Changing bogies

[Taunton]

I've always been surprised at the ease of changing bogies at international gauge-change borders. Off with one and on with the other.

There must be a lot of connections to be made, for air brakes, dynamo charging, and presumably individual testing of same. How does it all get done so quickly.

Am I correct that the bogie is not fully attached to the vehicle, this just rests on it. Photographs of overturned stock often show the bogie has gone its own way, as if little or nothing substantial connects the two.

 

[edwin_m]

In the UK at least, bogies started being attached to vehicles by straps made of steel cable after Potters Bar, when the separation of the bogie was considered to have worsened the consequences. But analysis of the Great Heck derailment couldn't replicate the sequence of events if the bogies hadn't been so attached.

Not knowing anything about the Continental stock that undergoes bogie changing, but if the bogies are unpowered it may only be the brake connection that needs disconnecting and reconnecting - I presume this would be an air pipe connecting to brake cylinders so quite easy to do. On-board power for lighting probably comes down the train via jumper cables.

 

[ac6000cw]

Am I correct that the bogie is not fully attached to the vehicle, this just rests on it.

As far as I know, that's generally the case - it's the weight of the vehicle that holds everything together.

I think an 'extreme' example of that is the standard North American freight bogie, which just has a transverse bolster (carrying the centre pivot hole and bearing plate) resting on the side frames via 3 coil springs per side. The side frames in turn rest on the axle bearing adapters. I suspect it's about as simple as you could make a bogie with decent (freight) ride quality. Diagram below from https://ascelibrary.org/cms/asset/a4b2c240-759a-4d19-9ab1-de005ec703ce/1.gif

but if the bogies are unpowered it may only be the brake connection that needs disconnecting and reconnecting - I presume this would be an air pipe connecting to brake cylinders so quite easy to do.

That would be my assumption too.

I guess they use 'drop tables' (after supporting the vehicle body on jacks) to drop out one bogie and lift up the replacement. I'm sure the speed of changing them is born of long practice...but still nowhere near the speed of rolling a Talgo train through gauge-changing apparatus in Spain...

 

[edwin_m]

As far as I know, that's generally the case - it's the weight of the vehicle that holds everything together.

Essentially, if the forces in normal operation were enough to make the body prone to jumping off its bogies, then the whole thing would also be prone to jumping off the track.

 

[StephenHunter]

They've had almost sixty years of practice at it, so they're pretty good at it.

 

[MarcVD]

I have been through this bogie change game 3 times. Each time, before lifting the car, someone came inside, opened a hatch in the floor at each end of the car, and then removed a metal piece with a kind of hammer. Once the car came back on its new bogies, same hatches were opened again and the metal piece came back in place. I suspect that this is what keeps the bogies in place.

Looking at what happened on the parallel track, I noticed that there was indeed only one pipe connection for the brakes, and nothing else. The power for lights, airco, etc, comes via the train line from the loco. Dynamos on bogies are a thing of the past.

 

[Adlington]

In the case of trains going to/from the ex-Soviet Union countries couplers need to be changed too. On the first/last carriage only, in practice.

 

[MarcVD]

In the case of trains going to/from the ex-Soviet Union countries couplers need to be changed too. On the first/last carriage only, in practice.

Couplers are changed on all cars, not only on the first and last ones. This takes place while the bogies are exchanged, and there are dedicated lifting equipments to handle them. I can post a picture of that if you wish so. There is a good reason for that : there is always a possibility that a car develops some sort of malfunction that requires to take it off the train. And then how would it be hauled without the right kind of coupler ?