Possible Electric Bicycle ? [ trolling motor ]

Discussion in 'Electric Bicycles' started by WIZARDOFOZONE, Dec 14, 2007.

  1. This is WAAAY off topic for me because I must be honest and say I have little experience in this area but know enough to say I have never seen any electric motor I felt IMO delivered the power nor long range freedom of an internal combustion engine for practical bicycle use .... I'd sure like to hear opinions from people who have experimented with electric power and get input from anybody who might have tried the following :

    I outfitted my boat with a new Minnkota 80 pound Auto Pilot trolling motor and the older 40 pound thrust motor has been sitting unused. Fooling with it yesterday has really convinced me that converting a 40 pound thrust trolling motor to a bike engine has worlds of possibilities for reasons I have always taken for granted in using them on my boat, but never considered the same features that make them work so well for pullling craft would surely be the same on land with such a light load as a bicycle.

    None of the points following are anything new to serious trolling motor fishermen but others might not be familier with how strong a trolling motor actually is ....

    1. A BASIC 40 pound thrust trolling motor costs about $250,used ones are on Ebay a lot too.

    2. 40 pound thrust (AS AN EXAMPLE) can move my 20 foot bowrider from dead stop with enough thrust to make you lurch back a bit if your not prepared,just to give you an idea of the load pulling capability.Were talking about 2500 lbs of mass in this case.

    3. Most interesting however, is run time from a 12 volt battery .... Any average 40 pound thrust troller will let you pull at full power (another plus,power is infinitely adjustable ) for AT MINIMUM in my 20 years of troller experience, about 4 hours and that's in the WORST possible scenerio ie,headwinds, fast water, lots of speed changing.

    In normal scenerios, with the battery saver circuitry that all the big trolling motor companys tout, 8 full hours from a full sized marine battery is not unheard of. 6 is absolutely common I do it all the time.

    4. Motors are already rigged to reverse (just for giggles)
    5.Propeller removes in 4 seconds,welding on a standard chain sprocket is a no brainer
    6.Fully waterproof of course
    7.sleek bullet housing would accept a variety of mounting tecniques,and the shape readily suggests mounting directly behind the seat over the hub with the battery occupying the normal place we put our chinese motor.

    8. Biggest problem is of course the size of a marine trolling motor battery or any large sized auto battery. Enen low on the frame we are talking a lot of weight. Anyway, has anyone ever messed around with a trolling motor for this purpose ?

  2. srdavo

    srdavo Active Member

    very interesting!!

    Do you know what the max. rpm's are for your motor?

    that will give us an idea of what to expect of it...on wheels.

    gear ratio adjustments, to fine-tune it.

    I think you are onto something.
  3. No I don't, but it's going to be fast enough .... my 40 pound thruster on full power looks like a table fan and easily blows my hair around wildly. As to gear ratio adjustments, I'd not considered that because trolling motors are variometer equipped and speeds are infinite adjust on most, or 3 speed click settings on the cheaper ones. Torque is probably the LEAST concern, in fact most experienced trollers will tell you the biggest concern wth accidental grounding or entering too shallow water is the damage done to the prop because the motor just never jams up and stops, it normally causes huge gouges in underwatwer logs, breaks its deliberately break away prop too, but stopping the shaft under power is not going to be a concern .
    Last edited by a moderator: Dec 14, 2007
  4. srdavo

    srdavo Active Member

    when I mentioned adjusting gear ratios, I meant in relationship to what speed & how much torque a bicycle will have, powered this way.

    variable speed on the motor is a big plus.

    wheels are turning here....:)
  5. It was so easy as I stared at it yesterday it was scary ... removing the control head while sparing the wiring that runs up thru it will take only no brainer work with a dremel, and retaining the speed/reverse potientiometer inside the head shell is probably the only part that takes a little slow careful restyling.
  6. srdavo

    srdavo Active Member

    I've been to the MInn Kota website. I took a crash course in "thrust".
    I emailed them about rpms & watts.
    here's their reply:


    All Minn Kota trolling motors average to being about 1400 RPM's as they are not designed for speed - just designed to push weight over the surface of the water so one can fish. The more thrust you buy - the heavier a boat it will handle on the water. "amp draw multiplied times voltage = wattage"


    Technical Services

    Minn Kota - Cannon
    Last edited by a moderator: Dec 15, 2015
  7. JemmaUK

    JemmaUK Guest

    This may sound a little weird - but why not make an inline battery tray that mounts in front of the crank aka the positioning of the 98cc engine in the old autocycles...

    That would solve the balance problem because the weight would be as low as possible.

