Please consider and discuss, hybrid motorised bikes, its not as silly as it sounds

Discussion in 'Photos & Bicycle Builds' started by libranskeptic, Jan 24, 2016.

  1. libranskeptic

    libranskeptic Member

    1/ legal issues affect many of us re petrol bikes. Laws are often largely honored in the breach, but why push your luck?

    2/ low torque petrol power is a pain to start and for stop go work (as are chain drives)

    3/ electric range issues ~go away with a regen capable motor and controller

    4/ adding a front hub motor is simple and cheapish (NB, i really think the premium for a 2 speed one is worth it)


    A front motor with regen and fast charge storage could charge the bike when under petrol power or braking. A; big, heavy, expensive battery is not mandatory. Just a; light, fast charge/discharge, ~5ah 36v one should do (36o watts of power for half an hour or 720watts for 15 minutes, even 1000 watts on a 3c max discharge battery like mainstream lifepo4 chemistry units).

    Getting rolling on electric and dropping the clutch = electric start convenience

    Use electric when cops are a risk, motor on back roads and hill climbs where the extra power is really appreciated. Once altitude is gained, a puny electric alone is fine. A QUIET petrol motor seems a must for similar reasons. Why push your luck.

    Much of life is factoring risk. Get this one wrong, and once the local cop has warned you once, your petrol bike may as well be scrapped. They dont like their rulings, no matter how silly, being ignored.

    Technically, it's only illegal if the petrol motor is powering it on a public road, maybe even if the motor is warm? "I only use that motor on private land officer" should work sort of.

    A simple example is a farm kid rides to the edge of town on petrol, and switches to electric around town. If he is sensible, the town cop may well turn a blind eye, even if he spots him on rural roads.

    Aside from the above, electric when it suffices, is so much more pleasant.

    Much as I love my mid drive ebike, the chain and cogs have been the most troublesome bit of an otherwise very maintenance free, joyous workhorse.

    For many, the extra traction of an AWD bike may have big appeal - mud/snow etc.

    I have to say, its kind of cool that such cutting edge prius like automotive technology, is so readily accessible to DIY folk in the bike world. I predict that for EV autos to work, they have to be lighter and simpler. The minimalist Nissan Leaf, is 1600 kilos for gods sake. Its just too big an ask for batteries to propel such mass very far for a long time to come. 150 kilos should be easily doable for a four passenger tuk tuk/mini moke type vehicle made from bike framing and bits.
    Last edited: Jan 24, 2016

  2. wheelbender6

    wheelbender6 Well-Known Member

    I understand the logic.
    When road conditions are unsafe (Or illegal for a gas motor), the e-hub motor can be used to propel you on the sidewalk or multi-use path without offending the joggers and walkers. A good 24v hub motor with Lipo batteries starts at over $600 around here.
  3. sbest

    sbest Active Member

    I am planning on doing just that.
    50cc Grubee engine for the open road and back trails, charging a very small Lipo 24v batterypack and a 500w motor for around town.

    I have a lot to learn before I get there. I have several electric bikes, all SLA powered, and HT powered bikes.
    I carry the electrics in my van and ride them around towns and cities, I use the HT powered rigs for long trips and experimenting.

    My end goal is to put the two together in a simple bike of under 40kg. Because pedaling and fuel are options, batteries don't need to be large. I am looking at a mid drive electric and maybe the gas motor too. I am a way from even starting to put it together.

  4. libranskeptic

    libranskeptic Member

  5. libranskeptic

    libranskeptic Member

    You do get it. Good. I am not alone.

    A great deal of the utility I get from my ebike relies on my ability to morph between being an honorary pedestrian and a road user. Screw parking hundreds of meters away. I park on the observable (and therefore secure even unlocked) doorstep or even inside of each of my errands premises. Relaxed and fast.

    Round Sydney Oz, it's a compulsory $1k P.A. before you even start/maintain/insure a car. So relatively, a once only cost of $600 is a rational choice for many. If a farmer mom can pass on driving kids to school even sometimes, its a bargain for a family. Range anxiety for rural folk is a killer factor, which precludes ebikes as an option for their needs, yet their need is great. A pre driving age rural kid is very trapped/isolated at home, and families are slaves to chauffeur duty for them.

    $600 sounds high. All i can say is based on firm quotes but hazy recall of FOB china prices maybe a year go received by me.

    A geared hub & controller kit, ~$80US, 2 speed hub motor ~$130. A 20ah 24v lifepo4 pouch cell lifepo4 battery $290 ~3 weeks ago. In theory, a 5ah should be 25% of that, which of course it isn't -maybe $150?

    Incidentally, I got a quote from a specialist re-spoker for A$100 ($70US~) locally. Given airfreight costs added by sourcing the bulky entire wheel in china, its tempting to just get the hub sent and scrounge a known quality rim locally.
  6. libranskeptic

    libranskeptic Member


    good for you. I plan similar, ONE OF THESE DAYS :). Trouble is, its just for a giggle. It doesn't suit me here in the city.

    As before, I love mid-drives, but I am a bit leery of having both motors power the same wheel. Sounds like a complex, stressed and awkward rear axle.

    Intuitively I would prefer the simplicity and the traction benefits of a AWD bike with a front hub.
  7. sbest

    sbest Active Member

    Hey, it has been done;:

    I have a spare 500w electric motor and drive for my Schwinn/Currie Izip I picked up off Ebay for $60, and am thinking of using these for battery packs:
    Total weight about 15 lbs and low enough torque to not destroy the chain drive. Range will only be about 5-10 miles but so what? Top speed at present is about 15mph and I don't think gearing will help. The battery packs are only 2.5 lbs each and the motor will take up to 48v so extra speed comes at little weight cost.

