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Re: Anti back driving screw threads
Re: Anti back driving screw threads -- gary2you	Post Reply	Top of thread	Forum

Posted by: jboggs ® 04/02/2007, 19:03:26 Author Profile eMail author Edit

Consult Machinery's Handbook or any good acme screw manufacturer, such as Nook. You'll find that back-driving is a function of pitch and friction. In a frictionless world, all screws would be "back-driving". Consider the difference between ball-screws and plain acme screws of the same pitch. As far as back-driving is concerned, the only difference is friction. In general, since the purpose of scissor jacks is to convert a small rotary torque into a large linear force, the more common question is how much torque to achieve a certain lifting force. Usually, by the time you design a mechanism to achieve the desired functional results, you are well beyond the "self-locking" pitch.

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Re: Anti back driving screw threads
Re: Anti back driving screw threads -- gary2you	Post Reply	Top of thread	Forum

Posted by: randykimball ® 04/01/2007, 11:49:27 Author Profile eMail author Edit

The finer the pitch the less back drive tendency you will get. The finer the pitich the more better forces will be tranmitted into extending force. The finer the pitch the more revolutions it will take to extend the ram X distance. But the best way to prevent back feed is to drive the rotation of the screw with a reduction gear box having a locking motor (motor with a brake method) or to rotate the screw with a hydraulic motor with a blocking type control valve. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Mon, Apr 02, 2007, 00:13:13

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