Hello again, everyone. As you might remember, last issue I told you about breaking the crankshaft for the Gade. Let me tell you, crow leaves a sour taste in my mouth, and I was really embarrassed telling Roland of my error. As I said last issue, the break was neither his fault nor the fault of the casting; it was just human error on my part.
Well, the new crank is now ready. I have cut it to the proper length and I have cut the key ways in both sides of it. I cut the key ways a little differently than called for, as a 3/32-inch end mill is small and other options are available, if you look around. I did have to get a 3/32-inch woodruff key cutter, but it was well worth the extra time spent doing it this way.
Key Way Cut
I locked the crank into place, set the key cutter in the mill head and let it take 0.015-inch cuts. Three passes 2 inches long had me where I wanted to be - 0.0469-inch deep - and the keys where nice and straight. Here again I had another question for Roland: The keys are 90 degrees from the throw rather than the usual 180 degrees - why? I spoke with Roland to see if this was correct, or if it might be because of some design flaw, and he assured me that this was how it was done at the factory, and Gade did this to all their engines. Gade must have had a reason for doing this, but neither Roland nor I know why. Was Gade the only manufacturer to cut their key ways this way?
I have now finished off the cylinder jug; it is bored to 0.8750-inch, a 7/8-inch hole, and is reamed and honed, I always drill a new bore undersized by about 1/32-inch, and then finish it with a reamer. The rear port is drilled and tapped; I changed this from the 5/16-40 thread called for to a 5/16-32 because that's what I had for a tap and I only needed to order a die. The 5/16-32 thread is the one I use most when model building or when making propane demand valves (I will cover this one day soon) because it is the thread size used on tire valve stems. I also drilled a small pilot hole for the oiler.
I have cut the jug to length and machined the face flat. I left as much material on the rear face plate as possible for mounting to the base, and as I get done with the head I will drill the top of the jug to match it. My trusty little die grinder did get some good use, as it was time consuming removing all the flash from the fins. But it was enjoyable to sit, relax and finish this part of the jug, knowing it is now ready for primer and a coat of silver paint.
I flattened the base on my table sander and then set it into the milling machine to square everything off of it; the mounting side of the cylinder jug is flat and square and I have set the proper height.
I have set the length and proper height to the middle of the bearing blocks, and have surfaced them and the bearing caps. I drilled and tapped the caps on the bearing blocks (5-40), and then locked the base into the mill and cleaned the caps to match the blocks. I also used some thin, 0.012-inch paper shim stock in the caps to help keep the drill centered. I then center drilled the cap and the block and finished drilling to fit my bearings. I split the bearings and have mounted them solid into the blocks and caps, and I drilled the caps for the little grease cups; 4-40, 14-inch size cups look just right here.
As with any new model, I ended up needing some new tools. My list was short, and finding what I needed was easy. I got a much-needed 5/16-32 die, a new 3/32-inch woodruff key cutter and I ordered a new 3/32-inch single flute mill cutter - just in case.
The next projects will include finishing off the head, the valves and the carburetor, along with the governor plate and weights. The piston and connecting rod are soon to follow. I might not use an O-ring for a piston ring because of the rear port, which might cut it as the ring passes by, but time will tell on this issue. I also have to decide what to mount the Gade on, and right now I am thinking of using some Osage Orange I have lying around. The model is coming along fine, and as with all my models it has been a fun project. Is this hobby great, or what?
This month's tip for model and scale parts source:
• Asbury Graphite Mills, Inc. of Asbury, N.J., has round graphite stock for pistons: (908) 537-2155; www.asbury.com
• Travers Tool Co. Inc. of Flushing, N.Y., has a large selection of hard to find tooling and equipment: (800) 221-0270; www.travers.com
These tips are for your thoughts only, and your fuel lines may vary.
Have a tip other model makers should know? Send it to Rusty Hopper at Gas Engine Magazine, or firstname.lastname@example.org