OLD LARGE 24V DYNAMO

[captain nodge]

would this be a practical unit to use, any feedback on this would be appreciated,icant really tell you much about the unit exept its quite old,maybe came off a coach or lorry, its very well made,to show its age it has the old screw down greasers,(prob 10 years older than God),its aprox 300mm long x 150mm dia and has a19mm taper shaft,not being that much of a wizz on this sort of thing i cant tell you how it is wired.ta

[wpowokal]

From your description it sounds like a generator which requires an external field source to begin charging, it is possible to use it but the biggest hurdle in my opinion is supplying the field (excitation) only when the wind is blowing, using it to charge at 12 volt will work (watch the experts shoot me down).

Early wind generators were compound wound, meaning the DC output after rectification by the commutator and brushes was fed through the field windings and then to the batteries etc, thus they were self exciting.

allan

[hiker]

seems like you could use a simple cintrifacule switch to activate the field coils..

[captain nodge]

Sounds interesting,whats one of them?

[Flux]

If it is from a coach or lorry it will be a shunt dynamo.

Usually they are too fast for direct drive at rated voltage but you may get it working with a fast 6ft prop. It will self excite being shunt connected, you don't need external switches. Without compound windings it may not match the load as well as some of the specialised wind generator compound machines, but Winco and Lucas used plain shunt machines.

Usually to get them slow enough for wind use you need to run at half volts ( 12v for a 24v dynamo or 6v for a 12v one). Not much demand for 6 v in this age. Often you had to reconnect the fields in parallel or series parallel for 4 pole but that increased field losses and sometimes that mod was not the best option.

Yes it can be done, it was done in days of old, we had little choice, but in this present age it will give you dreadful results compared with a modern pm machine. Is it worth the effort?

You could replace the field coils with neo magnets and with luck it may be reasonable, with bad luck it may cog and be a poor starter.

By a fast 6ft prop I am thinking of 2 blades like the old Lucas or 200W Winco. Don't expect blades copied from here to be fast enough. You are probably looking at tsr 10 at cut in and running at about tsr8.

Flux

[captain nodge]

CHEERS for all that info, thats really got my cranial gears turning,will have to make a big decision wether to take it any further,thanks again and give praise where praise should go to the people for running such a great altern energy site,being new,i spend hrs (mostly free lekey,as i have 2 aged rutlands whirring away)perusing and learning from this site,My main reason for contemplating using the old dynamo is 1, ive had it for years and allways wanted to make a turbine from it and 2,far as i was concerned as long as it gave something out 5 or 10 or 15 amp it would be free ( nigh on ) energy.plus having the satisfaction of seeing it working, at my present position south east coast uk plenty steady wind, new wind farm on romney marsh testifys to that,i am living on a boat but the old dynamo turbine would be land based atop an old lattice frame light tower,so its not going to be as straight forward as id hoped (what is!)if i was to forward some kind of drawing or photo of it would you be able to describe how to alter the feild coils for 12v,mucho appreciato CN

PS how does one insert attachements photos ect into this page?

[Flux]

If you have a good wind area with plenty of wind in the 15mph plus region then it should work ok.

If it is 24v then you are in with a good chance. If 12v you might still make it.

My suspicion is that it is a CAV bus dynamo and in the old days it would have been one of the better choices.

Connect it to a battery and check that it motors. You may have to link the D & F terminals as the field would have been fed from a regulator.

When it motors satisfactorily, wrap a piece of string round the shaft and pull it so that it turns in the same direction as it motored. You will feel a sharp jolt when it excites and you can judge the speed. If it comes in early it is good. if you have to pull the string to the end before it cuts in it will be fast.

I suspect it is 4 pole and you will see the screws holding the poles in place.

If you split the link between the middle set of poles and connect each end to the other end from the original connection you will have the fields in series parallel. This will most likely lower the cut in speed so you can see if you have made a significant improvement.

It should suit a fast 2 blade prop.

I had a drawing in my files but it doesn't seem to work any more.

Flux

[Flux]

Sorry you do say it's 24v in the heading. Then it should be ok for 12v.

It will probably work with the field as it is but the current will tail off at something below 10A. If you connect the field series parallel it will take a bit bigger and slower prop and the current will hold up more in high winds but don't push it too hard, these were not normally fan cooled and the power out at 24 v was not very high.

For wind conditions I would not push it much beyond 15A for any length of time.

Have a go at it, it will probably suit your modest needs.

Flux

[TomW]

Is this the photo?

.

Tom

[Flux]

Thanks Tom, that is the one. It's the Lucas Freelite 6ft prop, quite similar to the 200W Winco also. Should suit that dynamo.

[captain nodge]

BEYOND MY WILDEST DREAMS GUYS.

GOTTA GET MY BENCH TOP CLEARED OFF AND GET STUCK IN,

[captain nodge]

right,wet n windy day stripped the dynamo down, four field coils one wire going to field terminal,another to one set of brush holder, cant quite see how fields are linked without taking the shoes out,have uploaded some photos but unable to get in to this post,not exactly a whizz at this sort of thing.

so if i was to wire up fields series paralel that would make its output 12v?

which would give me better performance?

[Flux]

That seems normal. Just to check, how many brushes does this thing have?. If it is a very old unit it may have a 3rd smaller and movable brush used for current regulation.

If it is a 3rd brush unit you need to remove that brush and connect the field to the main negative brush ( case probably) the main positive brush will go to the A terminal near the field terminal.

It may be slow enough to run at 12v without modifying the fields but you certainly want to remove any 3rd regulating brush.

Rewiring the field to series parallel will bring it back to the full field value that it had on 24v. This will much increase the high wind output as otherwise it will field weaken due to armature reaction. The down side of connecting the fields series parallel is that you now take 4 times the current that the field would take in the unmodified state. This has to come from your output and the low wind performance will suffer. In light winds the mod might not be worth doing unless the cut in speed is way to high with full series field.

If you can drive it in some way and measure the cut in speed you will be able to decide if you need to try reconnecting the field.

If you can get it to cut in at 400rpm or lower I would try it as it is for now. If it sheds load at too low a current in high winds you could always try the mod. If you can get 10 to 12A I wouldn't modify it but if it saturates below 10A then it will most likely be better to reconnect.

With a short crank handle and lots of practice you can crank things at about 300rpm. I doubt that this one will cut in as low as that but if it does you are on a winner.

If when cranking it as fast as you can, you see the voltage starting to climb above the residual value it is on the verge of cut in. If you see 2v at 300rpm it will be fine.

I haven't tried posting pictures lately I am not sure how well things are working but if you can get your picture of the field to post I will try to get you a drawing of the series parallel mod.

Flux

[captain nodge]

It has just 2pairs of brushes, no separate one,i did drive it in a small diy lathe once to see if it put anything out, i had to exite it and once i had flashed it, (im sure i did the flash with a 12v cordless drill batt) it gave a considerable spark at quite a low speed, all this was done way back hence really i have only really gone back to it since i just got on the net and found this site, only found this site because i googled making turbine blades,

Anyway theres no name plate or anything on it to say what it is,you think cav,

Main pain here is i discovered theres an error on page sign at btm of task bar

maybe why i cant put photos on this page

[TomW]

Cap;

I am having a beach of a time getting any posts in today but here is a link to your file area with 4 photos for those who may not understand how to view them:

http://www.fieldlines.com/user/captain%20nodge/files

Tom