Jump to content

BR Mk1 Coach Dynamo output


Recommended Posts

Hi

 

Does anyone know the power output from a MK1 Coach Dynamo, I'm rewiring a support coach and want to know if it's got enough oomph to support a good size invertor.

 

JP

Link to post
Share on other sites

2kW doesn't seem much.

A modern car can do that with it's alternator.

 

Edit

My car has a 150A one and with an AC output of 15-16V that's 2kW+

(1.5L petrol engine)

No doubt bigger motors have more power.

Edited by melmerby
Link to post
Share on other sites

Two types of dynamo fitted to mk1s, the smaller on is 70a (WA) and 125a (WC) both basically a LMS design , W standing for Wolverton. Restaurant cars usually had needed a higher output and had a Stones tonum dynamo 150a +.

 

  • Informative/Useful 1
Link to post
Share on other sites

Our coach is a NNX Courier van which were converted from BSK, so I think I'd be petty safe in assuming it will have a 70A Dynamo.

 

Battery supply we have 4 x 220Ah 12v batteries, 2 in parallel and 2 in series, so a reasonable amount of battery back up, but not enough for a full inverter system. Think I've decided to have a stand alone 600W invertor with it's own socket, that should be enough for crew to charge mobile phones and locomotive TPWS/OTMR batteries if we get stuck in some sidings over night.

 

JP

Link to post
Share on other sites

Beware that the WA and WC dynamos have to be used with the correct regulator. The WA uses an MD regulator, and the WC uses the CMD regulator. Both regulators are the same size and physical appearance inside the box, but the field resistances are quite different. B.R. swapped many coaches over to WC dynamo / CMD regulator and fitted the higher capacity 400 Ah battery cells. Do not rely on what it has cast onto the lid of the regulator box ... I've seen a few of these with the wrong cover fitted !

 

The cells are the same height and width, but the 250 Ah ones were a square footprint, and the 400 Ah rectangular (more pairs of plates inside). As modern battery cells are much better capacity-wise than the original rubber-cased Wolverton ones, you can get plastic cased Crompton cells that are square, but high capacity, so for the deeper battery boxes the cells are supplied each in a wooden crate to make them take up the required space in the larger (deeper) battery boxes.

 

Output-wise, you don't get much at all until the coach gets up to about 25 MPH, at which point the dynamo should be producing enough voltage to get the cut-in coil to energise and connect it to the battery. It will then hold in until the speed drops below about 15 MPH. The output available increases with speed, so you don't get the full output till speed is quite high. I seem to remember 'B' stock such as suburbans that were limited to 75 MPH maximum originally had larger axle pulleys (needing longer belts), but many of the ones on the GN KX sets in later days presumably had undergone a few wheelset swaps throughout their lives and ended up with 'standard' 90 / 100 MPH 'A' pulleys. Some heritage lines have done similar, fitting oversize axle pulleys to get an increased dynamo RPM / output for the lower (25 MPH) max speed on such lines.

 

 

  • Informative/Useful 2
Link to post
Share on other sites

So as the BR batteries were killed off long ago, what is the easiest way to tell which dynamo our coach has?

 

The batteries are the main reason I've been tasked to sort the coach out as we keep spending a considerable sum on 4 220Ah leisure batteries and we're not getting a cost effective life out of them. Hence I shall be ..

Rewiring the coach to try and prevent earth faults.

Fitting LED lights to reduce the load.

Fitting a smart charger, as previously we have used a normal battery charger which people forget to switch off and boil the batteries dry.

 

JP

Link to post
Share on other sites

Before going exploring inside the dynamo or regulator, clean around the edge of the cover so no dirt drops in as you lift the cover off. Be particularly careful with the regulator - the cover is very heavy, and the electro-mechanical regulator inside has lots of delicate parts that are precisely set up and easy to damage if clattered by the cover. When refitting covers, make sure they seat properly into the felt seals.

