ANY FULL SUSPENSION FRAME IS SUFFICIENT. WITH ELECTRIC ASSIST, YOUR AVERAGE SPEED WILL BE HIGH. YOU WANT YOUR WHEELS ON THE GROUND. Unified rear suspension (URT) is the term describing the configuration of the rear triangle that is most conducive to suspension singlespeed gearing. Gary Fisher Joshua, Trek "Y", Klein Mantra, are some examples. I like to modify the rear dropouts into a track-bike style rear fork (The correct nomenclature for track style dropout is "rear fork").
You can buy aluminum or steel dropouts and rear track forks from frame builders or make your own. Measure, then hacksaw and grind off the vertical drop, and TIG or MIG weld new ones on.
Sadly, I'm not a decendant of an Italian frame maker. I make my welding jigs from Honduran mahogany, because that's what good carpentry levels are made from. It's incredibly accurate to set up using a bunch of clamps, strait edges and carpentry squares.
If you don't weld, Any welding shop will work with you if you have your jig already made. GEARING:
The motor eliminates the need for a multitude of gearing. Singlespeed affords clarity and freedom from dérailleurs and a dozen sprockets. Calculate your gearing to be about comfortable... 70 rpm cadence at 15mph is good for me. That's about 49 teeth on the chainring and 18 teeth on the freewheel. Once in a while, near the top of a hill, I might have to get up off the seat for a few hard pumps, but not often.
We should talk about speed here... If it is your fantasy to go thirty-five MPH on a bicycle (it was mine too at first), you might want a gasoline powered moped or scooter instead. It just isn't safe, or legal for that matter.
If speed's your thing, this Swiss made bicycle is pretty fast... http://www.youtube.com/watch?v=-vyOwvEKms8THE LAW:
There is a Federal law about electric bikes. Early in the days of the Iraq war a bill was slipped onto YOUR
Presidents desk, and I guess he signed it without much thought (surprised??). http://en.wikipedia.org/wiki/Electric_bicycle_laws#United_States
Generally, how I interpret it is as follows. First of all, it has to have pedals. It says... You can have an electric bicycle with one horsepower (750 WATTS) on demand, that is limited to powering itself up to 20MPH. You can pedal to make it go faster than 20MPH, it's just that the motor, by itself, isn't allowed to make it go over 20MPH. The bike requires no license to operate (no points on your driver's license for rolling through a stop sign?), and needs not to be insured like a motorcycle (unless there is a state or local ordinance governing this). It can be driven on any bike trail even when it says no motorized vehicles (and I stress BIKE TRAIL...PLEASE STAY OFF FOOTPATHS!!!).
The rest of the world is in awe of this USA law and very jealous. Many countries, Asia, Europe... are limited to 15mph and "pedelec" which is where you don't get any electric assist unless you are spinning the pedals. The twist of the wrist, "on demand" power is infinitely better.
I'm not sure how your local gestapo will enforce this law. On my way home from work, there's a long downhill run that I always pedal down furiously, tuck in tightly, and watch until my speedometer hits 35mph. Then I sit up and take a hard left over the river bridge. Kinda reminds me of my steel shoe half-mile racing days on my Bultaco. The speed limit is 25mph, so this behavior attracts cops. When I'm stopped and asked "Goin' a little fast there eh pal", or "Do you know how fast you were going?"... The cops never notice the hub motor or battery pak. I politely listen to the safety lecture, agree with everything they say, assume a submissive posture, display remorse.....look them in the eye, and begin my explanation with "Honestly, officer...". These days, I find a psychological approach more successful than my old ways of giving directions to the nearest donut shop. Anyway, even if the oinkers could detect that you had a motor, they have no means of determining the wattage. The law isn't clear about peak or continuous power. Many bikes claim peak power numbers in their motor advertizing. Wear a helmet.
20mph IS PLENTY FAST!!! AND...YOU CAN'T GET ENOUGH TORQUE OUT OF ONE HORSEPOWER TO GO MUCH FASTER.
