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eTraxx
Fireman



Posted - 09/19/2011 :  07:34:07 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
While at the NNGC I was talking with someone about my plans for the coke oven bank. I explained that in the design of the ovens at the Wharton Coke Works in PA they used 70-lb rail as cross-rails to carry the larry rail. I was going on about going to have to use plastic I-Beams for the cross-rail to keep from shorting the larry-rail. I said that I would prob use a gas-mechanical of some sort to move the larry .. that in the 'real world' the used electric w/trolley poles but that I didn't think my little bank of 16 ovens had a reason to get the electric out to my ovens. Well then .. it was suggested. You have a river .. why not build a small power station and .. DIY?

Well .. OH! Says I .. and the idea of a small dam to supply an equally small power station appealed to me. So .. rather then just toss up a hunk of stone and go .. "that's a dam" I decided to do a little research .. after all .. how much power was needed? How much power could my little stream provide?

Let's see ..

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eTraxx
Fireman



Posted - 09/19/2011 :  07:52:03 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
How much power? - In a 1920'ish book on Foundry operations it talked about using a 15-hp motor to operate a larry with six hoppers with each hopper capable of holding 6-1/4 tons of coal. That's a total load of 37.5 tons. I imagine with the weight of the hoppers added to that you could be near 50 tons .. all moved by that 15-hp electric motor. Doing a little proportional calculation and my larry .. which I figure at 5.5 tons including larry and load would only require a little over 2-hp. To be on the safe side I doubled that to 4-hp.

While doing this I happened on to this photo of a Scratch-Bashed larry built to carry coal to a power plant. What a beautiful critter! The motor on the front is the traction motor and wheels from a scrapped diesel loco. I willing to bet that based on the timeframe of this photo that it would have been between 40-80-hp.




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eTraxx
Fireman



Posted - 09/19/2011 :  08:20:03 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
Where? - If I put the dam JUST (and I mean JUST) upstream of the pumphouse that would make for some cool modeling .. said I to me. In the photo .. where the blue is.


That's 6-in wide there. I thought that a 3-in high dam would be 12-ft high (in REAL life) and not overwhelm the pumphouse.

The next couple of questions of course are inter-twinned .. each feeds the other. What size and kind of dam?, how much water is flowing, how much power can be produced, how much power is needed .. and so on.

Luckily, a book published in 1920 and titled "Power development of small streams" answers most of these questions.



Edited by - eTraxx on 10/08/2011 08:24:53 AM

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elwoodblues
Fireman

Premium Member


Posted - 09/19/2011 :  08:29:24 AM  Show Profile  Visit elwoodblues's Homepage  Send elwoodblues a Yahoo! Message  Reply with Quote
Ed, I'm assuming that you plan on modeling the dam but not the powerhouse. It will add another interesting element to the scene.


Ron Newby
General Manager
Clearwater Valley Railway Co.
http://cvry.ca

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eTraxx
Fireman



Posted - 09/19/2011 :  08:35:32 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
@Ron. Actually .. for a dam of this size the turbine and support equipment will fit well within the lower part of the pump-house. I'll cover that in a bit. That is one reason for posting this thread .. I found it fascinating the information I managed to pull from this one book. The book was written to show how a farm could be powered via water so it fits well within the constrictions of my module.


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eTraxx
Fireman



Posted - 09/19/2011 :  08:42:42 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
What size Dam? How constructed? -

Lucky me the book has a top, front and sectional view of a small concrete dam. It's only 8-ft to the top of the spillway but I could easily scale it up to my 12-ft need. Cool.

