Tadpole Reverse Trike Idea

Discussion in 'Motorized Trikes' started by lowracer, Aug 3, 2014.

  1. lowracer

    lowracer Member

    Hi all,
    Whilst pedaling my local roads early morning getting my exercise, I stumbled upon a jogging stroller being thrown away along the curbside trash. I took it apart made a quick pull behind trailer with its two wheels, pulled my daughter & doggy around the neighborhood for a few laps, then disassembled it since I really dont need a pull behind trailer & I had no space to store it. Then the item got thrown in my car trunk (not much room left for more bikes in my house, per wifey...lol).
    I'm thinking again about a new project using the fairly stout axle piece that the two wheels plug into. The wheels have 1/2" (13mm) axles. I think they are solid enough for my purposes?
    With the bicycle front wheel removed this piece can be mounted to a piece of wood and a U-channel. U-channel bolts to the fork with a long 3/8" bolt w/spacers. I've been successful with this U channel mount on '2-High' my motorized tall bike. I'll probably need to find a piece of throw away 2 X 4 (18" - 19") to mount across the aluminum axle, u-bolt to the wood and then bolt up to the u-channel.
    I know this isn't how tadpole trikes steer (or cars or that matter). There will be no Ackerman compensation or centerpoint steering.
    As a kid, I built an 8' oak motorized go cart using 4 skateboard trucks, 8 sticky skateboard wheels (Kryptos) w/ foot steering & a 2 hp Briggs for power. The go cart handled like a race car with that foot steering, low center of gravity and awesome traction (had to hold the sides very tightly on hairpin turns or risk getting thrown off).
    If this steering arrangement works somewhat well on an upright bike with its higher center of gravity, I might then construct a DIY, No Weld, recumbent platform around this very simple steering arrangement.
    Here are some mock-up pics with the aluminum posts left uncut (they will get cutoff).
    Please posts your ideas...

    Attached Files:

  2. HeadSmess

    HeadSmess Well-Known Member

    nice and simple, but i think you will encounter one issue...the tendency to lean OUT of a turn, rather than in. that could cause some consternation, if not amusement ;)

    no cure for that other than changing head angle to negative, or using kingpins on the wheels.
  3. bmg50cal

    bmg50cal New Member

    Just go slow everywhere... :whistling:
  4. wheelbender6

    wheelbender6 Well-Known Member

  5. bmg50cal

    bmg50cal New Member

    That design might have a little Ackermann geometry but what any good bike really needs is some caster angle (trail). Also that thing has a really large scrub radius which I really would not want for taking corners at any sort reasonable speed.
  6. lowracer

    lowracer Member

    Ok, I finally got this simple front end mounted up. I found a small piece of 2X4 and bolted the fork mount to it & then used 2 handlebar type clamps to bolt the axle to the underside of the wood. I took it for a short slow ride around my neighborhood to test the steering geometry.
    This thing is messed up!
    The angle of the steering head screws the handling up to about an almost unrideable state.
    Perhaps if the steering head angle was perpendicular to the ground it would handle better but I won't be working on this design any further.
    Chalk it up to failed experimentation...
  7. HeadSmess

    HeadSmess Well-Known Member

    was i right then? excellent :)

    i remember discussing the exact same thing some time ago over the same concept on an indian trike conversion kit, until i noticed it did have kingpins...

    with swinging axle steering using standard, positive head angles, the inside wheel, the one that moves to the rear...also LOWERS. the outside wheel moves forward and lifts up. that tilts the bike itself out of the turn. which makes the rear wheel try to go the other way.

    (think of the rear wheel as a barrel rolling on its side... due to the curve, you lean it over to the right, and it will turn to the right. exactly why they were made like that. its also the way that trains get a "differential" effect using solid axles... the wheels are tapered, not machined flat. without it, they would wear the rails and wheels out rapidly.)

    combined with the high CoG of a normal bike frame...you have the first hand experience now of the effects this will cause ;)

    try reversing the trucks on a skateboard, then dare someone to ride it ;) even tony hawk himself would break his neck :jester:

    interesting fact on ackermanns principle... it was originally designed by charles darwins father. he just didnt patent it.

    the other post of bmg50cal's... with the mention of scrub radius...the kingpins need to be angled so the pivot line is fairly well in line with the contact patch of the tyres. thats basically zero scrub radius. then tilted back somewhat, kingpin inclination... look at the amount of tilt they put on dragsters! almost 45 degrees! (wouldnt catch me trying to ride that thing thats pictured, with its alloy forks and such forth held together with a few bolts...:ee2k: not to mention the bump steer that would occur with its vertical kingpins! (if it used normal forks and had the pivots right on top of the wheels, "centre steer"...maybe...just maybe...)

    steering geometry is quite interesting to study :)

    im sure if you persevered, you could get something to work ;)

    but you will need a welder :(