This reminds me... There's a moron somewhere out in California that surfaces on eBay from time to time, advertizing a 55mph electric bike. He has some Brushless, Gearless, Chinese motor over-volted to 72 volts with an an array of NIMH cells strapped anywhere he can fit them all over his rigid framed aluminum bike. You are encouraged (only by him), to buy this thing. It might be an interesting way to die if you've been contemplating suicide. Come to think, haven't seen his ad on eBay lately...
Keep it in perspective...
I use my bike to go to work, park at the bank, park at the post office, get a couple bags of groceries, visit friends, and cool down on a hot summer night. Ann Arbor has big hills. There's no sweat with electric assist, so you can ride in comfort to work on a hot, humid day.
Sheldon Brown has a great gear calculator... http://sheldonbrown.com/gears/
Match the gear calculation with the 4QD roadspeed calculator... http://www.4qd.co.uk/faq/roadspd.htmlMOTOR:
I wouldn't use anything but Heinzmann. You have a lot of options...
There's much hype about brushed vs brushless, and geared vs gearless.
I stand by brushed and geared. The good stuff doesn't wear out and is repairable if it does. Any damn fool can clean an armature and replace brushes.
I weigh 180lbs, my bike weighs 50lbs. Performance wise, I can't tell much difference between a 400W and a 500W motor. The 400Watt motor gets better mileage.
There's a difference between continuous and peak power. A 500W continuous is about 750W peak. Electricity is a lot of fairly simple math. I "overvolt" 24V 400W Heinzmann motors to 36 Volts with no overheating of motor. It adds about 7MPH. I don't stress it and am always pedaling with the motor (there's not much else to do on a bike but pedal along, and it increases your mileage).
Link to Heinzmann... http://www.heinzmann.de/index.php?option=com_content&task=view&id=215&Itemid=277&lang=de
The best English speaking Heinzmann site in the world is the Kinetics bike shop in Glasgow. These guys have been very helpful, and I buy motors from them. It's painfully expensive, but the service great, and it is worth the cost. http://www.kinetics.org.uk/html/heinzmann_kits.shtmlBATTERY:
AVOID LEAD. ITS ONLY REDEEMING QUALITY IS THAT IT HAS A LOW INITIAL COST. IT'S WAY TOO HEAVY, TAKES FOREVER TO CHARGE, ALWAYS FAILS BEFORE ITS PROPORTED 300 CYCLES, CAN'T BE LEFT IN A DISCHARGED STATE WITHOUT DAMAGE, DOESN'T REALLY PERFORM AT ITS RATED AMPS (A 12 AMP LEAD BATTERY WILL ONLY HAVE ABOUT 7 USEABLE AMPS. BEYOND THAT YOU'RE DOING DAMAGE)
I FAVOR NICADS. THEY ARE THE BEST COMPROMISE. MY EVERYDAY BIKE (MY DEMO), HAS A 36 VOLT ARRAY OF SANYO "D" CELLS. THE BATTERY IS DATED NOVEMBER 1999 AND I CAN'T TELL IT FROM NEW. IT WORKS JUST LIKE DAY ONE. I CAN'T SAY FOR SURE HOW MANY TIMES I'VE CHARGED IT, OFTEN TWICE A DAY (a full recharge takes only two hours), BUT WAY OVER A THOUSAND TIMES FOR SURE. I USE A $250 NICAD CHARGER. That probably helps...
These fellas have lots to say and sell about battery cells and chargers...
KLEIN MANTRA BUILD LIST:
400 WATT HEINZMANN HUB
MAGURA POTENTIOMETER TWISTGRIP
HEINZMANN 36 VOLT BATTERY AND CONTROLLER
BROOKS PRO SADDLE
BROOKS LEATHER GRIPS
SUN MAMMOTH RIMS
PHIL MOUNTAIN SINGLESPEED REAR HUB
AC HEXMETRIC CRANK
DK IRON CROSS PEDALS
If you've never been on a Klein Mantra, try one.
They are Soooo..... Smooooth