A generator for Elmer.

[Joe d]

Abraham:

This is looking really good so far, I'm much enjoying following along.

Looking forward to the next installment!

Cheers, Joe

[PK]

Wow...just wow... I'm so impressed with the thought and skill that's going into this project!

[modeldozer]

Hi Joe, thank you for the kind comments.

Had to replace the bitumen felting of my shed’s roof so did not do a lot on the generator.

A parallel was used to set the post square while holding it in the lathe collet chuck clamped to the mill table.



A stepped slot was milled in each post.



for locating the brush holders.



The holders ready for soldering.



Cheers
Abraham

[modeldozer]

Hi all,

The shed roof is finally finished and will hopefully keep my machines dry.



Had to make an extension for the armature shaft to be able to fit a pulley, but try, as a may could not get it to run true once fitted to the armature.  For the fourth attempt ended up using an old wood router bit as a boring bar for he recess in the end of the shaft, witch seems to have done the trick.





Testing the run out with the armature fitted.



Armature with extension fitted.



Next up a fake bush end was turned from brass.



Fitted to the front bearing.



Made a form tool from a piece of mild steel to turn a small flat belt pulley.



Turned the pulley.



Faced the end after parting off.



Mounted the pulley in the mill vice with a few pieces of paper to electrically insulate it so I could use a multi meter and a piece of 3mm rod to locate the centre of the small hub.



A hole was drilled and taped for a grub screw.



The armature assembly.



The bearing posts were mounted on the lathe and the boss sections rounded over with a round over end mill.



The finished posts.



The generator was assembled.





My idea to use some small magnets to generate enough current to start excitation was not successful so for the moment it needs around 2.5A excitation current from an external source.  I have ordered some different magnets to experiment with and maybe have the field windings only as fakes.

Next up is a large pulley for the engine.  Does anyone know of a source for flat belts, have searched the web but could not find a supplier that would deliver to Spain?  Need one 700mm long 12mm wide.

Cheers.
Abraham

[Kjelle]

WoW!!!

Check sewing machine spares, or automotive spares for the belt... The dimensions look like a poly-v should fit... Yuo don't need the grooves for it to work.

Kjelle

[modeldozer]

Kjelle,   thank you for the info, will look into it.

For the large pulley that goes on the engine I went for a fabricated design.  Got a lump of steel from a local engineering firm, seems to be part of a large taper lock bush.
 


After dialing it in on the 4 jaw, it was hack sawed to size.



It was faced close to size and the inside bored to size, leaving a shoulder to locate the spoke part for soldering.



Flipped around add gripped on the inside, it was carefully dialed in.



The outside and other face were then machined, leaving it a little over size for cleanup after soldering.



A piece of 3mm plate was centered in the 4 jaw to a centre punch mark.



A hole was drilled and bored to fit on the hub.



One side of the hub was turned with a register to locate in the plate.  It was temporarily drilled and tappet.



After cutting down the corners of the plate it was mounted on the hub.



The plate was turned down to a nice snug fit inside the rim.



The hub was then bored out for the shaft, parted off, turned around and the end faced. A second hub was also made.



The parts so far.



One of the hubs and the plate was mounted on the rotary table and centered under the spindle.



The cutouts to form the spokes were chain drilled.



After removing the cut out material all the sides were milled to size.  Done very slowly as the outer ends were unsupported.



All the parts.



All the bits were brazed together.



The pulley was mounted on a mandrel and all the surfaces turned to final size.  The shoulder left to locate the spokes was also removed.



Fitted on the engine.



Made a temporary drive belt from insulating tape to test the combination.





Next will be a base to mount it all.

Cheers.
Abraham

[DavidA]

 This is looking better every time I see it.
Well done, Abraham.

Dave.

[modeldozer]

Hi Dave,  thank you for the kind words.

Cheers.
Abraham

[modeldozer]

Hi all,

Decided to extend the floor of the engine under the generator. A template was used to cut a piece of 6 mm plate.



This was milled square and to size.



Tile grooves were milled to match the engine floor.



Slots were milled to mount the generator and give some adjustment to tension the drive belt.



The part was flipped over and holes drilled and tapped around the outside for mounting to a base.



A base was cut from chipboard, milled to size and holes and slots drilled.





The engine and generator were fixed to the base.  A drive belt was made from some cloth harnessing tape.









The base still needs finishing, still looking for some decent wood to do it.
A short video of it running.



Cheers.
Abraham

[John Rudd]

Abraham, looks good.....
Do we have electricity yet? 

[modeldozer]

Hi John,

     Tank you for the kind words.  If you look at the lower right hand of the video the light bulb is powered from the generator, I have to use an external dc source to excite the fields.

Cheers.
Abraham

[DavidA]

Abraham,

looks very good indeed.

Couldn't you switch from external excitation to self excitation once the generator is running ?

Dave,

[John Rudd]

Abraham,

looks very good indeed.

Couldn't you switch from external excitation to self excitation once the generator is running ?

Dave,

I had thought of that, but given he is reading around 5v on the dvm, I dont think it will be enough.....
Given that the field coils are wound for 220v....less turns with thicker wire might work...

Abraham, how fast is the rotor turning? how much voltage are you applying to the field coils?

[modeldozer]

Hi Dave and John,

Like John said, it does not generate enough power to self excite, have even tried adding some small magnets.  My only other thought is, if i can find suitable magnets, to replace the fields.  Experimented a bit with the voltage and current and in the video was using 5V at around 2A.  At 12V the current goes up to around 3.5A but the coils start to get hot. The field coils have a resistance of 2ohm.  The rotor was turning at 1800 RPM.

Any advice is greatly appreciated.

Cheers.
Abraham

[John Rudd]

I'm no guru, but it would appear that the dc resistance of the field is too low.
Ordinarily the current through the coils would be alternating due to the commutating action of the rotor commutator.....

Rewinding the rotor with thinner gauge wire and more turns would probably improve things whereby you could externally excite it.....conversely, rewinding the rotor with thicker wire and less turns will increase the output, Hmmmm that doesnt sound right that bit....
I 'd try the field first, keep the rotor as is run it at the same speed....

[modeldozer]

Hi John,

Thank you for the information, might have a go at rewinding the fields.

Cheers.
Abraham

[John Rudd]

Just a thought, howxhave you connected the field coils?

Originally, the coil ends would have been connected via the brushes and the other ends would have been your supply......so have you just joined the brush ends?

2 ohms seems low.....,

[modeldozer]

Both fiels and the armature were in series.  For the generator I have the fields in series and the armature separate.  The fields are wound with fairly thick wire and do not seem to have a lot of turns.

Abraham

[John Rudd]

The fields are wound with fairly thick wire and do not seem to have a lot of turns.

Abraham

So you need more turns, if the formers are such that you cant accomodate, then reduce the wire gauge...field strength is down to ampere-turns...you may need to experiment a little to achieve a decent output voltage...

[modeldozer]

Thank's John, will try to wind a coil on a seperate former for testing, the way the formers are on the fields meens they have to be hand wound turn by turn.

[SteveT]

Just followed the build and I am very impressed, well done 

[modeldozer]

Hi Steve,

     Thank you for looking in and the kind words.

Abraham