The E-cumbent - A project by Matt Shumaker

That seems to play out in real life riding.

That last ride turned out to be 16.2 WH per mile. The same ride with the AXI was 15.69 WH per mile. So, I am seeing roughly 5% efficiency reduction in practice. But that is actually the best casse scinerio. Ultimately, in the grand scheme of all sorts of riding combined (aggressive, conservative, pedalling, no pedalling, etc) the actual drop in efficiency will be closer to 10% overall.

I guess that is OK considering the gearing is a touch higher, the motor is bigger and far more powerful, the primary belt is tighter to tolerate the added power, and the power delivery is sooooooo much better. :D

So, why is the heat buildup the same, if the losses for the Terminator are greater?

Matt
 
my guess is that the terminator is able to dissipate more heat because of the larger surface area and maybe the fan works better, the way you have your setup now the terminator isn't more powerful than the AXI, they are both powerful, but your controller can only put out so much power, you said 150A i think so 7200W is the max, so basically the motor with the highest efficiency will put out the most power, even if the controller could put out an infinite amount of power, the AXI would be more powerful because of the lower winding resistance. it seems like the terminator is wound for a higher voltage, the terminator resistance while running is 0.080 Ohms(calculated from the data on their site), im guessing that the AXI running resistance is double the cold resistance thats in the specs so 0.054 Ohms, in order for the terminator to put out the same power as the AXI motor it needs to be run at 48.0V * sqrt(0.080 / 0.054) = 58.42V. that all doesn't really matter though since this motor runs better than the AXI with the backemf problems.
 
Agreed. This is almost an apples and oranges thing. Both motors are so different in characteristics, it is tough to compare them.

Also, the AXI had a definate limit beyond which it did not want to go. The Terminator has no such limitation.

I have actually begun damaging one jack shaft bearing from the load!

Matt
 
I keep messing around with ratios between the primary, secondary, and final drive.

However, the motor pulley went up from a 15 tooth on the AXI to a 19 tooth for the Plettenberg. That made up for the lower KV plus an extra 3mph or so. :wink:

Oh, what I meant before about the AXI not wanting to go beyond a certain point is this;

The AXI would pull just so hard (not counting the back EMF issue. Once beyond that RPM). If I tried pushing it past that point, the motor would just not pull any harder. It made other strange noises, built up heat, and would just not pull any harder. According to my data logger (before I toasted it), 4,000 watts was the max the AXI would pull. If I pushed it harder, it would just take in more wattage without pulling any harder and it would make ALOT of odd noise.

I have not recieved my new data logger yet. So, I do not know about the Plettenberg's wattage draw. But, I can tell you it pulls harder than the AXI without any objection what-so-ever. Also, the Plettenberg is so much more powerful that I am able to skip the 15 wide, 5mm pitch primary belt even though it is tight! I am also running a few more teeth on the motor pulley than before. So, it should be harder to skip that with the AXI. So, with this new motor, my efficiency is down a touch. But, the output power is WAY up, the throttle tractability is top notch, no EFM issues, quieter running, smoother, anhd a wider overall "Powerband" (if I can call it that). Hmm, not sure if it was worth $1,000. But, it is definately a drastic improvement over the AXI,

Now I need to replace that one bad bearing at the secondary jackshaft.

Matt
 
i think the max wattage thing is the controller limit, as far as the terminator having more torque, it does a tiny bit more Kt is 0.044 for it, and 0.042 for the AXI, but i have a feeling that the reason you are feeling a big difference in power is that the terminator is made of better iron, its possible that the AXI motor's iron was getting saturated way before the controllers 150A max current, so after a certain point increasing the amperage would no longer increase the torque, but with the terminator it keeps linearly increasing torque all the way up to 150A, or at least to a higher point than the AXI motor.

just out of curiosity how long do you think it takes you to go from 0-20mph?
 
I have done alot of messing around with this;

0 to 20 mph is under 4 seconds. 0 to 30 is possible in 5 seconds if I run the clutch tight and do repeated launches searching for the sweet spot. But, that makes the primary belt skip if I am not careful and I am sure it is not good for the rear wheel (among other things). The ideal clutch tension set for normal riding is 0 to 30 in 7 seconds. It winds out (on flat ground) at 38 mph without pedalling. I want to gear it up for at least 45 to see what it is like. :wink:

The best judge of accelleration is done with the bike already rolling a bit. If I get it rolling at 5mph, then get on the throttle, it pulls really hard. However, that first 5mph is weird when trying to accellerate really hard.

It is funny, I tend to ride this thing like it is a 100 pound bike with lots of extremely sturdy equipment on board. Then, if anything objects to the hard launches, I wonder why. Sheesh, I am expecting alot out of my 13 pounds of E-quipment. :mrgreen:

Matt
 
i think the deal with the first 5mph is because the controller is commutating the motor in open loop mode, and when you get past 5mph, the backemf voltage is high enough to run it in closed loop mode with full power.
 
Probably so.

