Kona Stab, 8T Mac, 20S A123 20AH

Hey ES, thought you might like to see my 2nd build:


Here are the specs:

Bike:
Frame - '04 Kona Stab, Hayes Nine brakes, Fox Vanilla rear shock
Fork - '03 Marzocchi Junior T
Tires - CST Cyclops
Handlebars - Diamondback BMX Trail
Saddle - Schwinn cruiser

Electronics:
Motor/Controller - 8t Mac in 26" rim/45A 12 fet Infineon with DP CA
Battery - 20s A123 20ah

Everything Else:
Torque plate - McMaster Carr slotted washer, modified
Brackets - 1-1/4" round accessory clamp bracket
Supports - 6"x6" angle aluminum
Battery Bag - Ape Case 1000
Headlight - 12-80V 3W LED Spot Light

Here's my torque plate. I used a McMaster Carr slotted washer, thanks to migueralliart for finding these. The washer was slightly wider than the axle, so I made it pinch. I cut the notches out with an angle grinder and used a drill press for the holes.

View attachment 9

Like others, I was impressed by Oatnet's fork mounted battery solution. But I also wanted a quick release for the battery so I could take it off the bike when I needed. Here's what I came up with. Instead of mounting the battery directly to the brackets, I mounted 2 pieces of 6"x6" aluminum to use as supports.


I thought for a long time about how to make a quick release method; it had to be simple and use off the shelf parts. Eventually I settled on some stainless conduit clips mounted to the rear of the battery and a quick release pin.


When the battery is mounted on the supports, part of the hoop extends past the edge of the aluminum where the pin can be inserted. Due to the position of the handlebar stem, when the pin is inserted the battery is effectively immobilized. The pin is held in by friction which can be adjusted slightly by tightening or loosening the bolts that attach the clips to the battery.


I had originally planned to use a Hardigg Storm i2075 case for the battery, which is slightly larger than a Pelican 1300, but when I got it I found out that it tapers slightly from top to bottom and and the A123s wouldn't fit. So I looked for another solution and eventually settled on the Ape Case. It fits the A123s like a glove and IMO is quite attractive. I was a little concerned that it was a softcase, so I reinforced the sides and bottom with some steel plating cut from an old computer case. This also helps with the clips as it gives them something solid to bolt to.

The battery assembly is strictly low tech. Fold, crimp, repeat, Oatnet showed ya how. Right now I'm running without a bms and balance charging in 5s blocks with a hobby charger.


As you might imagine, the ride is way fun. I've been grinning ear to ear for a solid month. I love the looks I get from people - how's he going that fast on that bike? I'm having a ball cruising around at 31 mph (75% power) and having the ability to burst up to 37. My goal was to make a fast urban commuter and I think it succeeds. I've given some friends a ride and they all now want one.

More pics:

Awesome build! clean looking. love the battery mount..keeps ya from flipping over

Thanks skeetab! The battery mount is what I'm most happy with. I love it when simple solutions work out.

Excellent job on your 2nd build, a nice creative battery solution and I know it rides smooth too. It's good to have another high speed e-bike here in KC.
- see ya soon...

Nice and clean!!

I also have a Mac 8T and a 20s A123 pack. It gives me 25MPH max speed on a brompton.

Did you buy the cells from Victpower?

Great build, very practical machine

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+1

Beautiful, clean build. Love that front battery bag mount!

Looks excellent!

Tom

Thanks everyone for the kind words. I'm a true believer now, spreading the e-bike word to anyone who'll listen Can't wait to do my next build.

cwah - yes I got the cells from Victpower. Very easy transaction, would definitely buy again. Bet that Brompton has great acceleration.

geetarboy - yes, let's get together for a ride soon.

Very Nice Indeed!

It's my birthday tomorrow! 49......... last of the four-ties.... but still building and experimenting! woooo hoooo!

Beautiful build.....

How do you like the 8T Mac? I'm interested in a gear motor build. Is it loud?


Again.... Nice build

Tommy L sends... \\m//

HI Tommy, thanks and happy birthday!

