Cylinder heads

Profiling a head from round bar which has 11, 3mm  holes peck drilled by cnc each 30 mm deep.Four of these holes are for transferring coolant from the cylinders water jacket to the head. The other 7 holes are for the head studs.

This shows the reason I have not progressed as I could have. This image is the engine on the table of  a modified Aboga drill which has been a distraction since the 15th November .All the axis are on linear slides giving a working area of approximately 300mm by 400mm.

 The mill has been put aside for now to concentrate on the engine. The heads have the ports machined.

The head studs are made from stainless steel.The inlet  and exhaust ports are separate pieces brazed on .

This shows the water space pocket on top of the head.The raised part with the two holes is where the valve guides will be inserted.Note that the cover plate on the next cylinder is level to the top of the protrusion .

Movies of Caterpillar in action

We took the caterpillar out and used a electric drill to drive it from the live power take-off. Most of the noise is the drill.

Engine cylinders

Boring the engine block to fit the cylinders with a head made using a spindle from a scrapped Nichols mill. It is driven by a 4 pole 550 watt motor by V belt at about 400 rpm.

The engine is approximately in it's position.The cylinders , water inlet manifold and side plates are fitted. The heads are next to be made. These are fitted with 7 studs.

I have made the cylinders with wet sleeves which are sealed at the bottom with an o ring and flanged at the top .I believe the full size have the water jacket cored into the casting. I have made these from nickel chrome moly thick walled tube .You may think that my progress has been slow but turning the cylinders from solid  65 mm 4140 steel bar on my Hercus lathe with just 1 HP was very tedious. It also produced a huge quantity of swarf .Water enters the bottom  of the water jacket of the cylinders and into the heads.



This shows the sump which has a row of studs around the outside to make it easy to access the big-end bolts on the connecting rods. On the prototype the big-end bolts were accessed through the side plates but this is not practical on this model.




 360 of engine block.
 

Engine block

This is the rear plate of the engine set up to fit a 6000 roller bearing.The camshaft will have three 6000 roller bearings. The large hole will take a 65mm OD by 50 mm bore roller bearing on the crankshaft.










This image is of my home made centering microscope being used to set up the front of the engine to fit a 6202 roller bearing. .This bearing is fitted to a step in the bore and will be captive on the crankshaft by the timing gear.This bearing will control the end float of the crankshaft.








All the components were assembled with 4 mm scews ready for brazing, Note the center web which is to be bored for the camshaft ball race.

Note the top has been bored for the cylinders and the  holes for fixing.The valve guide holes are also drilled.Note also the relieved pattern on this side of the block

The block has been brazed in this image and is clamped to the mill table through the cylinder holes for facing the bottom.There will be a bolt on sump on the model.









Facing the top of the block.







   

   
Line boring the center camshaft  bearing.This apperture is bored oversize.The boring bar runs in brass bushings in the ends of the block with one end in the chuck the other end on a live center. The block is not clamped but free to float but is resticted to rotate by the parallel on the cross slide.The roller bearing is fitted in a sleeve.

Aproximate position of the engine in the model.

Engine Timing Case

Progress this past month ceased due to computer and hardware problems .I now have the system running on Windows  7 via a Smooth Stepper, which is availiable from Peter Homann Designs. This hardware allows the system to run from the USB .The new  computer has a parallel port which runs the Rutex drivers but would not drive the Gecko 540 .Modern PC computers  can be fitted with a parallel port .A plug in board is availiable for about $14 but is not suitable to run CNC drivers. The smooth stepper is powered from the USB but can easily be powered from a 5volt regulated supply. This should make it possible to run CNC machines from a laptop. The smooth stepper's output is two parallel ports. The stepper motors run very much quieter with this system.
  The intermittent problems with the y axis on both my CNC mills have been located and rectified.The plug on the servo driver board had a loose connection and one of the wires to the stepper motor had been sheared by the grub screw.In both cases these caused catastrophic destruction of the job and tool breakage
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This image shows the tool path for the back plate of the engines timing case.These apertures are the position of the crankshaft at the bottom , the fan drive directly above,the camshaft to the left and above and the magneto drive on top.The prototype has 38 teeth on the crank 76 on the camshaft,38 on the magneto drive and 18 on the fan which is driven off the camshaft gear. The design of the model engine had to be based  on the crakshaft being in line with the input shaft of the gearbox and the fan to be in the center of the radiator.To achieve these position I have chosen 1 module gearing ,30 , 60 , 30 and 14 teeth.
Now that these shaft positions have been set the engine can  be designed.The timing case has now been fabricated as in image below.The cylindrical housing is the cover for the governor, the other protrusion is the fan shaft bearing. The tube at the top is the breather for the engine which is also where the engine is filled with oil.The cover was brazed using manganese bronze filler wire which simulates the fillets of a casting.Shot blasting will further make the cover look as if it were a cast.
                                                                              
                                                                                 

Main Clutch

This is the clutch complete with the throw out fork with its linkage to the clutch lever. This clutch follows the prototype designs toggle action but I have made the clutch plate with four lug to fit into four keyways in the flywheel . In full size the plate is driven by reinforced rubber straps. The full size flywheel is relatively narrow and light weight.The flywheel in the model will be 130 mm in diameter and 40 mm thick to maximise its inertia for the engine to run at 650 r.p.m.The wide flywheel is not visible under the sheet metal cover.
The assembled clutch.The internal drive spline is a commercial part shrunk into the body









The components of the clutch.
The main frame was machined from 100 mm en25 bar with a cermet tip tool . A very tedious job on a small lathe.This frame is threaded for the spider which allows for adjustment for wear of the clutch plate .Note the bronze bush which is the bearing for the clutch plate. The clutch plate was profiled from 3.2 mm gauge plate. The plate is faced with leather.To assemble the clutch the plate is fitted first, next the splined nut which is pinned to the frame ,then the drive plate( which has a matching spline) is placed
over the nut. The spider assembly is scewed on top, adjusted to give appropriate pressure and clamped.
This image shows the spider which was first threaded in the lathe so that it could be mounted on the frame for machining. It has four slots for the cams .In one of the slots there is slit to the thread. A bolt across this slit clamps the spider



This is one half of the actuating trunion.

Radiator

The core attached to the top and bottom tanks. These tanks have been fabricated from brass and copper using silver solder. The caterpillar emblem has been engraved from a drawing traced from a photograph by David Micklethwaite who supplied me with a DXF file. Dave has a program for converting bitmap files to vector files. These tanks are joined by square headed bolts yet to be made.







The core under construction. The tube plates where jig drilled by CNC. The tubes are 3/16 thin wall copper salvaged from a Caterpillar tractors oil cooler. There are 100 tubes 5 rows of 20 soft soldered to the tube plates.






The radiator side frames where made from brass angle and flats silver soldered








This image shows the sixty logo being engraved. On this model these engraved signs are soft soldered in the frames .








This photo shows trial machining of the logo using a 1mm four flute end mill running at 12,000 rpm at a feed rate of 100mm per minute. The method was to pocket the sign and later profile each letter with different offsets to adjust their thickness. The final logo was inserted into a pocket machined in the top tank. This machine is an old BCA mill I converted to CNC using a Gecko 540 stepper driver. The Z axis is new with high precision NTN angular contact bearings. The original head with plain bearings was scrapped.