Class 86 traction motor mounting on Flexicoil bogies

[Justin Smith]

Can anyone help me with this rather esoteric question ? ! ?
I keep reading contradictory information about whether the class 86s which were upgraded with Flexicoil bogies had frame mounted traction motors or persisted with their original fitment nose suspended ones. This matters (a bit....) for they were re-bogied because the class 86s had excessive unsprung weight which hammered the track, promoted arcing in the motors and gave the drivers a rather uncomfortable ride.
I know at least three 86s had frame mounted motors (the 86/1s which were effectively prototype class 87s) but what about all the others ? The ones which retained the original traction motors / power ?

 

[a_c_skinner]

IIRC the motors were unchanged. Well covered here. There were different wheelsets too

 

[DJH1971]

The 86/1's had frame mounted traction motors (same type as the 87/0's), but the rest did not.

 

[Justin Smith]

The 86/1's had frame mounted traction motors (same type as the 87/0's), but the rest did not.

If they still had axle mounted traction motors (albeit nose suspended) how could the upgrade have worked ? Surely the unsprung weight would still be more or less as high ? And if there was no flexible drive between the motor and the wheels wouldn`t the motors still be suffering excessive vibration etc ?

 

[Justin Smith]

IIRC the motors were unchanged. Well covered here. There were different wheelsets too

I read that but I didn`t think it actually explained what we`re asking. I have a few books and articles in the RM that go into the C86 design, but the info on the bogies appears to be contradictory.
On the one hand the 86/1s defn have frame mounted traction motors.
On the other hand the C86s without the Flexicoil bogies defn have the original axle hung type.
It`s the others we`re not sure about !

 

[Mag_seven]

I'm sure it was just "flexicoil" suspension that was fitted to the 86/2 and the 86/3, 86/4 subclasses.

 

[captainbigun]

Axle mounted does not mean literally bolted to the axle, there's a suspension tube. 86/0/2/3/4/5/6 all have the same drive arrangement with a few variations in motor and gear ratio, otherwise mechanically the same.

Flexicoils and SABs were separate modifications, nothing to do with traction motor mounts/drives.

 

[Spekejunction]

86/1 had new class 87 style bogies with frame mounted motors good for 110 Mph
86/2 had flexicoil bogies with nose suspended motors and resilient wheel sets good for 100 Mph
86/3 as 86/2 but without resilient wheesets good for 80 mph ..not exactly sure..
86/4 as 86/3. All this from memory so open to correction..

 

[43096]

86/1 had new class 87 style bogies with frame mounted motors good for 110 Mph
86/2 had flexicoil bogies with nose suspended motors and resilient wheel sets good for 100 Mph
86/3 as 86/2 but without resilient wheesets good for 80 mph ..not exactly sure..
86/4 as 86/3. All this from memory so open to correction..

That's not as I remember it!
86/0 - Original bogies with nose suspended motors (type 282AZ after all 86/2 converted)
86/1 - Class 87 bogies with bogie frame mounted motors
86/2 - Original bogies modified with flexicoil suspension and resilient wheels; motors (type 282BZ) still nose suspended
86/3 - 86/0s modified with resilient wheels (motor type 282AZ)
86/4 - 86/0 and 86/3 modified with flexicoil suspension and resilient wheels; motors (type 282AZ) still nose suspended

 

[a_c_skinner]

I think that is correct. Only the 86/1s had frame mounted motors, all the other variously mitigated track wear - limited speed, flexicoils or resilient wheels. All of the mitigation was to avoid the expense of a complete redesign of the bogies at least that is the logic I assumed was in play. If the motors had gone to frame mounting the resilient wheels or flexicoil would have been superfluous.

 

[edwin_m]

If the motors had gone to frame mounting the resilient wheels or flexicoil would have been superfluous.

I don't think that can be right, otherwise the 86/1s and 87s wouldn't have had flexicoil as well as frame mounting.

The frame mounting reduces the unsprung by about half of the motor. Resilient wheels put some springing between the "unsprung" mass of the motor and the rail so will effectively reduce the unsprung mass too. Flexicoil was between the bogie and the body so a form of secondary suspension with no effect on unsprung mass. I assume it was to improve the ride, which may have had a secondary track benefit in reducing lateral forces etc. I recall standing on Watford Junction at the age of about 12 and the rocking and swaying of an oncoming electric was obvious even at 100mph - though I don't recall what class it was.

 

[Ken H]

were class 81- 85 fitted with axle hung motors?
My hazy recollection is that they didnt, and the axle hung motors on Cl86 was an ill considered economy measure.

