GSB's electric Felt Hardtail

GSB

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I wasn't going to post about this particular bike, since it's not retro, and it's certainly not the sort of thing normally seen on Retrobikes...

But, Another member asked me to enlighten him in another thread;
letmetalktomark":2l2yii30 said:
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Great Scott there is a lot going on in this pic:

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More details and pics please :cool:

So here's what became of all the bits and pieces I've bought from many of you over the last 18 months or so...

First up, the frame. A tired, well used Felt Q650 Hardtail that I got from Racin'snake for a very reasonable £40 inc postage...

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It was well past its best in terms of cosmetics, so I sent it, along with some other sundry parts, to Maldon Powder Coating for a coat of dark blue with slightly sparkly lacquer. I went for powder rather than paint because it's outrageously tough.

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Add a motor from a cheap Chinese e-bike kit;
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A basic variable speed motor controller, also from China;
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A set of laser cut brackets made by a very nice man in the USA;
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A supervising control computer (CycleAnalyst) from Canada;
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A 70 volt battery from Hong Kong (LiFePo4 chemistry, heavier than LiPo which is normally used for these things, and not able to deliver huge currents without doubling up the cells, but on the plus side they last ages and don't set fire to your house)
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Plus a few yards of wiring for throttle, selector switches, power feeds, speed and cadence sensors;
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Power from the motor is transmitted via an assortment minimoto and go kart chains and cogs via a jack shaft and a freewheel (so you can pedal without driving the motor), and then via a BMX half link chain to a freewheeling crankset, provided from an old scrap MTB by snowdonstumpy. There's an ACS BMX freewheel in the middle of the crankset that lets the motor drive the chainrings without the pedals turning.

Suspension up front is a set of carbon Pace RC40's purchased from ajantom, accompanied at the rear by a carbon USE Sumo suspension seatpost from SebRogers.

Brakes are Hope Mono's from VeloFrog. His 6 piston monster was perfect for a bike that isn't quite as lithe as its makers intended.
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Other parts came from ebay. Crank brothers wheels (no longer on it) pedals, stem and saddle, Sram rear mech and shifter (it runs a single chainring at the front, so no front mech), various plugs and sockets from the automotive world, a rear carrier for the battery pack, a framebag for one of the controllers and my sandwiches & waterproofs, and a set of carbon bars. It uses a sram gripshift mounted on the left side (takes a bit of getting used to) since the right side is taken up with twist throttle, selector switch, and the all important kill switch.

Power delivery in legal mode is a peak 250watts of assistance (the motor only works when you pedal too) up to 15mph. The CycleAnalyst computer manages the power and speed components, and is what makes this particular bike legal to run on the roads. All the Chinese ebike kits are technically illegal in the UK, as they are just to powerful. At this level you can happily commute to work without breaking a sweat, and could probably cover 100 or more miles on a single charge. Bear in mind that a tour de france cyclist puts out about 400watts, and you get a better idea of what sort of power outputs were talking about. The motor is a sturdy beast though, and some owners have reliably thrown 100volts and almost 3 kilowatts through them. Problem is that at that sort of power level, bicycle transmission lifespans can be measured in minutes, as can the endurance of your battery. The software in the computer allows you to select various levels of power assistance, throttle maps, even cruise control, or you can configure it to give the motor and its controller free reign, at which point your limited only by the amount of power you can physically pump through the thing. At present everything is limited in my bike at a more than scary 1200 watts. Depending upon your gear, this is enough to do about 33mph unassisted, or ride straight up a flight of stairs...

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Any questions on this decidedly non-retro machine happily answered...
 
What's the weight of this beast. 33mph you would get a lot of looks over taking cars in the high street. :)

Also are those crank bro's the xc cobalt variant.

Used to own the first edition champagne coloured ones ;)
 
33mph in the high street would also get me arrested!

UK law is a bit confused when it comes to ebikes, but someone will eventually do something monumentally dumb and the powers that be will crack down. Power is the key issue, but it's not clear where the power should be measured, or how. 250 watts is the key number though, and only up to 15mph. Electric motor output is dependenant upon many factors, not least of which is how many volts you run through it. I chose 70 volts since it makes for less wieght and longer range, and it runs the motor at an efficient speed that can can also be geared down enough to run the pedals at a speed where you can keep up with them without resorting to huge chainwheels. To be on the safe side and keep it legal, the throttle is not directly connected to the motor controller. Instead it's connected to the the PID controllers in the CycleAnalyst, which measures road speed, pedal cadence, battery voltage, and current flow, and outputs a fly-by-wire throttle signal to the motor controller. When the power to the motor approaches 250 watts, or the speed approaches 15mph, it tapers the throttle back so that neither parameter is exceeded. This was the only way to keep the thing legal, but it adds a massive amount of complexity to the build. Eventually someone from the DoT or the police is going to figure out that there are sellers all over the internet flogging kits that turn bicycles into unregistered, unroadworthy, and uninsured motorbikes, and when that happens I want to be squeaky clean, since the penalty for using more power than is legal is siezure of the bike, points on your license, and a big fine.

That said there are are other user programmable and selectable modes on the Cycle Analyst too, one of which is set to a more usable 750 watts, and the other is the full fat 1200watts. The motor will happily pull enough Amps to melt it if given free reign, some guys in the US are pumping 2 or 3 times as much power through them, but range suffers dramatically at these high power settings, as does reliability. So far I've found that chains don't last more than about 100 miles at full power, and tyre tread disappears before your eyes!

Wieght is an issue, nothing comes for free, and I think there's about 15kg of extra hardware on board. The battery is the worst bit, 9kg and mounted on a pannier rack, it has a pretty awful effect in handling. In a future rebuild (I want full suspension as wrestling this thing around is turning my arse to burger meat!) I might move it with the frame triangle lower the centre of gravity and get some agility back. I might change the primary drive to a toothed belt too, since the go kart chain is a bit noisy.

The wheels are 2012 Cobalt '3's in silver. They're not on it anymore as I didn't want to ruin them, instead it's running a fairly bog standard looking set of Hope hubs (tough as nails) with Mavic rims.
 
Reminds me of 'Madge' out of Benidorm for some reason, but it's good that you're not letting you're disability stopping you from getting out on a bike. Well done.
 
superstar1":tk5n72ma said:
...it's good that you're not letting you're disability stopping you from getting out on a bike. Well done.

:facepalm:

If that's a joke, it's really not funny...
 
Re:

Did I see this jalopy hurtling down the Hogs Back the other day?
Whatever it was was doing a fair lick!
 
Re:

suburbanreuben":3hbyox8w said:
Did I see this jalopy hurtling down the Hogs Back the other day?
Whatever it was was doing a fair lick!

Wasn't me, but these things are becoming more common now.
 
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