Safe to put an engine on a woman's bike?

Discussion in 'Rack Mounted Engines' started by Mary, Oct 22, 2009.

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  1. Mary

    Mary Guest

    I'm thinking about getting an Electra Townie 21D woman's bike and mounting a GEBE kit on it.

    My boyfriend pointed out that it may not be strong enough because it lacks the top tube. He said there would be a lot of flex in the frame from the engine.

    I currently have a Trek Navigator 200 men's bike with the GEBE kit and a Tanaka 40 cc engine.

    Any comments?



  2. moondog

    moondog Member

    I sure don't like it when I can shake the bike back and forth and feel a lot of flexing. It happens on some men's bikes too when you put weight on the back.
  3. augidog

    augidog New Member

    hi mary :)

    1- the suspension fork is going to help
    2- if possible, have some gussets added

    my (steel) frame flexes side-to-side if i wobble it hard on purpose, not a problem when riding (knock on wood)

    that's about all i got for now...what engine you have in mind?
    Last edited: Oct 22, 2009
  4. JemmaUK

    JemmaUK Guest

    I would be very suprised if you got noticable flex from a step through frame... in as much as it would make difference in handling of the machine.

    What you would need to watch for is frame failure.

    However from what I have seen of failed frames its more to do with the joys of china girl motors vibration causing metal fatigue and subsequent failure.

    Since there is a joint on the between the gebe mounting and the frame this should be less of a problem.. you can also minimise the vibration by mounting a rubber (maybe a doubled innertube section) between the U mount ends and the axle.

    The 40cc engine of any of them is likely to chew a weaker frame - but it tends to munch wheels before it munches frames.

    I personally dont think you would have a problem, but you have to be aware that a 40cc motor is going to be overpowered for that frame.

    I ran a 32cc piped engine but then my frame was a 65lb lump that was more made from girders than anything else.

    I think the best option is to get hold of the bike you want and fit up the motor *carefully*. Take it for a ride and see if its too much of a handful...

    If it is demount it and take the bike back... so long as there are no scratches just say its not what you need and they should refund you..

    Jemma xx
  5. spad4me

    spad4me Member

    I love Wallmart for this reason you can return it if you carefully install an engine .
    Try it out and return the bike to try another.
    Until you find one you like .
    I use masking tape to cover the paint when bolting on a support . LOL.
    I love Wall mart's Your fault, my fault, nobody's fault return policy, on bicycles.

    You would not believe how many times I have tried different frames .

    A steel frame is better in the $100 to $500 price range in my opinion.
  6. Mary

    Mary Guest

    I will probably transfer the 40cc kit I have now to the Electra Townie.

    I prefer the women's bike over the men's but I hadn't found one that I liked until now. I tried the Trek Navigator women's but the seat and handle bar distance was too short (my long arms and the fact that I like to stretch out when riding.) I really like the crank forward position of the Townie.

    My boyfriend mentioned that the flex could [over time] result in problems.

    I'm pretty sure that both the Townie and Navigator are aluminum frames.

    Augie, not sure what you mean by "added gussets". I really like the placement of your engine. It's out of the way so you can carry stuff on the rear. What engine do you have on Sabrina 2?


  7. moondog

    moondog Member

    It has to do with your weight and driving habits too.
  8. loquin

    loquin Active Member

    Keep this in mind. There shouldn't be any more side-to-side flexing than if you are peddling - the motor applies torque to the rear wheel, but, the force is logitudinal in orientation. In fact, the side-to-side flexing should be less, as you will be peddling less. Peddling puts stress alternately on each peddle, and tends to flex the frame from side-to-side. The motor puts virtually no side-to-side stress on the frame.

    Now, by traveling at a higher average speed, road stress (bumps/holes) will be higher, on average. As augi mentioned, the front shocks will hep a lot in reducing the impact stresses to the frame. Another suggestion would be to add a suspension seatpost on the bike. This will serve to reduce the road stresses on the frame (AND the rider!) as well.