What exactly are resilient wheels? Were the Cl86 ones like this?
https://www.gmtrubber.com/products/resilient-railway-wheels/ (Advert for rail resilient wheels with cut away views)

 

[a_c_skinner]

86 were the (IIRC) sole venture into axle hung motors. Resilient wheels have a rubber bit twixt tyres and axle to add a bit of springyness.

Flexicoil on others is a good point, but I do think the primary reason was track forces on the 86s as built.

 

[edwin_m]

were class 81- 85 fitted with axle hung motors?
My hazy recollection is that they didnt, and the axle hung motors on Cl86 was an ill considered economy measure.

What exactly are resilient wheels? Were the Cl86 ones like this?
https://www.gmtrubber.com/products/resilient-railway-wheels/ (Advert for rail resilient wheels with cut away views)

I think you're right on class 81-85. I don't know if the resilient wheels on the 86s were similar to that one. They are more common on trams, although the German ICEs had them and the failure of one was the cause of the Eschede derailment, after which I think they were retrofitted with solid wheels.

 

[Spekejunction]

The manufacturer of the resilient wheels was SAB ......and yes classes 81 to 85 all had various types of frame mounted motor systems..
Google SAB where's for details.

 

[Justin Smith]

Two sources presenting contradictory information :

“British Locomotive 196 to the present day” (O S Nock 1985)

p162 - One of the Class 86 locomotives was withdrawn from traffic and fitted with a redesigned bogie, with the motor mounted on the bogie frame (instead of axle-hung) and driving through a flexible connection ; while the secondary suspension took the form of a set of three Flexicoil springs...........This modification, applied to locomotive E3173*, was entirely successful.

p 163 -When authorisation was given for the building of the 35 new locomotive of Class 87, it provided also for a further 51 of the Class 86 to be rebuilt with new bogies having the traction motors mounted on the frames, instead of axle hung, and with Flexicoil. These also were geared for a maximum speed of 110mph. The rebuilt locomotives were designated Class 86/2.

* became 86 204 – note this is NOT an 86/1 (the 87 “prototypes”). Wasn`t this the loco temporarily fitted with the streamlined fibreglass nose which broke Mallards British Rail speed record by doing 129mph ? Did it really have axle hung traction motors !

“Anglia East – the transformation of a railway” (Ian Cowley 1987)

p69 – The problems [bogie fractures and track wear] were overcome by fitting 49 locomotives with new bogies incorporating Flexicoil suspensions and SAB wheels and reclassified 86/2. The forst three conversions (re-classified 86/1 in 1974) were fitted with new bogies and frame mounted traction motors and were intended as test beds for the equipment to be carried by the new class 87s, the less ambitious modifications according to what are now class 86/2 took place between mid 1976 and mid 1974, and by the end of 1974, similar treatment for a further nine was authorised.

Both reports seem authoritative, O S Nock even gives the number of the loco fitted with frame mounted traction motors and this didn`t become an 86/1. But they can`t both be right can they !

 

[a_c_skinner]

My collection of Platform 5 books seems to suggest the 86/1 had cl. 87 bogies, 86/2 had SAB wheels and Flexicoil secondary suspension and only 86/0 were unmodified other than a lower maximum speed. I suspect the 51 86s which were authorised to be modified to frame mounted motors actually became the less ambitious modifications referred to above and all except the 86/1 remained axle hung motors.

 

[ac6000cw]

I'm with the majority here - class 81-85 had frame mounted motors, and all the class 86 had axle-hung motors *except* the three later rebuilt with cl. 87 bogies (86/1).

If they still had axle mounted traction motors (albeit nose suspended) how could the upgrade have worked ? Surely the unsprung weight would still be more or less as high ? And if there was no flexible drive between the motor and the wheels wouldn`t the motors still be suffering excessive vibration etc ?

It's the dynamic track forces at higher speeds that are the problem with axle-hung motors - the resilient connection between wheel rim and axle on the SAB modified 86's reduces those forces to acceptable levels.

I suspect the 51 86s which were authorised to be modified to frame mounted motors actually became the less ambitious modifications referred to above

I agree - given BR's finances, it wouldn't have spent any more money than necessary to alleviate the WCML track hammering/deterioration problems caused by the 86's in their original form.

 

[Justin Smith]

My collection of Platform 5 books seems to suggest the 86/1 had cl. 87 bogies, 86/2 had SAB wheels and Flexicoil secondary suspension and only 86/0 were unmodified other than a lower maximum speed. I suspect the 51 86s which were authorised to be modified to frame mounted motors actually became the less ambitious modifications referred to above and all except the 86/1 remained axle hung motors.

