The E-cumbent - A project by Matt Shumaker

Yup, other than the videos, I have met with an electronics engineer about a custom throttle for the bike (with lots of bells and whistles), I made a handlebar console for the digital displays, and I have begun making a slipper clutch for it.

Log on and read teh web page. I have sent two major updates to the webmaster. He should have them up tonight or tomorrow.

Matt
 
There are two ways to limit the current to your motor. You can limit the battery current or the motor current. Most standard controllers limit the battery current... but because of the way motors work that translates to excessively high torque at low rpm. The other way is to limit the current entering the motor (armature current limiting) and that has the added bonus of also eliminating most of the heat related problems and tends to make you focus on higher efficiency power at higher rpm.

:arrow: So which limiting scheme are you trying?

In order to do the motor side limiting with a brushless controller it might be pretty difficult. I've built a circuit for a brushed motor, but have not gotten the bike together to try it.

The motor side limiting sounds like the ideal way to solve this because it means that the torque is contant across the entire rpm range... a big bonus that will prevent belts from slipping or multispeed hubs from breaking. :wink:

(I've spent a lot of time with this issue)
 
Great question!

We looked at various options. I also talked to Castle Creations (the controller manufacturer). To regulate the output to the motor would mess with the back EMF and confuse the controller. However, I do not want to just bleed off excess current. So, here's what we have come up with;

We are making a new, completely self contained throttle that will generate the required pulse width to drive the controller. That throttle will use a micro processor that will read the amperage between the pack and the controller. As the current limit is reached, the microprocessor will roll off the throttle by narrowing the band width entering the controller, thereby reducing the amount of power put to the motor. So, it will be a current sensing, throttle varying device. The current limit will be adjustable with a simple thumb wheel as will the roll off slope and roll off sensitivity. We are also writing throttle exponential program into the processor to soften the innitial 20 to 25% throttle. Oh, we are also adding a throttle ramp up feature (again, adjustable) to ramp the throttle up if this feature is selected. Each feature will be individually adjustable and reprogrammable.

Oh, I am nearly finished with the slipper clutch. I will post pics of it soon.

Matt
 
awesome work Matt.
I'm sure i'm not the only one rooting for your project to open up new avenues for us all.

Cheers


D
 
Thanks. It is going along pretty well, I must say.

I got a new rear sprocket today. I am going up from the 36 tooth rear sprocket to a 43 tooth. That will reduce the load on my belts. Then I will gear up the power unit to compensate for the lower ratio at the wheel.

I also am nearly finished with the slipper clutch. Pictures and text updates were just made and two more major updates to the web site will be up within the next day or so.

I am puting alot of effort into this project to get it done and debugged by June so I can use it through the summer.

I am already looking at updating the front brake to a larger disc. This is addicting! :wink:

Matt
 
recumpence said:
...will read the amperage between the pack and the controller. As the current limit is reached, the microprocessor will roll off the throttle.
Click to expand...
That's how my circuit was designed. I haven't gotten a bike together to test it. It's supposed to be on my Project #002 when it's done.

Check out the build thread:

http://endless-sphere.com/forums/viewtopic.php?f=2&t=3008&st=0&sk=t&sd=a&hilit=armature+current+limiting+circuit
 
Just a heads up, Aluminum is a shitty friction surface. It will gall even fiber friction pads unless it's anodized. (hard anodized is even better) This can actually be used as an advantage when an aluminum backing plate is used and the pads slip on a steel or brass/bronze surface as no glue/key is needed to lock the friction pad to the backing plate.

Marty
 
That depends on the material rubbing against it as well as the pressure and amount of slip.

Ideally stainless friction surface would be used. but, I do not have any stainless. This should work for the application it is intended. If not, I can make carbon fiber plates for the fiber pads to slide against. We shall see how it goes. :wink:

Matt
 
I know John from WISIL site as well as the ULEA forum. He is a good guy.

I have not seen your limiter before, I have only heard John talk about it.

