5 Cylinder radial (winter's project)

[Leucetius]

really beautiful!

but who wonders it's in tradition to all your previous work
-bookmarked-

 

[kvom]

Shaping that nose will be a nice challenge. :bow:

 

[Deanofid]

George, thanks for such nice (yes, properly done) assy drawings. Looking forward to another of your wonderful build threads. Thm:

 

[mu38&Bg#]

That sure will look nice. I think I saw one similar in size at this years NAMES show. I didn't get the tag in the photo so I'm not sure who it belongs to.

Greg

 

[gbritnell]

Well gentlemen it's time to start making chips. As with the other scratch build projects the first thing is to square up a block of aluminum and start on a plan of action. In this case the cavity will be bored out first and then mounted on an arbor for the remaining steps.
The block was squared up in the mill and then transferred to my 4 jaw chuck in the lathe. The usual center drill, drill and boring operations then took place.

 

[gbritnell]

With the cavity cut to size the block was turned around, indicated and the bore for the front bearing was completed.

 

[gbritnell]

With the part still mounted on the arbor it was transferred to my dividing head, indicated for center and front face and the surface cuts for the cylinder mounting faces were started.

 

[gbritnell]

The next operation was to put a pilot hole through the mounting face and continue with the surface milling. You will see from a difference from the second and third pictures where the cylinder faces come together. The long rectangular boss will be the oil sump.

 

[gbritnell]

The next steps were the drilling and reaming of the lifter bores and the boring and spotfacing for the cylinder barrels.

 

[gbritnell]

In the next 3 photos you can see the machining operations for the sump boss. This will be at the bottom of the crankcase between cylinders 3 & 4. To get the cavity formed I milled it out with a 3/16 end mill and drilled it for the 1/72 holes that will hold the cover plate on.

 

[Lakc]

Looking good. Not remembering the size of your lathe, what diameter is the crankcase?

 

[gbritnell]

The part mounted on the arbor was then moved to the mill vise, indicated square, center picked up and the 2-56 holes for the lifter guides were drilled. I haven't included some other operations which included turning down the nose diameter and drilling the holes from the cavity side of the part.

 

[gbritnell]

These final 4 pictures show the crankcase with most of the major machining finished.
gbritnell

 

[kustomkb]

Great looking crankcase George!

Thanks again for all of the detailed progress pictures.

 

[gbritnell]

Hi Jeff,
The crankcase is about 2.070 over the high points on the cylinder mounting flanges. The counter bore in the back is 1.625 diameter.
George

 

[ozzie46]

Following along breathlessly!

Up to your usual high standards George.

Ron

 

[Lakc]

Hi Jeff,
The crankcase is about 2.070 over the high points on the cylinder mounting flanges. The counter bore in the back is 1.625 diameter.
George

Wow, that's a lot more workable then the 4" crankcase of the Edwards, especially if you have priced a slice of 4" diameter 7075 lately.

 

[gbritnell]

Hi Jeff,
I use 6061 for most applications. Once in awhile I'll use 7075. The 7075 cuts a little nicer but like you I can't justify the extra cost.
George

 

[petertha]

Looking great George. Couple of dumb newbie questions.

What you call a dividing head has a chuck mounted on it. Did you make an MT or plate type adapter to mount the chuck? I was considering buying a dividing a head like this picture & was just curious. They just seem to have centers. I have an RT & made myself a simple adapter plate, I dont have the indexing plates though so it would be using the graduated vernier to index the 72 deg positions. I thought the detant holes on a dividing head might be more precice & repeatable, but OTOH the RT might serve other purposes for some of the 'in between divisions' contour milling I also have to do. (sorry, a picture will make this clearer).

In general for drilling, example your the crankcase mounting hole pattern for cylinders, do you preceed every drill hole with a center/spotting bit or just drill with the bit? I've always wondered if a bit alone would wander & add up to collective errors to worry about? Ive also seen some 5-cyl engines that use a drill guide to replicate the same pattern accross to the other cyl holes. But does that assume a transfer over to a drill press & freehand? Do you drill the same hole on each face, then rotate 72 deg & repeat etc? Or do you drill up one complete cyinder pattern & then move to the next face?

 

[xpylonracer]

Hi George,

Interested to know your approach to the old problem with radials of stroke/piston height @ TDC and timing. ? Do you intend to vary the spacing of slave rods to compensate ?

Thanks, Marcus