CRANKCASE

Like most of my material, this information is directed at people new to building something like this. It's my way of encouraging and saying "you can do it". Machinists and those in the know will probably get a kick out of the pictures and might even feel sorry for me because they know what a hinderance it is to work with equipment like I have. A real vertical knee mill like a Bridgeport would have saved me so many steps and so much time and aggravation. This is all I could afford but it works. As I've said elsewhere this engine is similar to HCI's radial engine but it is actually my design. I have a set of HCI's five cylinder plans which I purchased a long long time ago. At the time the "seven" was a gleam in Jack's eye so I set out on my own R&D.

I just got a DRO (digital readout) from Shooting Star. Figured it would be nice not to scrap the case because of a backlash accident or some other miscalculation. Sure, the case could be machined without a DRO but it's so much easier this way. For close tolerance work I choose to use the DRO as a double check against the dials on the mill's cranks. Surprisingly the cheap RF-30 mills leadscrews are very accurate! Maybe it's because I purchased my mill from MSC. (Better Q/C)

Since there is so little meat between case halves (you'll see) waisted studs have to be used for locating the case halves. These studs are high priority items since keeping the front half of the engine intact is important. Common sense dictates the need for quality hardware. Helicoil inserts and $120.00 worth of ARP studs keep the front case on. Three of the studs are long so the hollow dowels will have room to work. The other four studs are short without dowels. Hardened spherical washers are used under the nuts. To align the crankcase halves for final stud drilling, tapping and placement bearings were installed on a dummy crank. (case machining mandel on right) Since three of the studs were too long for the helicoil drill to reach I used a .0001 (Yes that's tenths) dial indicator to center the chuck. The three holes were reamed to 12mm so the holes were easy to center on. To me, a indicator like this is absolutely necessary. Co-ax or centering indicators will get you in the ballpark but theres no doubt when it's graduated in .0001 increments. On any machine, the simple act of locking X,Y or Z axes' will usually skew you from center causing you to readjust. It's amazing to see how ineffective .001 indicators are once you've used something like this. Everything has it's right place and time though.

Before the case could have it's cylinder and lifter bores made it needed to be hollowed out. The picture upper left is the only part of the case which hasn't been machined. Using a roughing mill as much material as possible was removed in a linear fashion using power feed. (It sure beats cranking the rotary table) The problem; finding a way to mount the machined side of case to the rotary table while allowing for easy adjustment.

A comical long shot was tried. I made a 1-1/2 -8 threaded adaptor so that my 4 jaw lathe chuck (or any chuck) could be mounted to the table. The 4 jaw chuck allowed me to easily center the case to the table's axis and kept the nicely machined surfaces from being marred. The setup was surprisingly rigid despite the long overhang. Naturally light cuts were made and alignment was rechecked often. A 1" ball nose end mill made some of the final cuts.

Since the work table of the RF-30 mill is not exactly huge I had to modify my rotary table so it could be mounted. Both the table and it's tailstock were at the furthest limits of the table. It's a cheapie Phase II rotary so my feelings weren't hurt when the half inch slots were made in it's base. (See right)