911hillclimber

Well, after a lot of faffing about finally got the front casting to match the one side of the main case, tapped and loctited in M3 steel studs, not screws. The number of times I took that Sparey engine apart to get it all to clear and fit the threads in the 'aluminium' castings would have the threads worn or stripped. Thus the nose is on and saved. That is 2/3rds of the £67 saved! The rear will be a solid alum piece not the ropy casting as that is as good as scrap now.

Tried the 300 rod again today, nothing doing, must be the material of the casting? Anyway, being that a none-starter, have screwed in some M3 screws with JB weld as an epoxy into the main case. This will fill the holes and bond the alum screws in place too (I hope). Easy to clean the machines faces with a light skim. I then glued some of the same screws into the untapped holes in the front casting, again, easy to face the surfaces when set. I have decided to machine the awkward rear cover/carb from the solid as a I have a nice alum bar the right size. Although a mess, it could rescue the situation!

Thanks for the post, and you are right. Still trying to work with what I have. The drill jig I have made is surprisingly accurate (it seems) and is 6mm thick so acting as a drill guide, not that robust but good enough I hope to drill just the holes for this set of castings. Really busy over the weekend, but will try to save the other castings with this rod if they prove to be compatible. The drill wandered off when drilling, the drill would progress well initially then I hit hard 'stuff' and the drill (2mm dia) would simply ride to one side of the hard inclusion. This was only in the end casting mounting bosses. The rod supplied via ebay is Alubuild 300. The description reads it should do the job!

Rods came from ebay, 300 deg MP as opposed to 400 and higher. Will look at those Outerzone designs.

Is there another source for the castings of the Atom Minor Mk3 other than Hemmingways?

Filler rod arrived today, I even read the instructions! Decided to test trial the job first, so found some nice alum sheet, 16 swg and formed a simple corner joint, about 30mm long. Thought I would try the butane torch first as per the instructions as it is butane gas. The torch could not get the sheet alum hot enough to melt the rod. So, reverted to my mini gas welding set that will gas weld 16 swg steel well, that should do! No, the sheet got hot ok, infact to melting point, but the rod simply would not take to the freshly cut surfaces. I opened the intended welded joint by hand after quenching. Frustrated (as ever) with this saga took, the cast back plate to the vice and csk sunk the one lugs with a centre drill, so the surfaces were very clean. The hole is about 2mm dia x 5 deep, open, the csk is open to about 5mm dia and 4 mm deep, a good funnel I hoped. Heated the casting gently for a minute or so and focused on the one lug. Heated and dabbed the rod to the csk hole, nothing happened, hotter still and the rod sort of lost it's tip on the surface, but did not flow, just there as a small lump. Tried more and the casting lug as good as melted. What rod was there picked out after quenching with a scriber. So, I conclude the casting are made of peanut shells, melts at a temp lower than the rod (300 degC) and the rod will not take to the casting, or sheet aluminium or peanut shell castings. All in all a waste of time, money and gas. Maybe one day I will buy some new castings for £67 and try machining again, but do not feel inclined to carry on.

Thanks for the details. Hemmingway are the company now selling the materials/castings for the Atom Minor Mk3.

Are those Hemmingway castings? Mine look nothing like as 'matched' as those in the running engine.

Sounds good, advice always appreciated. all a bit like chamfer the edges to be welded for best/total penetration. A good counter sink hole is easy as you know. This is for the end plate lugs. For the main case I have M3 alum screws on order so will red loctite them in and flush to the machined face. Once done I will intal steel M3 studs and hold the lot together with nuts.

I've ordered my aluminium 'welding/solder rods that melt at 300 DegC and need a proper welding set (gas) which I have, so the castings could be a Big Blob on the floor soon... Found some alum screws too which will be used to fill the tapped holes in the main case. Will Red Loctite them in place, leave to set and cut off flush etc. Fixed my £15.75 pillar drill by turning two very thin shim/sleeves for the head stock which was tricky, and took 3 attempts, but done and now the drill drills on the counter sink and stays true to the scribe lines. Used a pilot drill off the late to spot the holes first like a good boy! With that done, found a very nice piece of flat machined alum 8mm thick plate and made an accurate drilling jig, with raised boss on one side to locate in the case, and a female recess to locate on the end plates. This way the 4 holes will all be the same on all the parts when I've repaired them.

