Human Electric Trike Thesis

Design of an electrically assisted human powered trike

Archive for the ‘Performance’ Category

Testing begins

Posted by Bob Dold on Sunday, November 19, 2006 8:58 PM

 Completed the first test runs under electric power today, the first test was about 2.6 miles and unearthed a coupled of mild problems:

Test 1:

1. Chain from motor fell off after about a mile, this was being caused by the mid drive cog assembly unthreading from its hub and pulling the chain out of alignment. I believe this is a result of the rear hub not freewheeling correctly and the rear swingarm twisting from the motor torque.

2. The right rear dropout twisted down 5 or 10 degrees, the torque from the motor and chain drive apparently loosened the bond of this tube causing it to twist down. I will fix this by restoring the tube to the correct orientation and backing up the bond joint with several rivets to keep the tube from twisting in the socket.

3. The right disc brake was rubbing and making a lot of noise, adjusting the caliper position should fix this problem.

I attempted to get a shunt resistor from Radio Shack to measure the current draw using my voltage logger, but they did not stock any with the required .01 ohm resistance and 9 watt capacity. I ordered several from eBay and should have them in a couple of days, in the meantime I will use the average and total current and power measurements from the Drain Brain.

Test 2:

After fixing the rear dropout and adjusting the brakes I ran a second test lasting 1.9 miles. I added Loctite thread locker to the mid drive freewheel thread in hope of keeping it from unthreading, it seemed to have work as I did not notice any signs of it loosening. The new, stronger lower a-arms have eliminated the flexing of the old parts, but there is still more body roll than I would like in the corners. The table below shows the results of these two tests:

The Peukert range attempts to calculate what the range would be by using the average current from the test and the Peukert exponents which are characteristics of the battery model. The Peukert exponent and capacity were obtained using Uve’s battery calculator and the battery’s reserve capacity and 20 hour rating from the Odyssey website. Using the overly simplistic Time= AH Rating/Amps doesn’t account for discharge rate, a more accurate formula is:

Time = Capacity Number/Current^Peukert exponent

Since the exponent is in the denominator, the smaller it is the less capacity it loses at HIGH, not low, amp draw. To get the range in miles rather than time, the formula is:

Range (miles) = Capacity Number/(Speed * Current^Peukert exponent)

The first two test runs were run up ad down my street which is as close to level as I could get without traveling too far, by going down and back the average grade should average to zero. The elevation and grade plot from the Garmin GPS logger of the second test run is shown below:

Advertisements

Posted in Performance | 1 Comment »

Cleverchimp: Stokemonkey: Overview

Posted by Bob Dold on Wednesday, September 27, 2006 12:07 PM

Cleverchimp: Stokemonkey: Overview

Posted in Performance | Leave a Comment »

Gearing calculations

Posted by Bob Dold on Monday, September 25, 2006 11:50 PM

A spreadsheet was constructed to calculate the optimum gearing for the trike, by using a 14 tooth sprocket on the scooter gearbox and a 34 tooth cog on a mid drive, the motor can be geared down enough to allow the motor to make it up a 10% grade.

The picture below illustrates the chain drive layout:

Posted in Design, Performance | Leave a Comment »

Stealth 1000 performance

Posted by Bob Dold on Sunday, September 24, 2006 10:21 PM

Assembled the Stealth 1000 and took it on a test ride today to get an idea of the performance. After charging the batteries I was able to get a little over 4.1 miles of range on the first charge, this ride included going up several steep hills which cut down on the range. Top speed was about 18 MPH on level ground, one problem that popped up is that the motor controller shut down whenever the scooter went over 20 MPH, to reset it, the power had to be cycled on and off after coming to a stop. Schwinn Stealth 1000 Electric ScooterThis was probably due to the lack of a freewheel on the motor, this won’t be a problem on the trike instalation because there will be a freewheel to allow the trike to coast without backdriving the motor. Another issue was the scooter couldn’t make it up anything steeper than a 5% grade without the controller shutting off after the scooter slowed to about 5 MPH. The motor was not hot, so I assuming this was due to a current limiter in the controller. One work around for this may be to get a controller with an adjustable current limit so a higher shutoff can be set. On the trike the gearing will help reduce the torque required so the current draw shouldn’t be as severe as the scooter which has a fixed gear ratio. Best battery life seemed to be at about 12.5 MPH

