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Thread: Pig mystery - how do they move?

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    Default Pig mystery - how do they move?

    Pig here refers to the pusher used to run coal cars up a ramp for dumping. I think I've also seen the word "Barney" used for the same thing.


    I want to get one of these working on my layout and I'm wondering how the heck they move. They are on a small track (I'm thinking Z scale) between the rails.
    They wouldn't be internally driven because the pig track is smooth with no traction available.
    I was assuming the pig gets pulled up the ramp by a cable from a pulley at the top of the ramp. But that won't work; the cable would interfere with the underside of the car. Imagine the cable pulling taut, it would lift the front of the first car and derail it.

    Anybody know the answer? Guesses? Another pic and I've run across videos but no clues so far:

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    In that second photo, it looks like there is some kind of belt around the axles of the two wheels on that thing.

    Without seeing the second photo I would have guessed one of the following:
    1) it was pushed by something ( hydraulic or pneumatic cylrndrd perhaps )
    2) it was pulled by something ( a cable or chain )
    3 ) it has an electric motor.

    The second photo clearly rules out the first possibility, so it has to either bee eekf propelled or pulled.

    There is clearly some kind of cable running to the back of the pig. I think ( but am not positive ) I see that in the first photo on the ramp as well.

    But I don't really think this is being pulled on a cable either.

    My guess is that it is an electrically operated device, and that cable supplies power to the motor.

    This isn't the same thing we see in the photos, but there are electric rail car movers such as this one:
    http://www.djproducts.com/product/rail-car-mover/

    Paul

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    Could be on a cable system like in SF http://www.cablecarmuseum.org/mechanical.html
    "It's not whats best......It's whats best for you"

    Gary

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    I see the belt, it could be a chain link drive. But can't be driving the wheels - that is a 10 to 20 % grade and two 125 ton cars - polished steel wheel on steel rail just isn't going to cut it.
    Maybe the chain pulls the arm up and down?

    It is cable-pulled. I found this you tube video and at about 7:45 you can see the cable under the car. https://www.youtube.com/watch?v=RNhwKGWtK4U The angle of the photos makes it look worse than it is in reality - the cable barely slaps against the axles.

    This should be fun to model. From past experience the big problem will be the tight vertical radius on the rails at the top and bottom of the ramp - our N-scale cars just don't have that kind of swing.

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    I always figured it had to be on a cable, as there is no way for something that small to develop enough traction (steel wheels on steel guide rails) to push up such a hill, regardless of the power of the motor. The force exerted by the 100+ tons of coal would tend to push it back, not just down the slope, but even back away from the rails. So it seems to me that there must be something mechanically holding it down onto the rails, other than its own mass. Roller Coasters have wheels that run not just on top of the rails but also beneath and on the side, I wonder if there might be something similar here (perhaps gripping that center rail?); I certainly cannot see such a thing.

    As for creating your own working version, I'm not sure that Z scale track nestled inside the N track would be the right way to go. Notice that the pig's track dips well below the level of ordinary ties at the base of the slope, so that wheels can pass over it. You'll need to have a similar variable depth. I'm actually picturing a long slot in the center of the rails, with perhaps ordinary N track mounted upside-down. The pig then gets built close to scale, riding on a peg that drops down through the slot, where it engages the bolster pin hole of an ordinary N truck, which of course is riding the upside-down track. The pig would need its top-side "wheels" to hold it down from above, but I'm betting that you could get by with rigid or cast-in "wheels" that don't actually rotate. They'd just scrape along the top surface of your pig track, which rather than Z track, might just be a pair of sheets or plates.

    What I can't figure out, though, is how to maintain track gauge, if you have this long slot and a cavity for an upside-down truck to roll through. Because of this, it probably is better to figure out a way to have the pig's wheels actually rolling on the top side. The upside-down truck would have the advantage that you could make use of any old ugly chain or cable to drive it, as the connection(s) would be hidden from view.

    Maybe, if you can actually fit Z track between N rails, you could rely on the thinner web portion of the rails as a way to add guides that hold the pig down to the rails. I'm not even sure whether Z track has a skinny web portion; regular Atlas code 80 doesn't, for instance. Code 55 rail does tend to, so maybe... Anyways, if the pig was built around a truck, then maybe in between the two axles, you could have a stiff wire bend out like wings, such that its edge would nestle into the rail's web. This is the space where usually spike heads tend to be found, so you'd probably need to remove the spike heads and trust in glue or solder to hold the rail down to whatever is supporting it. The difference in width between the rail's railhead and web would thus become a lip that hold the wire wings in place. I'm thinking of wire bent to roughly the profile of a football, where the apex in the middle is what is snapped into the trough of the rail web. The football shape would give it a bit of springiness such that it could snap in and out.

    Interesting little engineering challenge!

