dann2707 Posted March 17, 2012 Report Share Posted March 17, 2012 (edited) Basically i've doing some work, im designing a finicular railway. Its two carriages attached to each other via a long rope, when one goes down the other goes up. The rop goes from one carriage up the hill over an idler pulley, then to the driver pulley, then to another idler pulley back down to the other carriage. I have worked out all the output torques from what I have been given. My gear ratio has worked out to be 69:1 The input speed from the motor is 3000rpm or 314 rad/s The motor is 80% efficient. At a power of 60Kw (not sure if you need this) Basically I don't know where to go from here to work out how many teeth I need on my gears. I'm stuck on the N1/N2 = N3/N4 Can anyone tell me how many teeth I should have on my gears, they are going to be spur gears. Thanks. Edited March 17, 2012 by dann2707 Quote Link to comment Share on other sites More sharing options...
TROYston Posted March 17, 2012 Report Share Posted March 17, 2012 18:12? Hahaa, nah, just reading that confused me . Quote Link to comment Share on other sites More sharing options...
ManxTrialSpaz Posted March 17, 2012 Report Share Posted March 17, 2012 I'm definitely no expert, but 69:1 ratio with a pair of spur gears seems a bit unrealistically high. Not too sure on the parameters on choosing tooth size, but one gear would have to have 69x the number of teeth\be 69x the size than the other one. Quote Link to comment Share on other sites More sharing options...
dann2707 Posted March 17, 2012 Author Report Share Posted March 17, 2012 I was thinking that yeah, but couldn't they be reduced over a few more gears if you get me? I hate gearboxes haha Quote Link to comment Share on other sites More sharing options...
monkeyseemonkeydo Posted March 17, 2012 Report Share Posted March 17, 2012 At some point you're going to need to consider the potential mass differential between the carriages which may come into effect (if one is full to capacity and one is empty the system will need to function). The other consideration I'd have thought would be the operational 'cruise' velocity in motion. If the motor is running at 3000rpm do you need a carriage velocity of 1ms-1 or what? Quote Link to comment Share on other sites More sharing options...
RobinJI Posted March 17, 2012 Report Share Posted March 17, 2012 (edited) Yeah, what output speed are you looking to get out of the gear reduction? Essentially though, if you know you want a 69:1 ratio, this will give you a 43.48rpm output with 10542Nm of torque, minus the gear box's efficiency, is that the right sort of speed and torque for what you're after I guess? (That's taking into account the motors efficiency, but it's not clear from your question if you should be taking in into account at this stage, 13178Nm if you're not accounting for it right now.) As you said, you're probably going to have to do it through a few gears. It might help to know that for compound gear sets, the total ratio is equal to the product of the driven gears divided by the product of the driving gears, but if you've already worked out what reduction ratio you need, then all there is to do now is work out a set of gears that will give you that total ratio. You'll be able to get the ratio nice and high quickly using a few sets of gears, but 69's quite an awkward number to work with. Edited March 17, 2012 by RobinJI Quote Link to comment Share on other sites More sharing options...
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