Heavy Bogies

[matacaster]

The bogies on trains appear to me to be extremely heavy and possibly over-engineered. Why don't they look at reducing the weight by using alternative materials in bogies and wheelsets?

 

[jp4712]

Bogies are a lot more than trolleys. They bear the load of the train but they also carry the train’s suspension (try riding along the road on an unsprung cart and you won’t believe just how bad it is) and in many cases they also carry the transmission and final drive. They have to withstand the hammering of the track from below and the weight of the train above for forty years.

Engineers try to save weight from bogies - especially unsprung weight: but they have a very tough job to do, and are made to the minimum weight that’s appropriate for the work they do. No one makes bogies heavier than they have to.

As for materials, there’s no getting away from the fact that steel has the rigidity and ease of manufacture that other materials can’t really match. Aluminium is light but it’s also soft and difficult to weld: and fatigue hardening at stress points makes it brittle. To see what I mean, try taking a thin rod of aluminium and try bending it, then bending it back.

 

[100andthirty]

Bogies and wheelsets are heavy. but they have to withstand very high loads. As an example, the bogies on an LU sub surface train weigh about 6t each complete with wheelsets, suspension and motors. This means that bogies represent roughly 40% of the tare mass of the vehicle. There are techniques used to make them lighter, such as hollow axles used on the class 22X vehicles and probably other fleets. Inside frame bogies tend to be lighter than outside frame designs. There is research going on to explore the use of carbon fibre instead of steel for bogie frames. This article - https://www.railengineer.co.uk/zero-carbon-not-here-carbon-fibre-bogie-frame/ - dates from 2020 and outlines the research which I'm sure has progressed since then.

 

[GB]

The bogies on trains appear to me to be extremely heavy and possibly over-engineered. Why don't they look at reducing the weight by using alternative materials in bogies and wheelsets?

Silly engineers, they should have consulted on RUK first I guess.

 

[GC class B1]

Unsprung weight mentioned in the post above is the most important requirement in reducing weight as it causes the most track damage. The unsprung weight is the usually the wheelset including axle boxes and any brake discs plus the transmission or motors. The inside framed bogies are not only lighter overall but the unsprung weight is less.

 

[Bald Rick]

The bogies on trains appear to me to be extremely heavy and possibly over-engineered.

have you weighed one?

 

[TRAX]

Silly engineers, they should have consulted on RUK first I guess.

I know right…

 

[skyhigh]

Why don't they look at reducing the weight by using alternative materials in bogies and wheelsets?

Who says they haven't?

 

[DarloRich]

The bogies on trains appear to me to be extremely heavy and possibly over-engineered. Why don't they look at reducing the weight by using alternative materials in bogies and wheelsets?

What would you suggest by way of change?

 

[Ken H]

Dont bogies have to be heavy to cope with the dynamic loadings over bumps in the track. The worst is over crossings. Fix that and you could reduce bogie mass

Of course on the Cl 91 they got the motors and brakes out of the bogies and into the body, so fully sprung. less mass in the bogie means less dynamic load.

 

[edwin_m]

The amount of vibration bogie equipment has to withstand is pretty horrendous.

Experimental carbon fibre bogie project: https://www.globalrailwayreview.com/article/102360/carbon-fibre-bogie-passenger-trains-irr/

Elliot Rothwell, David Crosbee and Simon Iwnicki, colleagues from the Institute of Railway Research (IRR) at the University of Huddersfield, discuss the latest findings from the ‘CaFiBo’ project, which seeks to develop a lightweight composite bogie frame that will reduce stresses on rail tracks due to rolling contact fatigue and wear.

 

[Fincra5]

It seems to me the heavier bogies provide a smoother ride.

The ride on lightweight Bogies, especially when you take a 700 vs a 377 is woeful.

 

[ComUtoR]

They have to withstand the hammering of the track from below and the weight of the train above for forty years.

I'm not sure of the lifespan of the average bogie is but it isn't 40yrs. It's also going to depend on what is defined as a bogie as they are formed of many many parts.

