Rockerblock I.C.--Something a little different-

[Brian Rupnow]

I can see some excitement with machining this cylinder head. It is too long to hold in my four jaw chuck, so I have determined that it will be a faceplate job. First set-up on the faceplate will be to machine the side which faces away from the cylinder, and has a raised boss on it. Then after that side is machined, I will machine an aluminum plug which is a "precision fit" into the center hole of the faceplate and has a hole in it for a "precision fit" of the raised boss. Then I will flip the part over, locate the raised boss in the hole in the aluminum plug, and machine the recess in the side which faces the cylinder.

[Brian Rupnow]

This is the "starting point" on the cylinder head. Most of the unwanted metal has been bandsawed away from a piece of 1 1/4" thick aluminum bar. the portion with the blue layout dye on it will become the raised boss.

[Brian Rupnow]

I was mistooken!!! Before I absolutely committed to a faceplate job, I had to try it in my four jaw. What do you know----it fit, barely. One jaw is out to the point where there are only two turns of the chuck key holding it, but it cleared the ways by about half an inch and tightened up just fine. After turning the spindle by hand, checking for clearances, I started the lathe on it's lowest speed (which is very slow indeed) and seeing that nothing was going to explode in my face, I ramped the speed up to 220 rpm and cut with an HSS tool. Everything seems to have went okay, and I'm finished with that set-up.

[Flyboy Jim]

I was mistooken!!! Before I absolutely committed to a faceplate job, I had to try it in my four jaw. What do you know----it fit, barely. One jaw is out to the point where there are only two turns of the chuck key holding it, but it cleared the ways by about half an inch and tightened up just fine. After turning the spindle by hand, checking for clearances, I started the lathe on it's lowest speed (which is very slow indeed) and seeing that nothing was going to explode in my face, I ramped the speed up to 220 rpm and cut with an HSS tool. Everything seems to have

Brian........it's going to be interesting to see this part evolve. I'm curious.........with the kind of clearance you have.......would it be possible to use a larger diameter chuck on your lathe? Not taking into consideration the cost.

Jim

[Brian Rupnow]

Jim--I could probably run a larger chuck, but it is very unusual for me to be turning a part as large as this. And really, what this tells me is that I could grip an 8 3/8" diameter  disc in the reverse chuck jaws. I never make parts that large.---Brian

[Brian Rupnow]

The cylinder head isn't completely finished, but it's about at 95%. Everything fits and follows the plan, so far. It is a cool, rainy, nasty day here, good time to be inside. Good wife is out in my garage rooting around thru a ton of stuff she has collected for a Parkinsons benefit yard-sale. I've machined enough today. Time to wash up and go read a good book.

[Roger B]

"I've machined enough today. Time to wash up and go read a good book."   

[Brian Rupnow]

As you can see from the pictures, I haven't put the large hole in the cylinder head plate like I show in this solid model. My initial theory was that I needed a hole that big so I could reach thru to the set screws to set the cams in their proper location. I normally set the cams by turning the engine over to the correct point in the cycle with the cam gear locked to the shaft, then turn only the cam until I feel it contact the valve, then tighten the set screw. The only problem with this is that such a large hole will weaken the structural support necessary to keep the cylinder in the right location. The alternative to this is to set both cams in the correct rotational aspect to each other, leave the cam gear loose on the shaft, turn the shaft and cams to the correct position and then lock the gear to the shaft. I'm going to leave that one to "cook" for a while and in the meantime finish the cylinder, piston, and primary con-rod. By that time I will have decided what to do.

[Brian Rupnow]

Todays project (If I don't get called away to work) is the cylinder. It's worth posting a drawing, simply because it looks so strange after all the finned cylinders I have built lately. I don't remember, but I think this stuff machines fairly good. I will let you know.---Brian

[Brian Rupnow]

Okay--the 316 stainless machines very nice, nicer than 1018 or 1045 steel. I'm running at 400 rpm with a .015" doc. using a brazed carbide, no cutting oil. The only issue I'm seeing so far is the fact that my brazed carbide has no chip-breaker built into it, so I'm getting some incredible "birds nests" which I clear with a pair of pliers after each pass. I'm not going to turn anymore off the o.d. until I get the bore drilled and reamed to size, then I will finish up the o.d. to finished size. I hope my hss drills have as little trouble as my brazed carbide has seen.

[Zephyrin]

Great thread as usual, thanks to share...
Nice to see so many of your engine in one go on the shelves, lot of well done work, impressive.

[Brian Rupnow]

Well, if that isn't the prettiest cylinder I've ever seen, it runs a close second. No issues at all machining the 316 s.s. with carbide on the outer diameter and drilling/reaming the inner diameter with my HSS twist drills and reamer. I still have a bunch of threads and counterbores to put into the flange, but the cylinder is close to being finished. I just have it propped up in the current position to take the picture.---Brian

[Brian Rupnow]

Ta-Da!! We have a finished cylinder. Today was the only time I have noticed any difference machining the 316 s.s. My #6-32 tap definitely did not like tapping the four holes that hold the cylinder to the cylinder head.--Then again, it could be that my tap is just dull and needs to be replaced. The cylinder fits where it is supposed to go and all the bolts line up the way I had hoped. I guess my next moves will be a piston and the primary connecting rod. Jeez, I was afraid that tap was going to break off in one of the holes and ruin the piece. Lots of cutting oil, breath holding and backing the tap off every half turn got me there, but I was worried.

[Art K]

Brian,
I'm sure that it was the breath holding bit that got you through. I had that experience with the rocker shaft on Val. I decided I wanted to tap and shim for the end play on the drill rod rather than use c-clips, and 0-80 was the right size. Note to self always use a center on a small tap. The second one was the good one. The first would be if I could get the broken tap EDM'ed out.
Art

[cfellows]

Tapping a piece that already has a lot of work done is a knuckle-biting experience.  I have found that since I started using a home made tapping guide that I rarely break a tap.  The tapping guide gives me a better feel for how much resistance I'm getting and, of course, the tap is never being bent from side to side.  The commercial made tapping guides, by the way, are way too big for anything under about 1/4".

Chuck