Electric trail bike

[earwig]

Originally Posted by Luke

No pictures today, but progress was made. The lack of pictures was probably for the best. The bike was almost looped, and the presence of a camera probably would have pushed it over the edge. The bike would've been fine. The rider, probably not so much.

You'd be surprised . . . he's pretty tough!

Originally Posted by Luke

I fixed the power problem, so now it has full power again- and still has the nice throttle response.

I had the privilege of a brief ride, and it is amazing! Considering how little time Luke's been able to spend on refinement, the throttle feels remarkably conventional. It's already very rideable and I know it will only get better. The power feels great, and the rider who almost looped it (and is much more experienced off road than me) said the front end came up really easily after he loaded the suspension a little. If it had some body work to protect it, I suspect there's a market for it even in this gestational state.

Originally Posted by Luke

It went on the scale this evening. 220 pounds, and roughly even front to back. A pretty good start.

A pretty damn good start, indeed!!!

Originally Posted by Luke

Trail testing is still on for tomorrow.

I assume OC is gonna get some tasty video!

[UngaWunga]

Man, wished I lived closer. I'm very interested in this, but my circuit building skills for the controllers and recharging controllers is lacking. That would be the only thing really holding me back.

Have any links on sites where I can read up on what's needed? I can write code, but building hardware is a new thing for me. Been a long time since I built simple circuits in college.

Anyways, rock on.

[oregoncoast]

Well, I got to ride Luke's electric bike yesterday -

BTW, I like the name "Luke's Lectrics" with a nod to the classic brand, Lucas Electrics.

His bike is really a functioning bike. Throttle control was very predictable, and he spent some time going slow, through a trials sections, just to see how it would go. When you want to go..and you twist the throttle..it just GOES!!!

Because he built it on a real dirt bike platform, and he's managed to keep the weight where a similar gas MX'er would be, it just feels right. Battery life was shorter than he would have wanted...and he mentioned something about slop in the throttle, but I didn't think it was an issue....Luke has done an amazing job with this thing.

Here's some video of the bike in action:

[BikePilot]

Cool! I suspect there's room for further weight savings. 2-stroke MX bikes aren't really built with weight in mind 'cause they are essentially at the AMA limit in stock form (hence heavy steel exhaust, thick engine cases, overbuilt gearboxes, huge clutches etc as compared to a four stroke). Some of this may carry over to the chassis. I know my '97 YZ had a bunch of steel bits where you'd normally find aluminum on a MX bike - internal wheel bearing spacers, subframe etc.

[Stagehand]

Do you have any idea of the amount of square acreage that is going to open up for riding in the continental US if this thing got out?


Does anything on it get especially hot?

[c.herman126]

Way to go! What an awesome project.

Very impressive work here. Especially the circuit and PCB design for monitoring the bike and massaging the throttle response.

[huzar]

Great build thread. Watching this with great interest.

[Luke]

So like the video (thanks OC!) shows, the first test went pretty well. What I wasn't able to video was riding on the singletrack. That went even better, it's faster than my XR400, mostly due to being 70 pounds lighter. Unfortunately, the range wasn't so good. Riding around in the trials garden was fine, but I took it up some fairly steep singletrack and the batteries went from fresh to flat in about a mile.

Nothing got hot- the motor was a little warm even with some of it's cooling holes taped over to keep mud out. The controller may have gotten a little warm, but I didn't notice that anything else heated up.

So, back to work.

[Stagehand]

Is there a way to impulse the power output? introduce some intervals in the voltage to stretch out the battery life, while not noticeable affecting power delivery?

[Mr. Fisherman]

Originally Posted by Stagehand

Is there a way to impulse the power output? introduce some intervals in the voltage to stretch out the battery life, while not noticeable affecting power delivery?

Maybe a pulse width modulator?

[Luke]

Originally Posted by UngaWunga

Man, wished I lived closer. I'm very interested in this, but my circuit building skills for the controllers and recharging controllers is lacking. That would be the only thing really holding me back.

Have any links on sites where I can read up on what's needed? I can write code, but building hardware is a new thing for me. Been a long time since I built simple circuits in college.

Anyways, rock on.

Alltrax has wiring diagrams to go with their controllers, they're fairly simple.

http://www.alltraxinc.com/Doc_Depot.html

I'm using roughly this one, it's the simplest:

http://www.alltraxinc.com/files/Doc1...v-wire-dia.pdf



If you want to get into general electronics, I've seen nothing online that's really well written. For books, The Art of Electronics by Horowitz and Hill is really good. It tries to give an intuitive understanding rather than just having everything fall out of a bunch of equations. It doesn't have anything particular to electric vehicles, though.

[Grider Pirate]

Originally Posted by Mr. Fisherman

Maybe a pulse width modulator?

That's basically what most brushed DC motor controllers do.

Stolen from the DIYELECTRICCAR.COM forum:
Old hot rod saying...
"How fast do you want to go? How much money do you have?"
New EV saying.......
"How far do you want to go? How much money do you have?"
I guess some things never change

... and they have endless perpetual motion threads there too.

I'm curious about the lack of BLDC motors in this size range. They seem simpler than brushed DC motors, but the big ones available are frighteningly expensive. The Controllers for them are expensive too.
I need to re-check but I don't think either Brammo, or the other one (Zerocycle?) are using brushless. Kinda' makes you go hmmmmmmm.

[Luke]

Originally Posted by Stagehand

Is there a way to impulse the power output? introduce some intervals in the voltage to stretch out the battery life, while not noticeable affecting power delivery?

Originally Posted by Mr. Fisherman

Maybe a pulse width modulator?

That's what the controller does. Like this:



The motor is powered (connected to the batteries) for some of the time and unpowered the rest of the time. In this picture it's on for 35 microseconds and off for 25 microseconds in a repeating cycle. Increasing the amount of on time relative to the amount of off time produces more torque.

[Luke]

Originally Posted by Grider Pirate

... and they have endless perpetual motion threads there too.

Maybe I should run the power cables through the cap of an MSR bottle. 'Cause hey, if magnets can align fuel molecules, then fuel molecules can align my electrons.

Originally Posted by Grider Pirate

I'm curious about the lack of BLDC motors in this size range. They seem simpler than brushed DC motors, but the big ones available are frighteningly expensive. The Controllers for them are expensive too.
I need to re-check but I don't think either Brammo, or the other one (Zerocycle?) are using brushless. Kinda' makes you go hmmmmmmm.

Mars makes some, but they're quite similar to their brushed DC motors. For a car or a street bike the lack of maintenance is more of an advantage than with a dirt bike IMO.

The brushless motor controllers are basically three standard controllers and some circuitry to synchronize them, which is why they're so expensive.

What I'd really like to try is an induction motor, but I haven't seen any that are small enough. They're all car sized.

[Grider Pirate]

Luke,
In a previous post, you mentioned having meters for distraction. I was wondering if you have noted your current draw at say, a steady 25 mph on level pavement.