Hot mod how to: Install a flywheel on a Trinity/Picco .12
In the building stages of our huge Super Nitro Touring Shootout (see the Fall ’99 issue of RC Touring Cars), we discovered that crankshafts in Picco engines step up to 6mm in diameter where the flywheel is mounted (other engines’ crankshafts remain 5mm throughout). The Picco design requires some hand-machining to fit a 5mm flywheel to be properly installed in some cars, such as the OFNA Nitro OB4 we’re working on here. All you’ll need to make the required mod is a drill, a 6mm drill bit, a ruler and a roll of masking tape. STEP 1. The OB4 requires that a prop washer (included with the engine) be installed before the flywheel goes on. Be sure to use the supplied Picco brass taper cone.
STEP 2. With the washer installed, measure the length of shaft left between the washer and the threads. This measurement will tell you exactly how much the flywheel needs to be bored out to clear the step in the crankshaft
STEP 3. Wrap a piece of tape around the drill bit to act as a depth gauge; the length of drill bit below the tape should be equal to the depth of the counter-bore you will drill in the flywheel. Measure carefully! If you drill straight through the flywheel, it won’t center property on the shaft. Hold the flywheel in a vise when you drill, and be sure to hold the drill perpendicular to the flywheel. Best bet? Use a drill press. While you’re at it, strap on some safety goggles.
STEP 4. With the flywheel mounted on the engine as per the instructions, the clutch nut should tighten without any problems. Cars that do not use a prop washer may need shims behind the brass cone to space the flywheel up to the threads, or the clutch nut may need to be drilled as described above.
Copyright Air Age Publishing Sep 2000
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