
29.3 |
27.0 |
24.8 |
22.6 |
20.6 |
18.2 |
15.3 |
12.8 |
10.8 |
| Recumbent | 59.3 |
54.4 |
49.1 |
43.5 |
40.5 |
37.5 |
34.4 |
31.3 |
28.2 |
25.3 |
22.5 |
20.0 |
16.0 |
13.0 |
10.9 |
|
| Velomobile | 132.3 |
119.3 |
104.9 |
88.8 |
79.9 |
70.6 |
60.8 |
51.0 |
41.7 |
33.7 |
27.5 |
22.8 |
16.7 |
13.0 |
10.9 |
Dangerous Speed: |
Illegal Speed: |
Slow : |
Painfully Slow: |
|---|
Discussion:
An example of a practical upright ebike would be an Xtracycle with motor. A practical recumbent design would be similar, but with the rider in a more comfortable and aerodynamic position. A velomobile would be a streamlined recumbent. For comparative purposes the total weight of each vehicle+rider+cargo was assumed to be 300 pounds. The Kreuzotter Bicycle Speed and Power Calculator was used to generate the data.
If a minimally acceptable 'fun' speed is 10-20 mph, the average person, putting out about 50 watts, will only occasionally have their need for speed met, and then only while going downhill. Their brief pleasure will fail to compensate for the time and effort needed to get up hill in the first place, and the overall experience will likely not be much fun--arguably a major impediment to the widespread voluntary use of bicycles. A 50-watt electric-only vehicle would certainly be judged to have extremely poor performance. With power assist, even flabby non-athletes can leave their cars parked and enjoy cycling again (and get back in better shape), but matching available power to needed power is problematic. The ideal would be a motor that could provide 100-750 watts while still operating within its efficiency range. This may be possible by using two motors, or one multi-volt motor. For motor speed to match vehicle speed, gearing would be essential.
The importance of aero-braking to control downhill speed in upright bikes is not well recognized. Velomobiles, on the other hand, quickly transition from too slow to too fast, and extremely dangerous (truly terminal) velocities can be reached. While exceptionally robust brakes would be a must, regenerative braking, desirable in most electric vehicles, would be highly desirable, if not essential, in a fully streamlined ebike if only for braking purposes. Assuming no cargo is carried, total weight for an upright would be lightest, and a velomobile would be the heaviest vehicle. Without regenerative braking, a velomobile would be a poor choice for use in hill country--slow up, and too fast downhill. With regen, a velomobile, lacking significant aero-braking, would allow significantly more energy to be recovered.
Paved public roads are rarely over 6% slope, and highways of 7% slope are signed to warn trucks to use engine braking and often have turn outs for runaway trucks. Steeper roads and streets exist, but few will need to contend with them. As a practical matter, being able to maintain a 10 mph speed up a 6% slope would be a reasonable goal with low gears for the rare (in most areas) steeper slopes.
Related articles:
The Case for Power-Assisted HPVs
Ebike Design: How much power is enough?
Related links:
Comments?
Then you must be interested in ebike design. Join the Practical eBike Builders Association and post a message.