Bogie Types The TMM’s SF 7000 bogies are double-axled, air-sprung bogies with two-level suspension for railway vehicles. They are of inboard bearing type. The SF 7000 bogies are used in EMU’s up to a max. operating speed of 160 km/h. They are designed to cope with high density operation. The bogies have been designed with focus on the main contributors to the life cycle cost as for example the maintenance costs optimising, weight reduction, improvement of the running behaviour and reduction of the wheel base (T-gamma/rolling contact fatigue)

Quote from an EMU technical manual. 'Weight reduction' is specifically mentioned

The ride on lightweight Bogies, especially when you take a 700 vs a 377 is woeful.

Is that the bogie or the suspension providing the better ride ?

 

[Islineclear3_1]

Perhaps for the benefit of the OP, what's the comparative weight of a lightweight SF7000 Class 700 bogie compared to a 1960s Commonwealth bogie?

 

[Taunton]

The early 1960s Commonwealth was particularly heavy. Its design came from the USA (Commonwealth Steel Corp), licensed to a Sheffield steel firm, so there were several irons in the fire which also made it expensive. But it did give a very steady ride. It is noticeable in the US, where such substantial bogies are the norm, that well-engineered tracks and associated points have far better riding than here. And on poor (sometimes appalling) track they still keep going, in conditions which in Britain would lead to a derailment.

Mentioned above are London Underground cars. I did read that each bogie alone of a tube car is the same weight as a complete London bus.

I'm not sure of the lifespan of the average bogie is but it isn't 40yrs.

Actually it normally is the overall life of the vehicle; one outlier was the Commonwealth, as mentioned above, which were sufficiently well regarded that when the later Mk 1 stock they were fitted to was withdrawn they were indeed reused in bulk, including under a number of 1960s emus as well as hauled stock. Are there any left, 60 years on, on main line Mk 1 charter sets?

 

[SynthD]

Dont bogies have to be heavy to cope with the dynamic loadings over bumps in the track. The worst is over crossings. Fix that and you could reduce bogie mass

What in crossings causes that?

 

[Ken H]

What in crossings causes that?

Sorry. Not level crossing, this type of crossing (circled).

 

[D6700]

Actually it normally is the overall life of the vehicle; one outlier was the Commonwealth, as mentioned above, which were sufficiently well regarded that when the later Mk 1 stock they were fitted to was withdrawn they were indeed reused in bulk, including under a number of 1960s emus as well as hauled stock. Are there any left, 60 years on, on main line Mk 1 charter sets?

I was pretty sure they are, so had a look on flickr, which confirms Commonwealth bogies are still active on the main line with stock used by (at least) Riviera, WCRC, SRPS and Vintage Trains.

 

[ComUtoR]

Ours have been replaced at least once and our fleet is less than 20yrs old

 

[GC class B1]

The early 1960s Commonwealth was particularly heavy. Its design came from the USA (Commonwealth Steel Corp), licensed to a Sheffield steel firm, so there were several irons in the fire which also made it expensive. But it did give a very steady ride. It is noticeable in the US, where such substantial bogies are the norm, that well-engineered tracks and associated points have far better riding than here. And on poor (sometimes appalling) track they still keep going, in conditions which in Britain would lead to a derailment.

Mentioned above are London Underground cars. I did read that each bogie alone of a tube car is the same weight as a complete London bus.



Actually it normally is the overall life of the vehicle; one outlier was the Commonwealth, as mentioned above, which were sufficiently well regarded that when the later Mk 1 stock they were fitted to was withdrawn they were indeed reused in bulk, including under a number of 1960s emus as well as hauled stock. Are there any left, 60 years on, on main line Mk 1 charter sets?

The commonwealth bogie weighs about 6 Tonnes. The B4 bogie weighs about 5 Tonnes. I suspect a modern trailer bogie weighs less than 4 Tonnes.

There are still a considerable number of B4 bogies in use that are 50 years old. The problem withB4 bogies was corrosion and this has been addressed by shot blasting and improved paint protection.

 

[edwin_m]

Sorry. Not level crossing, this type of crossing (circled).

Those shouldn't cause bumps. The width of the wheel, width of the groove and crossing angles are designed so that at least part of the wheel is supported all the way through. This becomes impossible at shallow crossing angles, hence the use of switch diamonds and swing nose crossings.

