The e-bike thread.
05-20-2012, 08:58 PM
#283
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Sidebar:
If you disconnect the brake sensor, you can indeed use the rear disc brake as a dyno load in order to calibrate your equipment with the wheel in the air.
This, however generates heat.
A lot of heat.
As in "Hmm, what's that smell? Oh, my rear brake is on fire. I should probably stop now."
If you disconnect the brake sensor, you can indeed use the rear disc brake as a dyno load in order to calibrate your equipment with the wheel in the air.
This, however generates heat.
A lot of heat.
As in "Hmm, what's that smell? Oh, my rear brake is on fire. I should probably stop now."
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05-21-2012, 08:46 AM
#285
Sidebar:
If you disconnect the brake sensor, you can indeed use the rear disc brake as a dyno load in order to calibrate your equipment with the wheel in the air.
This, however generates heat.
A lot of heat.
As in "Hmm, what's that smell? Oh, my rear brake is on fire. I should probably stop now."
If you disconnect the brake sensor, you can indeed use the rear disc brake as a dyno load in order to calibrate your equipment with the wheel in the air.
This, however generates heat.
A lot of heat.
As in "Hmm, what's that smell? Oh, my rear brake is on fire. I should probably stop now."
Did you get it on video perchance?
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05-21-2012, 11:34 AM
#286
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Not until after it ships, unfortunately. The fellow I'm dealing with on this does good work, but he is legendary within the community for procrastination. He's promised that it'll be within the week.
No video was running at the time. And fortunately, there wasn't much in the way of flames, just a lot of smoke and a very, very hot rotor. (Bet you've never seen that on a bicycle before.)
So, the lesson here is that bicycle brakes are not as robust as the brakes on a car.
No video was running at the time. And fortunately, there wasn't much in the way of flames, just a lot of smoke and a very, very hot rotor. (Bet you've never seen that on a bicycle before.)
So, the lesson here is that bicycle brakes are not as robust as the brakes on a car.
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05-21-2012, 01:05 PM
#288
LOL - that rotor probably weighs in at a whopping 2 ounces with design considerations based on stopping half of a 200lb cyclist on a moderate downhill grade from 20mph to zero over a time period of about 2 seconds, or maintaining constant torque on those rotors for that same sized man on a steep to very steep downhill grade at a rate of 2-3 MPH.
If your e-bike ever goes full Toyota on you, you're going to have a rough time slowing it down safely.
Got a kill switch?
If your e-bike ever goes full Toyota on you, you're going to have a rough time slowing it down safely.
Got a kill switch?
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05-21-2012, 01:33 PM
#289
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I didn't weigh it when I had it off, but it's pretty light. Very thin steel.
Well, even if the motor were to go full-bore, I think I could probably still stop it. During this test, I was dragging the brake at only moderate pressure, applying just enough load to hold the motor at a constant load, thus drawing a constant current so that I could calibrate the controller against an external ammeter.
In an actual panic-stop situation, I'm pretty sure that the brake could stop the motor.
Several.
The BCU itself looks at the throttle signal to make sure that it's in-bounds. The maximum output of the throttle under normal conditions is 3.8 volts, so I've told it that anything over 4.2 volts represents a fault condition (eg: short between +5 and signal) and that it should ignore this and shut down.
The rear brake lever is wired to an input on the BCU which also shuts off the output when engaged.
The front brake lever is wired directly to the controller, and behaves the same.
There's a power switch on the handlebars which controls the logic supply to both the controller and the BCU. If this switch is opened, both of them shut down.
And, since this is a brushless polyphase motor rather than a brushed series-wound motor, a short-circuit in the controller's FETs cannot cause a runaway condition. At worst, it would just lock the motor and then burn up the winding.
If your e-bike ever goes full Toyota on you, you're going to have a rough time slowing it down safely.
In an actual panic-stop situation, I'm pretty sure that the brake could stop the motor.
Got a kill switch?
The BCU itself looks at the throttle signal to make sure that it's in-bounds. The maximum output of the throttle under normal conditions is 3.8 volts, so I've told it that anything over 4.2 volts represents a fault condition (eg: short between +5 and signal) and that it should ignore this and shut down.
The rear brake lever is wired to an input on the BCU which also shuts off the output when engaged.
The front brake lever is wired directly to the controller, and behaves the same.
There's a power switch on the handlebars which controls the logic supply to both the controller and the BCU. If this switch is opened, both of them shut down.
And, since this is a brushless polyphase motor rather than a brushed series-wound motor, a short-circuit in the controller's FETs cannot cause a runaway condition. At worst, it would just lock the motor and then burn up the winding.
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06-02-2012, 01:54 PM
#296
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Hmm. Good question. Hadn't really sat down and done the math.
The bike itself was $475 including tax.
The whole assembly of battery / motor / controller / wheel was HK$$11,700 (about US$1,500) including shipping from China.
The CycleAnalyst BCU was $207 including shipping from Canada.
I re-used the tires, tubes, lights, mirror, etc from the last bike.
Plus maybe $75 total for the rear frame, racks, and all the little accessory bits.
All in all, a lot more expensive than my car.
And I finally got word a couple days ago that the battery has shipped.
(Bloody well time.)
The bike itself was $475 including tax.
The whole assembly of battery / motor / controller / wheel was HK$$11,700 (about US$1,500) including shipping from China.
The CycleAnalyst BCU was $207 including shipping from Canada.
I re-used the tires, tubes, lights, mirror, etc from the last bike.
Plus maybe $75 total for the rear frame, racks, and all the little accessory bits.
All in all, a lot more expensive than my car.
And I finally got word a couple days ago that the battery has shipped.
(Bloody well time.)
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06-02-2012, 08:19 PM
#299
So $2257 by my math. That's a lot better than the $12k+ I thought I saw when I skimmed your reply, heh.
I'm a little surprised you managed to spend so much on the bike itself. Steel bikes on Craigslist ought to be fairly cheap. But I think if I were in your shoes I'd probably pay the extra and not deal with old components too.
I'm a little surprised you managed to spend so much on the bike itself. Steel bikes on Craigslist ought to be fairly cheap. But I think if I were in your shoes I'd probably pay the extra and not deal with old components too.
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06-02-2012, 08:30 PM
#300
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So $2257 by my math. That's a lot better than the $12k+ I thought I saw when I skimmed your reply, heh.
I'm a little surprised you managed to spend so much on the bike itself. Steel bikes on Craigslist ought to be fairly cheap. But I think if I were in your shoes I'd probably pay the extra and not deal with old components too.
I'm a little surprised you managed to spend so much on the bike itself. Steel bikes on Craigslist ought to be fairly cheap. But I think if I were in your shoes I'd probably pay the extra and not deal with old components too.
I wanted to take this opportunity to upgrade the bike as well. I went with a fairly lightweight aluminum frame which came complete with disc brakes, a decent set of derailleurs, and so on. Figure if I'm gonna spend "real" money on the drive system, I might as well have a decent-quality platform to build on.
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