torque wrench

[flashlaser]

Hi i'm designing a torque wrench. But i need some help.

I have a drawing torque3.jpg

the gear connects to the socket. If i'm putting 300ft/lb torque on a nut using the socket connected to the gear. and the gear connection to the handl thru the gear locker, and the gear locker can push against the weight. Will the gear locker push against the weight with 300ft/lb? the weight is actually a sensor. I want the sensor to be able to sense that there is 300ft/lb of torque being exerted on the nut

Now my second drawing torque2.jpg uses a spring like a normal torque wrench.

at the end of the handle there will be a dial that will tighten and losen the spring which pushes against the gear locker, which in turn keeps the gear connected to the handle. say i put the wrench of 150lb/ft torque using the dial, then the spring pushes the gear locker with enough force to keep it connected up to 150lb/ft torque, if it goes over, the gear's teeth push the locker and spring back and it disconnects form the handle.

how would i calculate the spiring tension, etc to get this working. Can someone give me links, leading me to the right direction.

Pictures can be foudn here

http://gainguy.unixserver2.com/torque3.JPG

http://gainguy.unixserver2.com/torque2.JPG

Thanks for any answers.

 

[enginebob]

Well the way the drawing looks that the load is balanced and will not push at all against the spring.
To measure torque you have to have some kinda arm, acting against a scale of sorts. And if the radius of the arm changes at all that will affect the accuracy of the reading.

 

[flashlaser]

this is the real image

thanks

p.s. this forum really needs an edit button

 

[mloew]

flashlaser,

This forum has a preview button. I suggest you avail yourself of this option.

Best regards,

Matthew Ian Loew
"I don't grow up. In me is the small child of my early days" -- M.C. Escher

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[flashlaser]

so someone must be able to answer

 

[GregLocock]

Sure. You need to work out the thrust that the two gear teeth in contact (ie the one on the locker and teh one on the gear) will generate along the line of action of the spring, and hope that the friction between the locker and the handle is not so much as to lock the whole thing up.

The force at the point of contact will be roughly (?exactly?) normal to the tangent between the two contacting surfaces.

I imagine a good read of Shigley would be appropriate, this is a rather basic problem.

Cheers

Greg Locock