Engines > From Kits/Castings
RLE Last & First
Jasonb:
The cylinder casting was given a light fettle so I could take a few measurements and have reasonable surfaces to hold before being put into the 3-jaw and set so the three "rings" ran as true as possible. I then took a couple of light passes across the end to clean remove the draft angle and leave a clean surface. While in the chuck I also just cleaned up the middle ring to give me something to clock true and also run a steady on if I felt the need for one.
I've seen a lot of people use the 4-jaw and a steady to do the boring of the cylinder but I opted to clamp the freshly machined end to the faceplate, tapping the casting until the central ring ran true. The end was cleaned up both on the face and OD and then I used a 16mm boring bar with CCGT insert to bore to the required 33mm.
I did not do any more work on the cylinder but left it fixed to the faceplate while I made a start on the hopper. Again after a bit of a fettle and some measuring up I hot glued a couple of pieces of scrap aluminium to each end and marked out the centre of the bosses. The casting was then packed up and clamped to the lathe's cross slide and the position adjusted so the marks lined up with head and tailstock ctrs. I find this type of setup preferable to having an unbalanced lump in the 4-jaw and the between ctrs boring bar that will be used doe snot flex as much as a toolpost mounted one can do so you get a straighter bore. Not the ideal clamp positions but it was solid enough.
Initial cuts to enlarge the cored hole were done with a boring head. Then I switched a 28mm between ctrs bar, well actually between chuck and tailstock bar to take the hopper ends out to the required 54mm dia. Once this had been done I changed to a tool with it's cutting edge at 90deg to the bar's axis to face off the boss that will face towards the crank.
Now that I had a known bore I used the hopper as a gauge to get the final size of the cylinder, seems about right as it stays horizontal without swinging down but can be pushed on by hand.
I'll leave bonding the two together until a bit more work has been done.
Quick video of some of the operations described above.
http://www.youtube.com/watch?v=5wC7_IauokM
Amblejo1:
To see Jason's machining skills is truly inspiring, and such good news to hear that Alyn Foundry is back with us in the capable hands of "and Sons" who have already been very helpful to me regarding my 2005 vintage Gardner casting kit which I am returning to after a very busy first half of the year on our smallholding. Power to your elbows chaps :)
Jasonb:
Thanks
Before machining the main crankcase casting of the RLE it is worth getting the bearing caps ready. These are supplied as one so after a skim cut to flatten the bottom and then the ends with the now flat bottom against the vice fixed jaw the casting can be cut in two. Well actually you can cut it into three as there is plenty of length and it's quicker to saw away a waste piece than turn it into chips.
I can see how Graham made the pattern many moons ago simply by gluing a piece of half round timber moulding onto a flat piece and adding a bit of draft around the edges. This gives the profile shown top right in the following photo and if we assume the radius of the "hump" is where the green sharpie mark is then most of the material needs to come off the bottom which combined with a bit of flattening of the hump results in the section shown top left. I went a bit further and used the excess height of the hump to provide enough material to form a boss that can later be drilled and tapped for an oil pot - middle bottom. Clearance hole scan be drilled and spot faced so the caps are ready for when they are needed.
The crankcase was shimmed up on the mill table to get it to sit nice and level and not be distorted by clamping pressure and the facemill used to flatten it's bottom. Now that I had a solid surface it could be set up on the table with some parallel packing below and set to get the best centre line of the casting in line with the mill's X-axis. I started out buy locating the four hold down bolt holes so they sat reasonably central to the cast bosses noting their positions on the DRO before spot facing to give the nuts a good surface to tighten down onto.
Next the vertical face that the cylinder flange mates to was squared up, just taking off the bare minimum at the top and down low enough that the flange clears the step left by machining away the draft angle. I later blended that small step in to leave a smooth fillet where the vertical meets the horizontal as I'm fussy like that..
Moving to the other end of the casting the bearing split line was milled down to the required 41mm above the bottom of the base and the stud holes drilled and tapped M4. You can see in the photo that I'm using a spiral flute tap, I've almost gone over to these exclusively as they cut well, clean out the swarf as they go and it means you only need to tap once not two or three times as you do with the usual set of three taps.
For the following operations I like to use a machining plate as it gives good flat surfaces that you can run a DTI against when setting up the irregular shaped casting and also gives a good surface to clamp down.
Here I have clocked the long edge of my well used machining plate true along the mill's X-axis, located that edge and established my ctr line a known distance from it (50mm in this case) and then using the previously noted DRO positions drilled and tapped so the casting can be screwed to the plate. The bearing caps were then screwed into place ready for boring.