Motor information from nameplate:

36 VDC, 78% Efficiency

Rated Speed: 3600 RPM, 32A, 1000W

Model: XYD-18A

Posted in Performance | 3 Comments »

Current Cycle Bikes – Crystalyte Phoenix Hubmotor

Posted by Bob Dold on Thursday, September 14, 2006 1:37 PM

Link to hi-power hub motor bike:

Current Cycle Bikes/info@currentcyclebikes.com

Posted in Electronics, Performance | 1 Comment »

Visited Runabout Cycles

Posted by Bob Dold on Monday, June 19, 2006 8:19 PM

Today I made a visit to Runabout Cycles in Florence MA (Northampton) and spoke with Josh Kerson , the founder of the electric trike company. Josh mentioned he has been working on the human electric hybrid idea for about 5 years, has made several prototypes, and is currently in limited production of their  electrically assisted trike.

Production Runabout cycle:

Josh had two assembled trikes on hand, the prototype fully suspended unit that weighed in around 250#, and the new production model that weighed about half of the prototype. The production unit did away with the rear suspension to save weight and used  a 7 pound PMG 080 motor instead of the 25 pound eTek motor on the prototype. The production unit also looked to have smaller tubing that the ultra beefy prototype unit. I took a quick ride in the orange production unit in the parking lot and was very impressed with the smooth steering and quiet electric drive system. The unit I rode had a 19:1 gear reduction through a 2 stage chain reduction drive system with a freewheel to allow coasting and pedaling when the electric power is not used. Josh mentioned the gear reduction was necessary to get the high efficiency out of the PMG 080 motor, the prototype unit used a single stage gear reduction with the slower, more powerful, eTek motor.

Prototype Runabout cycle:

Josh indicated he designed the steering linkage to allow more precise control at higher speeds by increasing the steering handle throw in relation to the wheel movement. Compared to my Sun EZ-TAD’s rather twitchy steering, the Runabout cycle’s design was much easier to control at speed. The stock production unit is designed to top out at 20 MPH to comply with federal law for assisted bikes, although Josh mentioned the motor is capable of more. The design goal was to have enough power to cruise up hills at 20 MPH, something that can bring a lot of electric bikes to a halt. The prototype unit Josh was riding had been ridden all the way to the top of Mt. Washington, demonstrating the hill climbing capabilities of the trike.

Josh was very helpful in explaining the current market for human electric hybrids – because of their electric motors they are a little too complicated for a bike dealer to sell and service, eliminating a possible retail outlet for the bikes. Because of the pedals and electric drive they are not a natural sell for a motorcycle or automotive dealer. The best outlet for the trikes appear to be a network of electric bike dealers that currently stand at about 50 strong nationwide.  Josh mentioned he was hoping to market the Runabout cycle with a few of these retailers who will already have some experience dealing with the electric drive train. He mentioned that most commercial eBikes and conversion kits were designed for light flatland use – top speeds of about 15 MPH and max motor power of about 750 watts.

The standard runabout cycle comes with two 30 amp-hour 12V  lead acid batteries, which are good for about  40 miles range and 500 discharge cycles. The cycle comes with a "Drain Brain" which tracks the electrical usage, speed, miles traveled, and acts as sort of a ‘gas’ gauge for the batteries. Runabout is also a distributor for lithium -ion batteries which give the same capacity at half the weight and are good for 1700 cycles. Lithium-ion batteries give a relatively constant output until they are drained – unlike lead acid which slowly reduce output as they discharge. The cycle can be upgraded to lithium-ion for about $1000 more than the base cycle’s $4700 price. In addition to the trikes, Runabout also does custom electric conversions for bikes, Josh showed a couple of conversions using powered cranks with e PMG motor and lithium-ion batteries.

Recumbent conversion:

Josh spent about an hour discussing the trike and his company and was very helpful in answering questions and providing lots of detail on his trikes and the thought that went into them. He offered to answer any questions I might have in the future and even offered to have me take a longer test ride when I get a chance.

Posted in Performance, Trikes | Leave a Comment »

Initial performance calculations

Posted by Bob Dold on Wednesday, June 7, 2006 9:53 PM

Completed initial performance spreadsheet, results are listed below. Assumptions are as follows:

  • 26" rear wheel
  • rolling resistance coefficient  = .01
  • Cd = .3
  • frontal area = 9ft^2
  • net weight = 385# (250# rider)

These are initial assumptions and will need to be verified as the design develops. Using these assumptions, the best gear ratio to satisfy the 10% grade requirement was 19.1. This value would give a top speed on level ground of about 25 MPH. The limiting factors are the 10 minute current rating of the motor of 115 amps, and the motor torque vs. required torque.

