Roller Bearing Trucks

[pjm20]

I recently have been researching railroads trucks for projects that (hopefully) will see fruition later this year. While studying up on roller bearing trucks I realized this: how the hell do they stay in place? A photo I took earlier this year of a roller bearing truck:



And a patent drawing courtesy of Google:



Is the whole assembly really friction fit between the bearing, displacement adapter, and the pedestal jaws? Please feel free to use correct/technical terminology and educate me, I would really like to know. Blame the engineer inside me.

[Chris333]

Well I don't think trucks are attached to a car either.

[railnerd]

gravity

[MK]

Correct!  The weight of the car keeps it on the axle(s).

[peteski]

When seeing photos of derailments you sometimes see the wheelsets separated from the trucks.

[wazzou]

...and the trucks separated from the cars.

[pjm20]

Strange, thank you all for answering.

[peteski]

Strange, thank you all for answering.

Strange that they are not attached?
As I see it, not having the wheelsets or trucks attached makes it easier to swap/replace them as needed.

[Chris333]

There are a bunch of youtube videos showing wheel replacement.

[Missaberoad]

30 tons of tare and 100+ tons of cargo bearing down on it...

[nickelplate759]

No fasteners means there are not nuts to get frozen, threads to corrode and bolts to snap.    AND it all works at 79 MPH.    It's really quite brilliant engineering in my opinion.

[pjm20]

I took @Chris333 suggestion to look this stuff on Youtube (duh,  ) and I cam across this informative video:

As was said before, the engineering is phenomenal. I should chosen my capstone to be on the forces acting the on a bearing and bearing pin. As soon as the center of mass moves past that tipping point, I can only imagine the shear. Which comes to my next question. As was mentioned before, there is no physical connection between the bolster and car frame. Would I be correct to assume the reason for this is that if there was a physical connection, such shearing forces on any lateral displacements would shear the connection, so minds well make it a free floating friction connection with stabilizers on the sides?

[Chris333]

I remember something about the car number had to be painted on the track so if there was a wreck they could tell what truck went to which car.

[nkalanaga]

Part of the reason for not fastening the truck to the car is - where do you put the nut?  If it's under the truck, access is very difficult, unless you have a pit.  If it's above the truck, it's either inside the center sill, which is even harder to work with, or inside the car, in the way of the freight or passengers.

[fire5506]

At one time there was a "frame key" that bolted to the 4 inside pedestals. The frame key was to keep the bearing in place when either picking the truck up or in a derailment. In a derailment they either bent or the bolt sheared. They are generally no longer used.

As a side note, passenger and locomotive trucks must be attached to the frame. on some older equipment chains were used as the attachment, newer ones have some type of keeper.

Richard looking at MP 242 while working for the FEC Rwy.