A new engine for fall---

[Duffy]

Brian, as "they" said, cast iron is its own lubricant. If you added a fluid, whether for lubricant or cooling or both, there is a good chance that you will make a sort of gravy that could steal what little clearance you have and then BAD things would happen. Why not spot the slot head of your vacuum cleaner right over the cut. That way you have excellent cooling and all the chips are GONE.

[brian Rupnow]

Wendtmk---I thought about milling the flats first---But---A .093" cut off tool is "fairly" fragile to begin with. The thought of that big flat beating on the tool with every revolution makes my eyes water, Don't think I will try that one.----Brian

[brian Rupnow]

Duffy---I am going to machine it dry. If there is any sign of clogging or grabbing, I will use the vacuum cleaner trick.---Brian

[brian Rupnow]

Made a mistake. Kissed a snake. How many cooling fins did I make??--Well okay, maybe you're not into skipping rhymes!!! However, if you are paying attention, you will see that I have one more cooling fin on there than the drawing calls for. To make it even worse, the top 3 cooling fins are skinny little devils, while the bottom 3 are full size. I have absolutely no excuse for it, other than encroaching old age and gross incompetence. By the time I noticed that the first cooling fin down from the top was too skinny, I had already advanced the tool .040" into the work, and there was no good way to hide it or cover it up. I'm still a bit baffled as to exactly what happened, but somewhere in there, the math let me down. At any rate, I have convinced myself that since this is a prototype, it really doesn't matter that much. The cylinder will still function just as well with one extra cooling fin. Everything seems to bolt together okay, although I did have to use a ball end hex wrench to tighten up the bolts holding the cylinder to the crankcase.---Probably would have had to do that even without the extra cooling fin. And for my next amazing stunt---I will be making the combustion chamber that mounts on top of the cylinder.---And, Oh yeah---I machined the cylinder dry, and there was absolutely no binding, galling, or "scare the crap out of me cut off tool breaking".

[brian Rupnow]

This is the part I will build next. I will probably mess with the cooling fin spacing a bit so it matches my miss-machined cylinder cooling fins.

[Cuttings]

Brian - I have an explanation for you. An Engine generates most of it's heat near the top of the cylinder.
So the thinner cooling fins near the top of the cylinder will radiate the heat away quicker, thus keep a more even temperature over the length of the cylinder barrel.
Looks good so far. Keep up the good work.

[RichR]

Hi Brian

... I had already advanced the tool .040" into the work, and there was no good way to hide it or cover it up.

Sure there was. You could have stopped and recalculated the dimensions to make all the fins skinny. Or you could have gone a little artsy and changed to
a stepped design, for example. finish the thin fin, make the second one 0,01" thicker, make the third on 0.02" thicker, and so on until you got to the last
one at full thickness.

[brian Rupnow]

I like Cuttings explanation. A wild tale with a little logic thrown in is very hard to discount.---Brian

[brian Rupnow]

I don't post a lot of "in process" shots anymore, but tonight I thought I would put up a shot of the beginning of the aluminum combustion chamber. I have marked out the outer profile, bored the 1" through hole, and the 1.160" diameter counterbore. You can see the cylinder setting on the end of the work. When I bore holes to a critical fit, I do a lot of "try it and see if it fits yet" with the mating pieces. After a summer of engineering work avoidance, some of my customers are calling me up and asking to have their projects worked on "Right Now", and if I ignore these folks they find someone else and I never hear from them again. Between the engineering work and work fixing up the house I bought, I am sometimes hard pressed to find a bit of time to machine my own stuff.

[brian Rupnow]

I still have some fin cutting and finessing to do, but this is getting quite exciting!!! I have to buy some material to make a fixture to mount this combustion chamber in the 3 jaw chuck on my rotary table to let me cut the cooling slot that runs around the perimeter. There is a lot of work in this part, but I am pleased with how it is turning out.

[brian Rupnow]

For those of you who wondered about the fixture I would make to cut the groove in the combustion chamber and to round the curved side of it, here is how I am going to do it. I found a suitable piece of 2" round aluminum and bored it for a hard press fit of a 3/4" crs shaft. I then set it up in the lath and turned a spigot on the face to be a precision fit into the 1" bore side of the combustion chamber. I then drilled and tapped five #5-40 holes in it and bolted the combustion chamber to it, using bolt holes which were already in the combustion chamber. The third picture shows it set up in my milling machine with a 0.093" slitting saw mounted in the spindle arbor. In order to take a quick picture, I put the slitting saw arbor in my 3 jaw chuck. In reality, it will be mounted in a collet held in the mill spindle by the drawbar.

[brian Rupnow]

I get a great sense of accomplishment (and sometimes astonishment) when everything actually bolts together, and all of those random lumps of steel and aluminum begin to look like an engine. Today I have reached that point. The combustion chamber turned out great, and my experience with the .093 slitting saw was a success. The two yellow pencils indicate where the valves and tappets are going to be.Although there are many different directions I could jump in right now, I am anxious to see what the "overall" engine is going to look like, so I think I will machine the cylinder head next.

[brian Rupnow]

This will be my weekend chore----

[brian Rupnow]

Now I know what I DON'T want to be when I grow up!!!---A cooling fin slot cutter!! The .093" slitting saw works amazingly well, but at 0.100" depth of cut, thats 4 passes per fin-slot x 11 slots = One heck of a lot of cranking on a manual mill. The sparkplug is a 1/4"-32 Rimfire plug from Roy Sholl. I didn't get too crazy finishing the bit of combustion chamber inside the head. It will work just as well the way I have it as it would polished.--In fact, it might work even better. I am really pleased with the way the engine is looking.---Brian

[Jon Heron]

Beautiful!
Cheers,
Jon