Friday, October 29, 2010

Motor-pedal hybrid design






http://ledreview.info/2013/printers-terratrike-velomobile-skinning-is-completed/
http://bicycledesign.net/2015/02/a-collection-of-velomobile-links-part-1/








How to power a heavy Velomobile or Cycle-truck.


Velomobiles can get a get an efficiency of 40 miles to 85 miles per kilo watt hour of electricity. While it is easy to build a Vehicle light enough to get the really high mileage number at a slow speed on flat land, try thinking about how to power one that will hold two adults and 80lbs of cargo. Or a cycle-truck that will not be heavier than 600lbs (total combined weight) that will be driven up a 9% grade. We have worse hills but they are avoidable. If you think that is bad do the numbers on the new electric cars! 3.7 per kWh is high mileage.



I think the main reason that there is not much knowledge about this kind of vehicle is no one knows how to build one.



Most people build only for speed, unfortunately if your in a wreck and you get blamed for it the cops have to send your vehicle to be checked out by a technician, to make sure it cannot be driven faster than the speed limit for this kind of vehicle. So your best bet is to have it registered as a moped, or a motor-cycle. Using only one motor you could gear the motor down to the 30 mph limit, if it is still powerful enough to climb your steepest hills.



The motor I chose  can be spun up to something like 4500 rpm. Most hills with a really steep hump are not as steep for most of the hill. So you don't really need to be very close with the gear reduction, but it should help. Electric motors have a much wider range than internal combustion, but you still may want two speed ranges for efficiency.



The only way to have two speeds on a vehicle with out a gear box is to use two separate motors (unless there is something in the new AC motors and controllers). A hub motor for the high speed high mileage gear (set at a high voltage), and a heavy duty permanent magnet motor for the hill climbing gear (set at a low voltage). This should have as big a gear reduction as possible to help with the high torque climbing of a 9% grade. Try to calculate a gear reduction that is under the speed limit.


You do not want not to add speed to a 600lb vehicle. One of these motors can pop a bicycle drive chain easily. You will need a “Cycle Annalist” to help control the vehicle. And a controller that will read the Cycle Annalist. And at 600lbs with a speed of 30 mph, you will probably need hydraulic disc brakes. And I do not mean the small kind made for simple bicycles.


I calculated the power it would take to climb some our steep hills. There are other calculators on the internet, but they use metric. http://www.kreuzotter.de/english/espeed.htm

1600 watts to move 400 lbs up a 9% grade at 19mph2500 watts for 600lbs on that 9% grade at 20mph2500 watts at 48 volts will turn the motor much slower (1250 RPM) than 24 or 36 volts (2500 RPM)


Unfortunately this motor has a lot more torque on the 24 volt setting at 2500 watts. 110lb/in as apposed to 50lb/in for the 48 volt. And 70lb/in for 2500 watts at 36 volt setting? So for a heavy vehicle and steep hills it should be run at a low voltage setting. 

{quotes from endless sphere forum}
Efficiency pretty much doesn't change down to 80% max speed, may fall off some at 60% max, and may for certain motors fall off up to 10% at 30% max speed. That means if the bike can go 25 mph it may at most take a 10% efficiency hit if ridden at 7.5 mph (without pedaling). It also means that if the bike can go 40mph, it will take about a 5% efficiency hit if ridden at 20 mph.  36V 20A at 10 kph. Efficiency about 42%. Switch to 11V custom battery. Now at 10 kph, efficiency is about 72%.

Lower voltage systems are safer, have easier BMS requirements (less channels), less complexity, more compatibility (with DC converters and other components), and easier on electrical components

http://www.cloudelectric.com/product-p/mo-me0909.htm



 This motor has a lot more torque when run on 24 volts at 2500 watts. 110lb/in as apposed to 50lb/in for the 48 volt. And 70lb/in for 2500 watts at 36 volt setting? So for a heavy vehicle and steep hills it should be run at a low voltage setting.



This machine does not have pedals because it is better to classify these as motor cycles and use motor cycle brakes.
http://www.thecartimes.com/plug-in-electric-tricycle-piet-plugs-away-green-comfort/


http://wildnaturesolutions.com/


































 First stage gear reduction:






















Motor-pedal hybrid design

If you live with steep hills and want to drive a more than the usual bicycle-weight up them, you really need to put some thought into how to motorize the machine. Some people think that all e bikes do not last long, because most of them are designed for light weight duty on virtually flat land.

Hub motors are the most efficient, but not for this scenario. Climbing hills at legal speeds up steep hills with only one gear, is hard on a motor and controller. Even if electric motors do have a much wider range of ability than gasoline motors.

So most people build for momentum, that takes calculation. Or just a reasonably low gear on the drive wheel, and possibly a larger than legal motor.

The federal government says that one horsepower should be the legal limit, but in the state of Washington 1.2 hp is OK. Most people I know, chant the phrase “the cops don't care”. But when I asked the cops in Seattle they told me how they do care, and how they deal with it.