Several things have crossed my mind, plugging was one of them, alum 'solder' another for the twp covers and all the 8 lugs. The case would have to be plugged. Doubt you can get M3 aluminium screws to act as plugs, steel ones could lead to a wander due to the hardness over the alum if you get a 'half-hole' line. I have found my drill to be lacking, too much play so I'm shimming it to try to stop the wandering. I have used the centre drill from the lathe to eradicate 'wander', hope to report a success tomorrow. Have the morning to my self tomorrow so can try a few things. Thank you for the ideas and support, is helping a lot.

I am very disappointed in this. The 2.5mm tapping drill (M3 not 6 ba) just drifted all over the place and while drilling met all manner of lumps and bump imperfection along with buttery drilling too, but the drift was uncontrollable. I made a 'drilling jig', a good lump of dural and drilled 2.5mm and made to suit the location bosses (male and female) of the crank case. The lugs are poor material, the main casting much better and machined well on the lathe. It will all go in a box now and eventually I will order £67 of fresh castings and start again, but will get my friend to make a steel gauge plate jig i can bolt to the case and ends to get holes to match. This drilling is very hard to align without a milling machine and being able to position the pilot in X and Y accurately, but could take them over to Phil and get him to drill them on his miller along with the cylinder head bolts too. I'm too embarrassed to picture the mess... Will re-open this thread when I get fresh castings.

Terrible day on the engine today. Scrapped all 3 castings trying to get the screws to line up, utter shambles. At £67 for a new set of castings, I think i'll throw the towel in as I can't think of how to drill the case holes accurately with what I have. I think you need a milling machine to index the holes and drill accordingly. The cast lugs are partly to blame as they do not align to the main case well, 3 may be in-line, but the 4th is miles off etc. The rear cover can only fit in one place, and the lugs simply do not align, but the castings are like that everywhere. Wasting time and money, so will revert to what I'm used to!

Had a great day in the garage today making lots of casting swarf, but good results with only one very near cock-up but i dodged the bullet by luck alone. Lots of pics: Plan was to machine the crankcase casting, front casting and rear all bar the attaching screw holes, still awaiting my £15.75 pillar drill for that. Finished the exhaust port inside and out and machined the small engine mounting pads, far to small, so was very minimal in my milling. Spent a lot of time getting parts to fit into my tiny chucks, but got there ok. The front casting was dead easy, the casting remarkably true, so all machined and reamed, bushes over the weekend I hope. The rear cover was a pain. It is 'just' too big and lumpy to get into the 4 jaw, so had to chop the bulk of the venturi cast feature and will make a brass substitute and epoxy it in place into the plain hole I've drilled. The spot facing of the attaching screw hole pads was awkward too as I could not cut them by turning, only using the devilish compound cross slide, but got there. I made a mistake turning down the rear casting to fit the case, but had left some final material to cut so mamaged to get a nice fit after all, much as the front one is. The matching of all these features in the casting is laughable. Might file some once screwed together to get most to match, but probably will just leave them. All the pics:

Thanks for the support! Ok, a few more hours in the garage today. Today was far more fathoming out how to hold the main casting than machining it. This lathe is small so has small features. It came to me with a reasonable 'home made' face plate which is the chosen mthod of holding the casting. However, the 3" angle plate I now have is HUGE and weighs a ton, I would never balance it out for cutting, so used a nice piece of extruded alum alloy to be the substitute for the angle plate. This all worked out great and with the instructions to guide me managed to get the cylinder liner bore all done and re-jig the same parts to align the exhaust stub pipe ready for machining tomorrow. Hope these pics will speak a 1000 words: