Today I have finished machining the piston. It has been a long process which started on the lathe and has finished on the milling machine.The difficulty of manufacturing this component lies on the amount of features and accuracy required.
In terms of design it is a complex exercise, especially as boundary conditions are unknown at this stage. I have based the loads for a max. of 14000 RPM for inertial loads, pressure cycle is based on a conventional 4 ST IC engine, but adjusted to the IT3 engine. The piston is subject to 3000 g at 14000 rpm
All in all, the loads the piston see are 820N in compression and 391N in tension (that is 83,6 Kg, 39,9 Kg). This is quite extreme and is mainly due to inertial loads and pressure gradients from the combustion cycle. Temperature wise I have estimated 250C, which reduces the material strength. The diameter has been reduced to account for expansion of the piston with temperature.
The piston pin has a slight tight fit on the piston and H6 on con rod. The piston pin is secured by two elastic clips that sit on a groove. The groove is machined with a custom made tool, as shown in the next pictures. The initial development of the piston will focus understanding better the boundary conditions (RPM, temperature, etc) and how the piston performance is affected (wear on friction surfaces, distortion, etc)
Above is the piston blank after turning operations (right) and milling fixture in PA (left)
This is the piston during machining on the 3 jaw chuck used to fix it.
Above is the custom made cutter to machine the piston pin clip groves.
Piston and con rod assembled. As you can see there are neither piston rings nor piston pin clips. The con rod bolts are not final ones either. Piston rings are off the shelf from Honda. there will only be 2 compression rings, and no lubrication ring.
You give readers a lot to think about and I appreciate that kind of writing.maint-time
ReplyDelete