Surveying techniques?

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Surveying techniques?

Post by stickfigure » Sat Dec 30, 2017 8:17 pm

Maybe this is a dumb question, but I am new to the hobby (hi all!)

How do you go about deciding on the exact route, and how do you ensure that construction follows the plan? What tools do you use to ensure that grades stay even and within your planned percentage? Transits? Laser levels? Or do you just eyeball it? Are there any books or online resources that go over this stuff?

I guess I'm mostly concerned with the grade. Radiusing a turn with a length of rope seems straightforward enough... although now that I think about it, doing that on a hill probably requires an angle measurement and high-school trig. Right?

Thanks in advance,

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Re: Surveying techniques?

Post by jcbrock » Sat Dec 30, 2017 10:25 pm

You can make a career out of this Jeff, plenty of people do! One of the things you didn't mention which becomes a very big deal is planning and minimizing your borrow and fill and the distance you move them. Just throwing that out there so you think about it a bit, as one of the first things you want to do is get some rough elevations of where you'd like the track to go. Next thing is to lay out your critical curves, then joining them up is pretty 'straightforward'.

If you are going to work by yourself you almost have to have (edit: ok, it makes it really easy if you have) a laser level w/detector, we used a DeWalt DW079KD and it worked really well. If you have an assistant to hold the pole, then a transit is fine. The length of rope doesn't really work that well as the center of the curve usually ends up being in the middle of a tree or depression or somewhere else you can't stand. A quick and dirty way to do it is cut sheets of plywood up into a radius template - make a 20' long one by overlapping 3 eight foot sections a bit.

Lots of introductory civil engineering texts out there to help, but like you say, with some high school trig you can get by.
John Brock

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Re: Surveying techniques?

Post by Erskine Tramway » Sun Dec 31, 2017 12:13 pm

Hi Jeff.....

Welcome. The way I did the extension to my Erskine Tramway, was to first take my riding mower out and 'eyeball' some possible routes between the current end-of-track and where I want to go. You could call it a 'preliminary survey'. I did it first by eye, and ended up with three mowed possibilities. Then, I measured and marked 50 foot intervals on the ground. I have one of those DeWalt laser levels, so I then took it out and 'ran the levels' on the three routes. I'm trying to keep below 2% grades on the mainline, so the East route was out right away. I could pretty well see that, but I wanted to check, you can't always tell on uneven ground. I ended up on the West route, with a change at the final terminal to even out the dirt moving. I had the same guy who'd done the original dirtwork, and it only took him an afternoon to do the 500 feet of new grade.
11-10-17 Mainline grade North.jpg
I laid out the curves by eye, for the grade, but after you see what your minimum radius looks like you can pretty well tell what you want. I've got a seven foot wide grade, so there's room for a little re-alignment if I need to. Once you get the grade the way you want it, then you can refine the curves with that High School Trig.

Good luck, sometimes it's lots of work, but mostly it's fun.

Former Locomotive Engineer and Designer, Sandley Light Railway Equipment Works, Inc. and Riverside & Great Northern Railway 1962-77
BN RR Locomotive Engineer 1977-2014, Retired

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Re: Surveying techniques?

Post by Bruce_Mowbray » Tue Jan 09, 2018 11:29 am

Figure out a desired path. Walk it many times. It's amazing how you can feel grade changes when walking. Then get some marking flags. Space them 100" apart (reason later) along your desired ROW. Get an inexpensive transit and a friend, or make a deadman to hold your surveying stick. Find a fixed point as your reference. Start checking the grade change between flags. 1" equals 1%. You may have to cut, or fill, or simply change the ROW to get your desired grade. There are a lot of websites with info on how to survey grades. Lots of old neat railroad books on the subject too.
Curves you can use a center pin and a piece of rope. If something is in the way, a simple step over layout may be necessary. So many feet forward in a straight line (2 feet is a close enough amount), step over. Move another 2 feet, step over more. A circle calculator works good for figuring the step over amount.
Bruce Mowbray
Springville & Southern RR
TMB Manufacturing & Locomotive Works

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Re: Surveying techniques?

Post by rkcarguy » Tue Jan 09, 2018 12:05 pm

Good advice all given above.
I know at work we'll often have radius gages cut for placing curved sections of guardrail in the field. Basically a 10' long piece of thin sheet metal or wood with the proper radius on it, you could use as a guide as you lay track.
If you've got no one to help you, you can use a good level and string between wood stakes to figure out the elevation. I have one of those 6' long levels(72"), so if the string dropped away from one end of the level just a little under 3/4", you've got a 1% grade. For straight sections this is easy, as you can span the string as far as it's weight and the wind allows between two stakes. For curves you'll need to do short sections at a time obviously.

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Re: Surveying techniques?

Post by John Hasler » Tue Jan 09, 2018 2:18 pm

Don't forget the Euler spiral for the transition!

(Joking. I know you don't need that at low speeds.)

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Re: Surveying techniques?

Post by stickfigure » Wed Jan 10, 2018 8:36 pm

Thanks all - sounds like I'll have to wander the property with a laser level and various lengths of rope. I found a few youtube videos, it looks straightforward enough. A copy of Civil Engineering for Outdoor Railroads Vol 1 is on its way. Truss Fun arrived yesterday. Are there any other must-read books?

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Re: Surveying techniques?

Post by Dick_Morris » Mon Jan 15, 2018 7:14 pm

Relatively flat ground or on the side of a hill? The later makes for a more interesting railroad as it allows you to curve along the contours and use the occasional trestle or bridge. You take advantage of the terrain rather than modifying it to get a straight line.

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Re: Surveying techniques?

Post by stickfigure » Tue Jan 16, 2018 2:58 am

I have about 90ac of hills to work with, with an elevation differential of ~200'. Much of it will need to be "benched" into the hillsides. It should be plenty interesting but I'm a bit afraid of pushing the limits for grade and curve :-/

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