I really like the Mac a lot. Quite a bit of torque for such a small package. I don't think it's loud at all. It's just a tiny bit louder than my friend's DD, but not much. In fact, most people who've tried my bike have commented how quiet it is. I think they were expecting something louder. After you hit 15 mph all you hear is wind.

Personally I think the mac gets pretty loud when you approach 1000w. Kinda like a powertool sound. Definitely not what I would call stealth. Even in low setting I won't use throttle on bike trails as it draws unwanted attention.

Great build! I really love the torque of the mac, really yanks you back when you pull throttle.

I'm getting ideas for my imminent build. I've got some questions for you, if you don't mind:

* Does the fork-mounted battery bag affect steering/handling?
* Is the controller ziptied to the top tube stable? No side-to-side movement?
* Did you need a shim to connect the handlebar to the stem? How do you like the rise for comfort?

onlineaddy said:

I'm getting ideas for my imminent build. I've got some questions for you, if you don't mind:

* Does the fork-mounted battery bag affect steering/handling?
* Is the controller ziptied to the top tube stable? No side-to-side movement?
* Did you need a shim to connect the handlebar to the stem? How do you like the rise for comfort?

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Hey, I'll answer your questions as best I can:

1. Yes, the fork-mounted battery does affect the steering. To me it feels sluggish and I need to put more effort into making a turn. Also, the 1-1/4" mounting brackets reduce the amount the front wheel can rotate, so I can't make as tight of a turn. That said, after riding for a few minutes I don't really notice it. At speed the weight on the forks actually stabilizes the bike. If I was doing slower, more technical riding I'm sure it would be an issue but for street riding I think it's fine.

2. Yes, the zip-tied controller is stable. I put a couple of pieces of rubber between the controller case and the frame. This let's me tighten up the zip ties a little more and the controller won't move unless you put a lot of force on it.

3. Yes, the bar is a 7/8" tube and the stem is a 1" clamp so I needed a shim. Amazon sells them; I made my own out of a piece of scrap. I do like the rise for comfort (I'm basically sitting straight up and down) but it's not so good for aero.

Thank you, theGoPedal, so much for taking the time to answer my questions. I really appreciate it. Your build is impressive and has helped me and others as well, I'm sure.

Nice looking build there. Well done!

Just a couple of quick q's- what sort of power are you running through the motor (volts/amps) and are you monitoring temps inside the mac?

Very nice. Tidy and good engineering. I like the quick release battery and the clamping torque arm... but only 1 torque arm? 2 is good for safety
and you choice of bike, yeah, nice one.

Spicerack said:

Nice looking build there. Well done!

Just a couple of quick q's- what sort of power are you running through the motor (volts/amps) and are you monitoring temps inside the mac?

Click to expand...

My 20s pack is around 60V under load, with a 45A controller it will produce a maximum of about 2700W. But I only see that briefly during acceleration and going up steep hills. I like to cruise at about 30 mph which, on the roads around here, uses about 800-1200W. I did get the upgraded motor from cell_man with the thicker phase wires and the temp sensor, but currently I am not monitoring temps.

pendragon8000 said:

Very nice. Tidy and good engineering. I like the quick release battery and the clamping torque arm... but only 1 torque arm? 2 is good for safety
and you choice of bike, yeah, nice one.

Click to expand...

Thanks, I'm happiest with the quick release. It really works well and was so simple to implement.

I had planned to use two torque plates, but the bolts I used to attach it to the dropout interfered with the gears on the drive side. I just couldn't make it fit. It's winter here now, so I took the motor wheel off the bike and inspected the dropouts. Everything looks good - no deformation. But now that you mention it, I just had an idea where I could counter-sink the bolt holes on the drive side and use flat-head screws. I think that would work and not interfere with the gears. Thanks, I just put that on my list of off-season upgrades.

" Everything looks good - no deformation. But now that you mention it, I just had an idea where I could counter-sink the bolt holes on the drive side and use flat-head screws. I think that would work and not interfere with the gears."

Yeah that sounds like a good idea. If an axle spin out occurs at high speed in traffic you may get damaged.