    My Izip is single speed (like a hub motor) and is useless off road and needs help on city hills. Gearing the electric to the pedals makes sense. The gas motor is for distance and charging, so direct drive to the wheel makes sense. Also considering connecting the throttles somehow. I would consider a hub motor. One of my bikes has one:
    Again, not my bike but a picture of the same type, Schwinn 1020 Izip I gotta get a camera.
    It is even more torque limited than the larger bike. Goes FOREVER on a charge, 20 miles but at only 10mph or so.

    So, quiet electric in the city and thru areas where there are pedestrians. Power up the speed with the electric and kick in the gas at 10mph up to the legal limit or the present 60kph (37mph) I achieve with my present bike. A charging system may take some juice from this.

    Cheezy low quality pict, sorry.

  8. jaguar

    jaguar Well-Known Member

    the hub motor electric I had exhibited "rolling resistance" when the juice was not on, like a slight braking.
    so you need to consider that in your design process.
  9. sbest

    sbest Active Member

    Most of the electric motors have some drag, so all work best with a freewheel of some kid.
    My hub motor has that same slight drag Jaguar. Not a problem unless you are pedaling, and we all pedal some time.
  10. bluegoatwoods

    bluegoatwoods Well-Known Member

    I like the idea. I've considered it myself.

    Two different throttles could be a bit of a problem. Someone a few posts up alluded to this.

    One other thing, too. I'm no expert. But I've gotten the impression that re-charging from rolling is a neat idea in theory, but difficult in practice. My understanding is that the the circuitry becomes a great deal more complex and expensive, with little actual gain. No personal experience with this. It's just what I've heard. But it sounds believable.

    I wonder, though. Imagine two twelve volt bottle generators be mounted on the bike. Could their output be wired in series? Put a cheap automotive voltage regulator on each, then wire their outputs in series, giving 24 Volts.

    If that's feasible, then that would seem like a good way to charge the electrical part of the bike. A 24 Volt system, anyway.
  11. p4cm4n

    p4cm4n New Member

    I don't know if I ever posted about this a long time ago or not but I did do this - for exactly the reasons you said.

    Never tried regen tho. I just used it as a project that I drove to walmart and such.

    Was planning on a mini road trip/solo camping trip. Never did it.

    It was heavy tho
  12. libranskeptic

    libranskeptic Member

    Much as i like them, A mid drive wont give you regen. A pity. Regen would often mean a smallish battery would suffice.
  13. libranskeptic

    libranskeptic Member

    No comment on the electrics, but I suspect 2 throttles, one twist and other thumb, could effectively control both with one hand.

    In short, the main issue with regen is that its mostly? unregulated. Heavy regen braking could overload electric components.

    An easily avoided? issue, is that its not good to use regen if the battery is already fully charged, obviously.
  14. libranskeptic

    libranskeptic Member

    I would humbly suggest its a deeper issue than it seems.

    I dont think either users or makers have really grasped the the new balance which must be struck in the new paradigm that EVs are.

    The old paradigm was, historically, almost free, compact ~petrol energy. Massively heavy cars was a no-brainer, reliable solution.

    Now, We have the plug in ~Leaf or the hybrid ~Prius. Both absurdly heavy and arguably a poor balance of EVs upsides and downsides.

    Clearly the plug in concept works for some (and much loved by those lucky few), but range anxiety is surely a deal breaker for many.

    So what about a Leaf say, with an onboard ~petrol charger?

    Lets look at some rough numbers for the Leaf purely to illustrate?

    Off the top of my head, 680lbs of batteries. 16-20 kwh, claimed 100 mile range.

    generously assume 20kwh battery, that means each mile consumes an average 200w. Even if you double that to 400w per mile (ie-a range of 50 miles), its not much.

    Yet even a 110cc honda dream step thru scooter motor is 7000w maxed out, or 35x average 200w per mile usage. Even a superlight 25cc brush cutter motor should yield 1kw, or 5x average power use. So only exceptional power use need drain the battery at all, and if the motor isnt needed for range, it only weighs a few kilos. If it is used, perhaps half the heavy and dear batteries could be economised on. During an average mile, up to 6800 watts is available for battery charging. The above 20kwh should be able to absorb up to 10kw when below 80% charged, so to all intents, the battery can restore usable charge very fast.

    i.e., its a plug in, but by the time the batteries are flat, even w/o charging points, you are too tired to drive anyway.

    It covers all bases except continuous freeway speeds and no recharge points, yet is much lighter than either of these cars by over 300lbs (~150kg), which yields further weight savings in construction, as well as lower power use and better power to weight.

    The customer can opt for a configuration that just does his normal commute on batteries with ~no motor, but he has range anxiety relief if needed.

    NB, the prius oth, has similar powered engines to an equivalent ICE car like a corolla - 75kw~?, and it also has to have a gearbox/transmission to drive the wheels directly from the ICE, which is complex and heavy also.

    A gearbox isnt needed on newer electric only cars, they simply vary voltage i think, for torque vs rpm variation.

    Engine efficiency is a bit academic, if the engine is correctly, intended to ~never be used. Similarly moot, is electric motor power. You can have as much as you want, easily. The problem is feeding the motor.
  15. rexamillion59

    rexamillion59 New Member

    Yeah I know and love mine. Cruise the electric all around town and hit the gas on backroads

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