 

The equipment has a fairly large type identification & serial number plate (see photos to follow) - which if still legible should tell you which you have. You may have to chip off many layers of paint and crud to decipher it

 

The capacity of the batteries is not connected with the dynamo / regulator type as such, but in general the WA / MD is usually used with smaller batteries for coaches with lower lighting load, and WC / CMD with higher capacity for higher loading on the presumption that the combination of that and the different lighting load means you get roughly the same time 'on battery' after the coach stops moving.

 

This is the WA dynamo under a CCT, with the larger axle pulley used on 70 / 75 MPH stock. The CCT has an MD regulator, with alkaline NiFe cells. Alkaline was the standard fitment on CCTs, GUVs and other vans that might stand idle in sidings for extended periods, as the battery can be allowed to go completely discharged and not suffer damage or the electrolyte freeze in the winter. Lead acid batteries in contrast should be kept reasonably charged at all times to prevent freezing and / or sulphation, so vehicle must be moved regularly or batteries charged from the emergency lighting shore socket periodically.

 

IMG_0215.jpg

  • Informative/Useful 1
Link to post
Share on other sites

WC dynamo.

The terminal box cover is missing, showing the dynamo field and armature fuses.

 

Three brushes per box.

The arrangement of the flexible tails that control the rocking brushgear are visible at the back, beyond the brushgear. The setup on a WA is slightly different, but achieves the same result. The drag of the brushes on the commutator surface causes the brushgear to rotate 90 degrees if the machine rotation is reversed, thus ensuring that the polarity of the output of the machine is the same regardless of the direction of rotation (that being, direction the coach is moving).

 

 

IMG_0217.jpg

IMG_0216.jpg

  • Informative/Useful 2
Link to post
Share on other sites

MD regulator.

The large coil to the left of the frame is the cut-in relay, that connects the dynamo to the battery once it is generating sufficient output.

Regulator is in the middle. There is a hefty coil hiding within the iron yoke behind the contact fingers that alters the pressure on these fingers, opening or closing them in turn to progressively insert or bypass resistance in the dynamo field circuit, and thus alter the dynamo output obtaining.

The two larger coils next to the right are the lights 'off' and 'on' coils (trip / set). These are operated by the lighting control switches throughout the train through the RCH jumpers. They toggle a mechanism underneath the multi-leaf copper contact to open or close it and connect the lamp load into the circuit.  

 

Differences of MC compared to CMD are :

Only one 'main' multi-leaf contact at the back of the cut-in relay (CMD has two)

Middle contact arm on cut-in relay is a single leaf.

21 regulator 'fingers'.

Single contact on lighting trip / set relay.

 

IMG_0210.jpg

  • Like 1
  • Informative/Useful 2
Link to post
Share on other sites

MD regulator detail.

 

First image is the left side of the regulator, with the cut-in relay.

Note the three contact sets on the top of this relay - back one is the main current carrying contact that connects the dynamo into circuit. Middle contact is only a single leaf low current auxiliary contact (see CMD reg later).

 

Second image is the right side of the regulator, showing the lights trip / set coils and contact mechanism in a bit more detail.

 

Note that the multi-leaf copper contacts have a parallel carbon brush contact. This makes before the copper contact closes and breaks after the copper contact opens, thus ensuring that no arcing occurs at the copper contact that would weld it closed.

 

The armature of the trip coil passes through a hole in the bottom of the case, allowing the lights to be manually tripped by pushing the plunger upwards to operate the trip mechanism in the event that the lights have been left on and the battery allowed to go too discharged for the 'off' coil to operate. We used to routinely press this when stabling stock just to be sure the lights were really 'off'.

 

 

IMG_0211.jpg

IMG_0212.jpg

  • Informative/Useful 2
Link to post
Share on other sites

CMD regulator.

 

It says so on the lid ... but beware that the lid is not otherwise attached to the regulator inside, so may not have started life with it ! That riveted label looks suspiciously like it might be hiding an alternative identity beneath.

 

You will excuse that this one's had a hard life from the look of it - a few bent fingers.

 

Points to note :

There's an extra little relay at the far left. This performs the reverse current release function as there isn't space on the cut-in relay for all of the required contacts, because ...