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    Quote Originally Posted by WP&P View Post
    What I can't figure out, though, is how to maintain track gauge, if you have this long slot and a cavity for an upside-down truck to roll through. Because of this, it probably is better to figure out a way to have the pig's wheels actually rolling on the top side. The upside-down truck would have the advantage that you could make use of any old ugly chain or cable to drive it, as the connection(s) would be hidden from view.
    Maintaining the track gauge here shouldn't be any worse than maintaining the track gauge on an inspection pit. That's done by attaching the rails to the structure of the inspection pit walls. You then just have to keep the walls in gauge.

    As far as fitting z-scale rails between the n-scale rails, it certainly is possible. Guard rails (as used on steel bridges) actually end up being at about z-scale track spacing. Remember that n-scale track is only 3mm wider than z-scale track (i.e. 9mm vs 6mm).

    Paul

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    I'm hoping the pig will stay down if it has some heft and it has a raised arm. The raised arm in combination with pulling it from the front should cause all kinds of downward force; where does upward force come from that needs to be counteracted?

    The arm on the prototype swivels up; you can see the yellow probe extensions on it in the first photo; it appears to me that these ride up the rails to raise the arm to coupler height. You can even see where the insides of the main rails have been ground out to allow the probe to ride up on narrow gauge rails coming out of the hole, and then rest on the top of the rails for the trip up the ramp. I won't attempt that - just a fixed raised arm and a deeper pig hole to get it below track level.

    I have some Z track. It will not fit inside the N without some serious trimming of the tie ends. Also Z scale trucks are too wide to go between N rails. Here is my thinking on how to do this.

    Create a pig - slug of brass? with Z axles.

    Develop a profile for the N track. Checked my Atlas 90 ton hoppers with microtrains trucks, the vertical curve at the bottom of the ramp can be no sharper than 18 inches radius. Sharper than this and the inside wheels on the trucks will leave the track. The vertical curve radius at the top of the ramp can be sharper, looks like 12 inches will work. (The coupler boxes limit how far the trucks can rotate on the bottom curve but not on the top.) Then draw in the cable, making sure it doesn't go high enough above track level at the bottom of the ramp to interfere with the front axle of the hopper. I can play with the ramp length and to a lesser extent how far down the attachment to the pig is. The ramp height is fixed because I want to retrofit this to my existing dumper and kickback track. If this actually works out, proceed...

    Transfer the profile to wood (maybe two stacked 1x4s) and use a band saw to cut it. Then temporarily lay the N track on the wood and test it to make sure nothing derails.

    Develop a profile for the pig track that will work with the N profile and the pig, and cut that on another piece of wood. The wood will be the thickness of the pig trough width. Hopefully the Z track will not need to rise all the way to N track height, otherwise I have to trim the Z ties.
    Lay the Z track on this profile.

    Sandwich the profiles and glue them up so the pig profile is between the Ns.

    Glue styrene strips to the N profiles at the right gauge and use these as the rails for the hoppers.

    Add a pulley at the top, limit switches top and bottom, and motorize the cable.

    If it all works, remove the existing dumper ramp at replace it with this. Dress everything up so the wood profiles look like poured concrete, add the hand rails.

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    Quote Originally Posted by NtheBasement View Post
    I have some Z track. It will not fit inside the N without some serious trimming of the tie ends.
    I think you're going to want to hand lay all that... i.e. just use the rail, not the full track.

    Create a pig - slug of brass? with Z axles.
    you could use brass. If you do, don't use metal axles.

    Paul

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    Quote Originally Posted by NtheBasement View Post
    I'm hoping the pig will stay down if it has some heft and it has a raised arm. The raised arm in combination with pulling it from the front should cause all kinds of downward force; where does upward force come from that needs to be counteracted?
    I wrote that based on looking at the original photos you posted, which appear to show a relatively short pig. The connection point of the cable would theoretically be near to where the wheels bear on the pig's track, and the car weight on the coupler would be eccentric to this. In the follow-up video that was posted later on in the thread, the pig is longer, and the cable can clearly be attached at the front; the eccentric loading of the coupler then turns into downward force on the rear axle, as you say.

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    Not sure if you found this in your searches? This isn't uphill, but I guess it's doable, at least in HO.
    https://www.youtube.com/watch?v=BjPuna9gHNs
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    I have had the chance to work around a similar car dumping operation. The barney is cable propelled. The bar you see in the pic could be to trip the machine to return the car at the top of the ramp. The unit I worked around did not have a bar like that.

    As for your model, could you have a pulley at the top, bottom of the ramp with the motor underneath. Sorta making a triangle in your line/wire/cable?