Ours have been replaced at least once and our fleet is less than 20yrs old

That's unusual - the only ones I can think of are the D78 fleet, and I think the Central Line fleet. Normally the bogie lasts as long as the body.

 

[GC class B1]

Those shouldn't cause bumps. The width of the wheel, width of the groove and crossing angles are designed so that at least part of the wheel is supported all the way through. This becomes impossible at shallow crossing angles, hence the use of switch diamonds and swing nose crossings.

That's unusual - the only ones I can think of are the D78 fleet, and I think the Central Line fleet. Normally the bogie lasts as long as the body.

I agree that the common crossing is designed such that any impact on the wheelset is minimised. However in reality the crossing will not be perfectly aligned horizontally and the wheel tread profile will not be horizontal (it is not designed to be horizontal) therefore there will be some vertical force exerted on the wheelset which will be transferred to the bogie. Whilst I agree this is not the source of most of the the input to the bogie it is one element. Bumps could be felt at low speed on poor quality track.

 

[millemille]

Ours have been replaced at least once and our fleet is less than 20yrs old

Is it possible that you are confusing a bogie overhaul (a C4 in old school parlance) with replacement?

Bogie frames generally have a design life equal to that of the vehicle structure and only require replacement due to unplanned events such as crash damage or due to endemic/manufacturing defects.

Bogies will be overhauled, as a whole assembly, somewhere between 500k and 1M miles of running with the frames being non destructively tested to check for cracks and items such as bearings, dampers, bushes etc. being overhauled or replaced.

 

[LOL The Irony]

The problem with carbon fibre is that it doesn't really survive knocks and dings as well as steel does. I'll wait and see how Huddersfield's bogie fairs but I have a feeling it won't do as well in the real world as a steel bogie.

 

[Gag Halfrunt]

The Kawasaki efWING carbon fibre bogie has been around for a few years.

 

[mightyena]

Is that the bogie or the suspension providing the better ride ?

I'm not even convinced it is a better ride, at least not all the time. At least going up and down the MML, the 700s ride pretty well, where as the 377/5s and 387s were prone to lurching around violently at the slightest provocation.

I think the 700 ride is firmer, but not necessarily better. Although that's probably more to do with the suspension stiffness than the bogie design.

 

[LOL The Irony]

I'm not even convinced it is a better ride, at least not all the time. At least going up and down the MML, the 700s ride pretty well, where as the 377/5s and 387s were prone to lurching around violently at the slightest provocation.

I think the 700 ride is firmer, but not necessarily better. Although that's probably more to do with the suspension stiffness than the bogie design.

Then you get CAF who's bogies find seemingly non existent imperfections in track, which goes to prove it's just as much about the suspension set up, as the bogies themselves.

 

[najaB]

The problem with carbon fibre is that it doesn't really survive knocks and dings as well as steel does.

As I understand it, that's somewhat true. It's a harder material so it won't dent in the way that something made of steel would, but it's also brittle where steel is ductile so once it reaches the stress limit it will break rather than bend.

 

[No Fault Found]

Unsprung weight mentioned in the post above is the most important requirement in reducing weight as it causes the most track damage. The unsprung weight is the usually the wheelset including axle boxes and any brake discs plus the transmission or motors. The inside framed bogies are not only lighter overall but the unsprung weight is less.

To my knowledge, and certainly on every form of traction I’ve worked on, traction motors are ‘sprung’ weight, as they’re mounted to the bogie frame which is itself ‘sprung’ bu the primary springs.

 

[Ken H]

To my knowledge, and certainly on every form of traction I’ve worked on, traction motors are ‘sprung’ weight, as they’re mounted to the bogie frame which is itself ‘sprung’ bu the primary springs.

I think there are 4 arrangements
1. armature wound direct onto the axle. This was used in early electrification but isn't used now, I think. See Central London Railway locos.
2. Axle hung. One side of the motor is attached to the axle and the other to the bogie. So half the weight is unsprung, the other has primary springing only. See class 86
3. Bogie mounted. The motor is attached to the bogie and the drive transmitted to the axle via flexible couplings. See Cl 87. Fully Primary sprung
4 body mounted. Drive transmitted by a shaft. See Cl 91. All secondary sprung.

Primary springs are between the wheelsets and the bogie. Secondary springs between bogie and vehicle body.