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Building the Minimag

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madjackghengis: Hi John, I truly understand the issues you have, with my own with the M.S., but you've done a good job figuring out what you can and can't do, and rearranging your work so you can accomplish what you want, in the time available, with what equipment you have, and I admire your commitment to continuing to work, and I fully understand that it is far more desireable than sitting out life in a closed room, waiting for life to close in on a person.  I wanted to say, the mag, as it sits now, very closely resembles a Fairbanks Morse or the like, except being open rather than all in a sealable machined box.  The way the laminations fit right in, and the means of machining around them, and through them has given me confidence I can at least have a decent chance at getting a mag to work with the radial engine, and I really don't much like the two options the project gives for ignition, one being points and the other a hall effect distributer, both with big coils, batteries, and the like.     The way the machining cleared the way for the lams was very clean, and is the main source of my encouragement, as that was the issue I have been most concerned with, relative to getting a mag smaller than the engine, yet still with enough magnetic coupling to be an effective and responsive ignition system.  Are you going to have an engine to run a test sequence of the minimag on when it's finished? :beer: :ddb:  Just curious, mad jack

Bogstandard: Jack, The engine hasn't been built yet, but I have already got a little design for a test stand, to check that everything works OK. I will also be doing a couple of cable strain relief parts as well, but they won't be just yet. I still need to get to the end of the build program, just to prove it. Back into the shop again soon. John

arnoldb: Thank you for posting in such detail John.  It is, as always, much appreciated. --- Quote ---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. --- End quote --- There's a world of truth in that quote John - and I'll happily vouch for it as a novice with just a tiny bit of experience :-) Kind regards, Arnold

sbwhart: Lovely Job John  :clap: :clap: :clap: It came together very well, can't wait to see it on that engine. Stew

Bogstandard: Just a little bit this time, but still progress. I will just make a point about a couple of things. The materials that have been supplied in the kit have been spot on for the job they have to do, and up to now they have machined beautifully, especially the aluminium, no tears, rips or picking up. It has been a joy to use. The second concerns accuracy. For some of the parts made in the lathe, good accuracy IS required between certain ones, otherwise things will lock up or not, depending on what is required. This is especially critical on lengths of parts. So allow extra time just to make sure that things are really spot on. I am now starting to do the lathe work, which concerns mainly the spindle, points operating cam and bearing fitment. The first piece called for is a spacer to go between the two spindle support bearings. The instructions called for opening up the centre hole to a certain size with a drill and that is the job done. Unfortunately, I can't be like that, so I opened it up to one size smaller and finished it off to shown size with a boring bar. It only takes a few minutes longer, and the surface finish is much better. The outside size was turned down until it fitted into the thru hole with a nice sliding fit, not too tight as Loctite will be used, and that requires a bit of space to work in. The spacer was parted off and brought to exact length. The spacer needs to be fitted from the front face exactly the width of the bearing. So what I did, was to put the block face down with the bearing pushed all the way to the bottom of the thru hole and the back end of where the bearing sat was marked up with a felt tip. The front bearing remains free to be taken out, so I had to ensure that no Loctite could get to it. By putting the drops of Loctite further in from this mark and assembling from this front side, the bearing will be safe. The spacer was put in first, followed by the bearing, but not fully inserted. By pushing from the back of the mag block until the front hit the 321 block ensured that the bearing and spacer were in their correct positions, with the bearing flush with the front face. Another 321 was pushed up to the back face to keep things steady until the Loctite had done it's work, in this case, 5 minutes. Next came the cam, very easy to make, but this is one component that does need to be made the correct length for it to adjust correctly. The centre was first drilled then opened up with a 12mm reamer. The outside was brought to size, then parted off and brought to length. The cam blank was then tranferred to the mill using a square 5C collet block, and the flat face put onto the outside. There are lots of simple other ways that this could be done, so no worry on that score. The block was then rotated 90 degs and the hole for the retaining grub screw drilled in the correct position. It was then transferred back to the lathe to have the outside polished a bit and the flat blended a little into the side curves. Once the grub screw hole was tapped out, the cam was finished. The instructions suggest that if you wanted to, you could case harden it. I will make that decision when I have made all the parts. A bit more lathe work to follow. Bogs

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