Gear down Motor or Gears?

[farmersvilleRob]

So, to get around a 4:1 gear ratio, should I gear down with a gear box then run the chain system off of this with the same size sprockets, or should I gear down with the teeth on the sprockets in a 15 teeth to 60 teeth gear? Does it matter?

[Andrew Lawrence]

I don't think it matters. The purpose of a gearbox is to put all of that long, chaining through sprockets down to a smaller size.

[farmersvilleRob]

Ah okay thanks! I was worried with the CAD draw up that I would have to change it... ugh. lol So your saying I can achieve the same torque/RPM change with a 4:1 gear ratio in the sprockets as I would get from the gearbox?

[pfreivald]

Ah okay thanks! I was worried with the CAD draw up that I would have to change it... ugh. lol So your saying I can achieve the same torque/RPM change with a 4:1 gear ratio in the sprockets as I would get from the gearbox?

You can. Efficiencies can vary dramatically from case to case.

[farmersvilleRob]

You can. Efficiencies can vary dramatically from case to case.

What's that mean? Because I used the formula T = Ts - (N Ts ÷ Nf)

where T is the torque at the given rpm N, Ts is the stall torque, and Nf is the free rpm.

from http://www.gizmology.net/motors.htm

[farmersvilleRob]

You can. Efficiencies can vary dramatically from case to case.

What does that mean? Please help, because I don't understand* :]

edit: marked by asterisk

[pfreivald]

It means that how you gear a system up or down can have very different efficiencies. Case-by-case analysis is the only way I know of for determining which is best.

[farmersvilleRob]

It means that how you gear a system up or down can have very different efficiencies. Case-by-case analysis is the only way I know of for determining which is best.

Okay thanks! :] so basically, even a 4:1 gear down can somehow produce way less then calculated? by http://www.gizmology.net/motors.htm

T = Ts - (N Ts ÷ Nf)

where T is the torque at the given rpm N, Ts is the stall torque, and Nf is the free rpm.

[Madison]

Some energy is lost to things like friction, heat and vibration in every stage of your gearing.

Spur gears and sprockets and chain are both very efficient if built properly -- as high as 98% or so. That means that 98% of the energy input on one end comes out the other.

Losses due to inefficiency occur at each stage of gearing -- so a system with two stages would be ( .98 * .98 ) efficient, for example.

[farmersvilleRob]

Some energy is lost to things like friction, heat and vibration in every stage of your gearing.

Spur gears and sprockets and chain are both very efficient if built properly -- as high as 98% or so. That means that 98% of the energy input on one end comes out the other.

Losses due to inefficiency occur at each stage of gearing -- so a system with two stages would be ( .98 * .98 ) efficient, for example.

Cool! and... disheartening.. but, with 96% effieciency, that still falls within our range which is about a 75% wiggle room.