In Europe the cops are allowed to have road blocks and do any thing they want to keep the people from using a motor bigger than one-third horse power. That is almost impossible to drive even one person, with out cargo, up a steep hill.

It is possible to use more than one motor, see the white trike car above with two or three hub motors.

Geared hub motors are available in 5-1 gear reductions or less. When I calculated for a 30 mile range velomobile, I had to use a 6-1 gear reduction because lead acid batteries are very heavy. Better to use lithium. The price works out to be a little less than lead acid over the life of the battery.


geared hub motor

If it is true that electric motors must spin near peak efficiency RPM to get full horse power and that you need a very large gear reduction to allow the motor to spin that fast and still keep the vehicle down to a legal speed. Then most e-bikes are illegal.

For high torque at low speeds you'll need a motor and controller that can allow high amperage at slow hill climbing speed. If you get a programmable controller you can limit the power to legal levels.


Peak efficiency
Series wound motors have a peak efficiency rpm, when powered past that rpm the efficiency goes down sharply and they start stressing out [A brushed series wound motor becomes extremely hot with as little as 10% over gearing, or should I say “over powering"]. With a single gear configuration it is easy to know what the motor’s RPM is by the speed, if you know what that peak efficiency speed is. An ammeter with a volt meter is a good replacement for a tachometer in an electric drive train.



http://www.cloudelectric.com/product-p/mo-me0909.htm


http://www.cloudelectric.com/product-p/mo-me0708.htm


Bicycle drive chains are not strong enough for a heavy machine like these velocipedes I tore two bicycle chains with just my unassisted legs on my mountain bike last year. So motor cycle chains or automotive belts are best unless you can keep from accelerating hard enough to destroy the a bicycle chain.

The best reason not to use the bicycle gears with a motor for heavy utility machines, is that the motor can not give you much power at the gear reduction and speed you must have for cranking speeds. And if you use a large enough motor it will over power your drive chain, unless it is a very heavy duty old style chain (like a BMX chain possibly). And a heavy duty one-to-three speed rear gear hub. Even then try not to do any hard starting, like drag racing.


Hub motors cannot use 12 volts because the thickness of the wire needed for the higher current will not fit through the axle; that means you will not get as much power at a low speed simply because the controller lowers the voltage to move the motor slower.

Most electric motors can’t be run on 12 volts because the winding wires can’t handle the
increased amperage of the lower voltage. And large motors are heavy because of the thicker wires.

That's why most people don't even think about using such heavy duty motors.

Geared hub motors use three large planetary gears that waste enough energy to make a single gear reduction worth the extra thought.

Brushless motors do not over heat as easily as series wound brushed motors and they have a wider range of peak efficiency, ie: a wider range of speed variance under stress. And they are approximately 5% more efficient.

Gearless brushless hub motors were developed for light weight solar powered vehicles that do not have the limitation of speed limits, or excessive weight.

I just wish I could find a chart telling exactly what they can do in terms of weight, gradient, and speed. If you need more advice, ask the people at the “endless-sphere” forum and do not tell them that I sent you. They do not like me, I asked too many questions and had a hard time understanding the answers.



The ‘Cycle Analyst’ maybe able to control the speed with out eliminating the slow speed amps. But there may still be a chance you could burn out your power system if you run too many amps through it at too low of a speed. A heat sensor could be good.                          





http://www.ebikes.ca/drainbrain.shtml








If 3 to 7 years life span is long for a big hub motor, then forget them.
(For Life expectancy, hub motors could work 5000 hrs without damage in Lab.
In real life it depends on the motor's usage (e.g. hitting bumps and water getting in).

You can make a good heavy-duty motor like the brushed Mars 909 last twenty years if you do not over power them with a cheap controller.



For some reason most people do not understand that all electric motors do not produce the horse power on the label until they get close to the R.P.M. stated on the label. And if you chain your e-bike to a wall and turn up the wattage that much you will fry your motor. That is what climbing a steep hill in too high a gear with too much weight is like.


How to calculate a fixed gear

 First measure the average grade of your worst hill. Use a carpenter level and a metric or 'tenths of inch' ruler.
And divide the span by the rise to get the percent of grade.

Decide what the total combined weight of your machine will be. Include every thing!
Then use this calculator to find how much energy it takes to climb your worst hill, as a 'streamlined trike'.

Find a gear ratio that will bring the drive wheel RPM down close to the legal speed limit (or what ever you can live with) when at the wattage you need to climb the nasty hills. See graphs provided by manufacturer. (this motor should have enough torque for any hill)
Decide what you think maybe a good sized pulley for the motor, you may have to rethink the size later. Divide the diameter into the size of a larger pulley on the drive wheel.