    I can't begin to tell you how much my back appreciated my adding a suspension seatpost to my bike.
  9. fetor56

    fetor56 Guest

    The bike looks sturdy enough,but just to be on the safe side(if possible) i'de add thin(2mm) stainless steel brackets to the dropouts & connect the Mount Strap to them in a few connecting spots.
    I'de also atleast replace those front linear brakes with v-brakes.
  10. augidog

    augidog New Member

    mary, i was over-doing, as usual...gussets are extra braces welded into the frame. the engine's my same purefire 40CC, but it's got some new bling from ada racing.

    i think that jemma' & lou are right about flex not being an issue...i bet you'll know with the first ride if it is, tho, so yeah you could bail if you were careful with the bicycle.

    fetor', those brackets look nicely done...and i agree about the brakes, but i always agree with "better brakes" advice, so i'll up the ante and suggest a sturmey-archer drum...aint it nice "spending" someone else's money? ;)
    Last edited: Oct 22, 2009
  11. moondog

    moondog Member

    I have bailed with many bicycles. I like a step through frame too and the only one I found that feels right is my AMF Roadmaster moped frame and it is way thicker than a bicycle frame.

    I buy used bicycles at auction and I buy a lot of women's bikes.

    It is not uncommon to buy them with real nice seats, straight wheels and a bent frame. I have several of them. I buy them for parts.

    Men's bikes often will have worn out seats, bent wheels and axles with a straight frame.
  12. mlcorson

    mlcorson Member

    I used a women's Schwinn Skyliner from Walmart. Very sturdy because they use a triangular cross bar. Check it out.
  13. safe

    safe Active Member

    I have no plans to put an engine on a woman's bike. :jester:
  14. mlcorson

    mlcorson Member

    LOL...Some of us are more concerned with functionality than form.
  15. Mountainman

    Mountainman Active Member

    should be almost as strong ??

    should be almost as strong ??

    that's what I am thinking
    see many big men riding these THINGS

    let's not forget that they are engineered

  16. 5-7HEAVEN

    5-7HEAVEN Guest

    I installed 2.2hp Mitsubishi engines with friction drive on the front and rear wheels of my Raleigh girlie cruiser.

    No major drawbacks, except the fact that the bike weighed 95lbs.:whistling:
  17. moondog

    moondog Member

    I don't either. I have put motors on men's bikes, rode them and took the motor back off.

    I don't clamp steel sprockets to the spokes anymore either. I have read too many wheel building books and have seen what it does to spokes.

    I am getting pickey ! I like the way the old made in the USA iron pipe bicycles feel with a motor. I like the nice thick welds on them too. :D
    Last edited: Oct 23, 2009
  18. TerraPilot

    TerraPilot Member

    Will someone please clue me in here? Why all the perticulars about a bikes brands here. Most bikes are over build. This flex sounds like mumbo jumbo. You are only adding 14 lbs or so to any given bike. Other than some expensive and custom light bikes I cant see anyone over flexing anything. If I can measure the rear forks correctly with a the credit card then any GEBE will work. I've installed 2 Sabaru Robins on an Avalon from Walmart and Torker from the LBS. Both are quite satisfactory. Am I witnessing a tempest in a teapot here. Both are Ladies bikes. You guys sound more like your are trying to install one of those Chinese 4 cycles with the 50 lbs of chain and sprocket or something.
  19. augidog

    augidog New Member

    haha...ahem....ok, seriously...i think we've all learned a lot of lessons due to the increased sustained speed and the problems it can cause, so we're just playing it safe ;)

    speaking of...i recently welded a single 1" square gusset between the front of the chainstays and sabrina-2 doesn't wobble at all frame is unique and this method wouldn't apply (or be needed) on most bikes, but it was this topic that inspired me to finally find my solution :)
    Last edited: Nov 19, 2009