I'm going to go back to the earlier parts of this thread and raise some questions, since I'm still not quite sure what the consensus is.
It seems to me that the rack puller is the "proper" way to stop the engine. It also seems to me that the engine should be "fail safe". Lastly, it seems "simple is better." So, I've discounted air pistons (too complicated - two more systems to manage), closing off the fuel (not instant stop), and closing off the air (maybe impossible) I have a 12vdc system planned, so I have plenty of 12v power. That leaves electrically operated solenoid-type rack pullers - only one more system to manage, and a well-understood one at that.
The solenoid activates and pulls the pin back X.X inches. Then, an electromagnet (using much less power) holds the pin in place. In my fail-safe world, what I would do is actually not have the solenoid pull the rack upon engergizing, but in fact have the solenoid close the rack on DE-energizing, by allowing a compressed spring to extend and push the rack controls closed. Why? So if I lose the 12v for whatever reason, the solenoid would de-energize, the spring would be released, and the rack would be closed. I like fail-safe for stopping engines; having to rely on a power supply to stop the engine seems a little dangerous.
This means I need probably 150% the pulling power in the solenoid that is required for just the rack, since I need to pull back the spring, which will in turn be ~125% of the required force to close the rack.
Does anyone see anything obviously wrong with this method? It's a bit spendy (~$150 for both parts and some springs) but seems to be easy to implement.
My questions for the group:
- what's the the travel required to close the rack on your engine? 1.5"? 2"? other?
- how many pounds of force are required to close the rack on your engine? 15#? 20#?
- what kind of engine do you have? (brand and size)
I ask these questions so I can maybe come up with a "universal system" whose specifications would work for anyone's engine, and I'll post the notes here.
Some resources for people searching this thread:
http://www.trombetta.com/DefaultFrameset.asp?ShowContent=prod P613-A1V12 1.5" draw, 21 pound pull, $94 from
http://www.murcal.com/ http://www.murcal.com/s500-a60.htm S500-A60 controller, reduces voltage to coils after draw but keeps hold magnet engaged $53