The gear ratio is higher than I was anticipating so the next step will be to design a gear train to produce a 19.1:1 reduction –  the initial design goal of 20 MPH up a 10% grade looks feasible, but the level cruise top speed is limited to 25 MPH rather than the desired 30 MPH because of the gearing. Optimizing the aero and drag might allow the top speed to be increased.

Performance Spreadsheet Results:

Gear Ratio 19.1

Speed (MPH)

Grade (%)

Tire rolling resistance (Cr)

Total rolling force (lbs)

Still air drag force (lbs)

Relative wind factor (Cw)

Relative wind drag force (lbs)

Incline force (lbs)

Rolling drag force (lbs)

Total drag force (lbs)

Motor Torque Reqd  (ft-lbs)

Motor RPM

Max Motor Torque (ft-lbs)

Current Draw (amps)

5

0

0.011

5.19

0.17

2.74

0.47

0.00

5.19

5.84

0.32

1278

9.84

21.0

10

0

0.011

5.38

0.69

0.82

0.57

0.00

5.38

6.64

0.36

2555

7.59

22.8

15

0

0.012

5.57

1.55

0.42

0.66

0.00

5.57

7.79

0.43

3833

5.35

25.4

20

0

0.012

5.77

2.76

0.27

0.75

0.00

5.77

9.28

0.51

5110

3.10

28.7

25

0

0.013

5.96

4.32

0.20

0.84

0.00

5.96

11.12

0.61

6388

0.86

32.9

30

0

0.013

6.15

6.21

0.15

0.93

0.00

6.15

13.30

0.73

7666

0.00

37.8

35

0

0.014

6.34

8.46

0.12

1.03

0.00

6.34

15.83

0.87

8943

0.00

43.5

40

0

0.014

6.54

11.05

0.10

1.12

0.00

6.54

18.70

1.03

10221

0.00

50.0

45

0

0.015

6.73

13.98

0.09

1.21

0.00

6.73

21.92

1.20

11498

0.00

57.3

50

0

0.015

6.92

17.26

0.08

1.30

0.00

6.92

25.49

1.40

12776

0.00

65.3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

10

0.011

5.19

0.17

2.74

0.47

38.26

5.16

44.07

2.42

1278

9.84

107.2

10

10

0.011

5.38

0.69

0.82

0.57

38.26

5.36

44.87

2.46

2555

7.59

109.0

15

10

0.012

5.57

1.55

0.42

0.66

38.26

5.55

46.02

2.52

3833

5.35

111.6

20

10

0.012

5.77

2.76

0.27

0.75

38.26

5.74

47.51

2.60

5110

3.10

115.0

25

10

0.013

5.96

4.32

0.20

0.84

38.26

5.93

49.34

2.70

6388

0.00

119.1

30

10

0.013

6.15

6.21

0.15

0.93

38.26

6.12

51.53

2.82

7666

0.00

124.0

35

10

0.014

6.34

8.46

0.12

1.03

38.26

6.31

54.05

2.96

8943

0.00

129.7

40

10

0.014

6.54

11.05

0.10

1.12

38.26

6.50

56.93

3.12

10221

0.00

136.2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

20

0.011

5.19

0.17

2.74

0.47

75.40

5.09

81.14

4.45

1278

9.84

190.8

10

20

0.011

5.38

0.69

0.82

0.57

75.40

5.28

81.94

4.49

2555

7.59

192.7

15

20

0.012

5.57

1.55

0.42

0.66

75.40

5.47

83.08

4.55

3833

5.35

195.2

20

20

0.012

5.77

2.76

0.27

0.75

75.40

5.66

84.57

4.64

5110

0.00

198.6

25

20

0.013

5.96

4.32

0.20

0.84

75.40

5.84

86.40

4.74

6388

0.00

202.7

30

20

0.013

6.15

6.21

0.15

0.93

75.40

6.03

88.58

4.86

7666

0.00

207.6

35

20

0.014

6.34

8.46

0.12

1.03

75.40

6.22

91.11

4.99

8943

0.00

213.3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

25

0.011

5.19

0.17

2.74

0.47

93.25

5.04

98.93

5.42

1278

9.84

231.0

10

25

0.011

5.38

0.69

0.82

0.57

93.25

5.22

99.73

5.47

2555

7.59

232.8

15

25

0.012

5.57

1.55

0.42

0.66

93.25

5.41

100.87

5.53

3833

0.00

235.4

20

25

0.012

5.77

2.76

0.27

