I have several MPC-era and similar turnouts, which work fairly well. An unfortunate issue is that I want them to be set up so that whenever they receive a signal (flipping the maintained SPDT switch or a train going over the insulated rail) they receive a short electrical pulse that then shuts off. I can’t find a good circuit that would work for this.
I also looked into running the turnouts on DC. The results of this search seem to imply that it would not only work fine but that I could leave the solenoid running indefinitely without fearing it burning out. However, given the price of turnouts, I don’t want to risk them and this info seems somewhat dubious. Can anyone help?
Where, pray tell, did you read that the coils can be left energized indefinitely on DC?
It is my understanding that while the solenoids will certainly work on DC, and in fact may be quieter on DC, they will probably heat up faster, if anything.
As far as throwing the switch with a momentary pulse, I know one can find old threads here and on other forums about Capacitance Discharge circuits for throwing switches. I remember recently someone posted here about a timed relay that would automatically break power after a certain duration of time, this could also achieve the desired result.
It’s important to clarify, are you talking O27 turnouts, or Standard O (like the O22 remote control switch)? The latter have a design that will automatically cut power to the solenoid once the turnout has thrown. The former do not, but also have the issue of not being set up for constant voltage power, and require modifications in order to allow for this (as opposed to using track voltage for power).
-El
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I did see someone mention capacitance discharge circuits, but by the look of it that would not work quite properly for this application. However, I am going to keep it as a backup in case I can’t find something that fits exactly all my nitpicky preferences. Probably the timed relay is less practical in this situation as I do have a few electronic components on hand–but not specialty relays. I read about the DC at some electrical forum, but it kind of looked like the fellow who wrote the response was rather confused about which way the electrons run, thus the reason I considered it unreliable info. 
These are O27-style turnouts, but I intend to modify them in a cheap and simple manner so as to have continuous power.
On my layout, I control my turnouts with toggle switches similar to these- they are “momentary” which means spring loaded, they only close the circuit while you hold it with your hand, then when you let go, it returns to the center off position.
Momentary Toggle Switch
If you are doing insulated rails and are worried a train might park on a rail and continually energize the solenoid, check out my thread on time delay relays
Well, I would have used momentary switches except I’m such a cheapskate that I can’t bear to spend a few dollars when I’ve got a bag of brand-new maintained switches. Plus, I’m worried that one of my cousins would hold down the switch anyway. Similarly, since I’ve got a nice big bag of perfectly good capacitors, transistors, and the like (but not time-delay relays), I don’t want to spend money on fancy new relays either.
Good luck designing your own circuit from scratch. I’m not smart enough to be helpful with that. 
Ugh! I agree! I can figure out how to wire a lot of stuff, but once I get into the realm of capacitors, transistors, and resistors I need a good circuit planning program with a simulator.