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You stop squealing by reducing the wheelbase - the distance between the two axles -on the bogies. If remember rightly, the loop line curves were designed with new rolling stock which had shorter wheelbases but shortly before they were delivered, the order was diverted to the London Underground! Liverpool got refurbished 508s

The new trains should surely be designed with shorter wheelbases, If no, I'd like to know why not!

The problem is also how much angle the bogies can turn, trains just aren't supposed to be on long bends with a 210m radius. Shorter stock would help reduce the amount of steer required. To improve stability and vibration the bogeys have to have a centralising force and can't be allowed to free-steer.

The RAIB in 2006 was not able to identify any trains that would cope with the loop significantly better than the 508s

What about 2020?

It is certainly possible to do it. It should have been item 1 in the requirements specification included with the tendering information.

I believe the carriages are shorter, maybe that will help

It's hard to see, but looking at the video in Stafford, you can get a glimpse of the bogies and they DO look a bit shorter!

To quote Merseyrail about the new trains ...

"They will be a real transformation – state-of-the-art, safe, faster and comfortable and will be able to carry more people, more quickly, supporting the economic growth of the City Region.

The trains will be easier to get on and off, as we introduce unassisted access across the entirety of the new fleet. Journeys will be quicker, with up to nine minutes off the journey between Hunts Cross and Southport. The trains will be more reliable, easier to keep clean and will have the latest technology such as intelligent air conditioning.

There will be more space for disabled passengers, bikes, pushchairs and luggage and the train will be bright and open with no doors separating carriages. The trains will be slightly longer and made up of four carriages, rather than three and slightly more seats than now. "

Ok, who spotted the four carriages in the video? Well, there are four slightly shorter carriages - but if you were counting doors, then note that the end carriages only have one pair of doors per side, not two.

If you went to see the mock-up last year, then you would have noticed that the carriage floor was lower in the centre. To me, on the mock-up, the floor seemed to ramp up to clear the bogies at each end, but the publicity pictures don't seem to show that. And as we all know, the platforms were raised to make up the height difference. Well, other countries manage.

I've not seen any info on the bogies and motors, so far and I don't know how they measure a wheelbase when you have four axles. There's the wheelbase of the two axles on each of the bogies, and then there is the distance between the pivot points on each carriage, and I suppose the distance between the end bogie of one carriage to the next could be a factor, but it all adds up. I do know that the earlier 502's & 503's, together with the outgoing 507's & 508's that replaced them, all have 36" diameter steel tyres on their wheels. Naturally, it's the flange of the wheel against the inside of the rail that causes the squealing.

If I remember correctly, the 502's & 503's were using the 'Loop & Link' line before the 507's & 508's were delivered. Again, if I remember correctly, there were two problems. The old trains had difficulty getting up the incline from Moorfields going north and emerging from under Leeds St, which was reportedly one of the steepest inclines. The second problem was the squealing on the Loop Line, which seemed worse with the newer trains.

The strange thing is, squealing occurs at other places - even on straight sections that were designed and built for steam trains to operate on, and they had much larger wheels.
Need an example? Stand on Park Station platform and wait for the train from Liverpool. It squeals as it arrives. The track is virtually straight and flat and even the inside edges of the tracks have been greased!

I think there's more to this than just a 210m radius.

The new trains are longer because of four carriages but there lies another problem, they are too long for some stations! Presumably not all the doors will open at some stations, if you want to get off you will have to make sure you are not at the wrong door.

Yes, you are correct Norton the 502/503 stayed in operation for some years after the Liverpool Loop was built. You are also correct on the gradient 1:29, anything classed steeper than 1:75 is classed as extraordinary steep, no main line railways are anywhere near as steep.

Some of the squealing on the 508s may be due to bushes which wear much faster than most trains, the service interval is markedly short and are frequently found to be worn out.

The last time I went on the London Tube the trains were virtually silent from inside, Merseyrail is an embarrassment in this day and age.

Have you taken into consideration the tight curves on the underground loop line which means the rails themselves are been worn out quicker on the loop than on the rest of the underground section

added to the loop section of rails wearing faster, also the flange edge of the wheel on the bogies al well.

They used to use a different type of rail on the loop.

There may also be an issue with signaling:

https://lbndaily.co.uk/merseytravel-rejects-claim-delays-roll-new-460m-train-fleet/

As I said before, the end carriages only have one pair of passenger doors per side. They no longer have doors only a few rows of seats back from the drivers cab. Therefore you will still have six pairs of passenger doors per side opening out in roughly the same platform space as before. I imagine the '3 Car Stop' and the '6 Car Stop' platform signs will need to be changed.

Apologies for the bump, but unit 777004 (the second of the new trains to be delivered) SHOULD be delivered to Kirkdale depot in the early hours of Thursday morning

Timings: https://live.rail-record.co.uk/train/?c=H01440&d=13/05/2020

It does unfortunately stay at Crewe sidings for most of the day, running under the cover of darkness same as before, as seen in the timetable.

It's not in England yet but it should arrive through the channel tunnel tomorrow (Tuesday).

Redaing through this, it looks like the issue is with the eight car setup and not the 4 car

A Revised times link below as the one from yesterday in my post has been invalidated by a newer schedule.
https://live.rail-record.co.uk/train/?c=R02276&d=13/05/2020

The 2 links exactly the same Matt

Third unit ON ITS WAY today, train number 777007.
I understand some of them have been undergoing testing on the network under the cover of darkness. I don't have any further information on that