A Robinson from rejects.

[fidlstyks]

Jason , I know you have machined lots of  castings so I should not tell you what to do. So I just say what i do once I hit hard spots I put my castings in a coal forge and turn them orange. The thicker  the longer but some times just a quick orange does it. A chill Iis easy to take out .
   But other problems can exist.  I have melted some 25 tons of cast iron since the 80s which produced some 18-20 tons of castings. I know what makes hard spots. One mistake was using a Chrysler interceinterceptor block for iron.  They  have nickel in them.  So do Pontiacs. Very hard, it made nice ringing bells though. I like small  block  Chevy's. So soft you can scrape it away with a pocket knife.
Using a  carbon bonded crucible is very bad. Use only clay graphite crucible if melting in a crucible. I also stir in carbon and silicon carbide inoculate and Ferro silicon. What exactly they are made of I do not recall. It's stuff I buy at the local foundry.
  My experience with a slick shinny spot is that it is carbide . Black pepper spots are silicon. Both bet bad news but will melt or burn out in a forge. I like to test all iron before shipping and would never ship any bad iron. I throw it in the scrap iron or burry it. Maybe happened on 4 pots over the years.
    I think those wide shinny spots look like carbide to me. But pictures can be deceiving on the internet. If the grey areas are the hard spots look for black pepper spots.  Silicon in excess makes such pepper spots.
  In the large foundry they take a 1 " square grind it perfectly flat on a surface grinder, place a drop of Nitric Acid on it and hold it to a chart of 1" squares that looks like the solar system. You then find a square picture that matches your piece with small pepper spots counted,  half moons and other shapes. And there it has numbers that tell you what your iron is made up of.
 The books I have say mchinable iron is 1.75-2.5 % silicon. If you see the iron like this with many spots it may be 7.5 %.
Maleble iron is 7.5% and cast as white hard iron. Then malableized by heating orange or about a week. Not made much now days. Ductile rules. It also gets hard again if your cutter gets dull and heats it up. Then your done. That or heat it for a week again.
   Just thought some one might be interested as you chaps seam to be all befuddled by hard spots.

[Jasonb]

Thanks, I have used the heat method many times myself and was getting close to heating this one but don't really have the equipment to get it all upto temperature and did not want to risk local heating on what was already a flawed casting.

I should stress that right from the start I knew this was a reject casting and probably one of the worse ones that graham had, if it had been one that was upto his usual standard that went out to customers there would have been no issues with it.

I don't think the hard areas are any specific metal inclusions just typical chilled castings where the thin section has cooled too quickly, a lot of the edges on this casting are 1/8" or less and there was also a lot of flash where iron had worked its way around the core prints which left a lot of thin metal. Most of the hard stuff was not too deep so I was able to get back to a reasonable metal in most places.

Pics of todays machining to follow

[fidlstyks]

That's good news. I always grind on thin spots before machining. The chops from that will ruin a lathe or mill.
I local heat with a torch lot. Easy fix. Too bad his foundry closed up on him.

[Jasonb]

I posted the wrong photo at the end of the previous update, this should have been the one showing the feet being machined.



The next job was to clock in my machining plate on the mill and to get the casting sitting as true as possible averaging out any undulations in the surface. Once happy with that the holes in the feet were transfered to the plate and tapped for screws. I then skimmed the vertical face at the top of the slope and clocked that in before setting back 5/8" and zeroing the DRO on the crank ctr line, used an edge finder to locate ctr in the y axis too and then drilled the stud holes for the bearing caps.



In this close up you can see the surface has improved with just a few darker hard areas showingparticularly around the far bearing area.



I can now see why Jo likes having more than one of all machines as when you forget to machine the bearing caps before hand  it is easy to pop over to another machine to do them. These were much nicer to machine and the SX2.7 romped through them with a cheap 10mm rougher.



I tried with the rougher to do the inside faces of the bearings but just took the edge off it as soon as I got to the lower half so had to revert to the carbide insert little hogger which luckily has a 1" diameter cut as my carbide end mills were not long enough, again you can see the more polished hard areas in the top corners of the lower halves



Having the casting on the machining plate made it easy to hold and clock in to machine the angled face that the cylinder mounts to.



Once through the surface it was not too bad to machine and helped by another fresh corner of the inserts which had blunted again by now.



Again the plate made it easy to set up to bore the bearings. With teh caps being a nice soft iron and the lower half somewhat harder I could see the drill starting to deflect into the softer stuff so stopped early and changed to a carbide tipped bar in the boring head. Not 100% happy with the fit of finish of teh holes but will probably do for the little running this engine is likely to do but could squeeze in some thing walled bearing shells if needed, I kept the cap bolts a bit further apart than drawing to allow a bit more room for this if need be.





And a group shot to finish off with the crank and cylinder in place.



