ECCENTRIC CRANK ORIENTATION

Are you sure they're not oriented correctly?  If one set of drivers slips and the other does not, wouldn't the orientation be different even if it was identical before?  If the engine runs well, I suggest this is a "problem" that doesn't need to be fixed.  Removing the insert or other attempts to re-position the rods could cause a much bigger problem than you have now.  No one but you will notice it.

Using your second picture as the example, I set mine up as follows: with the crank pin hole on the driver at 6, set the crank 45 degrees toward the cylinders and tighten.  Repeat this on the opposite side.  You should be go to go and close to the prototype.

If you want eccentric cranks the forum is the place to be!

Since he is referring to an SP cab forward model, wouldn't the various eccentric cranks be "out of orientation" so to speak, since the running gear is essentially "going backwards"?

Steam Crazy posted:

Are you sure they're not oriented correctly?  If one set of drivers slips and the other does not, wouldn't the orientation be different even if it was identical before?  If the engine runs well, I suggest this is a "problem" that doesn't need to be fixed.  Removing the insert or other attempts to re-position the rods could cause a much bigger problem than you have now.  No one but you will notice it.

The eccentric cranks on both sets of drivers should be in the same position.

The angle of the eccentric crank in relation to the driver does not change on a steam locomotive.  On most locomotives, it should be angled "forward" or towards the front of the locomotive.  On articulated or duplex locomotives, the angle must be the same for both engine sets.

Rusty

Most cranks are oriented 45 deg toward the cylinders when the wheels are in rods-down position, as in the diagram. Some locos are designed with the crank 45 deg away from the cylinders, but this is not common. The Lionel AC should show whatever the prototype photos show.

The second photo above looks to me like the 90 deg change is exactly what you need, as the crank leans about 45 deg to the left; the top photo is not rods-down, so harder to tell.

The cab-forwards did not know that they were running "backwards" (which they weren't), so the rods and eccentrics orientation would not be affected for that reason. After all, they did run both ways...

And someone previously mentioned. How does how can the front set up drivers/wheels stay in sync with the rear set of drivers/wheels? Aren't they individual setups with individual cylinders powering them?

Train Nut posted:

And someone previously mentioned. How does how can the front set up drivers/wheels stay in sync with the rear set of drivers/wheels? Aren't they individual setups with individual cylinders powering them?

They don't stay in sync.  They don't have to.

The only reason most models stay in sync is because they are powered by the same motor.  A model with two motors will go in and out of sync.

Rusty

Your looking for a place to "worry" if the Locomotive runs, enjoy it and be glad. Nick

Rusty Traque posted:

Steam Crazy posted:

Are you sure they're not oriented correctly?  If one set of drivers slips and the other does not, wouldn't the orientation be different even if it was identical before?  If the engine runs well, I suggest this is a "problem" that doesn't need to be fixed.  Removing the insert or other attempts to re-position the rods could cause a much bigger problem than you have now.  No one but you will notice it.

The eccentric cranks on both sets of drivers should be in the same position.

The angle of the eccentric crank in relation to the driver does not change on a steam locomotive.  On most locomotives, it should be angled "forward" or towards the front of the locomotive.  On articulated or duplex locomotives, the angle must be the same for both engine sets.

Rusty

Okay. That's what I thought. But then I saw this post here and got confused. Must have just been luck that they were positioned exactly the same when the pic was taken

"If you want eccentric cranks the forum is the place to be!"

Indeed.

This should settle things.

Big Jim posted:

This should settle things.

It should but, as I posted earlier, an SP cab forward essentially has the running gear operating in "reverse", i.e. backwards. Thus, the eccentric cranks are aligned differently than say a "normal" 2-8-8-4.

The folks here might not understand why that is on a cab forward. 

AmeenTrainGuy posted:

How did the fireman feed coal into the engine if the tender was on the opposite side? 

At least in the case of SP Cab Forward locomotives, they were oil fired.  On some other designs, the firebox was on the rear and there was a separate cab on the rear of the locomotive or simply a deck plate for the fireman to tend to the coal.  Similar to how the Camelbacks worked.  They weren't common in US practice though.

AmeenTrainGuy posted:

How did the fireman feed coal into the engine if the tender was on the opposite side? 

Think "Jed Clampett".

OK I get it.  I think I tried to reorient the one set that was facing away from the cylinders at the 6 o'clock position but it caused the expansion link to bind.  Will look a little closer. 

Beyond this portion of the discussion, has anyone confronted the mistake by the factory of the expansion link being backward???

I think that Hot Water made a comment recently that on the cab forwards, SP slightly pressurized the tender oil tank with air to get the oil to flow down the entire length of the locomotive to the fire box.   The question of how the engines on articulated locomotives end up synchronized all the time has come up before, but I do not recall any conclusion being reached. They are not mechanically connected except by the rail.  With respect to the position of the eccentric, it is positioned based on the location of the valves above the cylinders. It does not matter if this is the front or rear of the loco.  

I guess that I should have mentioned that the photos that I posted only prove the orientation of the eccentric cranks, nothing more. Sorry if I have created any confusion otherwise.

The position of the eccentric crank (leading or following the main pin) is determined by the valve gear setup. 