The cut-in relay has two main multi-leaf contacts (back and middle) to share the higher current from the dynamo.

There are more contact fingers (and hence resistance stages), 28 on the CMD.

The lighting trip / set relay now has a double contact, again for the higher current rating.

 

 

 

IMG_0206.jpg

IMG_0207.jpg

  • Informative/Useful 1
Link to post
Share on other sites

And finally ...

Detail of the CMD regulator.

 

The back and middle contacts of the cut-in relay are 'normally open' and are closed by the solenoid coil lifting the armature and pushing up under the contact arms. Similarly, the front contact is 'normally closed', and is opened by the solenoid armature lifting the contact arm up and thus breaking its circuit.

 

Lighting trip / set relay, showing also the doubled main contacts, and the carbons.

 

IMG_0209.jpg

IMG_0208.jpg

  • Informative/Useful 1
Link to post
Share on other sites

Several of the regulators on RES stock were modified, removing the resistance control and cut in/out contactor . Control been done via an electronic regulator and diode.

 DO NOT MIX regulators and dynamos as they soon go bang.

 

  • Agree 1
  • Informative/Useful 1
Link to post
Share on other sites

I've no idea if this applies to rail vehicles, but I would be surprised if modern vehicles weren't so equipped

Dynamos are old technology, and paired with relay regulators. They are very inefficient at low rpm. Think of a 1950s car.

By the early 70s cars were fitted with alternators and solid state regulators (ie diodes) which gave a much improved efficiency particularly at low revs. Is it worth looking at modern rail vehicles to see if anything is useable?

 

Stewart

  • Agree 1
  • Interesting/Thought-provoking 1
Link to post
Share on other sites
On 11/02/2021 at 19:48, stewartingram said:

I've no idea if this applies to rail vehicles, but I would be surprised if modern vehicles weren't so equipped

Dynamos are old technology, and paired with relay regulators. They are very inefficient at low rpm. Think of a 1950s car.

By the early 70s cars were fitted with alternators and solid state regulators (ie diodes) which gave a much improved efficiency particularly at low revs. Is it worth looking at modern rail vehicles to see if anything is useable?

 

Stewart

Much to do with the alternator being spun much faster. Having a commutator limits the speed somewhat, whereas the slip rings of an alternator means it can be safely rotated much faster and hence provide useful output at lower engine speeds.

I had an old 1964 850 mini in the 80s and in traffic, with the heater, wipers and lights at night it couldn't charge the battery on the work run.

Replaced the 22A dynamo with a second hand Lucas alternator and trouble over.

(you have to take the regulator out of circuit and reverse the vehicle earth, otherwise fairly easy job)

Link to post
Share on other sites
51 minutes ago, melmerby said:

Much to do with the alternator being spun much faster. Having a commutator limits the speed somewhat, whereas the slip rings of an alternator means it can be safely rotated much faster and hence provide useful output at lower engine speeds.

I had an old 1964 850 mini in the 80s and in traffic, with the heater, wipers and lights at night it couldn't charge the battery on the work run.

Replaced the 22A dynamo with a second hand Lucas alternator and trouble over.

(you have to take the regulator out of circuit and reverse the vehicle earth, otherwise fairly easy job)

My Austin A30 was fitted ( by me with front and rear fogs, HRW,had a factory fitted heater with a fan,and I also fitted an ammeter and battery voltmeter. My 15 mile journey to work on a foggy cold morning rarely saw the ammeter go +ve - a slow crawl in the fog with everything on! At traffic lights I wound turn the lights down to sides only (actually as stated in the highway code etc at the time, which cut the discharge. I had fitted a battery with 3x the standard capacity, and if the weather persisted I couldn't get 3 days out of it, so it was on charge overnight. How we take our modern cars for granted!

 

Stewart

Link to post
Share on other sites
  • RMweb Gold

Putting an alternator on Morris Minors was a common upgrade. As was arranging a swinging hammer type device on a pull cord aimed at the fuel pump when it would regularly fail!

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.