Ron's Rudy's Radial Five

[RReid]

Yeah, you have five of those holes to make now!  And five of everything else from this point forward

Five I can manage (I think), but 28 of everything as on this P&W R-4350 radial that was at an engine and equipment show I went to this morning would be a bit much for me. Four rows of 7 cylinders each. Unfortunately they weren't able to start it while we were there.

[crueby]

Wow, what an awesome engine that one is! The neighbors would just love you for starting up something like that at dawn...!

[Kim]

Wow, Ron!  I'll say!  28 cylinders!  That would be quite the challenge!

5 is the most I've ever done (this engine that  you're doing now!)  Other than that, 2 is my max.

Kim

[RReid]

With the crankcase suitably Swiss cheesed, the next step is to tap drill for 2-56 the four holes in each face for the cylinder barrel mounting screws.


That starts with turning up a drill jig, “bottom Fixture C”. This has a 0.625” boss on one side to register into the crankcase openings and a recess of the same diameter on the other side which will be used later in drilling the mounting flanges of the cylinder barrels. I drilled the center of mine for an 8-32 screw which threads into piece of scrap bar passed through the lower openings, clamping the fixture securely to the crankcase. On the first face the fixture and the crankcase were both drilled. After that the fixture is just used to guide the drilling in the other faces.


With all four holes drilled, the fixture was removed and a 2-56 tap was started in each hole before rotating the dividing head to the next face and repeating the process. It's a fairly tedious process, so I have to be careful to stop before my mind goes numb and I do something I'll regret. Two faces was enough for this afternoon, should be able to do the rest next time.

[crueby]

Nice drill jig setup!

[Kim]

Yeah, there's a lot a-drillin' and a-tappin' goin' on with that crankcase!  I broke a tap in my crankcase and struggled to get it out.  I think the Alum trick eventually did it for me. But being careful is the BEST bet here!

Slow and careful, that's the ticket!

Kim

[RReid]

Thanks, Chris!

Slow and careful, that's the ticket!

I completely agree, Kim!

Once I finished drilling the rest of the cylinder mounting holes, and getting threads started in them, I set up to work in the concave radius that separates each face. I remounted the whole assembly to an angle plate so that the work would be horizontal. The cuts were made using a 1/2” end mill and plunge cuts. The C clamp was added as insurance against the cutting forces trying to unscrew the fixture from the spindle




I'm well pleased with how it came out.

[Dave Otto]

That looks great Ron!

Dave

[crueby]

Beauty!

[Kim]

I like how you did that, Ron!  I used a ball end cutter to make those round cut-outs.  But your method is really nice!

Kim

[RReid]

Dave, Chris, and Kim – Thanks guys, your comments are much appreciated!

Once I was done fully tapping all 20 of the cylinder mounting holes in the crankcase, it was time to return to the bearing housing that I had roughed out earlier. It got mounted to the fixture along with the crankcase and I completed the cone shape to size and faced the shoulder to the correct thickness.


Then back to drilling, this time the five holes for actually mounting the bearing housing to the crankcase. Except I ran out of “Z” on the mill!


Not a problem though, I just set up to do the drilling on the lathe. Just as easy as on the mill, maybe even a little easier, since I only had to find center on one axis. The indicator is set up because the tapped holes in the crankcase are blind, and of a specified depth, and so I'd know how far to go with the clearance drill through the flange. This went very well, but it wasn't convenient to start the tapping with this set-up, so I'll do that later, probably on the drill press.

[RReid]

With the bearing housing knocked out, it was time to complete the valve chamber, which attaches to the back side of the crankcase, opposite the bearing housing. While the shape is different, with straight sides and five flats rather than the turned cone shape, the steps involved were pretty much of repeat of those shown for the bearing housing.

One slightly different bit today came when I got to the point of finishing off the the end cap, which closes off the end of the valve chamber and also includes a flange for mounting to the engine stand. Earlier I had turned the OD and the register boss, and faced that side, but the back side was still rough so it needed to be faced smooth and to thickness. Being a thin part, I knew it would be possible but awkward to remount it in the 4J chuck. Then I thought of the Teknatool 4J scroll chuck I have for my (currently mothballed) wood lathe, which happens to also have a 3/4-16 spindle nose. Turns out it was perfect for holding that part for that job.






Makin' more holes, in the end cap and valve chamber.

[Kim]

That's a pretty slick 4-jaw chuck, Ron.  Where'd you get that?
Kim

[RReid]

Hi Kim. I don't remember exactly where I bought it, I've had it for some years, but this is the chuck:
https://www.teknatool.com/products/chucks/nova-g3-wood-turning-chuck-insert-type/

The step jaws I used in my post are an accessory set, they have various different types available, as well as different inserts to adapt to different spindles. It's main advantage for me was that was suited the job at hand, and was already sitting on the shelf waiting to be useful!

[RReid]

The basic crankcase sub-assembly is now complete and and assembled, ready for the addition of the bearings that will carry the crankshaft assembly.

As Kim said:

...there's a lot a-drillin' and a-tappin' goin' on with that crankcase!

45 holes tapped 2-56, five 4-40, one 5-40, and one 10-32.