High speed testing on WCML in the 70's

In late 1970 and early 1971, a series of high speed dipped joint tests was undertaken using the first Class 86 locomotive to be fitted with 'Flexicoil' suspension. The trials took place at Cheddington on the WCML and the loco, affectionately known as 'Zebedee' after a spring-mounted puppet in the popular 'Magic Roundabout' children's programme of the time, was tested with and without a glass-fibre nose cone during the series to assess its aerodynamic affect.

The tests were also used to monitor the vertical track forces imparted by the locomotive over an instrumented dipped rail joint and to check turbulence caused by trains passing at 125 mile/h.

Fitted to Mk2 coach No:E5625, one of the passenger coaches involved, was the then new 'DOC2' bogie. These runs were also used to assess the high speed riding qualities of this revolutionary bogie. This was the forerunner of the BT10 Mk3 bogie fitted and was fitted with coil spring primary suspension on radial arms and secondary suspension airbags, quite a novelty after the 'BR1', Commonwealth and 'B4' bogies which preceded it.

Our train was hauled by E3173 'Zebedee' with Test Car 4 and E5625 and was confined to the Down line. The train would start its test run just to the south of Linslade Tunnel and the southbound train would start from Leighton Buzzard. At a pre-arranged and synchronised signal both trains would start off and run at controlled speeds to ensure as far as practicable that the trains passed just to the North of Cheddington station.

As far as I remember, the other train was hauled in turn by another class 86 or by a Deltic class locomotive with another short formation.

The specially installed 'dipped joint' was in the Up fast line just north of the station where vertical track force measurements (P2) were recorded as the Up loco traversed the joint at high speed. Aerodynamic probes were also installed on the trains and alongside the track to measure the effects of turbulence inside and outside the trains when they passed.

Total possession of the Up and Down Fast lines was taken on three consecutive Sunday mornings (16th, 23rd and 30th May 1971) between Leighton Buzzard and Tring for the purpose of the testing to allow the trains concerned to set back 'wrong road' to the starting positions after each run.

I remember that we were based at Bletchley depot and had to leave there at around 05.30 on the Sunday morning. We had breakfast on the Test Car but at lunchtime the trains would stop and set back to Cheddington where food was especially provided and served in the Down platform waiting room.

It was during these tests that Test Car 4 (a GWR Hawksworth coach with GW bogies and plain bearings) was hauled at 130 mile/h!

E3173 was later named 'City of Carlisle' and was scrapped in 2003

Click on the picture for a bigger image - photos are the author's unless otherwise indicated


E3173 is pictured near Tring in an earlier test series in October 1970, when it was fitted with the streamlined nose cone.

C T Gifford


One of the test trains stabled at Bletchley depot with E3173 - this is probably from early 1971.  The author was not involved with these particular tests.

Note the grille over the windscreen of the loco and the ex-LMS Dynamometer car (now known as Test Car 3) and a couple of Mk1 coaches in the train

Authors collection


The instrumented Faiveley pantograph on E3173 viewed from inside the depot at Bletchley on an early test in 1971 - how this monstrous pantograph behaved at 125 mile/h is lost in the mists of time!

Authors collection

Tea break

In this very poor quality picture (Boots slide film) the Mk2 coach E5625 fitted with the prototype Mk3 bogies is shown in the Down Fast platform at Cheddington. Note the wasp stripe rear door cover with air horn on the top and the viewing window all of which were fitted to facilitate propelling during the tests.

over 120mph

The speedometer on the Western Region Dynamometer Car (Test Car 4) is off the clock in this view

BR official

Slow Lines open

This shot looking back from the test train on the Down Fast shows Cheddington station with all lines occupied. Normal traffic is confined to the Slow lines and the other test train is still in the Up Fast platform. 


Later re-numbered 86204 this is 'Zebedee' at Carlisle in the 1980s showing its Flexicoil suspension


Back to early days

Back to main index