Top -


Front -


Section -


I mean .. geeze! What else does a modeler need? :)



Edited by - eTraxx on 10/08/2011 08:26:34 AM

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eTraxx
Fireman



Posted - 09/19/2011 :  08:46:28 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
One of the cool things about using Sketchup is that you can import drawings .. such as the sectional view of the dam .. and then draw over them to create objects. Took very little time and when finished you can scale it easily. In my case I simply used the tape-measure too .. measured the 8-height to the top of the spillway .. and typed in 12'




Edited by - eTraxx on 10/08/2011 08:27:15 AM

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eTraxx
Fireman



Posted - 09/19/2011 :  09:11:51 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
Understand that all a dam does is .. well .. dam up water. The dam doesn't change the amount of water flowing in the stream .. it just provides a head .. the higher water falls the more pressure it exerts at the turbine. More on that later but first the question was .. how much water DOES my little stream flow?

My stream is 6-in wide on my O scale module. That's set by the rock walls of the ravine just upstream of the pump-house. Later it widens where it passes under the bridge but .. the amount of water that flows remains constant.

Since my stream is .. well .. imaginary .. it could be any depth and the water could flow at any speed (ok. REASONABLE depth and speed).

Time for some numbers:

Assumption: Measuring the stream immediately up-stream of the pump-house it has a width 24-ft (6-in). Now, let's 'suppose' that it is 3-ft deep at the center of the stream there and the banks slope at 45°. That makes it simple to calculate the sq.ft. of that section .. (24 x 3)-3^2. That would give me 63 sq.ft. in the section. Measure back up-river on foot and we have a slice of 63 cu.ft.

Toss a stick into the river at that point and how fast does it move? Let's 'assume' (like that since the numbers can be adjusted to make stuff fit later!) .. that the stick moves down the stream at THIS point .. at 2-ft a second which seems reasonable. That would mean that the 63 cu.ft. slice of water is also moving at 2-ft a second. We get rate of flow by multiplying the speed, 2-ft a second, by the quantity of water, 63 cu.ft. and find that the stream flows 126 cu.ft. of water a second. Multiply by 60 and we find it flows 7,560 cu.ft. of water a minute.

So. How much power can we get from this? Each cu.ft. of water weighs 62.5-lbs .. so .. 7,560 x 62.5 gives us 472,500 pounds per minute. One horse power equals 33,000 pounds dropping one foot in one minute. Dividing 472,500 by 33,000 gives us 14.32-hp! That's without any head .. meaning that is if we passed all that water flow through a turbine and not even using a dam at all. Of course there will be loss from friction and you have to take the efficiency of the turbine into account .. but you get the idea. Even if the stream was only flowing at 1-ft a second where we measured it we would still get over 7-hp without any head.



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eTraxx
Fireman



Posted - 09/19/2011 :  09:35:28 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
Looking at a chart in the book of capacities of Hunt-Francis turbines with the 7,560 cu.ft. water a minute we find that we could get 74.41-hp with a 36-in wheel and 12-ft head - requiring 3,992 cu.ft. min ..

but .. the casing that the turbine sits in is approximately three times the dia of the turbine wheel (or .. maybe not. See the bit later on the exterior mounted turbine). For a 36-in wheel that means a casing 9-ft in dia. .. and that for a horizontal mounted turbine .. it would be 4-1/2 feet from the shaft to the floor. That would mean that instead of 12-ft of head we would have 12-4.5 or 7.5 ft. of head. That would reduce our hp to around 37-hp.

What if we used a 24-in wheel? That would require a 6-ft dia casing or 3-ft from shaft to floor and leave us with a 9-ft head - and give us 22.24-hp.

Thing is .. the pump-house is already made. I have about 8-ft height in the lower section to put the turbine wheel and generator etc. inside. That would seem to restrict me to the smaller wheel and 22+ hp.




Edited by - eTraxx on 09/20/2011 10:11:17 AM

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eTraxx
Fireman



Posted - 09/19/2011 :  09:41:19 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
The turbine wheel/casing doesn't HAVE to go inside the power house. Check this out. Here, all of that is mounted outside with a shaft that pierces the wall to the generator. The Penstock (sluice/pipe) that comes out of the building is the feed (it is under the floor). There is a sluice-gate inside the building to control the turbine. The near pipe returns the water to the river/stream.

