Building the Minimag

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Bogstandard:
And now the final part about hacking this block into shape. Great cheers from the audience :nrocks: :nrocks:

This block seems to have taken an age to get to this stage, but what you must remember, I am now a very slow machinist and builder, so most reasonably experienced people could do this whole block easily in a full working day, if you have things organised.

This stage is now to get the block into the correct shape to accept the coil, which is sitting on top. If you look very closely, you can just see the layout lines for the required cutout.

The usual thing, straight down the middle with a big cutter, not quite to the bottom of the required slot, then go to each side in turn.

Just reaching the second side.

And this is what it turned out like.

This next bit is the final shaping of the block. The level bit is done first, then the angle.

Because the lamstacks were not quite flush or below the side faces, I used an extra set of paras, one either side, but not as far forwards as the lams, So allowing the block to be held rigidly. The horizontal cut was then taken to depth and the correct distance in.

Again, because I don't have a swivel base on my vice, I can't do the cuts as shown in the instructions.
Because this angle isn't super critical to the build, I continued to hold the block as before, with 4 paras, but eyeballed the angle and made sure that the bottom corner of the block was resting on both lower parallels.

Using a 10mm ball nosed cutter I cut up to the line by about 2/3rds down from the top. Then once the line was reached, I continued cutting straight down until it was almost at the horizontal face. Once it was taken out of the vice, I blended the radius in to the horizontal face with a round file and a bit of emery cloth.

That is all the cutting that is needed.
As can be seen from this side shot, the coil can now fit where it should.

And another shot from the front.

The holes in the coil were then spotted thru so that the holding screw holes can be drilled and tapped.

Even though the block is to shape, lots of holes need to be drilled. Their positions are all shown on the plans.

These holes thru the 'ears' are for a couple of grub screws, that if you haven't got quite a tight fit of the coil lams to the side lams, the coil lams can be forced down so good contact between the two is made.

Because I am a belt and braces person, even though I have good contact between them, I am going to use these as well.

The next job was to pick up the two spotted marks and drill the holding bolt holes to depth.

These four 2mm tapped holes are for a cover plate to fit over the rotor. This is optional, but I think it is a necessity, purely to stop bits sticking to the magnets in the rotor.

Then finally, the four magneto mounting screw holes.

All the holes were tapped to their correct sizes, and the coil checked for fit.
This block isn't quite finished with yet. It needs some bits making on the lathe and fitting, then the few remaing holes can be drilled. But other than that, this is that very complicated looking bit finished, just by carrying out some relatively simple machining exercises.

Onto the lathe next time.

Bogs

Ray:
Bravo Bogs :thumbup: :clap:
Ray

madjackghengis:
Hi John, very nicely done I must say. I would take you for a former/present teacher from the way you lay this out. You've provided some very needed info on the lams for a special project mag I have in mind. Your set ups are very simple solutions to challenges which could easily leave some misalignment, and things not quite fitting exactly. :nrocks: very nice, mad jack

NickG:
John, nicely done. This block was very similar to making the poppin frame - when I first looked at it I was thinking of different ways to do it as I couldn't imagine me making it. But when I started and followed mostly the sequence described, the block emerged (as you said) as if by magic and I can now see the virtues of doing it that way.

I used most of the techniques you have but when I make my next frame I will use this post to make sure I do exactly as you did and make a better component.

Thanks.

Nick

Bogstandard:
Thanks gents, the comments are much appreciated.

One thing you must remember though, the way I do things are my way, just to make things easier for myself, like boring, I have great difficulty setting up my four jaw on the lathe, so prefer to use my mill.

Nothing is written in stone, and there are usually many ways to obtain the same end results.

As the less knowledgeable amongst you gain experience, you will find your own little ways and shortcuts to get to where you want to end up. Whether they end up the same way as I do it, you will have to wait and see.

I was on my lathe this morning, and for me it is a lot more stressful than using the mill, so I had to give up early, so it may not be much of a post later.

John

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