# The Naked Scientists Forum

### Author Topic: Worm Gears and Force Maths  (Read 2597 times)

#### harry_neild

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• Posts: 2
##### Worm Gears and Force Maths
« on: 08/11/2006 19:05:34 »
I have an engineering project at school, and we are going to be using Worm Gears (for example ).

We will be attaching a Step Motor directly to the screw gear, and using it to convert rotary motion into linear motion (the spindle will move up and down the screw). How would i be able to calculate the force that could be exerted by the spindle with the motor attached? I'm guessing you will need to know the motors torque, and the dimensions of the thread on the screw.

For example, if i had a motor that supplied 50 oz-in (0.3531 Nm) of torque, and attached it to a screw with a thread that moved the spindle down 1mm per revolution (it has a 1mm pitch), how much force would the spindle be able to exert on an object?

I would appreciate any help!

Thankyou very much

Harry
« Last Edit: 08/11/2006 19:20:42 by harry_neild »

#### lightarrow

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##### Re: Worm Gears and Force Maths
« Reply #1 on: 08/11/2006 19:43:26 »
In one revolution, the work done from the motor is: torque*2π = 0.3531*2π and it must equal the work done from the spindle, which is F*h = F*0.001 (h is the movement of the spindle in one revolution = 1 mm). So: 0.3531*2π = F*0.001 → F = 2π*0.3531*1000 = 2218.59 N = 226.15 Kgp.

#### harry_neild

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• Posts: 2
##### Re: Worm Gears and Force Maths
« Reply #2 on: 08/11/2006 20:18:19 »
No it wasn't my homework. I am taking part in an engineering scheme and we have to create a machine to test an inhaler cartridge, for example how far it has to be pushed for it to spray the medicine out.

We need to find out which strength of motor, and what the pitch of thread is needed to exert enough force on the cartridge.

The only thing i don't understand, is the final unit Kgp. What is that all about? Also 2218.59 N! Thats huge! Is that realistic because i suspect there would be a lot of friction involved?

Thaks again :)

Harry

#### lightarrow

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##### Re: Worm Gears and Force Maths
« Reply #3 on: 09/11/2006 13:57:13 »
Kgp is an engineering unit probably used only on italian texts. Sorry! It means weight-kilograms, that is the  force made by a body with 1 kg mass; so, 226.15 Kgp means that you could lift a 226.15 Kg body. Of course, all this ideally, without any friction, which I certainly cannot evaluate (because it depends on the specific device and how it's lubricated, at which temperature ecc.). If you know which is the mechanical (yeld; performance?) η of your device, you can use it in the previous computations:

Output work = η*Input work, that is:

F*h = η*torque*2π → F = η*torque*2π/h

So, if, for example η = 80% = 0.8:

F = 1774.87 N.

#### The Naked Scientists Forum

##### Re: Worm Gears and Force Maths
« Reply #3 on: 09/11/2006 13:57:13 »