Class 91- 91/1 mods ?

Moog_1984 · 8 Feb 2012

What were the modifications made to class 91's when they were 'rectified' over to 91/1s ?

Are frame suspended or in-body traction motors a difficult technology?

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captainbigun · 8 Feb 2012

The Heavy General Repair (HGR) was a full internal rebuild and re-wire, no.1 cab was re-fitted. All equipment cubicles were removed, overhauled (including replacement of contactors and relays with more reliable alternatives) and refitted. Redundant equipment was removed.

The motors are body mounted, driving via a cardan to the Voith (was David Brown) gearbox. The motor/drive arrangement is complex due to the cardans which have caused grief from time to time.

Moog_1984 · 9 Feb 2012

captainbigun said:
The Heavy General Repair (HGR) was a full internal rebuild and re-wire, no.1 cab was re-fitted. All equipment cubicles were removed, overhauled (including replacement of contactors and relays with more reliable alternatives) and refitted. Redundant equipment was removed.

The motors are body mounted, driving via a cardan to the Voith (was David Brown) gearbox. The motor/drive arrangement is complex due to the cardans which have caused grief from time to time.

So were some of the electrics not up to the job, the Voith transmission too and there was some stuff not used from the original design?

HSTEd · 9 Feb 2012

Well I suppose they might have been fitted with anti wheelslip equipment meant for freight operations when they were first built, as IIRC there was that idea floating around of decoupling them from passenger sets and using them on freight runs at night.

captainbigun · 9 Feb 2012

Moog_1984 said:
So were some of the electrics not up to the job, the Voith transmission too and there was some stuff not used from the original design?

From original build, yes, a lot of reliability issues were found to be relays and contactors. The 91s used standard EE stuff that had been around for decades. The original David Brown gearboxes were replaced with units from Voith.

O L Leigh · 10 Feb 2012

Bear in mind that these are now getting quite old so they will require a heavy maintenance/rebuild from time to time. Also, as technology moves on there are often better, more reliable components available to replace the original equipment. This doesn't mean that they were rubbish as-built but simply that the opportunity was taken to make some improvements and upgrades.

O L Leigh

Class 91- 91/1 mods ?

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