Author Topic: Retlas "Manchester" Dynamo  (Read 6434 times)

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #60 on: November 18, 2020, 09:50:37 PM »
Hello MJM, yes the lip seals would be from another era. I was pleasantly surprised that so many felt washers could be bought so cheaply.
The old ten foot long laboratory benchtop consisted of 6" wide planks joined by lengths of plywood glued into grooves along the edges. I made a table with half of the benchtop and stored the rest. It is beautiful wood but I had to work around the gas tap holes and it needed a lot of scraping and sanding to get rid of the initials scrawled into the surface.
The laminate appearance was caused by the action of the hole saw - I had to stop every now and then when it started smoking!

Andy 
« Last Edit: November 18, 2020, 09:55:16 PM by Chipmaster »

Offline Twizseven

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Re: Retlas "Manchester" Dynamo
« Reply #61 on: November 18, 2020, 10:43:48 PM »
Andy,

That's going to be a beautiful model when completed.

Colin

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #62 on: November 19, 2020, 09:50:45 AM »
Thanks Colin, I feel pretty confident at this stage. At least there arenít the concerns with piston fits and sealing valves that we have with engines. Achieving a vintage appearance for the field coils is my current task.

Andy

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #63 on: November 24, 2020, 09:27:20 PM »
I have made progress with the field coil bobbins or reels, the teak flanges were glued to the white polyethylene waste pipe using an aliphatic glue which did the job on a test piece. After assembling the bobbins I gave the teak a coat of Rustins Sanding Sealer.
Here are my bobbins left drying on a broomstick
IMG_2453 by Andy, on Flickr

IMG_2454 by Andy, on Flickr

A narrow radial slot has been sawn in the inside of each flange as a route for the copper wire leading to the first layer of the windings. A small rebate was also cut around the inside of each flange which should help to achieve a neat finish when the coils have an outer layer of string serving.

I also started making the Armature Reaction Compensator.

Armature Reaction Compensator by Andy, on Flickr

This is going to be fabricated.
First a brass ring 1.5" od 1.2" id x 0.375" machined to be a sliding fit over the end of the pedestal.

IMG_2443 by Andy, on Flickr

Followed by a piece of 1/4" thick brass plate to be silver soldered to the brass ring.

IMG_2437 by Andy, on Flickr

IMG_2442 by Andy, on Flickr

IMG_2445 by Andy, on Flickr

IMG_2447 by Andy, on Flickr

IMG_2448 by Andy, on Flickr

IMG_2449 by Andy, on Flickr

That was it for today.

Andy
« Last Edit: November 25, 2020, 06:15:19 AM by Chipmaster »

Online Alyn Foundry

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Re: Retlas "Manchester" Dynamo
« Reply #64 on: November 24, 2020, 10:15:54 PM »
Those bobbins really look the " business " Andy, well done.     :ThumbsUp:

This is going to be one of the nicest Retlas dynamos I've ever seen.

Cheers Graham.

Edit....

Re your email....

http://www.modelenginemaker.com/index.php/topic,9323.msg228168.html#msg228168
« Last Edit: November 24, 2020, 10:37:39 PM by Alyn Foundry »

Offline Jasonb

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Re: Retlas "Manchester" Dynamo
« Reply #65 on: November 25, 2020, 07:21:11 AM »
Silk, now that is posh ;)

I've used these people for period lighting cable in the past, they don't do singles but you can untwist the 2 core

https://www.urbancottageindustries.com/light-fixtures/lighting-and-power-cable

Also look at some of the vintage and classic car electrical suppliers who will have cotton braided single strand in various gauges, this is what I use on the Hit & Miss engines

Offline Bluechip

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Re: Retlas "Manchester" Dynamo
« Reply #66 on: November 25, 2020, 09:45:53 AM »

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #67 on: November 27, 2020, 09:32:11 PM »
Wire?
Yes D thanks for the information.
I have their copper wire for making the field coils,
IMG_2239 by Andy, on Flickr
 
I had also noticed that they sell the silk and cotton covered wire but haven't decided which wire to use yet, I have been referred to a few sources. I would like to wind up curly leads the same as seen in this picture of an early Crompton dynamo copied from the Queensland Energy Exhibition Centre website.

 EARLY CROMPTON DYNAMO by Andy, on Flickr

Over the last couple of days I have continued fabricating the Armature Reaction Compensator by silver soldering pieces of brass together then using a slitting saw to make a gap for a pinch bolt.

IMG_2460 by Andy, on Flickr
IMG_2467 by Andy, on Flickr
IMG_2463 by Andy, on Flickr

While awaiting delivery of copper braid for the brushes it seems I should get on and wind the field coils. Mounting the brushes should be straightforward and I might have a go at making a wooden handle and covers for the oil chambers.

Can anyone advise whether I should limit the number of turns or just keep going until I run out of copper wire. I calculate that I have enough wire to put between 300 - 350 turns on each coil, also assume the number of turns on each field coil should be the same. I bought this stroke counter from RS Components which I intend to use to count the windings.