This would be cool simply because of the added 'stuff' for the scene. The up-side is that you could use a larger dia wheel/casing since the bulk is outside the building.

I just think this is neat!



Edit: I did some proportional calculations from the photo. The casing dia and lenth is about 1.6 x the dia of the smaller discharge pipe on the end and the casing. That elbow is perhaps 1/2-inch thick (or so) .. so .. I'm going to make a WAG and bump those numbers up to 1.7-1.8 x the ID of the pipe. The reason for that is that from the book you can get the needed pipe dimensions for whatever combination of wheel dia and head .. from which you get Cu.Ft. Per min .. and roundy-round back to the pipe. I'm seriously thinking of this since in 'my world' the 1st floor of my pumphouse was retrofitted by installing a generator. Putting the turbine on the exterior works for two reasons .. 1) it would just LOOK COOL .. more 'stuff' to look at .. and 2) originally the pumphouse has that 1st level containing just the sluice-gate and assorted filtering stuff (like the trash rack). A small generator wouldn't take up much room. A generator is basically an electric-motor that is driven externally and electricity taken off of the leads. I figure if I am generating 35-hp from the turbine then the generator should be approximately the same size as a 35-hp electric motor (about 10-in dia and 15-in long let's say).



Edited by - eTraxx on 12/29/2011 08:44:51 AM

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eTraxx
Fireman



Posted - 09/19/2011 :  09:46:58 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
Back to the dia of the turbine wheel. I put the early bits of dam I am making (styrene) in place .. and realized that if the area that the dam sits was raised up that 3-ft (1-1/2" in O scale) .. like there was a step in the stream here .. a falls .. then I could get back that 12-ft head. Besides .. it would add more 'stuff' to the scene .. in this case a step/falls for water. Cool. A 12-ft head with the 24-in wheel gets us 34.3-hp! Yea .. happy dance! :)




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eTraxx
Fireman



Posted - 09/19/2011 :  09:48:47 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
Here's where I was last night with the dam itself ..




Edited by - eTraxx on 10/08/2011 08:28:03 AM

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eTraxx
Fireman



Posted - 09/19/2011 :  09:52:57 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
This is interesting and more 'stuff' for the scene. At the top of the dammed water is where the intake is. Here's what the book says about the diagram below:

quote:
In the left background at A is the dam. In the foreground at B is the forebay. C is the trash rack and D the gate hoist to control the flow of water into the penstock E. When this gate is closed the penstock E is emptied by opening the gates of the wheel, in which case it is frequently an advantage to have the little air inlet valve F in the penstock to let air into the penstock automatically, thus relieving the penstock of outside air pressure, as the draining of the penstock naturally creates a vacuum within the penstock. Such a vacuum would be a heavy strain on any type of construction, but in this case the simple little air inlet valve relieves the pressure immediately. This picture shows an ideal arrangement for the home or small town power plant. It has every practical convenience and refinement that the huge water power plants have.





Edited by - eTraxx on 10/08/2011 08:29:08 AM

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mabloodhound
Fireman



Posted - 09/19/2011 :  09:55:18 AM  Show Profile  Reply with Quote
What an excellent idea and I like that outside turbine.

Dave Mason
D&G RR (Dunstead & Granford) in On30
“Those who would give up essential liberty to purchase a little temporary safety, deserve neither liberty nor safety.”~Benjamin Franklin
The 2nd Amendment, America’s 1st Homeland Security

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eTraxx
Fireman



Posted - 09/19/2011 :  10:22:01 AM  Show Profile  Visit eTraxx's Homepage  Reply with Quote
I have the modules in the LR .. wanted to work on the 'back' and then when I decided to add the dam I have to get there to work the back side of that so .. they are set up there until .. whenever. So .. just went in to take a measurement and .. I have monsters!




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railman28
Fireman



Posted - 09/19/2011 :  11:06:15 AM  Show Profile  Reply with Quote
LOL At least they didn't try to eat it or sharpen their claws on it.


It's Only Make Believe

Bob Harris

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