Flexicoil suspension & resilient wheels

(Courtesy http://www.drehscheibe-foren.de/ )

Flexicoil suspension

During the 1960s the Deutsche Bundesbahn were running at 125 mile/h with a secondary suspension using helical springs to deal with vertical, lateral and bogie rotational displacements. This system of suspension was termed ‘Flexicoil’ and in May 1969 loco No.E3173 was fitted with the ‘Flexicoil’ secondary suspension, consisting of twelve coil springs mounted outboard of the bogie sideframes at each corner in groups of three.

Whilst this alleviated the problem of rough riding to a certain degree, Class AL6 locos still suffered from the use of the axle-hung traction motors with their high unsprung mass and this severely punished the track resulting in a spate of broken rails.

Pioneer E3173 at Cheddington in 1971 - this was the first AL6 to be fitted with Flexicoil suspension Class 111 A side view of a class 111 loco of DB showing the Flexicoil suspension - photo from 1984

class 111

A better shot from Frankfurt on 3rd April 2009 Flexicoil Flexicoil suspension as fitted to a class 86 locomotive - Note: the loco is pictured on a curve to show the effect

The following diagram is courtesy http://www.waggonfabrik.eu/

Flexicoil suspension -  the term was originally coined by General Motors.

Springs straight (left), deflected and inclined (right). One of the first applications on DB was on the secondary suspension of V160 (later class 218). However Flexicoil suspensions had already been used in vehicles in the 1930s for Spain, the former Soviet Union, and Africa.

See also Wikipedia


Resilient wheels

The problem of track damage was addressed by the use of resilient wheels. The firm of Svenska Aktiebolaget Bromsregulator of Malmo, Sweden  provided the solution in the form of a rubber-cushioned wheel where pairs of rubber blocks were compressed between the outer, middle and inner wheel centre discs. Taking the initials of the firm this was termed the SAB resilient wheel .

One locomotive No:E3129 ran extensive tests with these wheelsets fitted.

From the 1970s ‘flexicoil’suspension and SAB resilient wheels were fitted to the entire class achieving a reduction in the unsprung mass from 4.5 tons to 1.5 tons bringing about a 50% drop in dynamic forces on track and sleepers at 100 mph compared to the standard solid wheels of Class AL6.

Click on the image for a bigger picture - all pictures courtesy http://www.drehscheibe-foren.de/

Note: These are NOT the  resilient wheel design used on BR

Exploded view

The components of a typical resilient wheel produced by SAB


Typical tyre assembly


Typical section through a resilient wheel

AL6 bo-bo No:E3129 fitted with SAB resilient wheels at the head of a test train somewhere on WCML in the early 1970's. From the body profile of the coach it was probably the ex-LMS vehicle Test Car 3

Mick Wright


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