Monday, November 16, 2015

Mid Frame Motor Mod

If your looking for a way to sell hand made electric bicycles, you need an extraordinary design. This is one of the best ideas I have seen, even if it does use a hub-motor. At least it is a geared hub.

One of the main problems with hub motors, besides the lack of gears, is the lack of ventilation. This modification uses fans to cool the interior..

Most people just use a direct drive hub motor that uses much more energy than is needed to climb steep hills. Some make self contained hub motors and claim they are the next big thing; ending up with a wimpy machine that does nothing for real hill climbing with cargo.

Even the Elf car has a less than perfect power system; they use a hub-motor set at a 1:1 gear ratio with no ventilation; and no gear box! Even if it has a voltage multiplier circuit, it is a waste of energy!!! And no one knows enough about why gears were invented to say anything about it!

Read how this bike was built on the Endless-Sphere forum:

MidMacMod (Mid-drive Mac motor Mod)

Thursday, October 29, 2015

eVox electric bicycle

This is the first electric bicycle that I’ve seen that has a good drive system. Most e-bikes waste too much power just getting up to speed, because they are in the wrong gear. Especially hub motors; the only way to lower the very high gear that hub motors are set at, is by lacing them into a smaller wheel.

It may not be geared right for hill climbing with cargo on our steep hills. But when you consider that brushless motors are able to produce much more power than is posted on the label, you can see why this e-bike has so much potential. This is the way the Elf car can climb steep hills with only a 750 watt motor.

To keep the battery size small, the eVox cruises at about 500 watts, up to 20mph on flat land (more if you pedal). But when you need more power, you can climb steeper hills with as much as 750 watts for up to five minutes with out frying the motor and controller; longer than most e-bikes simply because they use a high voltage motor.

The majority of the heat that can damage the motor and controller comes from the amps of current. By choosing a system that has higher volts, you can achieve the same amount of power with fewer amps.

The display panel will actually show you real-time wattage draw from the battery; this is not available on all e-bikes. They chose a micro-V belt to help keep a hard acceleration from destroying the spokes. And because routing most of the power through a belt will make your drive chain last much longer. Most human’s power is only about 186watts, bicycle drive chains were made for a little more power but not 750watts.

This e-bike could use a lower gear to move 400lbs up an 8% grade. With 750 watts a 12mph gear is needed; if lower gears are available they do not want to tell me exactly how much lower; after all that would require calculations.

If you have strong enough legs you could add 250w for a 1000w hill climb. That is enough power to climb a 6% grade with 400lbs at close to 17mph, or a 5% grade at just under 20mph. Or 350 lbs up a 6% grade at about 18-19mph assuming the powered side is in the right gear. But Remember I am talking about total combined weight.

 If you have an 8% grade your going to slow down to about 10mph or less with the gear set as high as it comes from the factory (I do not know exactly what the power drop is when the gear is not set right). Too bad they don’t just do a graph of what it can actually do with at least 350lbs.

Unfortunately this does not use a disc brake. It is very difficult to fit a disc brake with a belt drive.

So until enough people complain about it not being strong enough you will have to build your own motorized cargo bike. Hauling cargo on a bicycle will become essential very soon.

Mass produced electric cycles are made for generic flat terrain. But this is good for people that know what it takes to climb hills with cargo. There needs to be at least one person in every town with steep hills, turning people’s cycle trucks into powerful hill climbers.

Don’t be suckered into buying a big over powered mid drive, you don’t need it. Read more about why this kind of gearing is so good:

Thursday, October 15, 2015

Fixed Gear Drives

This is the original way to motorize a bike. Gasoline motors used it with a small gear box to extend the range of the power. Electric motors have a larger usable power range. So a two sped gear box would work ok for a bicycle with 750 to 1000 watts. Maybe a three speed gear box for a moped at 1500 watts.

Out of all the drive systems for an electric bicycle, a fixed gear is not just the only truly legal method, it is simply the best. Motors have a sweet spot where they operate the most efficient and coolest, and if your fixed gear runs at or very close to that spot your motor will last much longer with less heat.

If a hub motor was to be turned in to a mid mounted direct wheel driver, turning at a sweet spot of 500 RPMs it would take about a 2.77:1 gear reduction ratio to slow your 26” wheel down to about 14 mph. That should be enough to climb an 8% grade with 350 lbs (total combined weight) at 1000watts.

The majority of the heat that can damage the motor and controller comes from the amps of current. By choosing a system that has higher volts, you can achieve the same amount of power with fewer amps.

And if you really need a lower gear try using a two speed gear box, or possibly a two speed hub motor.

One gear set at about 10-12 mph and one at about 18-20mph you would have much better mileage. And some people claim “gears” rob too much energy form your drive train, HA! Unfortunately it is hard to find a gear box at an affordable price that is made for e-bikes.!

