Ratchet Brake
Ratchet Brake
(OP)
I am trying to size a spring which will engage a ratchet into a ratchet wheel. There is a solenoid which diengages the ratchet (by overcoming the spring force) and then the spring will re-engage the ratchet when electricity is shut off.
Is there a 'rule of thumb' or Standard which suggests how much force the spring should inflect upon the ratchet in order for engagement? This force will have nothing to do with holding the brake...the profile of the ratchet will take care of that...this is unusual I guess because gravity won't be acting on the linkage...it is coming up from underneath the ratchet wheel.
Any help would be appreciated.
Thanks.
Is there a 'rule of thumb' or Standard which suggests how much force the spring should inflect upon the ratchet in order for engagement? This force will have nothing to do with holding the brake...the profile of the ratchet will take care of that...this is unusual I guess because gravity won't be acting on the linkage...it is coming up from underneath the ratchet wheel.
Any help would be appreciated.
Thanks.





RE: Ratchet Brake
Kevin
RE: Ratchet Brake
Thanks for any help.
RE: Ratchet Brake
The required force to engage the pawl will depend of the bearing the pawl pivots on and the conditions it is operating in. Is this operating operating outside in a mill enviroment or enclosed inside a oil filled box? In the past I have found that having a cheap fish scale handy as a force indicator often was the best way to wag a required force.
Barry
RE: Ratchet Brake
Therefore, the solenoid should be able to overcome the maximum friction force between the ratchet weel and the pawl plus the spring force.
RE: Ratchet Brake
We have a special design that requires the hoist to be raised prior to the solenoid acting to release the brake...this will take friction between the pawl and ratchet wheel out of the equation. It would take me an hour to type out the reaons why we are doing it this way...but trust me that it is required.
The application is inside in controlled conditions.
I guess my concern was, I want to select a spring that will give enough force to the pawl but would not be compressed beyond its recommended max. compression when the pawl is opened (when the solenoid is acting). The spring the desinger selected only barely overcame the weight of the pawl unless its initial compression was at a point that when the solenoid opened the spring would be 'overcompressed'. The spring I have selected would put a 5 pound force on the pawl in the direction of the wheel...I just didn't want this to be too much of a force so that it would cause a loud bang everytime the solenoid released.