One interesting phenomenon which I noted this morning that I hadn't expected- you know how when we were kids on BMX bikes, you occasionally wanted to stand up and fling the bike sharply left to right (like a NASCAR driver scrubbing the tires) while coasting downhill? When you do that, you can really feel the gyroscopic stabilizing effect of the newly massive rear wheel. It's not really problematic, I just wasn't expecting it.
Ok, the complete rolling assembly, fully loaded with all the electrons it'll hold, is about 67 lbs. On par, that's about double the weight of an average steel-framed 26" MTB. I found a spec on the wheel/motor assembly, which is 14 lbs. Seems about right from what I recall- about the same as an obese chihuahua.
Not too bad, actually. Of the total weight, the battery is about 9 lbs. So doing the math, a person rolling around with an equivalent 12Ah worth of high-rate SLA would chime in at about 86 lbs, plus the weight of a substantially more robust rack than the one I'm using. (And, of course, SLA isn't going to deliver the same DoD as LiMn, so a fairer comparison would probably be something in the neighborhood of a 20Ah SLA stack, which by the time you add a rack and support structure capable of carrying the pack would tip you just over the century mark.)
Seems pretty reasonable. The rubber I've got on the bike is surprisingly heavy, actually. I did a little research, and I'm rolling around on 4.6 lbs of tire and about 4 lbs of tube. A small price to pay for all that kevlar- hopefully you won't see me roadside with the bike upside-down and inflator in hand.
Which reminds me, I need to stop by the grocery store on the way home today and pick up some more Bacardi-brand ethanol.
EDIT: Huh. Just realized that was post #10,000 for me. And it had nothing at all to do with Miatas, turbochargers, or cats.
Any idea how much of that 67 lbs is the original bike, pre-modification? While it would change the budget of your build, it's not too difficult to find used MTB's in the sub-25 lb range, particularly if you avoided anything with a suspension fork.
Wow! Is that an SLA pack sitting on a seatpost rack? You're a braver man than I.
Yeah, it's kind of hard to know with AmpedBikes exactly who is copying whom. Their DD hubmotor is apparently a copy of a NineCo design, made by a different factory on a line which is specific to Amped. The controller itself (the black one, anyway) is an actual NineCo part- says so right on the label on the bottom. And the battery pack, well, that's an interesting one. BMSBattery sells one which is very similar, but appears to be smaller in diameter and has a lower AH capacity, along with slightly different control placement. However, the Amped battery tube actually has Amped's name and patent number molded directly into the upper cap, so it's clearly a unique part to them.
So, the update: last Thursday while on the way to the office, I was climbing a 10% grade at full throttle while pedaling hard, and the whole system just went dead.
Figured maybe I'd tripped some kind of overcurrent protection, so I shut the system off for a bit, tried again, and still nothing.
Continued on to work, cursing rather furiously. Caught a ride home that afternoon, and brought the bike back home on Friday.
Meanwhile, I called the vendor, and they told me I'd probably blown the controller and that I shouldn't be trying to climb hills unassisted. I very politely informed them of the approximate number of times that the word "hill" appears on their website and marketing literature (quite a few), and that I was not trying to race up the side of Palomar Mountain on knobby tires, but that this took place on a very pretty paved city street with bike lanes, sidewalks, and well-groomed flowers in the median.
I also explained that since the "fuel gauge" on the throttle was dark, this seemed more like a battery problem than a controller problem, but they persisted and sent me a new controller, which arrived Monday and did not fix the problem.
I then did something I should have done Thursday morning, which was to remove the battery from the frame and measure the voltage on its output terminals. Zero.
Called 'em back and they had no explanation. Suggested I ship the whole package of battery and controller back to them for analysis.
So on Monday evening, I'm standing there looking at the battery as it sits on the workbench and I notice an odd-looking little cap on the bottom of it. It's not labeled, but it's got a philips-type cutout in it, so I unscrew it.
A fuse falls out. Well, both halves of it, anyway:
I'm dumbfounded. A glass fuse in a lithium battery? I'd been assuming that they'd have used a solid-state overcurrent protector, like a polyfuse or something.
It gets worse. This fuse is rated at 20 amps. The controller self-limits at 22 amps.
Get out the calipers and measure the mortal remains. It's a 5x20mm fuse, which isn't exactly a common style in the US.
Ok, so now it's fuse-shopping time. Yesterday, I go to Fry's at lunchtime. They've got a whole rack of 5x20 fuses, but none larger than 10A. I stop by Grainger, same deal. The auto parts stores don't even carry 5x20 fuses, despite the fact that they still stock those stupid open-frame fuses that German cars used 40 years ago.
Digikey, Newark and Mouser all have 5x20 fuses, but 20A seems to be as high as they go. What the heck? I ordered ten 20A fuses from Mouser. Nine of them will be going into my roadside repair bag.
Exchanged a few emails with the owner of AmpedBikes, and apparently they've "been having some problems with our batteries." Apparently he didn't even know about this fuse (?!?) because he thanked me and informed me that I may have just solved the problem they've been having. He's on a quest to find larger fuses now, and supposedly has a source for some 28 amp units. I have no idea where he's getting them.
Meanwhile, I've apparently become some kind of hero over on the AmpedBikes forum, as some other folks have been experiencing mysterious failures, and nobody could figure out why, despite a bunch of pointless and erroneous diagnostic suggestions. (Are the wires connected? Did you try power-cycling it? Maybe your controller is blown?) I mentioned the tiny little fuse holder, and what do you know? They've got blown fuses too.
Neither. Lightbox as in a box constructed of a frame and translucent white walls to diffuse lighting, especially for macro photography.
Oh, I gotcha. (I was an ENG cameraman, not a studio photog.)
No, I just set the fuse on top of a sheet of paper on my workbench, brought my gooseneck lamp (with a CFL bulb) down above and to the front of the fuse at a distance of about 12", and used my Canon S90. I didn't record the exposure settings, but I think I was at something like ISO400 and maybe F6 or thereabouts with a 1/60 shutter speed.
For the record, the S90 is the second-best compact camera ever created.