Why was the Island Line electrified with the third rail system?

[HSTEd]

Does anyone know, why the Island line was third rail in the first place?

Given that is/was entirely self contained and the only stock on it would be ex-LU tube stock, why wasn't it laid for fourth rail?

Even if the fourth rail was simply bonded to the running rails it would have avoided the necessity of conversion work.

 

[trebor79]

Does anyone know, why the Island line was third rail in the first place?

Given that is/was entirely self contained and the only stock on it would be ex-LU tube stock, why wasn't it laid for fourth rail?

Even if the fourth rail was simply bonded to the running rails it would have avoided the necessity of conversion work.

Possibly cheaper to do the conversion of a few units than provide 8.5 miles of 4th rail?

 

[Chris125]

Does anyone know, why the Island line was third rail in the first place?

It's what the Southern Region was familiar with and busy installing elsewhere. With some relatively minor alterations to the trains they also avoided 10+ miles of extra conductor rail - that's a lot of steel to buy, ship to the island, install and maintain.

 

[Gloster]

The technical gubbins has credited me with someone else’s question. I entirely agree with Chris125’s answer.

 

[Wagonshop]

I remember talking to Alen Barter who was project manager for LT stock conversion for the IOW when he was DTE south east div. Said easy job

 

[Journeyman]

BR converted the LNWR DC lines in London from 4-rail to 3-rail in the seventies, which involved modifying the 501s. It was clearly seen as a simple job that reduced maintenance costs.

Brian Hardy's Tube Trains on the Isle of Wight book explains that the conversion on the Standard Stock was very simple, and didn't involve much more than removing the negative shoes and some minor rewiring. It enabled testing on the main line before being shipped to the island.

There's a picture of a couple of London Transport Standard Stock cars in departmental service sitting in the bay platform at Kingston, so clearly LT didn't consider the conversion a big job either, and presumably converted them straight back again once on Underground metals.

The 38s were a lot more complex to convert, but that was mainly all the wiring being completely rotten. The electrical system was quite extensively modified, mainly because the compressors were never previously fitted to driving vehicles, and the heating system was upgraded. PA and fluorescent lighting was a big change too.

 

[pdeaves]

In case of interest, there is a little more discussion on the subject in this thread https://www.railforums.co.uk/thread...in-being-preserved.211609/page-2#post-4929603 from about post 51