I know the slipper will not be needed with the limiter. But, it may be a month or so before we get our limiter setup. And, what the hey, I have the ability to make the clutch, so why not? :mrgreen:

Matt
 
I took the bike out for a "Long" ride today. Bascially I rode it full throttle (30 mph in its current gearing) on a very hilly road for 7 miles. My 48 volt pack used up 3400 milliamps in that run. Not bad for that speed and hilly road. The bike only slows down 2 to 3 MPH up hills due to all the torque. So, I am looking at 16 to 18 miles on a charge at full throttle (worse case scinerio). It runs about 25 miles averaging 20 mph.

I will be back at the shop tomorrow working on the clutch. I will probably finish it, but I cannot promise it will be installed tomorrow.

Matt
 
Yes, it used 3.4 ah (I am used to milliamp ratings from my RC experience).

It is a 10 AH pack.

If I averaged 20 mph, it would have used 2 ah or less. But, I was running it full throttle the whole way. :mrgreen:

Matt
 
I have been doing alot of testing lately. The bike is currently geared for 37 mph (varified with my radar gun). It accellerates HARD! On my shake down run, I got it up to 10 mph to get a feel for it, hit the throttle and watched the speedo. It only took 3 and 1/2 seconds to go from 10 mph to max out at 37 mph (and that is alot considering I weigh 190 pounds). The big surprise, though, was the data from the run. During the accelleration, the bike pulled over 5,000 watts and promptly froze my Eagle Tree data logger (the display froze up from over-amping it)! The slipper clutch is awesome. I have a touch of primary belt skip between 7 and 8 mph. But once above that, the skip goes away and the bike just launches! I just recieved my longer primary belt today. I will install that belt to increase pulley wrap to cure that small amount of skip. But, beyond that, the bike just rips!

One problem, though, is the effiency. Geared for 37 mph kills the efficiency. It takes 380 watts just to run the drive line with the wheel off the ground. That is twice the wattage used when it was geared for 30 mph. So, I am gearing it back down to 30 or 31 mph (the legal ebike limit in Illinois) to bring my efficiency back up and reduce the load on the power unit. But, I am shocked at the performance available from this thing. It is a beast! :mrgreen:

Matt
 
recumpence said:
One problem, though, is the effiency. Geared for 37 mph kills the efficiency. It takes 380 watts just to run the drive line with the wheel off the ground. That is twice the wattage used when it was geared for 30 mph. So, I am gearing it back down to 30 or 31 mph (the legal ebike limit in Illinois) to bring my efficiency back up and reduce the load on the power unit. But, I am shocked at the performance available from this thing. It is a beast! :mrgreen:

Matt
Click to expand...


I think a lot of that power is being consumed by the spinning spokes of the rear tire. I bet the rear tire makes a good fan at full speed? Hm... the power consumed to overcome drag goes up with speed^3, and 37^3 is almost exactly double 30^3.

Having the motor spin a naked hub would give a better idea of this setup's no-load current. Have any long hills with a consistent slope nearby? Should be able to compare the calculated power requirements to clime a hill to what the eagletree shows to get a better idea of efficiency.

Marty
 
recumpence said:
One problem, though, is the effiency. Geared for 37 mph kills the efficiency. It takes 380 watts just to run the drive line with the wheel off the ground. That is twice the wattage used when it was geared for 30 mph.
Click to expand...

Imagine what it would have been like with the original gearing, Matt :mrgreen:
 
Before you change the gearing, shoot a couple of vids for us to see it in dragster mode.
 
It is wierd riding a bike with so much power. I am surprised how much power the rear wheel is taking without objecting. The mounting screws for the rear sprocket are showing signs of stress too. I may have to go up one size on those to take the torque.

At any rate, I will pick up a higher capacity data logger (150 amp), gear it down a touch (it is too fast right now anyway) and enjoy it.

The big thing about this setup is the rideability of it. It feels really strange being able to pedal the bike without any discernable drag, then hit the throttle and run it up hills or do a fast run, then just pedal as a normal bike again. That is what I like the most. The problem is, I have gotten used to 30 mph. So, when I pedal the bike at 16 to 18 mph, it feels SLOOOOOWW! :mrgreen:

I have gotten spoiled.

Matt
 
hehehe,

awesome work again matt :)
yes, some more vids would be great - im loving that little motor already, now how do i get it in my kona? :twisted:
more pics and vids please matt, your running gear is totally awesome - i think i will adopt the controller and stuff for sure!!!
thanks for a great thread :mrgreen:

cheers


D
 
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