Power Steering Pump Repurposed for Great Speed

Electric bikes are getting a lot of attention lately. Pretty much anyone can buy a kit online and get a perfectly street legal ride with plenty of range. But if you don’t want to take the kit route, and you’d rather take a tack that will get you noticed more around these parts, take some notes from [Jule553648]’s recent build that definitely isn’t using any parts from a kit.

The motor from the build is an electric power steering pump from a junkyard car. This gets mounted on a one-off rear bike rack and drives the rear tire with help from some gears from a pocket bike gearbox from eBay. A lot of the parts in this build were designed and built using CAD and a machine shop, and the parts for the battery and the power controller were sourced via China to save on cost.

The whole build has a homemade vibe that we find irresistible. The bike can go 35 km/h on level ground without breaking a sweat and has about 40 km of range which is nothing to scoff at. It might even be street legal depending on the wattage of the motor and whether or not you live in Europe (where throttles are generally not allowed on electric bikes). If you’re lacking a machine shop, though, we featured a very well-built kit ebike a while back that you could use as a model to get your feet wet.

45 thoughts on “Power Steering Pump Repurposed for Great Speed

  1. Good experimental use of ex automotive gear :-)
    Now could you use the hydraulic side to also do something interesting, shockie’s pressurising to change mode of suspension perhaps. With enough of those motor/pump combos could be lots of possibilities. Nice to see a completed bike project with different approach, satisfying when diversity leads to outcomes with good utility :-)

      1. As it seems we know that now which was noted after my post, please note there are godamme date/times our comments :P
        In any case, aren’t there vehicles around with electric driving a game hydraulic pump, may be they go back a bit, essence of my post still stands :-)

        1. *vane not game
          Android auto-correct, an edit mode would be helpful, even with 5min timeout.
          Iirc early model MR2 Toyota had electric driving hydraulic pump, some nice overlapping control options there when you can feed into proportional valves.
          Hey ! Make your own hobby press-brake off a 12v DC supply, just needs & to V block :-)

          1. almost every vauxhall(GM) and VW/Audi group car here in the UK has electric-hydraulic power steering pumps. tho they are all self contained units.

            most cars nowadays (again, in the UK as that’s where my experience lies) have electric motors on the rack or column to provide the assist. I changed the EPS motor in a Citroen c3 picasso yesterday and it’s substancial to say the least. much bigger than the motor used on this bike.

          2. Hydraulic power steering is run mechanically off the engine, but there’s no clutch so it’s inefficient. An electrically driven hydraulic pump runs on demand and so saves energy, but the motor has some inefficiency which cuts into the gains. An electrically driven assist has no hydraulics, so is most efficient and doesn’t have all that hydraulic crap to worry about: hoses, pulleys, belts, fluid. Before they got the technology figured out, a motor-hydraulic hybrid might have been a good compromise. Or not.

          3. the electro-hydraulic pumps run at all times, certainly every one I have seen or diagnosed. .. the electric only assist is indeed enabled based on load tho.

            (Am an auto-spark and garage owner)

    1. Well yah you remember your little econobox from back in the day, your first car, that had power nothing, it barely had power starting, and steering was direct mechanical turning those little 155 wide tires, and think power steering is for wimps…. and then try turning the wheel on a modern beast with 285 wide tires with the ignition off… ooof.

    1. EU requires pedelec to be only assistance motor, ie you have to pedal.
      Motor should cut at 25km/h and limited to 250w peak. Otherwise it’s a motorbike and should be treated as such (plate, lights, mandatory helmet, insurance..)
      Note that in some EU countries like France, as soon as you have a motor driven vehicule, you should have insurance for it, even if always used on private ground. It even applies to seated lawnmower (but most house insurance take care of it). EU is going to move in this direction also, mandatory motor vehicule insurance.

      1. https://en.wikipedia.org/wiki/Piaggio_Ciao

        Piaggio Ciao was a moped with pedals made from 1967 to 2005. It had a 2-stroke 50-cc engine and pedals: to start the engine you had to use the pedals, and you could use them when using the engine to helpi it on steep hils or when you emptied the fuel tank…

        You you can have a moped with pedals. By the way I think one could do a nice hack on one of those mopeds.

