Torque Increase from Speed Reduction

[AlZilla]

I've wondered how much torque increase we get from speed reducers. Is it inverse to the speed reduction?

Turns out it is. If your speed reducer provides 1:3 speed reduction, you're getting a 3:1 torque increase.

(The following assumes a start up speed of 100 rpm at the motor)

But, even though you can put a 30MM (basically 1.18 inch) pulley on your motor against a 3" hand wheel and end up with a final decrease of 1:2.5 (39 rpm) and corresponding torque increase, you're still better off throwing a 1:3 speed reducer in the middle.

Adding the typical 2"/6" speed reducer to the above gives you a speed reduction and torque increase factor of a whopping 7.58.

Most of what I've read indicates that servos want to run at or above 300 rpm for cooling. The setup imagined above with the speed reducer would be around 40 stitches per minute at a 300 rpm motor speed. (it's not only imagined, it's bolted onto my 111W153, patiently awaiting the 30MM pulley)

duck.ai provided confirmation about the torque increase. Now properly credited, here's what it had to say:

Understanding Torque and Speed in Pulley Systems

Torque and Speed Relationship

In a pulley reduction system, torque and speed have an inverse relationship. When the speed of the driven pulley decreases, the torque increases. This is due to the mechanical advantage provided by the pulley system.

How It Works

• Larger Driven Pulley: If the driven pulley is larger than the driver pulley, it will turn more slowly. This results in increased torque at the output.

• Smaller Driven Pulley: Conversely, if the driven pulley is smaller, it will turn faster but produce less torque.

Calculation of Torque

The torque available at the driven pulley can be calculated using the following principles:

• Torque Multiplication: The torque at the driven pulley is multiplied by the ratio of the diameters of the pulleys. For example, if the driven pulley is twice the diameter of the driver pulley, the torque is effectively doubled, while the speed is halved.

Practical Implications

This principle is commonly used in various applications, such as:

• Automobiles: In low gear, the engine speed is high, but the wheels turn slowly, providing more torque for acceleration.

• Conveyor Systems: Slower speeds can help manage heavy loads without slipping.

In summary, in a pulley reduction system, as speed decreases, torque increases, allowing for greater force to be applied at lower speeds.

 Sciencing aimsindustrial.com.au

So, until someone comes up with a servo offering 7X more torque than current offerings and running at a minimum 50 to 100 rpm, torque increasing speed reducers are king.

 

[friquant]

Can you post a link to the 30mm pulley you bought?
I ordered one but it arrived today and it's narrower than I expected. Only a 7mm gap for the belt, and my belts are 6.5mm wide on the inside edge, 9.5mm on the outside edge.

 

1 hour ago, AlZilla said:

Adding the typical 2"/6" speed reducer to the above gives you a speed reduction and torque increase factor of a whopping 7.58.

Once you get it set up I'm curious to hear how it is to move the handwheel manually. I've been wondering what is the optimal motor size and gear reduction that gives plenty of torque but is still easy enough to manipulate at the handwheel. I've got a 1-hp 3-phase gearmotor (4.5:1 gear reduction) on the way, it will be my first VFD setup and my first system that is geared down more than just putting a small motor pulley on it.

[AlZilla]

1 hour ago, friquant said:

Can you post a link to the 30mm pulley you bought?
I ordered one but it arrived today and it's narrower than I expected. Only a 7mm gap for the belt, and my belts are 6.5mm wide on the inside edge, 9.5mm on the outside edge.

I ordered the same one you did. I couldn't find one for a 3L belt. If it's a problem, I'll just throw a round leather belt on it. I ran that machine for several months on one.. They work fine.

I think the narrow pulleys are intended for those round rubber belts you melt together.  PU, maybe?

There are also narrower V belts.  I'll make it work.