Fuel rack control automation

[jmw]

I'm seriously in need of some creative Engineering minds on this one.

This was my original thinking. Use a latching pull solenoid to open the rack up and keep it open while the engine is running. This is a great 'fail safe' system as the engine will shut down if 12vdc is not supplied to the solenoid - wonderfully simple.

The problem is that having inquired with a few solenoid suppliers, there are no latching solenoids in existence that can pull the necessary 50N, nor are there any available with anywhere near enough stroke travel (I am estimating at least 1" is required).
The only solenoid I have found that can do the task does not latch, and therefore consumes a good 50W, and it costs more than the engine.

My current thinking is to use an additional spring that will open the rack to a set position (speed) and then have a more traditional stop solenoid to pull against this additional spring that will close the rack. The downside with this idea is that it is going to involve a lot of extra mounting brackets (and possibly even a little pulley wheel), and it is not a fail-safe setup (if power to the stop solenoid fails, then engine will run forever).

One other idea I had was to have a butterfly valve in the air intake that is held open by a smaller/cheaper solenoid against a spring that would close the valve. The downside here is that it involves even more Engineering, and I don't like the idea of shutting an engine down while there is still fuel (and possibly a lot if the genny is loaded) being squirted into the combustion chamber as the engine stops.

Anybody got any suggestions?

Mark

[AdeV]

How are you governing the engine, and what engine is it?

If you're using the standard governer, and the engine is a Lister(oid), then you could use the solution Lister came up with. Basically, a BFO solenoid pulls back the decompression tab, which is mechanically linked to a fuel rack shutoff "pointer". So, as the decompression comes out, the fuel rack is released to be governed as normal.

Lister's solenoid then switched to a "maintenance" mode, i.e. it continued to pass a current, but a lesser one than was needed to release it. The system was spring-loaded such that if the solenoid was switched off, the decompression release would re-engage, which also pushed on the fuel rack to keep it shut.

Personally, I'd be tempted to come up with a system which, after the initial rack-and-decompression release, then latched against an unpowered solenoid (so, when the system is running, nothing happens). A circuit with a decent sized capacitor would basically keep the latch solenoid turned off. If power to that circuit failed (i.e. the engine stopped generating for some reason), the capacitor would fire the solenoid, releasing the spring-loaded rack-closer-and-decompression-releaser back to the "off" position. So, just like Lister did it, only with the extra solenoid. That way, you're not driving a solenoid continuously, so the wasted power should be much less.

If you're one of these chagga.... chigy... fangcha... high-speed diesel buzz-o-box fans, then the scheme might have to be a bit different...

[jmw]

I use a two step solenoid - one coil for pulling the core in at high power and a second coil for keeping the core in (low power).

Jens,

Isn't this what is termed a latching solenoid?
Can you show me a picture of such a device, and a supplier and/or model number?

Thanks,

Mark

[mobile_bob]

Mark

here is one

http://cgi.ebay.com/ebaymotors/FUEL-SOLENOID-_W0QQcmdZViewItemQQhashZitem3a5b089e55QQitemZ250635394645QQptZLHQ5fDefaultDomainQ5f100

they come up on ebay frequently, just do a search for "fuel solenoid"

bob g

[jmw]

Bob,

That's a stop solenoid, and good one by the looks of it - long stroke.
The stop solenoids are not continuous duty - they only work for the time it takes the engine to stop.
Jens was referring to a latching solenoid that stays on, without using much power, continuously.

Mark

[mobile_bob]

take a good look at them, yes they are used as stop solenoids, but
they have to be energized to keep the fuel rack open, loose electrical power and the solenoid
will drop the rack to off position

they have dual coils one is a high current pullin and the other is a low current hold coil, there is generally
a set of contacts internally mounted to switch from high current pullin to low current hold in

so setting them so that they are fully retracted when energized is of paramount importance or you burn out
the intermittent duty pullin winding.

they are used in many applications over here in north america doing exactly what you want to do.

its my solenoid of choice and i will be using one to do precisely what you are asking to do
that is power on to pull the rack to a set rpm point, power off will drop the rack back to no fuel position
for shutdown

bob g

bob g

[jmw]

Excellent. Thanks.
Just need to find me some now.

Mark