    Just a thought...

    Jemma xx
  8. Srdavo, do you have an idea then of what this means to us speedwise ? What would 1400 rpms do ? I'm basing my belief that it would be adequate based on a bicycle shop here that sells a factory built motorized bike with just a friction roller on the tire that does about 14 mph on a motor about 3 inches in diameter and about 4 inches long ... seems just on a loosey goosey site comparison, a 40 pounder should get at least 20 mph no ?

    Not to mention that my boat alone when underway on just that small motor shows at least 10 mph with all that weight plus water drag ... Actually, I guess knowing what the chinese engine is doing rpm wise would be a good gauge ... or even better,since I wasn't thinking about an electric motor matching the speed of a gas engine ... what is the average rpms of most factory made electric bikes is the best question.
    Last edited by a moderator: Dec 14, 2007
  9. Jemma, yes that's not weird at all ...in fact I don't think theres a much better or lower place to put it .... those super large marine batts are at least 45 pounds or more I'm guessing.
  10. JemmaUK

    JemmaUK Guest

    1400rpm would have to be geared down somehow but so far as I know its not the revs of an electric motor that are important its the torque like a diesel... the rpm is low but at a given speed the torque is high so it will take a high load...

    What you *could* do is put a slow-speed centrifugal or a lock out manual clutch between the engine output and the sproket (assuming you are using chains) an since the engine is already forward/reverse it should be possible to run a tensioned chain from the front to the deraillier (assuming you are using one via the output on the clutched engine..

    This would need a lot of work on tensioning to get right but with the clutch disengaged it should allow normal pedalling & a multispeed transmission without the need for a jackshaft...

    Jemma xx
  11. JemmaUK

    JemmaUK Guest

    The only other thing re batteries I can think of is two 20lb batteries to each side of the rear frame... much like storage bags on harleys.... someone gimme a Nimbus...

    With the chain idea I was thinking of a single long chain... tensioned correctly with the engine over the rear wheel/ drive on the derailler side of the bike...

    I think that would munch a hub in short order..

    Jemma xx
  12. Well, If I can first get an answer on what the average electric bike does rpm wise, I'll give it a try. I would do it in a minute if I can be assured that 1400 rpm on the current chinese sprocket and my 36 tooth final drive would equal at least 20 mph and I'd be suprised if it doesnt. I shouldn't compare apples to oranges but still, if 40 pounds at 1400rpm shows 10mph on my electronic speedometer for such water drag and boat weight, expecting 20 mph on land from a bike seems reasonable.
    Last edited by a moderator: Dec 14, 2007
  13. srdavo

    srdavo Active Member

    1400 rpms seems really good. no gear reduction will be required.
    it get's better....using jpilot's gear ratio calculator, a 10 tooth sprocked on the motor, and a 44 tooth on a 26" wheel, 1400 rpm's will net 26 mph.
    add a projected 4 to 6 hours battery life...an wow!!

    me thinks you stumbled onto something big!!:D
  14. Thanks for this needed info Srdavo ... I'm really tempted as I will never need this motor again .... I'm also thinking of a simple (what is the proper name of those 1 way slipping gears ?) gear that lets me forget about any dis-engagememt needs when motor is off.
  15. srdavo

    srdavo Active Member

    My currie motor goes into a planetary gear for reduction,,,then to a sprocket with a clutched bearing. which allows the bike to freewheel without turning the motor.
  16. Yes, that's what I would have to do .... this seems like it would be a fun time killer of a build ... I'd actually like to do it on a 24 inch bike .... hEH ! gotta think about all this before destroying my trolling motor ..
  17. srdavo

    srdavo Active Member

    scroll down this page to see the "roller clutch assembly"

    I don't know if this would work for your application....very small chain...tiny. But that's the general idea
  18. Oh yah ! That was an "ADD TO FAVORITES" big time ! Thanks, I can see I'd be needing this sight I think, and they show several easy possibilities to change the current trolling throttle to better suit handgrip type control ... just found this DICTA one way sprocket in a junk drawer ... never used and no idea why I bought it .... maybe I can do this for just the price of a lightweight bicycle ...

    Attached Files:

    Last edited by a moderator: Dec 14, 2007
  19. srdavo

    srdavo Active Member

  20. I made the last post, went fumbling through my junk drawer for an old prop because I wanted to note the motors shaft size and found this sprocket ... very cool, and I think it would save me tons of work .... grabs on the motor pull, slips when motor is off and if I'm peddling ... of course I mean to make this a 2 chain system just like we have on the chinese engine ...