If I had to give a single sentence describing the difference between these two motors I would say;

The AXI is efficient and innexpensive with decent power, but limited in total output (with EMF issues), while the Terminator is an all-out performance machine with tons of power, very smooth delivery and likes to be run HARD. :mrgreen:

Matt
 
recumpence said:
This setup is much different than the AXI. I just got in from a 5 mile ride. That ride was mostly full throttle on hilly roads up at 37mph. My WH per mile on that ride was 24. I used to see 17 to 18 WH per mile at 35 to 37 mph with the AXI.
Click to expand...

Hi Matt
Could you do the tests on flat roads only ? At 10, 15, 20, 25, 30, 35 mph average ? Two tests per one speed. It is hard to believe you could reach 18 wh/mile at 35 mph average.
When we will know results at flat terrain than we could compare them to hilly roads results later.
You could also do the tests with the sail (air brake) to simulate the same results for higher air drag bikes.
If we will know more results it would be easier to get some new ideas i think.

Best regards
 
eP said:
Could you do the tests on flat roads only ? At 10, 15, 20, 25, 30, 35 mph average ? Two tests per one speed.
Click to expand...
Yes, "there and back" on flat roads, at constant speeds, would be great - otherwise, there are too many variables.... Hope the eLogger arrives soon :mrgreen:
 
There are precious few flat roads out here. You have to remember the issue is my fontal area more than anything else. I have talked to a few others running typical ebike drives on recumbents who see pretty much the same numbers. My drive system is not what is giving me good numbers as much as reduced aero drag from my low recumbent layout.

There are obviouly a few things that contribute to it related to the drive system (obviously). As I mentioned, the AXI was noticeably more efficient. I think I had that motor running in its perfect sweet spot. But there were more drawbacks than benefits with that motor.

Also, a couple other things contribute to my efficiency;

#1 Freewheeling. I shut the motor down going down hills. Many ebikes have drag when coasting. I don't. Plus, again as a recumbent, this thing coasts for a long distance. This increases range substancially. I bet (once I get my data logger), we will find that the actual wattage to run my bike consistantly (never shutting the motor down to coast) will show very typical (if not higher) current useage to standard ebike drives.

#2 My riding style. I like cruising and carrying alot of speed through corners. I try not to stop and restart if at all possible.

Matt
 
recumpence said:
There are precious few flat roads out here.
[cut]
There are obviouly a few things that contribute to it related to the drive system (obviously). As I mentioned, the AXI was noticeably more efficient. I think I had that motor running in its perfect sweet spot. But there were more drawbacks than benefits with that motor.
Click to expand...

So maybe you should do the tests on uphill roads only (for different speeds) ? I'm sure half a mile distance should be long enough.
This way we could see what is your true average power consumption when motor is running.
18 Wh/mile and 24 Wh/mile - that is huge difference for the same average speed. So we need definitely more datas to get to resonable conclusions.
The gear ratios (different) maybe significantly contribute to such huge power difference i suppose.
 
I agree. I was surprised to see such a difference from one motor to the other. Also, the last 37mph average run netted 22 WH per mile. So, it is improved. Hmm........

Anyway, the best option for me would be running it on the same road in both directions at the exact same speed. That would average out any wind and elevation from the equasion.

Again, I am willing to bet my efficiency is not any better (maybe a touch worse) than typical ebikes with the motor running constantly. I have a 3 stage reduction. That, alone, pretty much assures less than ideal efficiency.

At any rate, what I am happy about, more than anything, is the performance, range, and operating ease (as well as durability) of this thing using only 13 pounds of equipment. Good numbers are not too hard to achieve (efficiency numbers), but doing it with a high performance bike that is so light is what I am most interested in.

I still cannot believe I get 20+ miles out of an 80 ounce battery.

Matt
 
recumpence said:
Anyway, the best option for me would be running it on the same road in both directions at the exact same speed. That would average out any wind and elevation from the equasion.
Click to expand...
It would be an option on flat, but uphill and downhill you cannot out wind factor that way.
The better way is to do a few short tests in the same direction, switch motors and do next tests serie for the same one direction once again for the same speed.
You cannot cancel elevation difference influence by running in both directions.
One direction tests should tell us more i'm sure. Do them for 3 speeds (15, 25,35mph) and we will see much more.
 
I agree.

What would be most helpfull is looking at the active data as the bike is ridden (once my data logger arrives). That would be very easy data to compile "400 watts to mantain X speed, 500 watts to mantain Z speed" etc.

Matt
 
Miles said:
An Inclinometer sensor for the eLogger would be handy...
Click to expand...
Inclinometer is not necessary. If you compare results for low and high speeds you will see what is the slope. :mrgreen:
Handy weight ballast could be more useful to simulate higher motor loads.
 
Miles said:
Sure, but I'd like real-time data :)

They already have Altitude and GPS.
Click to expand...

Maybe i'm wrong but i'm not sure the altitude would be accurate enough if the accuracy would be +/- 10 meters.
 
Miles said:
It would still be nice to read directly, as you go.

How about something like this?
Click to expand...

I think it should work fine IMHO. But still i'm sure that it is not necessary for solving efficiency riddle.
 
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