Need help to calculate angle

[electrolove]

I'm building a little bridge with 2-3 bents. The outer posts are angled 2" to 3" per foot on the prototype. This angle is called batter. Can someone please tell me how many degrees that is?

Look at this picture if you don't understand what I wrote. I need to know the angle of the 2 outer posts in the picture.



Batter is expressed as a ratio of spread to height, e.g., 2 in 12 or 3 in 12.

This is impossible for a Swede to understand [xx(]

[Anonymous]

Can't you use a protractor to figure it out? If I understand it correctly, you want the angle difference between the cap and the post. If that is so, it's 60degrees, on my screen anyway, If that's not correct, sorry for waisting time and space[%-)][%-)][%-)][|)]

[electrolove]

I don't even know what a protractor is, sorry.

QUOTE: Originally posted by dannydd

Can't you use a protractor to figure it out? If I understand it correctly, you want the angle difference between the cap and the post. If that is so, it's 60degrees, on my screen anyway, If that's not correct, sorry for waisting time and space[%-)][%-)][%-)][|)]

[electrolove]

My own calculations gives me 9 and 14 degrees for 2 to 12 and 3 to 12. But I don't now if it's the right answer.

[Anonymous]

A protractor is a ruler made in a circle. Don't tell me you yanks have a different name for it. I got 7 degress from vertical with 2".I hope that helps, cause this is a german is Australia helping a swede[:D][:D][tup] With the added info I got more of an idea. Have you tried using a scale ruler to make a small equivilant?

[electrolove]

I tried to calculate in it Photoshop and that's where my two numbers 9 and 14 comes from.

A German in Australia helping a Swede, what a mess, hahahah. We will see what the other people says about it, thanks. [:D][:D][:D]

[Anonymous]

According to the instructions furnished with the Black Bear Construction Co's jig for a five pole bent for trestles, the outside pile should be at 10 degrees and the next one in is at 5 degrees and the center one is sraight up.

I've built several trestles with these angles and they look pretty good - even if I do say so myself.

[ndbprr]

Simple trigonometry will give you any angle in the triangle. The top angle Sin is the length of the bottom distance divided by the length of the bent on the left side. You can then look up the angle in a chart. The other angle is 90 degrees minus the first one since there are 180 degrees in a triangle and one is 90 the other two have to equal 90 also.

[electrolove]

10 is between the 9 and 14 that I calculated so I think it will be good.

QUOTE: Originally posted by TEFFY

According to the instructions furnished with the Black Bear Construction Co's jig for a five pole bent for trestles, the outside pile should be at 10 degrees and the next one in is at 5 degrees and the center one is sraight up.

I've built several trestles with these angles and they look pretty good - even if I do say so myself.

[electrolove]

I do not have the distance between the top and botton beam at the moment because I don't know how high it will be. And in my version of the bridge there will be no beam at the botton. Just 4 posts that are driven directly into the ground

QUOTE: Originally posted by 8500HPGASTURBINE

Give me the measurements of the top and bottom beam. Also the distance between the top and bottom one and I can give you the EXACT angle.

[cacole]

electrolove,

Once you determine the angle of the pilings (support posts), their length is not going to matter. If you have five piles with the center one vertical, the first on each side at a 5 degree pitch, and the second one out at 10 degrees, they will all be the same, so you can make yourself a pattern on which to construct them. The angle was not consistent between locations either, so draw yourself a pattern according to what looks good to you.

For my G-scale outdoor layout, which is supported on over 100 trestle pilings that were made of cedar and redwood, I drew a pattern onto a piece of plywood with a permanent marker. I started with the top beam by drawing a rectangle of the desired height and width. From there, I drew the pilings at the desired angles all the way to the bottom of the plywood. I clamped a piece of wood onto the top of the pattern against which the top beams and pilings could be butted. As I determined the necessary height of each bent, I clamped another board at that height against which the bottom beam could be abutted. Then measure the width for the bottom beams and length of the pilings according to the pattern, and cut them accordingly.

