Pitts 40.
06-05-2008, 01:52 PM
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Join Date: Nov 2005
Location: Poolesville, MD
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RE: Pitts 40.
Using a ruler mark the vertical and horizontal center points lines.
This will be where the engine camshaft at the tip ( by the prop washer ) should be aligned to.
Now mount the engine on the engine mount temporarily ( I use clamps ) at the correct distance. I put both of the mount "arms" pointing up on a table, and then clamp the engine to the arms at the correct height. BE SURE that the engine is perfectly "square" with the base ( table top ) and sides ( arms )... use a "T" square to get things right. Adjust the engine position until it is perfect.
( at this point you also want to make your engine bolt marks so you can drill these out later ).
Hold the fuselage with the nose pointed straight up. I clamp mine to a table to make it immobile.
Put the engine on the firewall, and center the shaft with your marks. Sight down from "above".
Because of built in right thrust you'll note that the base of the engine will be ofset about 1/4" or less from the marks you made while the camshaft is centered.
Use a Great Planes Center Hole finder to mark the positions for the blind nuts, using the engine mount holes as a guide.
Even if things are not PERFECT most engine mounts have ovoid holes permiting some final adjustments.
Drill out your holes using increasing sized bits, to avoid fracturing the wood. PRESS LIGHTLY as you drill, let the drill do the work.
Test fit the blind nuts to see if the hole is of the right side. If so remove the blind nuts and apply thin CA to harden the holes and surrounding area. Let dry.
Install the blind nuts and "pull" them into the wood using a washer ( sometimes I also add a few nuts ) and a cap screw of the appropriate size. Be sure that the blind nut is almost flush with the wood and it's teeth have dug in.
Affix your engine mount and engine then do the "cardboard" trick to determine where cowling holes and openings will be required.
Have fun.
This will be where the engine camshaft at the tip ( by the prop washer ) should be aligned to.
Now mount the engine on the engine mount temporarily ( I use clamps ) at the correct distance. I put both of the mount "arms" pointing up on a table, and then clamp the engine to the arms at the correct height. BE SURE that the engine is perfectly "square" with the base ( table top ) and sides ( arms )... use a "T" square to get things right. Adjust the engine position until it is perfect.
( at this point you also want to make your engine bolt marks so you can drill these out later ).
Hold the fuselage with the nose pointed straight up. I clamp mine to a table to make it immobile.
Put the engine on the firewall, and center the shaft with your marks. Sight down from "above".
Because of built in right thrust you'll note that the base of the engine will be ofset about 1/4" or less from the marks you made while the camshaft is centered.
Use a Great Planes Center Hole finder to mark the positions for the blind nuts, using the engine mount holes as a guide.
Even if things are not PERFECT most engine mounts have ovoid holes permiting some final adjustments.
Drill out your holes using increasing sized bits, to avoid fracturing the wood. PRESS LIGHTLY as you drill, let the drill do the work.
Test fit the blind nuts to see if the hole is of the right side. If so remove the blind nuts and apply thin CA to harden the holes and surrounding area. Let dry.
Install the blind nuts and "pull" them into the wood using a washer ( sometimes I also add a few nuts ) and a cap screw of the appropriate size. Be sure that the blind nut is almost flush with the wood and it's teeth have dug in.
Affix your engine mount and engine then do the "cardboard" trick to determine where cowling holes and openings will be required.
Have fun.