For an extra low hill climbing gear you should be able to use a controller with a voltage multiplier. But here is really no substitute for multiple gears, even if an e-bike can get buy with only two.
The laws need to change to reflect the amount of gear reduction you have.
ie: if your controller is limiting the power and the gear reduction is set so that the machine cannot move faster than the law allows on flat land, you should be allowed to use as much power as you need to climb your worst hill.

Two motors?
Two identically geared hub motors with two controllers, could be an asset in slippery or extra steep conditions; 2WD will have better traction. I don't know how well two separate kinds of power systems would work together, but having an extra motor on the front hub can't hurt if it is geared low enough.

The only reason that you can’t buy a factory made bike like this is simply that people are mesmerized by high tech scams and want to turn their bicycles into illegal motorcycles. 20 mph is just not fast enough for them; nor is the moped’s 30mph. The fact that energy is going to become very much more expensive should change all that, but education is needed.

People claim that direct drive hub motors are so much more efficient than geared motors. Yet the best a hub motor can do is 75% efficiency. While a high speed high voltage motor like the Lightning Rods kit uses is up to 90% efficient, even with a very large gear reduction.  Gearless direct drive hub motors are made for racing, not for hill climbing. They operate at a slow RPM and therefore can create more heat than they know what to do with; fast high voltage motors create more kinetic energy, and pump less amperage through the windings, thereby creating less heat!

The only thing that would keep a mid-drive system legal is a speed sensor connected to the controller and the wheels. But these are too easily bypassed accidentally. See why most electric bicycles are illegal.

 Custom Pulleys

Wednesday, September 30, 2015

Two speed motors?

Most hub motors have a hard time climbing steep hills unless they are built like tanks. Big enough to ram more than enough amps through them and they will move up steep hills despite the lack of gears. 

In the state of Washington 1000 watts is the legal limit of output for a motor on a bicycle; 1500 watts for a moped. Unfortunately it is harder to get a moped registered than a power assisted bicycle.

1000 watts will drive 400lbs up an 8% grade at about 12-13mph; possibly a little more if pedaling hard, but only if the gears are correct. That is too slow of a gear to drive around in all day if you want good mileage.

The new Xiongda two speed hub motor has a max out put of only 720-740 watts (when run on 48 volts) and will slow down to about 9-10 mph with 400lbs (total combined weight) on an 8% grade; and you may need to pedal hard. I need to test out one of these motors.
If you live in Canada you will probably need an additional gear reduction to the drive wheel at 500 watts, and it will be crawling up the steep hills of Vancouver. 

I think the best way to motorize a cargo bike would be to use a Nuvinci infinite gear hub like the Elf car does. But use a two speed gear box to reach the desired gear reduction from the motor. Then directly to the brake side of the Nuvinci with a Gates GT3 belt; thereby using the Nuvinci to help your legs keep up with the motor. But this Xiongda hub motor looks like it has fabulous potential.

Mid-drives are popular, but for a cargo bike with 400-450lbs (total combined weight) they can destroy your drive chain fast, way too fast at 1000 watts! If you’re obsessed with a large motor like the Stoke Monkey you would be better off using it as a mid-mounted motor, driving the rear wheel through a stronger chain or belt. But don’t let me stop you from finding out the hard way; after all if you accelerate slowly and don’t stress the chain out much it may have reasonable life span.

Also be aware that these Chinese two speed hub motors are new and unproven for durability by power obsessed Americans. But keep in mind that the only bicycle power systems that are proven by time are old technology, and have problems that the sellers will never tell you about.
See this review on Endless Sphere forum.  The internal gears of the Xiongda may require better grease.

Some e-bikes have torque sensors that make the motor run intermittently, making a jerky motion. The Xiongda has an independent throttle that you can use at any time and a five-level PAS setting that you set in the LCD. You don't have to pedal to use the throttle.

Much more information on this article

Bidirectional hub motor with unidirectional two-speed output
US 20120302390 A1
A two-speed bidirectional hub motor includes an electrically driven hub, including an electrical motor, oppositely aligned one-way bearings, and a planetary gear system connected to the electrical motor. A fixed shaft is connected to the stator of the electrical motor. The first of two one-way bearings connects the electrical motor to the planetary gear system, and the second one-way bearing connects the electrical motor to the hub casing. When the rotor is electrically activated to spin in the forwards direction, the second one-way bearing engages the hub casing and rotates the wheel forwards at high speed. When the rotor is electrically activated to spin in the reverse direction, the first one-way bearing engages the planetary gearing system, rotating the wheel forward at lower speed by a gear reduction. This design gives two-speed output without a transmission.