Primary leads or lags secondary?

[wsmcycle]

Which is it? Should the smaller/primary cylinder lead or follow the larger/ secondary cylinder in the forward direction? I have seen compound engines setup both ways. My Stuart 6a is very difficult to start. PLEASE. What is the procedure for starting a two cylinder compound engine? I shake the shift lever back and forth sometimes successfuly. Maybe it will start and maybe it won't.
It seems to me that If you put the smaller cylinder at 300 or 900 oclock, it should take off. But it doesn't always.

[barts]

Which is it? Should the smaller/primary cylinder lead or follow the larger/ secondary cylinder in the forward direction? I have seen compound engines setup both ways. My Stuart 6a is very difficult to start. PLEASE. What is the procedure for starting a two cylinder compound engine? I shake the shift lever back and forth sometimes successfuly. Maybe it will start and maybe it won't.
It seems to me that If you put the smaller cylinder at 300 or 900 oclock, it should take off. But it doesn't always.

Simpling valve?

E.g.dump some hp steam into the receiver.

- Bart

[wsmcycle]

E.g.dump some hp steam into the receiver.

Bart, please explain this some more for me?

What is the "receiver"?
Thanks

[barts]

The receiver is the name for the pipe/passage between the high pressure cylinder and the low pressure cylinder. Connect a valve just downstream of the throttle and plumb the output of the valve into the receiver. When starting, rotate the engine so the low pressure piston is a bit after TDC and open the simpling valve; then crack the throttle. She'll start.

-= Bart

[wsmcycle]

OK great, I understand your statement. I don't have a fitting on the "reciever". It is just a piece of copper pipe between the two cylinders.

[barts]

I'd suggest silver soldering in a brass bushing in the receiver, then. This doesn't have to be a huge pipe; 1/4" would be ample and 1/8" would likely work just fine as well.

- Bart

[wsmcycle]

Thanks Bart. I understand. Is this what is called a "simpling" valve? I never quite got "simpling" but i understand this.
Thanks

[Lopez Mike]

As Bart says, it doesn't need to be a large valve and pipe at all. Our marine engines are starting under essentially no load conditions. On the few boats I've been on with a compound and simpling valve it wasn't necessary to position the engine for starting. It acted like a simple twin and took right off.

A low pressure gauge at that point can be illuminating.

For compound locomotives that had to produce maximum torque at zero speed to get a train moving there were rather elaborate sampling valves with a bit larger passages but still nothing that huge. As soon as the train was moving (a few m.p.h.) the locomotive was shifted back to compound operation.

The other time that the locomotive was shifted to simple operation was when warming the cylinders by opening the drain cocks. It takes a fair amount of steam to warm up a ten to twenty thousand pound cylinder casting.

[wsmcycle]

Now the term makes sense "simpling". Make "simple" out of compound.
What about the back pressure we are putting on the primary piston? It seems like that would need to be cut-off. Just wondering?
Thanks

[Lopez Mike]

The efficiency of operation during 'simpling' doesn't matter as it is only for a moment during starting.

In practice (since before any of us were born) it works.