• Inside Admission or Outside Admission
• Direct or Indirect Valve Motion 

The vast majority of American Steam locomotives were inside admission using direct motion. With that combination, the eccentric crank FOLLOWS the main crank pin by 90 degrees.

If the eccentric follows the main crank in forward, it leads the main crank in reverse. If it leads the main crank in forward, it follows the crank in reverse.
If the valve gear in forward motion is direct, it is indirect in reverse and if it is indirect in forward, it is direct in reverse (but this is not what is in question here).

OGR Webmaster posted:

The position of the eccentric crank (leading or following the main pin) is determined by the valve gear setup. 

• Inside Admission or Outside Admission
• Direct or Indirect Valve Motion 

The vast majority of American Steam locomotives were inside admission using direct motion. With that combination, the eccentric crank FOLLOWS the main crank pin by 90 degrees.

So in this illustration, is the eccentric leading or following?

I would think the main thing you want to make sure of is that they don't bind. I have a MTH RK Imperial 0-6-0 that arrived with a loose crank and had a heck of a time getting it corrected and running smoothly.  Had to look at a few photos to get the orientation correct.

On our models, the motor and gearing drive the wheels. On a real steamer, the steam pistons rotate the wheels via the siderods.  The siderods (and other valve gear) on our models are mainly for looks.  Heck, some engines don't even come with everything you'd normally see on a real engine.

loco2124 posted:

OGR Webmaster posted:

The position of the eccentric crank (leading or following the main pin) is determined by the valve gear setup. 

• Inside Admission or Outside Admission
• Direct or Indirect Valve Motion 

The vast majority of American Steam locomotives were inside admission using direct motion. With that combination, the eccentric crank FOLLOWS the main crank pin by 90 degrees.

So in this illustration, is the eccentric leading or following?

Unless I have my forwards and backwards mixed up: Leading, like 765...

While Soo 1003 is following:

Rusty

loco2124 posted:

OGR So in this illustration, is the eccentric leading or following?

Following in forward, leading in reverse. It is also direct in forward, indirect in reverse. Inside admission.

Rusty Traque posted:
Unless I have my forwards and backwards mixed up: Leading, like 765...

Rusty

Yes, you are mixed up. The eccentric pin is following the main crank pin in forward.

It is easy to tell on the 765. The angle on the bow of the 1003 makes it hard to tell.

Let me suggest that for those of you who are interested in seeing valve gear in motion, go to:

Steam Engine Valve Gear On The Computer

...and download the animations you desire. If these are still the same (I've had these for years now) you can fiddle with the settings, Fwd/Rev, Fast/Slow etc. to see how things move in relation to one another.

This discussion is getting way to technical for me!  I just want to have fun running my steam engines.  I don't care if the rods are perfectly oriented, as long as they're not loose or binding.  Just one operator's opinion.

Big Jim posted:

Rusty Traque posted:
Unless I have my forwards and backwards mixed up: Leading, like 765...

Rusty

Yes, you are mixed up. The eccentric pin is following the main crank pin in forward.

It is easy to tell on the 765. The angle on the bow of the 1003 makes it hard to tell.

Couldn't find a good rods down photo, but found a Soo Mike builders photo:

I was incorrectly referencing the eccentric relation to the axle.  Mea Culpa...

Rusty

Big Jim posted:

Let me suggest that for those of you who are interested in seeing valve gear in motion, go to:

Steam Engine Valve Gear On The Computer

...and download the animations you desire. If these are still the same (I've had these for years now) you can fiddle with the settings, Fwd/Rev, Fast/Slow etc. to see how things move in relation to one another.

That was a very interesting and informative site.   Am gonna keep it around.  So another question:  Other than looking at the orientation of the eccentric, leading vs. following, can you look at a cylinder arrangement on a locomotive and determine inside vs. outside admission?

loco2124 posted:

So another question:  Other than looking at the orientation of the eccentric, leading vs. following, can you look at a cylinder arrangement on a locomotive and determine inside vs. outside admission?

Yes you can by looking at the Radius Arm connection to the Combination lever.
If the Radius Arm is connected to the Combination Lever between the ends (below the valve stem), it is outside admission.
If the Radius Arm is connected to the Combination Lever at the upper end (above the valve stem), it is inside admission (as seen in JDADDY's post above).

Thanks everybody.  Been very informative and fun...

Just checked in - figured this was a loose eccentric.

Note that, as Hot says, the cab forward engines are running backwards.  All else being equal, just grabbing a Northern engine and turning it around means the radius rod would be "up" when the cab forward moves "forward".  That is not desirable, apparently - what if something breaks and the radius rod drops to the bottom of the link at 40 mph and a hundred cars behind you?

To get the link down while the engine is moving "cab forward" you need to re-orient the eccentric.  Note in the photos above the eccentric is inclined toward the front of the locomotive, and not toward the cylinder block.

On a model articulated the two engines are always synchronized unless two separate motors and gears are installed.  I have done that, and it is complicated.  The easy way to have them go in and out of synch is to use different gear ratios on each engine.  I have done that, too, and it so angered one of our participants that it ended a friendship.  It does work.