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Couplers and Throttles


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#21 atsf37l

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Posted 03 March 2006 - 09:54 PM

QUOTE(wmghobbs @ Mar 3 2006, 03:21 PM)
Oh yeah, and link and pin couplers.

How many fingers am I holding up? laugh.gif

#22 S. Weaver

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Posted 04 March 2006 - 03:13 AM

Nice posts. Some comments:

Herb is correct in that there is no "riding the hump" with early control valves like the "K" and its predecessors. They will just release unless one is very careful. There was just release, running, lap, service application and emergency - all from the same reservoir.

Most early practice - pre-retainer - with automatics that I've read about involved the following:
1. The train stopped at the summit or nosed over dead slow;
2. The engineer took his inital set, based on experience, that would hold the train below 10 - 15 mph;
3. As things slowed due to leakage, the engineer would whistle for brakes - one long blast;
4. "Shorty" and "Earl" would take to the tops, tying down the handbrakes and meet in the middle;
5. The engineer would note their progress, and release and recharge accordingly;
6. He would then take another set, whistling for release (two shorts);
7. Our intrepid brakemen would move back towards the ends, releasing what they had set;
8. When the train slowed too much again, the engineer would whistle for brakes and our brakemen would begin tying them down again.

If "Shorty" and "Earl" were good, they would fine tune this back and forth with the engineer, keeping a nice, consistent descent under 15 mph.

Before modern realignment, most grades had sags and rises at convenient intervals that would also help the engineer in releasing and reapplying. (KUJU's original Marias comes to mind ... rolleyes.gif ) After WWII, everything was ironed out on most grades to give consistent gradient. (Notable exceptions being some of the Colorado grades like Tennessee Pass and the narrow gauge lines.)

The development of retainers was a tremendous thing and welcomed by the crews. As Bill noted, the crew would choose between high pressure (20 psi), low pressure (10 psi) or slow discharge (of cylinder pressure), depending on the grade. "Shorty" and "Earl" could then relax in the caboose.

The longest I've ever dropped a train on early triple valves with one set was a mile. I had to release because of physical characteristics, not leakage.

For the ON, I wouldn't change much. Brake pipe would be 70 psi. Bill's current wag settings for the St.L.&N.A. capture the feel of an early triple. The only adjustments would be what Bill appears to have well in hand: car weights, braking force and handbrake settings. Handbrakes should be used to hold the train when needed. Andre, tell 'em to keep that F9 window open on the descent from Fly Gap!

#23 wmghobbs

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Posted 04 March 2006 - 06:47 AM

Its beginning to look as though we might be able to get a "twofer" here! tongue.gif If we look at the handbrake as being able to do duty either as a retainer or a true handbrake.
After I posted my last reply, I realized that I hadn't noted a fact about how I am setting braking forces for cars these days. After realizing that the adhesion statements don't function in .wag files, I now calculated separate braking forces for loaded and empty cars, with the upper limit of empty cars usually being determined not by the braking force, but by wheel adhesion: when wheels start sliding, they are no longer increasing the braking force.
So my thought is that the handbrake force ought be set at at least 40% of the maximum braking force with this question for Steve: What % of the max airbraking force do you think a brakeman could have achieved working from the top of a car with the train moving?

Bill Hobbs

#24 laming

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Posted 04 March 2006 - 07:40 AM

Don't know about the boys "back when"... but I momentarily slid a set of wheels on a loaded car (265,000 lbs) with a handbrake doing a roll-by this past Thursday.

Given their brake jacks didn't have leverage working for them like today's... it may have depended on how stout the brakeman was, and how strong their brake staff was.

Bill: Think you can factor that in too? smile.gif

#25 wmghobbs

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Posted 04 March 2006 - 09:30 AM

Andre,
No, you get one shot to set the handbrake force. So some reasonable assumptions will have to be made.

