radialdetails2

Currently HCI is using bronze bushings in the link rod's master rod pin. The piston pins ride on the link rod material which is aluminum. The Focke Wulf's master and link rods are steel necessitating the use of bronze in both the link rod's journals. The master rod shown in this FW-190 case is the type of rod that a home machinist could easily make with a mill and rotary table. HCI's current master rod for the 7 is the scalloped design which needs CNC equipment or specialized tools to make. Although the scalloped type master rod could be made at home it would take considerable time and run a high risk of being scrapped due to a mistake. (See Pictures page for a comparison of both types)

Things may have changed, but in the old set of plans that I got from HCI the cam profile was not called out. The seven cylinder radial gets two cam rings, one for intake and one for exhaust. This allows for better performance because you don't have to have the symmetrical valve timing profile as used by HCI's five cylinder engine. With the five's single cam you can move the lifter side to side(during construction) to change timing but the duration will be the same for intake and exhaust events.

On a seven cylinder radial you can use a four lobe cam turning 1/8 engine speed or a three lobe cam turning 1/6 engine speed. The cam on the right has a much shorter apparent duration than the R-2600's cam. They actually have about the same duration. The four lobe cam has the easiest gear setup as it turns with engine rotation. The three lobe cam turns against engine rotation therefore needs the internal gear or some other means of reversing cam direction.

Although HCI's design relies on roller or ball bearings for it's shafts I was surprised to see that the FW's cam ring and reduction gears rode on bronze bushings. This method eliminates the possibilty of catastrophic failure that can happen with anti-friction bearings. It was also neat to see how they of kept the rollers straight and aligned with the cam. A simple channel was cut in the lifter retention housing. On the R-2600 they used a similar idea as well.

HCI's design uses anti-friction bearings for these all rotating shafts. Fortunately Jack has reported that the bearings used in HCI's test engines have shown little wear and play even after extended use. In other words you won't have to grit your teeth when the tach shows it's almost at overhaul time! They'll go way beyond it.

Since most of us will have our engines in a cowl instead of short pipes we'll need to make an exhaust collector. The radial experts in the days of old figured out how to make an exhaust system that could do it's job while enduring the vibration associated with a radial. The two contenders are the "slip fit" and the clamped exhaust. From what I've been told the slip fit does the best job. It is also simple to make.