Nomenclature question.

[Terry Toenges]

Bachmann makes the Bridge 'N Trestle set 46225. Since it has a bridge and it's called bridge and trestle, are the piers considered the trestle? Or, is the bridge consider the trestle? If so, then why not call it trestle and pier set? Or, is the flat piece the track is on the "bridge" and the super structure the "trestle"?

[Trainman203]

Consult Google and Webster.

[Len]

Short answer: If an elevated span is supported by wood or metal 'bents', with or without a truss structure in the middle, it's a "trestle bridge". Commonly referred to as a "trestle". If the elevated span is only supported by piers at the ends, with approach tracks on some type of fill, it's a bridge. The bridge structure could be wood or metal. Multiple bridge spans may be connected by stand alone piers at the joints.

With the Bachmann set you could use the bridge section as a stand alone bridge span supported by piers, and use the bents alone for a trestle. Either 'up & over' or for level track to cross a valley. That flexibility may be why they called in a "Brindge 'n Trestle" set.

Len

[Terry Toenges]

I did do some consulting first and there seemed to be different answers.
When I Googled it, this came up -
"tres·tle
/ˈtresəl/
noun: trestle; plural noun: trestles
   a framework consisting of a horizontal beam supported by two pairs of sloping legs, used in pairs to support a flat surface such as a tabletop.
       short for trestle table.
       an open cross-braced framework used to support an elevated structure such as a bridge.
       noun: trestlework
       each of a pair of horizontal pieces on a sailing ship's lower mast supporting the topmast.
       noun: trestletree; plural noun: trestletrees"
Merriam Webster said -
trestle noun
tres·​tle | \ ˈtre-səl also ˈtrə-\
variants: or less commonly tressel
Definition of trestle
1 : a braced frame serving as a support
2 : horse sense 2b
3 : a braced framework of timbers, piles, or steelwork for carrying a road or railroad over a depression

Bachmann's set says "bridge and trestle" and Google seemed to bear that out, that the "trestle" is only the supports and not the bridge itself.
Len called the bridge a trestle so it got me to wondering about things I had never thought about. I always thought the whole thing like what you see spanning valleys and such was a trestle. That was obvious. I never really thought about it being separated into the bridge and the trestles.
I guess I was really wondering if it was ok to call just the bridge a "trestle" without saying "trestle bridge".

[Len]

"Len called the bridge a trestle..."

Not exactly. Maybe some pics will make what I was trying to say clearer. It should also be noted that in general, trestles were used to cross depressions with relatively level track, not do the "up & over" stuff we do with our layouts. Although a trestle might cross another track following the length of the depression.

1. Example of a wood "trestle bridge", commonly referred to as a "trestle", supported by wood bents:


2. Example of a metal "trestle bridge", commonly referred to as a "trestle", supported by metal bents:


3. Exemple of a wood "trestle" supported by wood bents, with metal center spans supported by concrete and metal bents:


4. Exemple of a wood "trestle" on wood bents, using metal girders to span a road. The girder section could just as easily been a metal truss section.


5. Exemples of truss, curved cord, and arch "bridges". These are metal, but in an earlier time period they could be wood. Note they are only suppored by abutments at the ends, or intermediate piers at joints between spans. Interestingly enough, the arch bridge feeds onto a metal trestle supported by metal bents.


Examples 3 & 4 could be what the Bachmann set are trying to emulate. Although there's actually nothing that says the truss section couldn't be used as a standalone bridge, supported by abutments, somewhere else on the layout.

Len

[Terry Toenges]

Len - I always love cool pics.
This is your comment that prompted the question. Where you say "the trestle itself".
Lay the bents that support the track out so you have two of each size, going from lowest to highest. One of each size is used for going up, the other is used to go down. The trestle itself goes between the two highest pieces. A bent goes directly under the joint between two sections of track on the inclines to keep it from sagging.

[jward]

Len,

Obviously you do not live around a navigable waterway. In areas where bridges have to clear marine vessels, it is common to use trestle like approach ramps to the major spans over the waterway, similar to what the Bachman bridge and trestle set does, except on a much larger scale. Thus, if you had a river on your layout and used the bridge span to cross it, you'd be pretty close to what the real railroads actually do.

[Len]

Len - I always love cool pics.
This is your comment that prompted the question. Where you say "the trestle itself".
Lay the bents that support the track out so you have two of each size, going from lowest to highest. One of each size is used for going up, the other is used to go down. The trestle itself goes between the two highest pieces. A bent goes directly under the joint between two sections of track on the inclines to keep it from sagging.

Like the above picture of the trestle with the girders over the road, if a truss section like that in the Bachmann set had been used instead it would be part of the trestle. If it were used by itself, supported by a pair of abutments, it would be a bridge.

Len

[Len]

Len,

Obviously you do not live around a navigable waterway. In areas where bridges have to clear marine vessels, it is common to use trestle like approach ramps to the major spans over the waterway, similar to what the Bachman bridge and trestle set does, except on a much larger scale. Thus, if you had a river on your layout and used the bridge span to cross it, you'd be pretty close to what the real railroads actually do.

I'm aware of that. Which is why I pointed out the arch bridge in picture 5 connects to a trestle structure on the right side in the picture. The bridge itself is supported by abutments on each side of the river.

Len

[Terry Toenges]

Supported with abutments, it's a bridge. Supported with bents, it's a trestle. Correct? I'm just trying to educate myself.

[Len]

Supported with abutments, it's a bridge. Supported with bents, it's a trestle. Correct? I'm just trying to educate myself.

According to my uncle, who explained it to me as a kid, that's pretty much it in a nutshell. He worked for Great Northern most of his life, so I figured he would know.

Len

[Terry Toenges]

I thank you for your help. I am that much the wiser now.