You'll have to excuse some members here for not knowing what a protractor is or how to compute angles -- it seems such basic math is no longer taught in our public schools. They even allow students to use calculators to add 2+2 nowadays.

[electrolove]

The ultimate solution...

I just made a document in Photoshop that is 2 x 12 inch and 3 x 12 inch. Then I used the Measure Tool and draw a line from the upper right corner to the lower left corner. Then you have the answer in the Image > Rotate Canvas > Arbitrary Window and that is 9,45 degrees (2 to 12) and 14,175 degrees (3 to 12). This is not 100% accurate but good enought for this. When you use Photoshop for things like this. Remember to use a high resolution for greater accurancy. I used 600 Pixels/Inch in this example.

Sorry for the computer talk, lets talk trains again [:D]

[selector]

A little story for you: the Great Sir Isaac Newton was not known to be a particularly humorous man. Yet, as the holder of the Lucasian Chair of Mathematics at Cambridge, he had established himself as the great mathematician that he was.

One day, while explaining to an advanced class how his 'fluxions" (calculus) had superceded Euclid's geometry in the ability to find infinite series and points on a curve, one sycophantic pupil raised his hand and asked, "Sir, then what is the use of studying Euclid?"

It was the only time the relater of the story ever heard Newton laugh.

This thread makes the story seem especially quaint.

[Anonymous]

The numbers you got using photoshop are right. I was going to try to tell you how to get them, but I have trouble waving my hands in front of the screen. A little trigonometry shows that the angles were arctan(2/12)=9.46degrees and arctan(3/12)=14.04 degrees. Good luck with the bridge!

[electrolove]

baldwinjl:

Photoshop did it pretty close, nice to get feedback on this, Thanks

Ad as you all already know, I was a sleep at school when they talked about arctan and things like that. [zzz] I'm not good at mathematics.

[Anonymous]

If yall think the dudes that made real trestle bents for prototype trestles did this much thinkin, yall are nuts. Especially on things like logging lines. Good God, these guys weren't engineers. Most of them never made it through grade school. Yall are just makin ot too tough. Period.

[dehusman]

If the batter is 2 in 12 (or 1in 6) and the distance between the horizontal members is 13 ft 6 in (just pulling numbers out of the air), convert everything to one measure (13' 6" = 13.5 ft) and multiply 13.5 by 2 and divide by 12 ((13.5x2)/12) which gives you 2.25. That is the distance the bottom of the piling is in feet from a vertical line. No geometry, just simple math. That's how they did it in the 1860's. In Sweden even.

Dave H.

[electrolove]

I understand your point of view but the things is:

If we want to model the prototype we must use the angles and numbers they used. It does not matter how they did it and what skill they had, the real bridge is there, nothing we can do about it. The bridge I'm talking about is a Rio Grande bridge that existed in real life. So if I just glue some wood together without thinking I will end up with a bridge that is not prototypical. Even if there are many different ways of building bridges in real life I must take one of them and measure it to be sure that my model bridge will not look like a toy. [:D]

QUOTE: Originally posted by On30Shay

If yall think the dudes that made real trestle bents for prototype trestles did this much thinkin, yall are nuts. Especially on things like logging lines. Good God, these guys weren't engineers. Most of them never made it through grade school. Yall are just makin ot too tough. Period.

[tatans]

I would think the angle is completely different in every bridge ever built of this type, just try and make it as close to the diagram as possible, you're not designing a door handle for a Mercedes-Benz (over-built & over-designed) close is good enough, these were very rough, utilitarian structures.

[selector]

QUOTE: Originally posted by tatans

I would think the angle is completely different in every bridge ever built of this type, just try and make it as close to the diagram as possible, you're not designing a door handle for a Mercedes-Benz (over-built & over-designed) close is good enough, these were very rough, utilitarian structures.

I am sure you are right, but he stated that he wants to 'model' this particular trestle, and can therefore be expected to want to be a stickler for details...to the extent possible and afforded by the forum members.

He hasn't asked for the scale spikes....yet . [:D]