Endless-sphere.com member “MattyCiii” decided to put together an extensive build based on a Norco A-line full-suspension off-road bike. With most builders, I have to pry important details from them so our readers will be able to know that “if I do this, I will get that”, but Matty?…he readily supplies all of the details to anyone who is interested.
“…I’m using Magura Gustav M brakes on the rear because of the tiny, ~10mm clearance between the left-hand chainring and the brake rotor. The rear suspension shock will be a used Fox DHX 5.0
BB kit is an Schlumpf/ATS drive. The wheel gears are a NuVinci N360 with a 20T sprocket, electric power on the left via a Recumpense DaVinci drive. Chain tension is an upgraded Surly Singleator.
I’m aiming for 12S LiPo (32-Ah), for ~50V hot of the charger. That’s all the Castle HV160 can take. The motor is an AstroFlight 3220, 4 turns of wire, terminated in WYE. I have to reduce that speed back down to something useful, with the large diameter of those monster tires. The motor mount is water-jetted aluminum that is 0.375″ (9.5mm) thick from bigbluesaw.com.
I started with high C-rate (30C if I recall correctly), 8-Ah batteries, that were bundled as four parallel, ensuring the load on any one cell is not too high even under high demand. Eventually I’ll be using MethTek Low Voltage Cutoff (LVC) boards to ensure I don’t bottom out any one 4-parallel cell bank. The batteries came with 5.5mm bullet connectors on 8awg wire, and I changed them to 6mm bullet connectors.
Now, I normally ride with just a 12S/2P 8AH for 800-WH of power @ 50V. This easily gets me through the 16 mile commute with 1/3 of the pack to spare. Plus I have room in the enclosure for the other half pack to re-install if I ever want to go on a looooong ride.
I charge through the balance taps now with a BC-168.
Primary drive belt is 20T/100T 5:1, and the chain secondary is a 13T freewheel to a 52T chainring 4:1, for a total of 20:1. It’s good for a 33-MPH top speed.
I checked out the data log on the Castle HV-160. I never peaked more than 70 amps. Watt hours per mile was in the high 30’s, acceleration is great…and the motor is only slightly above ambient temps when I touch it at at stops.
Acceleration with an RC drive is always insane. I consistently dial the throttle mapping to within 10% of its minimum on the CA-V3. So on Prelim 6, I run the bike at 0.09 volts per second on a scale from 0.01 to 99.99.
I now have an ebikes.ca analogger. Initial tests show the motor never gets above 50*c in aggressive urban riding with lots of stop & go and hills. I plan soon to start gearing down (say 15:52 on final reduction) for more top speed, knowing my motor will get hotter, but…will likely still be within its heat tolerance.
My first wheel-set: Spokes by JRH, rims from the Recumpense 47mm wide, 406mm diameter rim group-buy. The tires were Pirelli 16″ x 2.5″ ML75 moped tires. Something I never would have thought would fit a 406mm diameter rim without the ES collective knowledge base. It turned out they dropped the bike too low.
So then…I upgraded to the 21″ x 1.6″ motorcycle rims, I found a road/slick tread, 21″ x 3″ tire. http://endless-sphere.com/forums/viewtopic.php?f=6&t=37207&start=100#p618044 JRH carries 13-Ga spokes that have oversize nipples using #10 stainless steel washers, I stacked two washers on each spoke nipple. I only have about 4mm clearance between the Lefty and the tire up front!…”
“…I took a short test ride…the beast is heavy…It’s about 120 lbs with battery. I’ve ridden it quite literally up and down a flight of stairs, which is easy for the bike but challenges the gonad fortitude of the driver.”
“…The N360 plus a Schlumpf High Speed Drive gets me 360% gear range at the rear, and 250% at the front. There’s some overlap so it’s not quite as tall a range of these ranges combined – but I’ll tell you I have a granny gear so low it’s hard to stay upright at 80-RPM cadence, and yet can pedal power to the right side freewheel at 33-MPH, so it’s a good gear range…”
“Up front the fork is obviously a Cannondale Lefty (of course) that was custom machined by Project321 (http://www.project321.com/), who was incredibly helpful in getting me the right parts to fit a lefty fork to the Norco”
Getting the rims anodised the same green color as the frame was a wonderful touch.
Even though the bicycle spokes were fairly large, they needed washers to allow the motorcycle rim to be mated.
I really am fascinated by water-jetting, laser-cutting, and 3D-printing. You draw something on a screen, and hundreds of miles away, a machine does all the difficult cutting. Here, Matt drew this custom motor-mount and rear axle drop-out holder combination, which also extended the wheelbase a little.
The “750 Watt” wording is a joke. 750W is the national power limit in the USA, but Matts bike is occasionally seeing peaks of ~48V X 70A = 3400W
Matt was fully aware that adding weight near the rear axle adds “unsprung mass” to the suspension. However, he contemplated a wide variety of options, and this was the least objectionable for his goals.
He decided he wanted a “front basket mount” for the weight of the battery pack to have an acceptable weight distribution and balance.
The custom-ordered drop-out extenders/holders were machined by a CNC mill (Computer Numerically Controlled).
It looks like Matt made sure every part of his build was designed for strength instead of shaving grams for the lightest weight…I like it!
Here’s Matt with his creation at a July 2013 “Boston Bike Party“
Edit: Matt just sent me an update:
I’ve gone ahead and reduced the gear reduction from the previous 20T:100T / 13T:52T (1:20 reduction ratio overall) to 20T:100T / 15T:52T (1:17.3 reduction ratio overall). The motor runs a little hotter (50C/122F very consistently at the motor) as does the controller (temp peaks of 70C/158F at the controller) . [electricbike.com recommends 93C/200F as the MAX safe temps to shoot for, so Matt’s temp ranges are perfect!]
I’m seeing up to 120 Amp peaks now via both the CA-V3 and the Castle Creations data-logging. And my new top speed is 37-MPH. My goal is to get this bike up to a 40-MPH top speed, then install a 3-speed toggle switch where position: (1) is a kill switch, (2) is speed governed to 25-MPH tops (street legal in Massachusetts, and (3) is unlimited “for off road use only”
build log: http://endless-sphere.com/forums/viewtopic.php?f=6&t=37207
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Written by Ron/Spinningmagnets August 2013