Flywheel has been fettled and seems soft and the faceplate is on the lathe ready for some turning tomorrow, got to get these castings out the way and into a finished engine ASAP, can't see the point of having them to fondle. There is also a risk that the Welsh Gold coating may be catching

[RayW]

I too have been "fettling my flywheel" Jason! Having removed the last of Grahams special coating, I thought I'd better get a coat of protection on it before the brown stuff started to re-appear. After removing all the flashings with my Dremel and filling a lot of the imperfections with car body filler, I applied a first coat of high build primer, which just showed up even more that need filling!
I have yet to cut the keyway, so some of this coat will inevitably get damaged then, but it will need several more coats anyway once all the filling and rubbing down has been finished.
In case you are thinking that my choice of colour is a bit odd, I studied the tin for ages before I bought it and nowhere did it say what it was, so the cream/pale yellow colour was a complete surprise!

[Jasonb]

As the Robinson flywheel is quite fat I could not get either the jaws from either the 3 or 4 jaw chucks in between the spokes so used the faceplate. A piece of hardboard between flywheel and faceplate allowed me to run the tool right across the face and also allowed for any slight undulations on the unmachined casting to seat down firmly. The iron was softer at either edge of the rim and decidedly harder towards the middle with a marked increase in noise from the tool as it moved from one to the other. Maybe Graham had been melting down manhole covers and drain gratings of iffy supply to do these castings I bored it out to a firm pushfit on the completed crank which will mean no wobble.



I knew from the photos that Graham had sent me prior to purchase that there were defects on the other side of the flywheel and suspect I may need more than one coat of High Build filler/primer to deal with these I quite like the cream colour of the UPOL High5 version of this paint and actually use dit as the colour for the small oscillator I built over Christmas, comes up OK with a coat of clear gloss over the top.



After a good seeing to with a grinding bit in the Dremel it was time to slip all the bits together.



The exhaust block casting had been consigned to the Rejects pile due to some mold shift so I took the angle grinder to it which got it back into something like the right shape.







While doing this the sparks were coming off quite bright and big not the small fine red ones you should get from a nice graphite rich cast iron so I played safe and gave it a cooking.

[Alyn Foundry]

It's Robinson mania.

Your engines coming along nicely Jason and looking at the flywheel that Ray has just painted a light colour seems to suit or offset the chunkiness, doesn't it?

Young Alan's been a little busy today!   

Cheers Graham.

[RayW]

Just been thinking about lubrication for the little end. I have drilled a hole in the top of the little end block of the con rod and through the little end bush, but how does any oil get to the con rod in the first  place? Should there not be a hole in the piston to allow oil to reach the inside of the piston from the cylinder wall?

[Jasonb]

I put a hole in mine

[Alyn Foundry]

Good morning Ray.

Before you go drilling holes “ willy nilly “ just consider the engines arrangement, Mr Robinson was an amazing designer.

Because the piston is facing downhill, so to speak, oil that passes from the sight feed lubricator onto the cylinder wall is scraped back and deposited into the piston. Effectively the gudgeon pin and bush are
“ awash “ with oil. With horizontal and vertical arrangements this situation cannot happen.

Cheers Graham.

[RayW]

Good point Graham. That's one less hole to drill. Still waiting to do the flywheel keyway but can't face an icy workshop yet. Must do some drawings for the sight feed lubricator ready for when it warms up a bit.

Regards Ray

P.S.Did you get the car sorted out or are you still stranded?

[Alyn Foundry]

Hi Ray.

No we're still stranded, the electric pump has been playing up for a little while, but now the fuel is a little waxier, nothing. There's a new one on its way.

The Robinson engines were fitted with a " wine glass " lubricator but finding a 1" genuine one these days would be impossible. I had a quick look on eBay it seems the Chinese are still producing 1" by 1/8" BSP lubricators in both Brass and Steel, the Steel ones being ridiculously cheap!

Going back to my rallying days, on our circuit the Holland brothers always seemed to have a few nice examples available at reasonable prices.

Cheers Graham.

[Jasonb]

The Robinson engines were fitted with a " wine glass " lubricator

No doubt Jo will be needing one of those for her Robinson.

Should not be too hard to turn up the bowl shape from a bit of acrylic rod and polish it up with some Micromesh. rest can just be like a cylindrical one.

[RayW]

Looks like I will have to make a slightly bigger version of the ones that I made for the Otto then! I  still have the full size one that I scaled them from, so will use that as a pattern again. This time, I might actually do some drawings first.
Jason has kindly offered to email me some oiler plans, so might even be able to adapt those.

Hope the car is fixed soon, not that the roads are in a fit condition to drive on anyway. Just started snowing hard again here, so staying indoors and keeping warm.

Regards

Ray

[ettingtonliam]

Not strictly a Robinson from rejects, but I understood that Anson Museum were marketing a couple of the Alyn Foundry designs. I've looked on the Anson site, and can't find any mention. Have I got it wrong?

Richard