Knowing the exact lathe ctr height above my cross slide and the thickness of the plate it was simple to work out how much packing was needed to bring the bearing split line upto ctr height, clock the edge of the plate true across the lathe and then start machining. First I used a 16mm 4-flute cutter to produce a flat edge by machining away the draft on the base and stopping just as the cutter touched the bearing cap. I followed up with a 6mm ctr cutting 3-flute cutter to remove the pip left by the conventional non ctr cutting endmill.
This flat surface could then be spot drilled followed by a 6mm stub drill and then the far end was done with long series ctr and 6mm drills. Following that a spot facer I had made for a previous engine was used to flatten the remaining three faces.
I could then drill out 10mm followed by reaming size for 12mm. If you want to take the option of having the crankshaft run in the cast iron then just drill to 9.7mm and then ream 10mm
A machine reamer was used to finish the holes to 12mm ready to accept the bearings.
That's enough for one night, next time the crankcase can be completed and these three main castings brought together. In the meantime a quick vid of the drilling and boring on the lathe and no the reamer is not going backwards!
http://www.youtube.com/watch?v=JIiLPLkGVEU
Jasonb:
While the crankcase was still mounted to the machining plate I clocked it vertical on the mill, located ctr and cylinder height and then off set each side to drill and tap for the two studs to hold the cylinder in place
Once I knew the ctr to ctr distance of these holes I did the clearance ones in the cylinder's flange. When it was in the lathe I had scribed a horizontal line at mid point across the flange. Here I have clamped a parallel to that scribed line and clocked it true along the X-axis, located ctr of bore and then offset each side to drill the holes
While held like this I used a smaller homemade reverse spot facing tool to machine a nice surface for the nuts to sit on.
Using the heads of a couple of cap head screws poked into the holes and resting them on a parallel the cylinder could be clamped horizontal to an angle plate to flatten the area around the lubricator hole which was also drilled and tapped.
Next was to bond the hopper onto the cylinder, I opted for high temp Loctite 648 on the cylindrical surfaces and a small amount of JB Weld on the radial step towards the crank end of the hopper. To make sure the hopper was sitting upright I mounted the crankcase to the base and the cylinder to the case, a couple of stops in a tee slot set the base true along the X-axis and then an edge finder between the two bearing caps set the engines ctr line in Y. You may just be able to see at the top edge of the image towards the right hand side a pointer in the mill spindle, this was lined up with the central parting line of the hopper so all was centred up and left to set.
After a couple of days the hopper and cylinder were machined to final length at the head end, quite happy with the joint which can barely be seen.
Jasonb:
I suppose the cylinder head is the next logical casting to get out the way. After a quick clean up I made a start by holding it in the 4-jaw slipping a parallel under each of the stud bosses in turn to make sure the outer cast surface was reasonably true across the lathe's axis and than machined the underside of the head so I had a good flat surface to work with. I also took the smallest of cuts off the OD to get the head round but not far enough up the sides to remove the draft angle.
Next the head was clamped to the mill table on a piece of MDF, I held a straight edge against the two valve bosses and eyed that up along the X-axis so the valves would sit horizontally. Then the three ends of the "Tee" where milled flat, the inlet and exhaust ones just want the minimum taking off so you get as much thread depth as possible for the pipes but the one for the rocker bracket should be machined to dimension. The clamps will need moving about to allow access to all three faces. The tops of the valve bosses can also be leveled off at this stage.
The bosses for the four head studs are not equally spaced around the head so I spend a bit of time getting the best centre for each boss and noting the DRO readings before spot facing and drilling 4mm. Ignore the fact they are tapped in the photo, I was going to hold the head one way for the next op but did it another.
I like to do the valve guide, valve cavity and valve seat on the lathe rather than use a CSK bit in the mill which can chatter and I've not yet had to make a valve seat cutting tool for any of my engines doing the seats with the topslide set over. So I made some simple standoffs from tube and screwed the head to a scrap piece of square aluminium plate which could then be held in the 4-jaw to position each valve hole in turn.
The square piece of plate also made it easy to index the head around to drill and tap the inlet and exhaust connections. The M3 tapped hole for the rocker could also be done at this stage though I did mine later as I wanted to tweak the rocker post casting to suit having the exhaust valve on the far side
Still holding you the plate the spark plug hole was drilled, spot faced and then tapped M10 x 1 for a CM-6 plug
When I did get round to doing the holes for the rocker post this is how I set it up to do the tapped hole using two drill bit sin the valve holes to set the work vertical and then using the side of a drill bit to run the edge finder against.
The two drill bits were used again for the 3mm clearance hole being pressed against a table tee slot to line up the head and run the edge finder against then the hole was drilled and the opposite side countersunk.
lastly the carefully noted stud hole positions can be used to locate the holes in the cylinder so they can be drilled and tapped making sure not to go too deep and break into the water space. You could spot the positions from the head but I seldom use that method since fitting the DRO.
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