Are railroad cars or locomotives built with any camber in them, the way semi trailers are built?
No. The wheel is rigidly pressed onto the axle and has no deflection from perpendicular… unless something goes very wrong.
Yes. Some locomotives, some cabooses, and most flat cars are/were built with camber. The primary issue it to control coupler height. Since truck bolsters are at a standard height, flexible cars or cars with some distance from the bolster to the coupler need to address this issue.
I was thinking more of camber in the frame.
He means camber in the carbody, not camber in the suspension. And yes, there are some classes of cars that display it, although the heavy underframe required to meet FRA buff standards usually provides enough stiffness even in low-tare-weight freight cars to minimize visible camber even when the car is new and unloaded… as noted, there’s also the need to keep coupler height constant between loaded and unloaded condition.
Many of the early Amfleet cars when delivered showed visible camber, as did (IIRC) the first generation of NJT push-pull cars in the early 1970s.
Old cars with truss rods might have displayed camber when unloaded if the rods were adjusted to eliminate any tendency toward swayback at full load.
Almost all the locomotives I’ve been around had a subtle camber to them. It’s actually one of the things I look for when I’m buying or leasing and engine.
What do you call the reverse of camber such as the slight manufactured swayback you see in some tank cars and most truck side frames? I have thought about the intention behind the tank car swayback, but have never heard it discussed or technically explained. Perhaps it is only to aid in draining.
Thats a funnel flow car, its made to empty more completely.
Is that like checking out how sway-backed an old horse is?
Excellent answer. [bow] Someone with access to the AAR specifications for new car construction could provide the technical details.
For locomotives, most of the camber of the bare frame as manufactured is then ‘taken out’ when the weight of the engine, generator, full fuel tank, etc. is added. However, some camber is usually left in to counteract the bowing effect of the pulling/ stretching through the couplers and draft gear and/ or from the tractive effort of the trucks, which are each mounted/ suspended about a foot below the ‘center of gravity’ (actually, the centroid of inertia) of the frame.
Camber was (is ?) most evident on the 89-ft. long TTX piggyback flat cars, if you can get the right view (telephoto down the side). They’re so thin and long, and most of the weight could well be in the middle portion, that something had to be done.
Cars that are shorter and taller/ ‘beefier’ / stiffer have less of a need - contrast a center-beam flat with a bulkhead-end flat.
- Paul North.
EDITED around 4:00 PM to add:
For what happens when there’s not enough camber, look closely at this photo (not mine) of some flats with heavy steel plate loads:
http://1.bp.blogspot.com/-68W01q6K-aY/U4T9kgRlimI/AAAAAAAAOoQ/SffhKC6r_g0/s1600/blog308drawbar3.jpg
I would expect a center-beam flat to be a fairly stiff structure, so long as the beam is connected to the frame of the floor. At least what I remember from the solids class ###ty some years ago suggests that. (To this day, I’m sure the professor wonders if the two EEs in that section had gotten lost or something.)
That connection matters mainly when carrying the shear load and minimizing the deflection from it are governing criteria - which they definitely can be for a railroad car load, as those loads can be short, heavy, concentrated, dense, etc.
In contrast, imagine a center-beam car without that connection - essentially a rectangular box, without much in the middle, but definitely a major structural piece along the top. Such a car would have much better beam strength - hence the name - against 'bending moments" (the type of force that bows the middle of the car downward) as compared to a plain flatcar or a bulkhead end flat, as the top piece would be in compression and the bottom / frame would be in tension. However, as a practical matter it would/ should have at least a few connections to the frame of the floor, to: 1) “develop” or transfer enough of the shear - which creates the bending moment - to the upper member; and 2) provide stiffness to prevent the upper member from buckling as a long slender compression member.
As with many things, it’s mainly a matter of having enough pieces in the right places, and then proportioning them to match the task at hand.
- Paul North.
At CRRM in Golden, they have one wood frame narrow gage combine/caboose that is so swaybacked that the roundhouse staff has put a ratchet jack under the centerbeam just to keep it from collapsing until they decide how to save it.
Having just spent a week staring at standard plans and utility installation specs, you can add newly installed pipe at a shallow depth to things with camber for structural reasons.
I suspect that’s to counteract future settlement ? For fairly flat gravity lines only (stormwater sewer and sanitary sewer) where the slope is critical, but not pressure lines such as potable water - or them too ? (why ?)
- Paul North.
I’m still waiting to see a locomotive cab with a steering wheel.
When I worked at Burns Harbor, IN in the early 70s
we would reject JTTX flatcars which were used for long
steel loads if they sagged in the middle. They had to
have a slight arch upwards in the middle.
Future Settlement of surface water runoff piping.
No matter how good a contractor thinks that his compactive effort is and dirt being dirt, it’s gonna settle. That train over the top will be the most effective E-80 vibratory compactor ever known.
(Uncle Pete’s industry track construction specs get into it pretty deep)
You just want the hogger to lose his mind.
But how is he going to sweve without one? [*-)] [}:)]
Well, in the Polar Express movie, they steered the steam locomotive on the ice by pulling the reverser lever back and forth while working the throttle in or out.
I don’t know what you’d use in a Dismal. Maybe play with the horn and ditch lights switches?