Friday, May 23, 2008

clever dynamo circuit, light power assist

"My assist philosophy has been based on the concept of truly low power giving just enough assistance.

This allows for a lighter weight system such that when the assist is not in use it doesn’t detract from the overall efficiency of the vehicle/rider combination. This means the low assist weight requires very little additional energy from the rider when climbing or accelerating (a lightweight vehicle also helps).

My design goal was around 100 input watts to the motor and less than 10 pounds total system weight. It came in at 4.2 pounds, 1.9kg ! -- That’s every thing – motor/gearbox/freewheel/mounting bracket assembly, battery, electronic controls."

D: I priced the components at c. 1/2 of a full-power electric assist.
(D: their own website index was a dead end. Huh. Helluva way to run a business...)
D: prices vary from $1100-1800 for 250-500Watts.
Weight is 17-16lbs. That sounds funny, but the high-end system uses lithium-ion batteries.

D: a combustion motor is 'in the works' but is not yet on the market- the Revopower.
Powered by: 25cc two-stroke engine; 1 HP or 0.8 KW power maximum output at 7500rpm;
Power Train: The Wheel is driven by a series of sprockets & chains which drive the engine (and the wheel) around a fixed axle
Top Speed: 20 mph (32 kph) over flat terrain; normal bicycle brakes are sufficient to stop it
Fuel Used: Standard two-stroke fuel (a mixture of normal gasoline and oil)
Fuel Consumption: Over 100 miles per gallon
Weight: Less than 15 pounds (5 kg); 12 pounds net of additional weight once the original wheel is removed
Noise Levels: Less than 65 dB at a distance of 7.5 m; very quiet operation
Emissions: Extremely low; using the latest technology, it meets EPA and CARB regulations; The Wheel stops when you stop, eliminating idling and emissions caused by idling
Clutch Operation: Automatically engages when engine is running
Starting & Stopping: Single user interface of throttle and starter; User must pedal to start the motor; no idling possible

D: I contacted Revopower for additional technical information. They sent the usual generic canned info packet. I wonder if these companies realize how many sales they lose, doing that.
I-motion did the same, refusing to divulge the gear combos by gear for the I-motion 9.
I reciprocate their contempt for me.
For example, I'll be going with a NuVinci instead of a SRAM due to that.

Anyway, back to Mr. Tetz's idea.
D: I did a thought experiment for a solar-power assist. The Watts provided are marginal.
Solaris 26 Features
  • 12V output for charging laptops or running cameras and DVD players
  • Overall dimensions open: 21.5”x37.5”
  • Overall dimensions folded: 11"x8.5”x1”
  • Weight: 28 oz
  • Max output: 26 watts
D: Not cheap - a coupla would run c. 1000 bux!
I figured a Wisil Missile top fairing, with a 2x3' section fore and aft, with a gap being the 'windshield'.
This works better with my secure-clamshell idea (another day).

The idea of a12V setup is of benefit. This will never move you much without pedalling, but it can be recharged by a car battery, and from the solar appliance product listed above.

A 12volt motor could double as a serious generator, able to power motorbike LED lights.
Or, during the day, power a consumer appliance like a cellphone.

The solar setup could allow:
1) a capacitor/battery pack for brief high-power assist and ? an hour of partial assist.
2) park and secure it at work, with the solar power recharging.
3) come out after work to find the battery pack recharged.
Your bike solar could power camping electronics in the field.
I found the Powernet pseudo (high voltage) setup using D-cell sized ultracapacitors.

I'd like to stow the batteries in an oversized mountain bike tubing frame, but I hear overheating would need to be addressed.
D: reasonably cheap, though I hear they might have power leakage issues.
D: this author was also willing to correspond with me.
We both lamented that nobody seems willing to use just electronics v.s. computers for an auto gear shift changer. More on that tomorrow!

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