Choo Choo Trains

Captain

Captain

Final Approach
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The numbers thread has quite a few photos of trains and got me thinking. I understand the basics of how a steam engine works but one thing has me puzzled.

If the drive piston linkage to the wheel is at the Three or Nine O'Clock position when initially starting to roll how would that work? Seems like it would just push into the wheel and result in no roll. So how would a train start rolling if the wheel happened to stop at either of these two positions?

Does the engineer have to be careful of where the wheels are in their rotation when coming to a stop or is there something I'm missing?
 
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Captain said:
If the drive piston linkage to the wheel is at the Three or Nine O'Clock position when initially starting to roll how would that work? Seems like it would just push into the wheel and result in no roll. So how would a train start rolling if the wheel happened to stop at either of these two positions?

Does the engineer have to be careful of where the wheels are in their rotation when coming to a stop or is there something I'm missing?
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The wheels on either side of the train are 90 degrees out of phase so only one side can end up at the 3 or 9 o'clock position where, as you surmise, one is S.O.L.
 
Capt. Geoffrey Thorpe said:
The wheels on either side of the train are 90 degrees out of phase so only one side can end up at the 3 or 9 o'clock position where, as you surmise, one is S.O.L.
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Ah, so simple! I was missing the 'other half' of the train.

I guess I envisioned both wheels 180 out giving that rhythmic chug chug. But they're really 90 out giving a chugchug...<pause>...chugchug? Still seems like it'd cause issues if one side was at full extension while the other was in retraction. The piston only pushes and doesn't pull right?
 
Captain said:
Ah, so simple! I was missing the 'other half' of the train.

I guess I envisioned both wheels 180 out giving that rhythmic chug chug. But they're really 90 out giving a chugchug...<pause>...chugchug? Still seems like it'd cause issues if one side was at full extension while the other was in retraction. The piston only pushes and doesn't pull right?
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Steam engine pistons give a "chug" in both directions. It's not like an internal combustion engine piston. The switch doesn't relieve steam pressure. It reverses it.
 
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MAKG1 said:
Steam engine pistons give a "chug" in both directions. It's not like an internal combustion engine piston. The switch doesn't relieve steam pressure. It reverses it.
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So the piston pushes AND pulls?
 
Captain said:
Ah, so simple! I was missing the 'other half' of the train.

I guess I envisioned both wheels 180 out giving that rhythmic chug chug. But they're really 90 out giving a chugchug...<pause>...chugchug? Still seems like it'd cause issues if one side was at full extension while the other was in retraction. The piston only pushes and doesn't pull right?
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Yep, the axle acts the same as the crankshaft on a 2 cyl engine.
 
Henning said:
Yep, the axle acts the same as the crankshaft on a 2 cyl engine.
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Doesn't a 2 cylinder engine have a starter or pull rope to get the thing going? That negates the point as trains don't have to be pushed to get going.
 
Captain said:
Doesn't a 2 cylinder engine have a starter or pull rope to get the thing going? That negates the point as trains don't have to be pushed to get going.
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That is because in an internal combustion engine, the piston provides the compression as well, so the starter motor is needed to introduce that energy. In a steam engine the Boiler provides the compression energy, the piston only absorbs it. So the boiler is the starter.
 
Captain said:
I said piston, not steam. Does the PISTON push and pull?
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Depends on the engine but for many steam engines, yes. Steam is released on one side of the piston "pushing" it and then steam is released on the other side of the same piston "pulling" it (with reference to the connecting rod.)

My grandfather had a Stanley Steamer which only had one cylinder. He said you had to be careful not to park it against a curb with the cylinder at TDC. You could run the engine in either forward or reverse but if you were at TDC you had to roll the car and if you were against a curb having to roll it uphill was a pain.

He also said he would go to the car, start the boiler and crack the throttle. Since there was no steam built up nothing would happen immediately. He'd walk away form the car, turn around and whistle and (if he timed it right) the car would gently roll up to him.

John
 
Henning said:
Yes, the piston applies force in both directions.
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jsstevens said:
Depends on the engine but for many steam engines, yes. Steam is released on one side of the piston "pushing" it and then steam is released on the other side of the same piston "pulling" it (with reference to the connecting rod.)

My grandfather had a Stanley Steamer which only had one cylinder. He said you had to be careful not to park it against a curb with the cylinder at TDC. You could run the engine in either forward or reverse but if you were at TDC you had to roll the car and if you were against a curb having to roll it uphill was a pain.

He also said he would go to the car, start the boiler and crack the throttle. Since there was no steam built up nothing would happen immediately. He'd walk away form the car, turn around and whistle and (if he timed it right) the car would gently roll up to him.

John
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I did not know that. Thanks, I feel like I learned something here today...and it's not even 10:00 yet.
 
