enginehistory.org

[dpennings]

The center of the tool is not involved in the milling, the surrounding is cast geometry and only the washer area is mashined. I doubt that a countersink tool will give a better surface quality with its single cutter an week support.

Today, a spherical cutter with a slightly smaller diameter than the mashined surface would do the job better, but therefor a comlex motion is needed, almost unpossible back than.

[rwahlgren]

[avasko]

Crankcases, steel or aluminum (WAD vs P&W) didn't seem to fail. However, a mechanics view of the differences may be biased.
As mentioned, WAD steel crankcases used cap bolts on special conical washers to retain cylinders. P&W with their aluminums cases used studs and nuts with washers. Both methods worked well to my experience so far as holding the jugs in place.

It was in changing a cylinder there was a difference. I am here talking about the late model big ones, not a Kinner, much beloved in A&P mechanic schools for its huge space between cylinders.

The R-2800 and the R-3350 were tightly baffled and these needed to be removed. Replacement later was interesting as you tried to figure out how the pieces fit together. There were the intake and exhaust pipes to remove. No difference here between WAD and Pratt.

The nuts fitted to Pratt studs were self locking nuts. Once torqued, they stayed there, no further work required. A special offset extension wrench was use. Slip down between the cylinders, seat, lay on some force with a breaker bar and work it down the stud, turn by turn. Torque all nuts, then recheck.

WAD's cap bolts are not self-locking. Also, sounds minor, but a jug slipped down over studs is aligned. Try getting your hands down in the gap holding bolt and conical washer and rotate cylinder slightly L & R trying to find the hole. Then they are safety wired in place although a late innovation mentioned later was used. It was interesting and shaved some skin to reach down between the jugs holding a pair of ?dikes? (cutting pliers) to snip the stainless lock wire.

The conical washers mentioned in posts above have to be installed with the conical side down to nest in the jugs recessed holes. They were then torqued and rechecked and safetied. This was done with 0.032 thick stainless steel safety wire threaded through holes in the cap bolt head. It had to be placed in the ?tightening? direction and then the two wires twisted together over to the next cap bolt with a final twist-off. Later, WAD came out with a soft aluminum plate with three round holes in it. This was placed over the cap bolts and a special tool was forced down over the plate. It was pressed down and the round holes in the plate deformed to the hex shape of the bolt head. This locked the bolts. Bit hard to get off though but beat trying to snip safety wire in a tight place.

I have run on here but from this mechanics view, aluminum cases with studs beat steel cases with cap bolts.

[avasko]

Crankcases, steel or aluminum (WAD vs P&W) didn't seem to fail. However, a mechanics view of the differences may be biased.
As mentioned, WAD steel crankcases used cap bolts on special conical washers to retain cylinders. P&W with their aluminums cases used studs and nuts with washers. Both methods worked well to my experience so far as holding the jugs in place.

It was in changing a cylinder there was a difference. I am here talking about the late model big ones, not a Kinner, much beloved in A&P mechanic schools for its huge space between cylinders.

The R-2800 and the R-3350 were tightly baffled and these needed to be removed. Replacement later was interesting as you tried to figure out how the pieces fit together. There were the intake and exhaust pipes to remove. No difference here between WAD and Pratt.

The nuts fitted to Pratt studs were self locking nuts. Once torqued, they stayed there, no further work required. A special offset extension wrench was use. Slip down between the cylinders, seat, lay on some force with a breaker bar and work it down the stud, turn by turn. Torque all nuts, then recheck.

WAD's cap bolts are not self-locking. Also, sounds minor, but a jug slipped down over studs is aligned. Try getting your hands down in the gap holding bolt and conical washer and rotate cylinder slightly L & R trying to find the hole. Then they are safety wired in place although a late innovation mentioned later was used. It was interesting and shaved some skin to reach down between the jugs holding a pair of ?dikes? (cutting pliers) to snip the stainless lock wire.

The conical washers mentioned in posts above have to be installed with the conical side down to nest in the jugs recessed holes. They were then torqued and rechecked and safetied. This was done with 0.032 thick stainless steel safety wire threaded through holes in the cap bolt head. It had to be placed in the ?tightening? direction and then the two wires twisted together over to the next cap bolt with a final twist-off. Later, WAD came out with a soft aluminum plate with three round holes in it. This was placed over the cap bolts and a special tool was forced down over the plate. It was pressed down and the round holes in the plate deformed to the hex shape of the bolt head. This locked the bolts. Bit hard to get off though but beat trying to snip safety wire in a tight place.

I have run on here but from this mechanics view, aluminum cases with studs beat steel cases with cap bolts.