I need 745 watts to move 350lbs up an 8% grade at 11.5 mph, I had to calculate what speed I could get from the pulleys first. And then use the “streamlined trike” setting (because it does not work for any of the bicycles) to get the speed that the wattage will produce on this calculator. So I would choose a 1 HP motor, with as much torque as possible; do not use those wimpy motors with quarter inch diameter spindles

ie: 3”/14”= 1:4.666666 ratio; 745 Motor RPM / by ratio (4.666666) = 159.64285 drive tire rp

ie: 2”/ 17.75”= 1:8.875 ratio; 2500rpm / 8.875= 281.69014 rpm

ie: 2”/12”= 6; 2500/6= 416.66666 rpm

Then use this formula to calculate a gear you can use to match the speed.

Tire diameter x 3.14 = inches of circumference x Drive tire rpm = inches per foot /12= feet per minute x 60 minutes = feet per hour /5280 ft per mile = mph.


Example of formula:

[on my small cycle-truck]
24” tire x 3.14 = 75.36” circumference x 159.64287 tire rpm= 12030.686”/12 = 1002.5571 ft per minute x 60 =
60153.426 ft per hour /5280 = 11.39 mph. If I used 1200 Watts with the same 350lbs and same gears (ratio of
1:4.66666) I would get 18.35 mph very close to the 18.2 mph that the calculator says it would be, close enough.

[Large cycle truck 600lbs] 
26” tire and 2” pulley (1:8.875 ratio) it would be about 21.77 mph (just a little over the speed limit for a pedal-powered vehicle) All these calculations are estimates

[Velomobile 600lbs]
20” tire with a 12” rim pulley on the wheel and 2 pulley on the motor (1:6 ratio) on the drive wheel would give you 24.7 mph. Or with a 1.5” pulley (with a ratio of 1:8) it would be about 18.58 mph. [for a Velomobile]


RIMS TO CHOOSE FROM:
Depending on the thickness of the belt you may have to subtract up to an inch of the diameter to get a closer estimate.
ie: a half inch thick belt may not need any adjustments. All this math just to estimate what I would need. Yeesh!

26” 559mm / 24” 508mm / 20” small tires 451mm (17.75” diameter pulley)/ 20” tire 406mm (16”diameter pulley)/ 18” tire 355mm (14” diameter pulley)/ 16” tire 305mm(12” diameter pulley) /






















 Look for a 

"One-Way Locking Ratcheting Bearing" 

to make a ratcheting pulley.


"One-Way Locking Ratcheting Bearing" 



Trapezoidal or square drive Timing Belts??

A thin section belt my be the best,where as the pitch change at the periphery would be quite small




This should be ratcheting so it will eliminate the drag of the motor when just pedaling 




get the pulley at the same time your finding the length you need.








http://www.volksrods.com/forum/showthread.php?t=37725 
















Trike stability

Delta trikes and quads need a differential to use a single stage reduction; unless you can live with a lopsided traction drive (but that can push the nose of a delta trike to one side on wet hills).

Two-wheel positive traction can be had with a jack shaft, but will need a two-stage reduction.Delta trikes also have a tendency to roll over on a fast turn. The only thing that can be done for that is to weight down the rear wheels and lower the seat, then slow down.

A tadpole trike can spin out of control if the rear wheel is too close to the front and may be forced into a spin by too much weight on the rear; don’t use slick tires. But if the rear wheel is farther back it will need more weight to keep a grip on the road in an emergency stop-turn. In line tandem tadpole trikes probably will not have this problem. But the front wheels of heavy tadpole trikes should be built with the spokes all the same length to handle the lateral forces.http://commutercycling.blogspot.com/2007/10/trike-wheels.html

Low seats help keep trikes from flipping over, but they could still use a crash cage even if just to climb out of the seat.


Wheels should have at least 36 14-gauge spokes, 20" wheels with box wall rims are stronger than big wheels, although there have been good results from using the new tubular rims with only 32 spokes for down hill racers (jumping off cliffs).



Tires are a problem for this much weight. High pressure tires are essential but will give you a rough ride. I have a lot of expensive tires split down the middle. Maybe Moped tires?


http://commutercycling.blogspot.com/2007/10/tire-liners-expose.html


Brakes are the most important thing


Only hydraulic disc brakes can be synchronized perfectly, but a double lever is not available, except for the Magura BIG brakes: http://www.greenspeed.com.au/magura.html

But you will still need a third brake on the rear wheel with extra large rotors.

Drum brakes modulate better and give you more control over stopping than cable pull disc brakes, but are available only in cable pull and are no good in the rain.




If you insist on using a bigger motor than 1hp like the mars 909 ( the name has changed)


with out adequate gear reduction you will need to use motorcycle brakes, lights and tires.

Actually I don't know if it is possible to build one of these that is perfectly legal unless you can keep the weight (450lbs?) and speed down to about so the brakes work like they should.




'Build your own electric motorcycle' by Carl Vogal. I think people who lust for speed should be building electric motorcycles.


When the center of weight is so far forward, it is possible to drop your feet, and have them dragged under the front axial. It is much safer  to have the crank behind the front wheels.


Note that the crank should be behind the front wheels. But the front wheels should also be wider apart.


This one could use three hub motors

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