MAKG1 said:
Steam engine pistons give a "chug" in both directions. It's not like an internal combustion engine piston. The switch doesn't relieve steam pressure. It reverses it.
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I guess it was right here in post 5 and I missed it. sorry
 
mikea said:
Now.

How does the train stay on the track? (Not what you think)

The wheels are welded to solid axles.
How do does the train handle making curves without a differential?


https://www.youtube.com/watch?v=y7h4OtFDnYE
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By chewing up the rail head. The outside rail wears away on the gauge side of the head, and the inside rail head mushrooms out with razor sharp slivers that I bear many scars from. This gets ground off occasionally by a company called Speeno. This often results in defects called Vertical Split Heads. In tight mountain country they run rail greasers to reduce the wear.

The best rail I saw in the mountains was Nippondenso Head Hardened rail.
 
Henning said:
No, steam can't pull, the valve switches which side of the piston the steam pushes on.
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Actually, it can. It just isn't used that way in steam engines. You can only make 1 atm of vacuum. You can make a lot more than that of pressure.

My son's favorite experiment is to take an empty aluminum can, put a teaspoon or so of water in it, then heat it on the stove until boiling. With a pair of tongs, grab the can, turn it upside down, and quickly immerse the top in a bowl of room temperature water.

Boiling the water fills the can with steam. Sticking the can in a bowl of water flash-condenses the steam, and it sucks the can in, rather spectacularly.

Not a very efficient way to crush aluminum cans, but it does work.
 
Henning said:
By chewing up the rail head. The outside rail wears away on the gauge side of the head, and the inside rail head mushrooms out with razor sharp slivers that I bear many scars from. This gets ground off occasionally by a company called Speeno. This often results in defects called Vertical Split Heads. In tight mountain country they run rail greasers to reduce the wear.

The best rail I saw in the mountains was Nippondenso Head Hardened rail.
Click to expand...

But what keeps them on track on tangent track is the taper of the wheel treads. The flanges have little to do with it. On curves, they do rub the gauge side of the rails.
 
This thread makes me think of my son's favorite song to dance to:

 
MAKG1 said:
Actually, it can. It just isn't used that way in steam engines. You can only make 1 atm of vacuum. You can make a lot more than that of pressure.

My son's favorite experiment is to take an empty aluminum can, put a teaspoon or so of water in it, then heat it on the stove until boiling. With a pair of tongs, grab the can, turn it upside down, and quickly immerse the top in a bowl of room temperature water.

Boiling the water fills the can with steam. Sticking the can in a bowl of water flash-condenses the steam, and it sucks the can in, rather spectacularly.

Not a very efficient way to crush aluminum cans, but it does work.
Click to expand...

I want to try this. Only a teaspoon of water?

Do you leave the can intact, or do you need to cut the top off (so it's open on one end)?
 
LoneAspen said:
I want to try this. Only a teaspoon of water?

Do you leave the can intact, or do you need to cut the top off (so it's open on one end)?
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use a 1 gallon paint can with a good fitting lid. add 2 oz water set the lid on, bring to a boil until you see steam coming out of the lid. remove from heat and press the lid on tightly. see what happens.
 
Norman said:
But what keeps them on track on tangent track is the taper of the wheel treads. The flanges have little to do with it. On curves, they do rub the gauge side of the rails.
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Yep, I know about the taper centering, I was commenting on the 'no differential' question. Not having differentials on those axles is expensive and destructive. Mostly on rail, some on wheels. The problem found with the good Nippon rail is that it wore out the wheels instead.
 
cirrusmx said:
the real question is, can you lean of peak a steam locomotive???:rofl::rofl::rofl:
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Depends on the fuel. With natural gas it would be easy, with oil you could probably get the draft set well enough. Coal and wood would likely require a blower.

The real question though is what would LOP do for you in a boiler rig? Where would the advantage be to be leaner than peak?
 
Henning said:
Depends on the fuel. With natural gas it would be easy, with oil you could probably get the draft set well enough. Coal and wood would likely require a blower.

The real question though is what would LOP do for you in a boiler rig? Where would the advantage be to be leaner than peak?
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No blower required. Draft will do it. You want to be a little bit lean to reduce CO, but any excess air actually reduces boiler efficiency because you are reducing the temperature achieved for the fuel burned and reducing the heat transfer into the steam.
 
Waste steam acts as a blower. It is exhausted through a nozzle in the smoke-box and enhances the draft through the firebox.
 
LoneAspen said:
I want to try this. Only a teaspoon of water?

Do you leave the can intact, or do you need to cut the top off (so it's open on one end)?
Click to expand...

No need to modify the can. It will self-modify soon enough.

You just need enough water to fill the can with steam. Excess liquid makes no difference, except it takes longer to heat up.
 
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