That sounds plausible apart from the fact Nock`s book was written in 1985 and the modifications took place 10 years earlier in the mid 1970s, though I have to say those books * do seem to be reprints of earlier articles / books by Nock.
But what about the specific loco mentioned by Nock : E3173 / 86 204 ? Did that get frame mounted motors as Nock specifically states ?
Article about the dip rail joint tests for which E3173 was used, though even that doesn`t definitively mention if the loco had axle hung motors. I have to say I feel it probably did and Nock has got it wrong ! The problem with finding an error like that in any non-fiction book is you start thinking well if he`s got that wrong, how much else could be wrong in this book ? I get that a lot in books about WWII, my other area of interest.

* there are three, 1900 to 1930, 1930 to 1960 and 1960 to the present day [1985], I have all of them.

 

[Justin Smith]

I'm with the majority here - class 81-85 had frame mounted motors, and all the class 86 had axle-hung motors *except* the three later rebuilt with cl. 87 bogies (86/1).

It's the dynamic track forces at higher speeds that are the problem with axle-hung motors - the resilient connection between wheel rim and axle on the SAB modified 86's reduces those forces to acceptable levels.

I agree - given BR's finances, it wouldn't have spent any more money than necessary to alleviate the WCML track hammering/deterioration problems caused by the 86's in their original form.

Nock also mentions the fact the axle hung motors were suffering commutation problems / arcing, which is even more significant in the 86s because they had rheostatic braking. Would leaving the motors axle hung have cured those problems ?

 

[a_c_skinner]

It think the SAB wheels should have lessened the motor troubles.

 

[Ken H]

Nock also mentions the fact the axle hung motors were suffering commutation problems / arcing, which is even more significant in the 86s because they had rheostatic braking. Would leaving the motors axle hung have cured those problems ?

eh? Why would a motor being unsprung cause commutation issues?

 

[507 001]

Wasn’t the flexicoil suspension simply done to improve ride quality after driver complaints? That’s what I seem to remember reading.

 

[ac6000cw]

eh? Why would a motor being unsprung cause commutation issues?

Just think about the several tonnes of wheelset+motor hitting a rail joint/switch at 100 mph and imagine the amount of vibration transmitted through the motor and probably causing the brushes to bounce so they don't contact the commutator surface properly. Remember the brushgear is handling many hundreds of amps - these are large, powerful motors (1000hp+ each).

(I can't find any figures for the AEI cl. 86 motors, but as a guide, EMD's D77 motor - as used on the cl. 59s - is rated at about 1100 amps and weighs about 2.7 tonnes).

 

[ac6000cw]

Wasn’t the flexicoil suspension simply done to improve ride quality after driver complaints? That’s what I seem to remember reading.

That is my understanding as well - flexicoil to improve the ride at high speeds, and SAB resilient wheels to reduce the impact of the high unsprung mass of the axle-hung motors.

 

[Justin Smith]

One thing we can all agree on, the decision to fit the Class 86s with axle hung traction motors has got to be one of the most significant false economies in traction procurement history ! Can anyone think of a bigger one ? Excluding the decision to build the BR standard class steam locos, there were political and world economic reasons why that was never just a straight forward cost / return issue.

 

[edwin_m]

One thing we can all agree on, the decision to fit the Class 86s with axle hung traction motors has got to be one of the most significant false economies in traction procurement history ! Can anyone think of a bigger one ? Excluding the decision to build the BR standard class steam locos, there were political and world economic reasons why that was never just a straight forward cost / return issue.

Buying a batch of 56s from Romania?
Anything to do with the APT?
Specifying all sorts of complicated kit for the 50?
Buying more than a handful of Claytons before the first few had proved themselves (or failed to do so)?
Ditto for quite a number of other Pilot Scheme clasess.

BR's procurement record seems to be to be somewhat less than spotless.

 

[43096]

One thing we can all agree on, the decision to fit the Class 86s with axle hung traction motors has got to be one of the most significant false economies in traction procurement history ! Can anyone think of a bigger one ? Excluding the decision to build the BR standard class steam locos, there were political and world economic reasons why that was never just a straight forward cost / return issue.

Fitting GEC traction motors to a batch of HST power cars was a big screw up.

 

[a_c_skinner]

Flexicoil suspension would reduce track forces, wouldn't it? It didn't change unsprung mass (obviously) but would have sprung the sprung mass a good deal better.

 

[Taunton]

I'm afraid that Nock's substantial writings (Cecil J Allen said* he had juniors at Westinghouse ghost writing for him, under his name) have been found to have a significant number of errors over time. Although a senior mechanical engineer, his expertise was in brakes, which his company manufactured.

* : Quoted in Mr Ian Allan's autobiography.

Most modernisation plan main line diesel-electrics, no less than the Deltics, had nose-suspended traction motors, without the issues of the class 86.

Resilient wheels were a 1930s US invention for PCC tramcars, which spread to an extent over time, but not greatly.