IMG_2490 (2) by Andy, on Flickr

Andy



Offline Roger B

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Re: Retlas "Manchester" Dynamo
« Reply #68 on: November 28, 2020, 08:06:45 AM »
Use all the wire or as much as you can fit on the bobbins. More wire will mean a higher resistance and less current through the coils for a given voltage but there will be more turns so that the ampere turns value will be much the same. Less current through the field coils will mean more for the load and less heating of the coils. The downside is you may need a higher voltage to achieve full excitation, but without full details of the system it will be hard to estimate. You also have the option to connect the coils in series or parallel (make sure that the phasing is correct  ::) )
Best regards

Roger

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #69 on: November 28, 2020, 09:54:06 AM »
Thanks Roger, I hope to be posting pictures of the wound coils later today.

Andy

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #70 on: November 28, 2020, 09:13:18 PM »
The field coils were wound using my lathe this afternoon,

The set up, first a video taken at the wrong angle.


IMG_2494 (2) by Andy, on Flickr

IMG_2496 by Andy, on Flickr

I used a hot glue gun to keep the copper wire in the wooden flange so I could start with a little tension on the wire simply holding it between finger and thumb.

For the first coil the lathe was set to it's slowest speed of 35 rpm, I was expecting to have enough wire for 350 turns on the coil taking about ten minutes. The first three or four layers were very neat not a turn out of place but as the job progressed I couldn't maintain the standard and things became untidy. As the stroke counter went past 400 and there was plenty of wire left on the spool it was clear that my elementary calculations were rubbish. After about 25 minutes the copper wire ran out and I had just over 800 turns on the coil. As I had overshot my estimate by nearly 500 turns I was concerned that I had gone too far. I phoned Graham (Alyn Foundry) for assurance that 800 turns was ok and he agreed with Roger B, "Use all the wire or as much as you can fit on the bobbins".

Winding the second coil went the same way as the first first few layers rather neat then it went a bit free form, not a tangle but I forgot to take picture before I covered it up with masking tape.  :embarassed:

I tested the coils with a 12v battery, they are certainly powerful electro magnets.

Here are the coils back on the dynamo.

IMG_2497 by Andy, on Flickr

IMG_2498 by Andy, on Flickr

They will receive their cosmetic treatment ( cardboard and string serving) after I have attached suitable lead out wires.

Andy


Online Dave Otto

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Re: Retlas "Manchester" Dynamo
« Reply #71 on: November 28, 2020, 09:27:27 PM »
Nice progress Andy!

Dave

Offline Jasonb

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Re: Retlas "Manchester" Dynamo
« Reply #72 on: November 29, 2020, 07:02:52 AM »
It's coming together well. I had similar problems when I did my little electric engine with the first couple of layers going where you want and then it starts to go down hill as the wire wants to drop into the "U" formed by the previous layer rather than run over the top.

Online Alyn Foundry

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Re: Retlas "Manchester" Dynamo
« Reply #73 on: November 29, 2020, 11:29:10 AM »
Does it motor yet, does it motor yet ??  :)

Seriously, the coils look great Andy. Don't forget to mark up the starts and finishes so you won't get the polarities mixed up. Are you going to bring the pairs out of a single hole? Or one at either end?

Because you have some room to spare before the final serving you can now firmly secure the windings with either PVC electrical tape, hot glue or even Shellac and Indian cloth tape ( purist approach ) lol.

The important point is a decent electrical connection between the solid Copper magnet wire and the more flexible output wires. I'd suggest soft solder but please use the 60% Tin 40% Lead  ( TinMan's ) grade. Once soldered sleeve and firmly anchor the connection to the bulk of the coil. Any wire that carries a current will try to move towards a magnetic field, a firm, mechanically strong fixing is recommended.

Cheers Graham.

Offline Chipmaster

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Re: Retlas "Manchester" Dynamo
« Reply #74 on: November 29, 2020, 02:49:22 PM »
Thanks for the comments Dave and Jason - nice to know that someone else had the same experience winding coils.

Patience patience Graham  :)
I had an unsuccessful motor test this morning. One field coil was connected to a 12v battery and wires from a separate battery were held against the opposite sides of the commutator. The armature certainly jerked but the sparks would have damaged the commutator if Iíd persisted. I have ordered some copper braid and Tufnol so Iíll test it again when the dynamo has the proper brush gear.
The solid copper and flexible output wires will be soldered together. I have cored 60/40 solder, is that ok or should I use plain 60/40 blowpipe solder ? The pairs of wires emerge together from the top of the coils, at present it is easy to identify each wire but I appreciate the need to ensure they arenít mixed up when the windings are secured and served.
I have an old Hammant and Morgan model railway controller left over from my childhood, using a lower and variable voltage would lower the risk of damage to the commutator, would that be suitable for the motor test?

Andy