More progress with IT3 engine

After a few months without doing much work, I have been putting in some hours in the last weeks at the workshop. It is nice to start seeing the parts in real live that I have been designing for some time, although it has been quite painfull in some instances. Camshafts, cranshaft and valves are all quite triky to machine for its geometry, tolerances and material of choice.

I have been doing external parts of the engine first, then internals that require turning and will finish with internals that are mainly milled. It is intersting to see the nice learinign curve from the IT1 to the IT3 at all levels: resources, cost, materials, design techniques.

Every component requires a lot more time to manufacture, and uses the equipment´s capabilities more extensibely. One noticeable example is the engine head. On IT1 it was made with 3 axis machining, with two main ops. On IT3 it has to be done with 4 axis machining, and it takes 13 ops, aproximatelly 10 times as much machining time, and 6 times as much cost in cutting tools. This is true for most of the parts and will have a big impact on final cost of the V8 engine and time required to manufacture.

On the design side of things, although it is more complex, it is more enjoyable. The better I learn how to use my equipment, the freer design becomes. On the other side, there is still a limit of resource and times available, although this will be enhanced with the use of DMLS and rapid casting techniques I am planning to use for most of the engine external and structural parts. I am considering outsourcing some components of the internals as cost would not be that high compared with the amount of time and tooling costs it would take me.

See some components that I have made so far, although not fully finished:

I have made now the 4 valves that will be used on the IT3 (2 exhaust valves and 2 inlet valves). The one on the picture below is a inlet valve. The stem has Ø3mm on its sliding surface, and Ø2 mm on the wet section. The valve head is Ø14 mm. On the image, the valve still has some material to be removed at the top. I will do that on a secondary op, as the top needs to be grinded to achive a high level of flatness and height tolerance. Material is stainless steel AISI316L for both types, and was not too hard to machine.

 Cam shafts. there are two camshafts, that operate the inlet and outlet valves separatelly. They are slighly different, as the pitch between the IN valves is different to the pitch ont he EX valves. This arrangement allows the maximum valve surface with a given cylinder diameter. The material for the cam shafts is EN24T and is quite hard to machine. At the stage shown, the cams have not been milled yet. For the IT3 engine I will mill the valves, with interpolation as the tests I have made are quite good. See the next picture below. The cam profile was calculated in Excel, then transferred in Catia using a macro, and then into Visual mill. The profile is different from EX valves to IN valves. I will post more pictures after the cams have been milled. The millign of the front flange is also missing, and it will accomodate the features to connect the timming gears. Both cam shafts, have a Ø8 mm diameter on the main shaft, and are bored to Ø6 mm, making it quite light. I will try to keep this arrangement on the V8 engine, although it will be a challenge to drill such a lenght in this steel.

Below is the sequence of pictures of the crankshaft machining. It is also made in EN24T, and is quite hard to machine. The nice thing is that it is turned using this arrangement, rather than with the chuck. This is to allow the turning of two differnet axis of the main and rod journal. I started with a billed of Ø30 mm in diameter. See the bracket on the left to spin the part that I made. 

Below is the first op finished. This is basically the turning of the main journal, which consists of different diameters, that will be used to fit the timing sproket and the fly wheel. On this engine I have not added any feature to spin the engine. I will rather use a friction wheel on against the fly wheel as it is quite a big one (for what I am used to). The main journal is Ø10mm and the rod journal is Ø12 mm.

 The next op consists of milling the material around the rod journal, rather than turning it. I just did it like that because it is much safer. See as well, that the cranshaft now is fixed on the secondary axis, ready to turn the rod journal. The next picture shows the rod journal being finished.

The next steps are to mill the camshaft to form the counterweight area, and key groves for the timming sproket and flywheel. There will not be any oil passages on this one, to simplify the component, it will use a splash type of crank case. 

Below is a picture of my workshop being busy on a late dinner time. Many more to come.