Engines > From Kits/Castings
Retlas "Manchester" Dynamo
Chipmaster:
After a twelve month gap in this thread I have started to build the dynamo. Here are extracts from Grahams drawings that I photographed back in 2017.
Dynamo Base by Andy, on Flickr
Dynamo side view by Andy, on Flickr
Dynamo end view (2) by Andy, on Flickr
Dynamo bearings by Andy, on Flickr
There are a some differences between my castings and the drawings.
1. My two pedestal castings have lugs on each side for bolts or studs whereas the drawings show two bolts 1.1/2" apart coming up form the underside of the base.
2. The base casting isn't quite as long as the drawing.
3. The height of the pedestal castings and the pads they sit on had to be reduced to ensure the keeper or yoke would be a reasonable thickness after machining it to clear the armature and eventually look right.
In this picture I had machined the mild steel field coil cores to a height of exactly three inches then determined the height of the armature shaft.
IMG_2116 by Andy, on Flickr
IMG_2103 by Andy, on Flickr
Milling the underside of a pedestal flat.
IMG_2100 by Andy, on Flickr
I spotted through the base into the keeper casting.
IMG_2118 by Andy, on Flickr
Tapped the base and the field coil cores 1/2" Whitworth and used short studs in the base and short bolts through 1/2"
holes in the keeper to hold it together.
IMG_2119 by Andy, on Flickr
IMG_2121 by Andy, on Flickr
Andy
Alyn Foundry:
Hi Andy.
As always, excellent workmanship.... :ThumbsUp:
The Retlas Dynamo evolved, please see my earlier post. It moved from a practical working machine to something, I hope could be considered, nice looking?
As members of the FB group will know we've been discussing the field coils. The Lucas unit has field coils that had, in general around 6 Ohms resistance per coil.
I've been doing a little mathematics and a 1Kg spool of 22SWG which is approximately 0.75 mm ECW has a resistance of 0.04 Ohms per Metre. This equates to 10.1 Ohms. I'm of the opinion that each bobbin will require 500 grams of wire for a close match to the original machine.
Looking forward to the next instalment Andy.
Cheers Graham.
Dave Otto:
Interesting project Andy,
I'm looking forward to following along.
Dave
Chipmaster:
Thank you very much Graham and Dave.
I hope I haven't painted myself into a corner with my sequence of operations, my concern was how to machine the pole pieces and have a minimal air gap between them and the armature. The only way I can machine the pole pieces is to use a between centres boring bar with the dynamo mounted on the lathe cross slide. However, I will need to be able to check the gap with the assembled armature and the dynamo remaining on the cross slide. The outcome will be dependent on how well the armature shafts fit and run in their plain bronze bearings.
I decided to mill the surfaces of the two pedestals so that I could bolt them in turn, directly to an angle plate and faceplate to ensure the centre heights matched. There were differences between the pair of pedestal castings which meant I had to compromise on the thickness of the bearing housings but perhaps JB Weld or Milliput can be used if necessary.
IMG_2127 (2) by Andy, on Flickr
Boring out the pedestals to 1".
IMG_2140 by Andy, on Flickr
IMG_2144 by Andy, on Flickr
Being able to rotate a length of 1" diameter ground bar mounted in the pedestals without binding confirmed that the centre heights matched.
IMG_2151 by Andy, on Flickr
In this picture you can see what I meant about compromising on the thickness of the bearing housings.
IMG_2154 by Andy, on Flickr
To reduce the height of the armature I milled away the pads that the pedestals sit on, that gave me about 0.09".
IMG_2156 by Andy, on Flickr
IMG_2158 by Andy, on Flickr
The faces and underside of the base and keeper castings were flat and in the same planes / in line before I started machining them so I assume they had been machined years ago before they acquired the 'special coating'.
image by Andy, on Flickr
Unfortunately the 1" precision ground steel bar isn't long enough to be used to position the dynamo between centres on my lathe so another one has been ordered. However, it was sufficient for keeping the pedestals lined up as they were bolted down to the base.
IMG_2191 by Andy, on Flickr
Andy
Roger B:
Looking good :ThumbsUp: :ThumbsUp: :wine1:
I am following along :)
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