# Rotational to Linear Gear Reduction calculation

• posted
I am trying to backcalculate a fixed gear ratio of a linear drive
mechanism.
I have a DC motor and a linear motion lead screw geared to it.
If I have a linear velocity of 0.1 in/min and the rotational speed of
the motor is 10 rpm
Then what would be the gear ratio? 100:1?
• posted
not enought info
what is the output rpm or angle per minute
the reason being how do you measure the linear velocity
how far from the center of the output shaft
• posted
That would depend on the pitch of the lead screw, wouldn't it? You need to know the distance the slide travels for 1 lead-screw rotation.
I'm assuming you are looking for the motor-to-lead-screw gear ratio.
Dave
• posted
What I did was set my output to 0.1 in/min of linear travel of a leadscrew. I then measured the time for 1 rotation of the motor shaft (before it entered the geared linear device) which was 6 sec. From that info I wanted to backcalculate the gear ratio of the linear mechanism.
• posted
I measured 0.01 inch of linear travel of my leadscrew with 1 rotation of my motor.
• posted
1 rotation of your motor, but aren't you looking for the gear reduction between the motor and the leadscrew?
If you're looking for the relationship between the motor rotation and the linear travel, you already have that.
Dave
• posted
Yes, The gear reduction between the motor and leadscrew is what I need to know. I need to order a second linear device and I have no nameplate to go by so I was looking for alternative drives once I calculated its ratio.
• posted
"gtslabs" wrote: (clip) If I have a linear velocity of 0.1 in/min and the rotational speed of the motor is 10 rpm Then what would be the gear ratio? 100:1? (clip) ^^^^^^^^^^^^^^^ I'm having trouble visualizing the setup. The best I can come up with is that you have a motor that is geared to a screw shaft. A nut is riding on the shaft. The nut moves 0.1 inch for each 10 revolutions of the motor. Is this right? There IS no gear ratio between the nut and the motor. A gear ratio is defined only for rotation to rotation. If I've got it wrong, please help me clarify the picture.
• posted
I have a motor turning what I believe is a Ball Screw Jack. I need about 2000 lbs of force and very low speeds of about 0.0001 in/min. So I am looking to find the gear reduction of the ball screw jack based on the motor rotation and linear advancement of the lead screw as I have given before.
• posted
OK, so all you need to do is be able to see the leadscrew and either measure the pitch or measure the table movement for 1 rotation.
If you can't establish the leadscrew pitch you can't establish the gear ratio.
If you can see the leadscrew and the motor shaft, though, you can just count turns directly.
Dave
• posted
if the power is a worm gear that is calculated as a 1 tooth gear

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