0.75

93.25

5.60

102.36

5.61

5110

0.00

238.7

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5

30

0.011

5.19

0.17

2.74

0.47

110.48

4.97

116.10

6.36

1278

9.84

269.7

Motor Torque Curve:

Posted in Electronics, Performance, Theory | 3 Comments »

City-el

Posted by Bob Dold on Saturday, June 3, 2006 9:55 PM

Overview:

Number of seats

1+1

Maximum speed

50

km/h

32

mph
Range

30-50

km

19-32

miles
Price approx..

12

TDM

9000

dollars

Technical details:

Road performances and consumption:

Consumption

4-10

kWh/100 km
Max. climbing performance

16

%

Battery:

Number of batteries

3

Piece
Total voltage

36

V
Capacity [ ah ]

90/100

Ah C5
Battery manufacturer 90Ah

Yuasa

Trojan 30XHS AP
Battery manufacturer 100Ah

Versch.

Motor:

Rated output

2,5

KW S2 3.35 hp
Maximum performance

3,5

KW 4.69 hp
Rated voltage

36

V
Rated current

90

A
Max. torque approx..

70

Nm

 51

Ft-lbs
Type

GS/Comp

Manufacturer

Thrige titan

Type

TTL 140B

Cooling

Air

Motor control:

Type

Pulse Width

Modulation
Rated voltage

36

V
Rated current

275

A
Working frequency

15

KHz
Manufacturer

Curtis

Type

1204X

Power transmission:

Number of transmission steps

1

Speed ratio approx..

7,2:1

Transfer

Poly V belt

Battery charger

Type
Rated output W
Charging time to 75 %

3

Std
Charging time to 100 %

8-9

Std

Mass and weights:

Length

2741

mm

9

Ft
Width

1060

mm

42

in
Height (hood closed)

1260

mm

49.61

in
Height (hood open)

2380

mm

94

in
Wheel base

1810

mm

71

in
Track width

930

mm

36.61

in
Turning circle

8550

mm

28

ft
Ground Clearance

120

mm

4.72

inches
Unloaded weight

290

Kg

640

lbs
Additional load

110

Kg

242

lbs
Admissible total weight

400

Kg

882

lbs

Tire:

Type

80/70 -16

Manufacturer

Continental

Brakes:

Type

3

Drum
Operation

Hydraulically

Brake circuits

2

in front/in the back

Heating:

Type

Electrical

Amount of heat

400+400

W
Blower

2

Levels

Configuration:

  • Heater/Defroster
  • Glass sliding roof
  • Two outside mirrors
  • H4 55/60W main headlight
  • Windshield wiper and washer

Safety configuration:

  • Three point inertia reel belt
  • Roll bar
  • Laminated glass windshield
  • Safety glass side windows
  • Energy absorbing body

Options:

  • Radio console
  • Loudspeaker installation console for roll bars
  • Lap belt for protecting a child seat
  • H-belt for child of 3-9 years + backrest for child
  • Ashtray (Pfui!)
  • Battery heating
  • Soil mat

Body:

Plastic sandwich structure self-supporting

PURELY foam with PMMA+ABS bowl

City-El Driving resistances


Marco Reichel, a fellow " el " driver, has worked out a program for driving resistances, here the results.

Input data:

Mass 400 kg
Rolling friction number: 0,01
Air resistance number: 0,3
Frontal Area: 1 m²
Wheel diameter: 0,52 m

Required power at the wheel in Watts as a function of speed with different gradients

km/h

Ebene

5 %

10%

15%

20%

10

113

658

1203

1748

2293

20

248

1338

2428

3518

4608

30

428

2063

3698

5333

6968

40

675

2855

5035

7215

9395

50

1013

3738

6463

9188

11913

60

1462

4732

8002

11272

14542

70

2046

5861

9676

13491

17306

Posted in Performance, Trikes | Leave a Comment »