Bill

#26 S. Weaver

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Posted 04 March 2006 - 02:21 PM

QUOTE(wmghobbs @ Mar 4 2006, 08:47 AM)
So my thought is that the handbrake force ought be set at at least 40% of the maximum braking force with this question for Steve: What % of the max airbraking force do you think a brakeman could have achieved working from the top of a car with the train moving?

Good question.

With a stout brake staff I can get just the force needed to kick out the pawl on a simple winding handbrake that was set after the brakes were dumped. This is under ideal conditions, with the car sitting in the yard.

I cannot put that same force back on the rigging winding from release (and it's not because I'm a wus). But we need to remember something: the brakeman was winding down on something that was partially set. In other words, he had help from the air. So, making an educated guess, I would say that if I'm getting sixty percent of the full force while riding a rocky top, I'd be doing pretty good. Put in the slippery footing factor in rain, sleet or snow, maybe it drops to fifty percent.

Your call, maestros.

#27 S. Weaver

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Posted 04 March 2006 - 02:25 PM

QUOTE(wmghobbs @ Mar 4 2006, 08:47 AM)
Its beginning to look as though we might be able to get a "twofer" here! tongue.gif If we look at the handbrake as being able to do duty either as a retainer or a true handbrake.

Further thought, Bill:

I think history requires us to look at the late 19th century handbrake in that dual capacity.

#28 wmghobbs

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Posted 04 March 2006 - 04:35 PM

I'll do some testing tonight, including seeing if I can get a train down hill with handbrakes and engine brakes only. I won't take the air brakes off, just not use them.

Bill

#29 wmghobbs

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Posted 04 March 2006 - 08:18 PM

I set the handbrakes at 40% of the air-brake pressure and started down the grade from Fly-Gap using only handbrakes and engine brake. I believe that is a 4% grade. The train was my coupler test train: several empty gons followed by several loaded box cars and a caboose (this order was chosen to stress the couplers as much as possible). I did not let train speeds exceed 8mph while going down, averaging 6 - 7mph most of the way. Things worked just fine, though the brakemen did have to set every brake, working forward from the rear of the train. Brakes were gradually released as the depot came into site and then the last couple of cars reset to help the loco slow down at the depot instead of bunching everything up using only the engine brake.

Bill cool.gif

Note: these results may not be typical etc etc.

#30 pnrailway

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Posted 05 March 2006 - 12:37 PM

If you aren't to careful with Mr. Bill's coupler values, this is what could happen:

IPB Image


Paul wink.gif laugh.gif

#31 wmghobbs

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Posted 05 March 2006 - 03:25 PM

Why did you go and do that?.... ohmy.gif
Seriously, I am still looking for feedback on the coupler settings. I've got two sets of freight cars, passenger cars and locos waiting to be finalized and couplers have become one of the factors.

Bill

#32 S. Weaver

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Posted 07 March 2006 - 04:33 PM

Bill:

Did you get my PM?

Also, as a further thought, you could try a mix, if it wasn't too much trouble. Some cars with the spongy draft gear; some with stiffer gear. It certainly would be prototypical. In any event, you'll probably have to raise the Break Value to what you suggested in order to keep us from littering the ROW with drawheads.

The handbrake test sounds good. Onward and upward!

#33 wmghobbs

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Posted 07 March 2006 - 04:58 PM

Thanks Steve. I figured that the break values would have to be raised, but I wanted to see how often they were causing problems. I've been playing with them while working on sounds and keepinga close eye on things.

I finally figured out how to set up the equations to test the couplers but have not yet had time to set up a spreadsheet to do it. Had to get a bit of help on solving for the initial conditions as my knowledge of the required math is growing fainter by the year. I am comfortable that couplers can be made to work pretty realistically with the exceptions of the loco front coupler and the break values (because of the node problems).

On sound, this week I hope to have some more time to finish getting the .wavs for the Eureka Springs #1 blended. That will make 3 different rod engines and one shay that I have + assorted whistles, bells, air pumps and other sounds to customize with.

Bill
I will be sending you a regular email as well.