does anybody know if a linear actuator or solenoid exists that will extend when it recieves power and retract once power is removed, or so you need to reverse polarity on it?

 

solenoids and electromagnets don't work that way. the current causes magnetism which pulls a rod that activates whatevers attached to the solenoid. if you change the direction of electric flow, it still causes magnetism, and since the rod doesn't have poles it can't be repeled in the solenoid. so no, you cant get a solenoid like that. tell me what you need it for and i might be able to help you find something else that will work

 

Im looking for an actuator that is activated by an rpm switch, but when the power is cut, i need it to retract...I would use door lock solenoids, but like you said, you need to reverse the polarity...What its for is a dual stage manifold, but i want the set of butterflies to open by rpm activation, and not by vacuum.... Does a v-tec solenoid open and close based on on/off?

 

honestly, im not sure off the top of my head. i would suggest searching for a company that deals in actuators and solenoids and posting this question to them. im sure a quick search of google and you should be able to find someone that deals specifically in something that you could use. also, something that you might be able to rig up is a hobby servo. you can find them at any hobby store that sells model airplane parts. as long as where you're mounting it doesn't get hot enough to melt the internal gears or case, that could be used. they can extend a pushrod of sorts in either direction and they return to center once the power is cut on them, but they don't have a big range of motion. it's worth a look into.

 

http://www.acpd.co.uk/51.html

here, read through this and see if this will work for what you want

 

i feel retarded, all i need to do is have some sort of weak spring on the throttle rotor so once the power is cut, there is no more magnetic field and the actuator will return to its original position....nevermind, thanks for all the input tho, i guess i answered my own question