Torque/Gear Box

Discussion in 'General Questions' started by Bonefish, Aug 11, 2010.

  1. Bonefish

    Bonefish Member

    Was just wondering.....................................................

    Say two gearboxes have both have a gear ratio of 5:1, however one has a gear combination of a 12t pinion to a 60t spur gear to arrive at the 5:1 ratio, while the other one has a 20t pinion to a 100t spur gear to achieve the same 5:1 gear ratio as the first gearbox.

    Now both have the same 5:1 gear ratio, but will the later of the two (20/100) have greater torque or will both be the same regarding torque output?


  2. Swede

    Swede New Member

    Every time you reduce input speed (rpm) you increase output torque (lb/ft).

    In the scenario you described above there is a 5:1 reduction driving another 5:1 reduction. This equals a total reduction of (5*5=25) 25:1 reduction.

    Basic gear principles dictate the order being driven member over drive member when calculating ratios and torque increases when rpm decreases. This leads to the conclusion that the rpm will decrease by a factor of 25 while the torque will increase by a factor of 25.

    eg. 1 lb/ft from engine @ 2500 rpm will equal 25 lb/ft @ 100 rpm at the wheel.


  3. Bonefish

    Bonefish Member

    Thanks for your input.

    Not sure if I made the objective clear........

    Lets say this........................................

    You have two identical bicycles with two identical engines on them. Everything else on the bicycles are same EXCEPT gearboxes.

    Both gearboxes are the same in gear ratio reduction output at 5:1 but at arriving at the 5:1 ratio in the gearboxes, it is gotten DIFFERENTLY.

    One bicycle you have a gear combo of 12Tooth on the Clutch bell Drum, while it drives a 60T gear to arrive at a 5:1 ratio.

    Next bicycle has a gear combo of a 20Tooth on the Clutch bell Drum, while it drives a 100T gear to arrive at a 5:1 ratio.

    Now you have two bicycles with two drivers at the bottom of a 40degree incline hill. Both of them floor it at the bottom of the hill. If both drivers weigh the same weight and all other variables being constant/same. Who will make it to the top first?

    Will the 12T on the clutch bell drum provide more torque than a 20T, or vice/versa?

    Hope I made it a little more clear,
  4. Swede

    Swede New Member

    Identical gear ratios with identical input power will result in the same power and torque to the rear wheel and therefore the same acceleration and speed.