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    If your cars are properly weighted you can just use magnets to pull them up the ramp.
    Daniel Dawson

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    Quote Originally Posted by Tred View Post
    Not sure if you found this in your searches? This isn't uphill, but I guess it's doable, at least in HO.
    https://www.youtube.com/watch?v=BjPuna9gHNs
    My N-scale version of the same style modern dumper that works with rotary couplers (a major challenge project and of itself): https://www.youtube.com/watch?v=coHBHzDrQRQ&t=4s
    These cars load at an operating flood loader. Mine is all mechanical with SPDT switches, DC motors, and a center tapped +/- DC power supply.

    I also have an old style up-and-over unloader and a New River Mine to load them. You can see a piece of it in the foreground of the movie and that is the one I hope to modify. Currently I have to shove the cars up the ramp with a locomotive and uncouple them there.

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    Quote Originally Posted by Mobile One View Post
    If your cars are properly weighted you can just use magnets to pull them up the ramp.
    The Atlas hoppers do have a steel bar in them to weigh them down. But if I got a magnetic mechanism to work it would look like Yoda was using the force to roll the cars uphill.

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    Quote Originally Posted by NtheBasement View Post
    But if I got a magnetic mechanism to work it would look like Yoda was using the force to roll the cars uphill.

    ...or the magnet could augment the model pig, which might be just decorative or non-working that looks like its playing the part. That sounds a bit easier to design than a mechanical version... (added 2 cents)
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    Drew out a profile with 15% grade. The geometry won't work unless the pig arm is hinged. Which means it needs to lift. Time to re-think - stack two more styrene strips under the N track strips to create a slot for a crossbar attached to the pig arm...

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    HO scale again, but it does have an uphill barney. https://www.youtube.com/watch?v=FWa3UhV96WQ
    Doesn't look to be hinged, using an extra drop in the barney track to get under the cars.

    This area is also interesting to look at in satellite view: https://goo.gl/maps/nhRNdD4fSYp

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    Quote Originally Posted by conrailandrew View Post
    HO scale again, but it does have an uphill barney. https://www.youtube.com/watch?v=FWa3UhV96WQ
    Doesn't look to be hinged, using an extra drop in the barney track to get under the cars.

    This area is also interesting to look at in satellite view: https://goo.gl/maps/nhRNdD4fSYp
    I've seen the video and others, they are inspiring. The McMyler is awesome! I can't wait til someone comes up with a working Hulett. I kept looking at Nolan's model here http://www.nscale.net/forums/showthr...ghlight=hulett thinking how it could be done.

    The video emphasizes how N imposes a lot of limits that HO just doesn't have. For example the transition from flat to slope at the bottom of the HO ramp is less than half a car length. N scale cars just don't have enough - for want of a better word - rocker in their trucks due to the interference with the oversized coupler box. They need a gradual large-radius transition. But this video led to my original question about the cable. At the 17 second point do you think it is fowling the hopper's front axle and its just not enough force to derail the car?

    The other ongoing problem I have with the current setup is that the cars coming off the kickback track tend to derail when they slam into the preceding car. Their rolling resistance varies such that some move quite a ways down the yard while others do not. I have to send the engine to get them once there are 3 or 4 and pull them away from the kickback.

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    Quote Originally Posted by Bessemer Bob View Post
    I have had the chance to work around a similar car dumping operation. The barney is cable propelled. The bar you see in the pic could be to trip the machine to return the car at the top of the ramp. The unit I worked around did not have a bar like that.

    As for your model, could you have a pulley at the top, bottom of the ramp with the motor underneath. Sorta making a triangle in your line/wire/cable?
    Where abouts was the one you worked with? I can look it up on google.
    Good idea about the pulley configuration, either that or a windup at the top and a weight hanging on the trailing line to make sure the pig backs down the ramp when the windup goes in reverse.

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    Google earth's ruler shows the Toledo Presque Isle ramp is 175' long. I tried to calculate the ramp height from the first photo as follows to get an idea of the grade. I am uncertain about the height of the car at the top of the ramp but measuring one of my N scale coalporters I get 12.5 feet from top of rail. On the photo I can't really tell where the ground level is under the end of the dumper, guessing at about the top of the yellow end-of-rail marker in front of the ramp. I had to print a pic (darn touch screen!) and measure from that - car is 4 cm, ramp is 9.6 cm. Math says the ramp is 30' high which happens to be the height of the ramp on my layout. That would make the grade 17% but some of the 175 ' is transition and horizontal so calling it 18%.

    So here's the plan for now.

    I'll create a profile based on 18% with 18" vertical radius at the bottom and 12" at the top. I'll install the track and test the radii by seeing if cars go up and down with no derailing.

    Then I'll see if the cable will derail the car by pushing the front axle up. Tie a thread to the center of the last tie at top, hang the other end off the back of the profile near where I think the pig pit should be (I'll have to drill a hole), park an unloaded car at the base of the ramp and load weight on the cable to see how many ounces it takes before the car starts to lift. I'm guessing I need at least 2 ounces for the whole thing to work.

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