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    Discussion in 'The main mechanical design forum' started by MariaNatalia, Aug 23, 2013.

    1. MariaNatalia

      MariaNatalia Member

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      Hello everybody, i'm new here. I have pretty low experience on mechanics.. so i decided to register here in order to see if the pro's wants to help me.

      i'm building a vehicle with a 52cc (2-stroke) engine, it should have more torque than speed. (it should carry weight (200lbs) at pretty low speed(5-10mph) and i want it to make it "4x4". (that is why i'm using a small gear on the output of the engine and big gears on the shaft, in order to get more power than speed, am i right?).

      so, what do you think it will be the best gear system to apply or order to distribute the power to the 2 shafts?

      please see attached the 3 systems that I can imagine.. there should be and probably better, but as i said before i'm not experienced. so if you think there is a best way (it should be not so hard to achieve ..pleasee!! i'm making it myself and i'm a mom..) please share it.

      thanks in advance,


      IMAGES:
      Option A:
      [​IMG]

      Option B:[​IMG]

      Option C:
      [​IMG]
      Nat
       
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    3. Dana

      Dana Well-Known Member

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      If that's a 2-stroke engine and you want low speed, you will need more reduction than that, multiple stages for sure. If the motor incorporates its own reduction gearing, then you might get away with how you've shown it. Of the three you've shown, A would work the best, B isn't good because there isn't enough of the chain in contact with the top sprocket and would put high side loads on the motor shaft, and C would not be as strong.

      First you need to work out what gear ratio you need, based on the engine's RPM, the wheel diameter, and the desired speed.
       
    4. mechaboy

      mechaboy Active Member

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      in my opinion you need a gearbox before sprocket to achieve a suitable torque.i agree with Dana the first one is the best because:
      1-it's stronger and more effiecent
      2-nice balance and assembly
      3-easier for lubrication
       
    5. MariaNatalia

      MariaNatalia Member

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      Hello Dana!, a woman (no ofence, just surprised)!! thats great!
      i found a really small pinion, 6 teeth and connected to a 55 teeths..
      so i should have more torque. if not, i'll try to get a stronger clutch.
      if you have any advice, please let me know!!

      thank you so much!

      Nat


       
    6. MariaNatalia

      MariaNatalia Member

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      Hello Mechaboy, thank you for your reply!!.
      great, so there's no doubt that system 1 will be the best..

      regarding the gearbox.. i've been looking for that.. but what i only found was a CVT for pocket bikes.
      http://www.scooterparts4less.com/web_gas/x1_pocketbike_cvt_logo.jpg

      i was thinking also to include a Bike gear system, but i don't think is going to work, isn't it?

      thanks!

       
    7. mechaboy

      mechaboy Active Member

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      why not?CVTs are nice.but what is the ratio of that?
       
    8. mechaboy

      mechaboy Active Member

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      it's input shaft's direction is not right .but CVTs are nice and what is it's ratio?
       
    9. Dana

      Dana Well-Known Member

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      Sorry to disappoint, I'm a guy...

      I'll repeat what I said above, first you need to work out what gear ratio you need, based on the engine's RPM, the wheel diameter, and the desired speed. Doing the math is the first step, before you start thinking about gear or sprocket arrangements. Just as an example, if your engine turns 8000 rpm (not unreasonable for a small 2-stroke) and your wheels are 10" diameter, you'd need a 286:1 reduction... by contrast your 55:6 is only 9:1, which (if it had enough power, which is unlikely) would propel your vehicle at 317 mph!
       
    10. MariaNatalia

      MariaNatalia Member

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      oh sorry Dana, i'm from Uruguay, and here "Dana" is a woman name.

      well.. regarding what you said.. then i'm far from what i need..
      i have 8.2 inch wheels.
      Gear and Pinion 55:6

      The engine specifications say:
      Disp: 52cc
      Speed without weight on the engine: 10.000rpm
      the guy who sold me the engine said that this engine is around 3HP but i'm not sure.


      how can i be able to make a 286 reduction? i mean.. i can't get a bigger gear for the shaft.. cause this 55 teeth gear is almost the same radius than the tire.. so, is there a way to make the reduction bigger?

      sorry for this question. i really don't know anything about mechanics.

      thanks.

      Nat

       
    11. MariaNatalia

      MariaNatalia Member

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      hello Mechaboy.
      the ratio says 7:1


       

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