Timber Truss Bridge Tension Rods Diameter

[Fred Seider]

Hi everyone. I am looking for some info on the general diameter of mid to late 1800's (though not critical at all) timber truss bridge tension rod diameters. The wood dimensions are easy enough to get, but those tension rods I can't seem to locate. If it's all over the map, which I suspect, be good to hear what a typical min/max was in actual inches/mm.

Thanks in advance
Fred

 

[Rhinochugger]

Hi everyone. I am looking for some info on the general diameter of mid to late 1800's (though not critical at all) timber truss bridge tension rod diameters. The wood dimensions are easy enough to get, but those tension rods I can't seem to locate. If it's all over the map, which I suspect, be good to hear what a typical min/max was in actual inches/mm.

Thanks in advance
Fred

That's generally going to be a question for stateside dwellers, as that type of construction was not used in the UK for bridges. Having said that, I suspect that someone might be able to find an example on a small railway, but I'm doubtful.

I also suspect that it was an imprecise science, so it may be possible to have a reasonable stab at a workable dimension by comparing sizes on photographs.

I wonder if there are any examples in Oz or NZ

 

[PhilP]

I would think it will be more down to what you can practically source (and handle) in your neck of the woods?
I would think 2mm or 1/16 inch would be most practical?

PhilP

 

[korm kormsen]

i used, what i could find - bicycle spokes!

 

[Paul M]

What seems to "look right" is probably the best way forward

 

[Fred Seider]

Thanks everyone for the input. Nice work Korm!

I have plenty of stock on hand, but looking for some prototypical sizes. I did finally come across (of course, after days of searching and posting) an example for a Howe truss that uses a diameter of 1 3/4 inch for all the tension rods except the ends where it called for 2 inch rods. There was also another reference in a different context calling out 3 1/2 inches, but not sure if that was for a cable or a tension rod, nor the specific type of bridge.

So the best I have if helpful to others:

(1.75 inches) / 24 = 0.0729 inches
(2 inches) / 24 = 0.0833 inches

Fractions​	Decimal​	Millimeters​
1/16	.0625	1.587
5/64	.0781	1.984
3/32	.0937	2.381

 

[Rhinochugger]

i used, what i could find - bicycle spokes!

View attachment 319379

OK, but how do you ride down the road to the shops now?

 

[korm kormsen]

OK, but how do you ride down the road to the shops now?

well, you named it: ride. 25km to the coop-shop.

til mid '81 either on horseback or with a twohorse-buggy. (that was the era of my first southamerican dust/mud-layout - powered by a honda-motorpump via car battery sans car)

(the big advantage: it was impossible to come home drunk)

 

[Monty]

Chapter 1 - Truss Book

There is a lot of reading here and at a quick glance through Chapter 2 cannot see any specific reference to dimensions of the rods used but also included are some photographs of various bridges as constructed and they may help.
There may be more info in Ch3 but I haven't looked.
Hope this helps a little bit.
Ian

 

[Fred Seider]

Chapter 1 - Truss Book

There is a lot of reading here and at a quick glance through Chapter 2 cannot see any specific reference to dimensions of the rods used but also included are some photographs of various bridges as constructed and they may help.
There may be more info in Ch3 but I haven't looked.
Hope this helps a little bit.
Ian

That's a great link! Thank you. Unfortunately no ref to rod diameter, but still a great reference I'll keep.
Thanks,

 

[Andrew Foster]

A good resource is Paul Mallery's "Bridge and Trestle Handbook" p 71-76 (mine is the 4th edition) published by Carstens. There are good dimensioned illustrations showing that the rod diameter varies from 1" for the lightest structures to 2.6" for the heaviest that he noted as being built in 1910. It appears to be out of print, so I am sure I could scan one or two pages if that would be useful.

Andrew

 

[Fred Seider]

A good resource is Paul Mallery's "Bridge and Trestle Handbook" p 71-76 (mine is the 4th edition) published by Carstens. There are good dimensioned illustrations showing that the rod diameter varies from 1" for the lightest structures to 2.6" for the heaviest that he noted as being built in 1910. It appears to be out of print, so I am sure I could scan one or two pages if that would be useful.

Andrew

Thanks Paul, very helpful indeed! And yes, a scan would be appreciated, if possible.
Thanks,
Fred

 

[Fred Seider]

Thanks Paul, very helpful indeed! And yes, a scan would be appreciated, if possible.
Thanks,
Fred

Ugh, I ordered the book (Used) as soon as I saw this. Wife just found my old railroad books from my N Scale days when I was a kid. Packed away in a musty / dusty box since we have been married, for over 40 years. Low and behold - I have a copy. Didn't recall having it, but then that goes with age. I had the answer all along in some dark crevice I didn't know still existed. So, Murphy strikes again.....

Thanks everyone for your responses

 

[Gavin Sowry]

2" was a pretty common diameter for tension rods. If you needed more strength, then use more rods. If the rods were thicker, they would be too heavy to manually handle.
Now, rough rule of thumb for G, take 1" prototype as being 1mm actual size.... so 2mm rod is ideal !

 

[justme igor]

If wantend 2mm rods?
In the construction we use a steel wire to tie up the steal enforcement.
Dirty cheap per kilo.
If you need more weather proof for a decade or so, go to a garden store, they sell the same wire but with a zinc coating.

If you have a vice this is the way to go:
Cut off a piece of 2 meters or so.
Put one end in the vice and clamb it tight.
The other end you grab it with a plier.
Strech a bit, till you are at the tension point.
Now move a bit forward and jank it back.
This will make you a very strait piece of wire.
If not you did it to soft.
Jank it harder.

I tried to search on yt for a vid for what i was refiring about, but i only found people fiddling around with a drill....
That is not what i mean.

i hope you understand what i mean my bad English.
With best regards Igor.

 

[Paul M]

i hope you understand what i mean my bad English.
With best regards Igor.

Never worry about your English Igor, it's far better than most of our Dutch.