BR Mk1 Coach Dynamo output

[PatB]

2 hours ago, Bucoops said:

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!

Isn't tapping the electric fuel pump what the starting handle's for? . 

 

Back on topic, I would tend to agree that that looks like an awful lot of complex and delicate electromechanical gubbins to do a relatively simple job. Whilst it might be outside the OP's scope of work for the immediate future, I'd be thinking in terms of getting hold of a big truck alternator and seeing if it could be inserted into the existing housing. That should give a reliable, largely maintenance free 24V under most running conditions. OK, it's not the 30V of the original, but if you're using an inverter to get to mains voltage, and stuff like Led lights, which aren't fussy, does that matter much?.

[melmerby]

9 hours ago, PatB said:

Isn't tapping the electric fuel pump what the starting handle's for? . 

 

Back on topic, I would tend to agree that that looks like an awful lot of complex and delicate electromechanical gubbins to do a relatively simple job. Whilst it might be outside the OP's scope of work for the immediate future, I'd be thinking in terms of getting hold of a big truck alternator and seeing if it could be inserted into the existing housing. That should give a reliable, largely maintenance free 24V under most running conditions. OK, it's not the 30V of the original, but if you're using an inverter to get to mains voltage, and stuff like Led lights, which aren't fussy, does that matter much?.

Looks like something out of pre-history

I was thinking along the same lines (sic), hence my question about voltage earlier.

24v kit is much more common than the original's 30v and a truck alternator would do away with all that electro-mechanical clap-trap.

 

 

[45125]

17 hours 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)

The only thing the slip rings do on most alternators do is provided a circuit for the excitation circuits. On the ones in use on most coaching stock three slip rings are provided, one is common, one will be a boost field, and one the buck field. These types of alternator rely on residual magnetism for self excitation, then regulator/rectifier unit takes over to control the output.

[HGR]

22 hours ago, melmerby said:

I may have missed it but what voltage is the coach system?

The system is nominal 24 volts.

 

The battery is 12 off individual lead-acid cells at 2 V each, or in the case of alkaline NiFe cells used with parcels vans, CCT / GUV, etc. 19 cells are used to obtain the same 24 V. The two battery boxes under the coach are connected in series, with six (for lead-acid) cells in series in each box. NiFe cells usually have one normal size and one smaller battery box - the capacity being much lower than the cells used on passenger coaches.

 

When the dynamo is generating, the charging voltage on the battery can be as high as 30 V depending on coach speed, lamp load, and state of charge of the battery. To keep the lights at 24 V at the bulbs, the lighting resistance is cut in in two stages in series with the lamp bulbs as the dynamo / battery voltage rises. Each of the two stages drops about 3 volts at normal lamp load. 

 

[HGR]

8 hours ago, melmerby said:

Looks like something out of pre-history

I was thinking along the same lines (sic), hence my question about voltage earlier.

24v kit is much more common than the original's 30v and a truck alternator would do away with all that electro-mechanical clap-trap.

 

 

The Wolverton Lighting patent goes back to 1931. In it's day it was cutting-edge technology. It's a remarkable piece of engineering. Lots of progress since then of course once semiconductor rectifiers became readily available and thus alternators came about in the 1960s.

 

Mk.2 coaches with the B4 (or B5) bogies were fitted with an alternator hung off the inner end of the No.1 end bogie. Driven from an axle-mounted pulley by six 'V' belts. Because of how difficult the job of replacing the belts was, a spare set was stowed inside the pulley. If these had already been used, you had to jack up the bogie to get the weight off the springs at one end of the axle so you could winkle the new + spare set of belts in past the spring packing cones. B.R. seemed to have given up on this idea in the late 1980s / 1990s and a cunning setup to use link-belts came in so you could fit them without having to disturb the bogie suspension. 

 

TPO coaches with B4 / B5 bogies had two independent alternator / battery systems (one off each bogie) to cope with the extra loading for VHF radio etc. and provide a bit of hardware redundancy / fault tolerance.

 

[45125]

38 minutes ago, HGR said:

The Wolverton Lighting patent goes back to 1931. In it's day it was cutting-edge technology. It's a remarkable piece of engineering. Lots of progress since then of course once semiconductor rectifiers became readily available and thus alternators came about in the 1960s.

 

Mk.2 coaches with the B4 (or B5) bogies were fitted with an alternator hung off the inner end of the No.1 end bogie. Driven from an axle-mounted pulley by six 'V' belts. Because of how difficult the job of replacing the belts was, a spare set was stowed inside the pulley. If these had already been used, you had to jack up the bogie to get the weight off the springs at one end of the axle so you could winkle the new + spare set of belts in past the spring packing cones. B.R. seemed to have given up on this idea in the late 1980s / 1990s and a cunning setup to use link-belts came in so you could fit them without having to disturb the bogie suspension. 

 

TPO coaches with B4 / B5 bogies had two independent alternator / battery systems (one off each bogie) to cope with the extra loading for VHF radio etc. and provide a bit of hardware redundancy / fault tolerance.

 

Those fee link belts were used well before the late 80s, remember been shown how to use the newer form oft link belts in the very early 80s.

 

As for Nife batteries some ordinary MK1s had them fitted 18754 been an example.

[LNERJP]

Thinking as we now use Leisure batteries as a cheaper alternative to actual rail Lead Acid ones, is 30V a bit high for them and likely to damage them?

 

Anyone care to comment?

 

JP

[melmerby]

A good car battery can be 14.4v or a little higher under charge so 30v for 2x12v doesn't seem too far off.

(A fully charged 12v battery in good condition off load is actually around 13v)