        1. In my region it has to have pedals to be called a “moped!” A moped is something most people only see once every few years, too. If it is bigger than a bicycle and smaller than a motorcycle, and doesn’t have pedals, that’s a scooter.

          But anything speed-limited to 15mph or less that has 2 or 3 wheels is automatically considered either a bicycle or a “personal mobility device,” which have the same rules.

        2. The traditional moped is a motorized bicycle and so have pedals. Then legislation changed in many (but IIRC not all) places to not require pedals and so the “modern” moped was born. Given that this happened in (IIRC…) the 60’s most people associate moped with a super-light motorcycle rather than motor assisted bicycles.

      2. AFAIK you can still have a throttle, but you need the pedal sensor also. I.e. you can adjust power level any way you want, buttons / switch / throttle, as long as the motor stops when you stop pedaling.

      3. Where i come from, 0-250W, no throttle, max 25 km/h is a “electrically assisted bike”. +250W-1kW is an electric bike, can have a throttle, no need to peddle, but max speed still 25 km/h, needs a traffic insurance. Over 1kw and over 25 km/h is a moped.

    2. Because there’s a difference between an motor assisted bicycle and a moped/light motorcycle. The electric motor is only allowed to provide some extra power.
      Fun fact: it’s often legal to manually pedal much faster (>2x) than the assist motor is allowed to help.

  2. This is a pretty impressive span of fabrication methods; cnc/lathe, laser cutting, 3D printing, hand welding etc. all with very good results (clean build, good speed/range and 2 – 3 hour recharge time) making it a reasonable bet for modest commutes.

    With all of that (and with nearly of these builds), nobody puts a freewheel on the drive side to allow the beast to be pedaled in any reasonable fashion without spinning the motor in reverse against the gear train.

      1. A clutch on the brake should work to engage the motor-generator. I wouldn’t want the motor spinning all the time while coasting. As light as a bicycle is, there is not much energy to recover though.

      2. You could use a Shimano Front Freewheel (FFS) from an old Schwinn Suburban. It was always described as a solution waiting for a problem, this might be the problem! A few other bikes used it, but the Suburban was the only mass-market one I think. I’ve got one from 1975.

        Unfortunately, the vast majority of these bicycles have been “upgraded” to use a normal freewheel.

        Basically, you have a freewheel in the front so that the chain still spins while the pedals are stationary. This allows shifting while coasting, something they thought might make things easier for new riders. So anyways, then you can steal power at the back wheel for braking!

        The only problem, there is a second freewheel, called a friction freewheel, in the back wheel, but it has plastic shims that prevent it from spinning unless the force exceeds some fixed level. The purpose is so that if your toe gets caught in the chain, it is less likely to get cut off. So if you leave this important safety feature, then you can still apply braking force at the motor, as long as you stay below the toe cutoff.

        So you do have to have both the intact bottom bracket, and also the original rear wheel, to do the conversion.

    1. Thanks! I did not put a freewheel because I wanted to experiment with regen and engine braking. I didn’t put a freewheel because the build was already too complicated to start with and I had no appropriate freewheel at hand. I would added it later if I needed it, but I found out that I don’t need it. The bike is quite heavy, it has a steel frame, it weighs 19kg before transfomration to electric. I did not weigh it yet, but it should weigh close to 30kg. If you want to pedal it, you will not get far freewheel or not (the motor doesn’t drag back significantly), so you can use it only as a motorbike, and you pedal only when the hill is too steep. My controller currently doesn’t have a regen, but it has a motor brake which can come in handy, and you save some brake pads which weren’t intended for such weight. As for the regen, I found out that I don’t need it, because I have 40km range already. And you don’t want to sit on a small bike like this for this long.

    1. +1 but I got sidetracked by the whole “can’t have a throttle in eu” thing, bit what they mean is. You can have an electric bike but to ensure its pointless you still have to pedal.

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