Single Cylinder 4-stroke machined from bar stock - Westbury's Kiwi Mk II

[Vietti]

Forgot to say when machining the valve head, it is center drilled and a center used to steady the work.

 

[Eccentric]

Thanks everybody. It took me four tries before I had an acceptable valve, but then I made one this morning and it turned out better than the first. Using the advice given here I did several things different. First, I turned it with the top of the valve toward the headstock in the lathe. I center drilled the end and used a live center to steady the work.

I turned the section of the valve head, .375” in my case, to size, then began turning the stem down toward .125”. I started with larger cuts, .015” off at a time and as I got smaller, I move to .010” cuts, then down to .005”. I used a live center on the stem end of the valve and noticed that the OD near the headstock was smaller than toward the live center. I assume this is due to some side play in the live center. So, as I got close to final dimension, about .030” away, I switched to a dead center and this helped a little but did not totally eliminate the OD difference between the two ends of the stem. I also used a carbide cutter for the majority of the material removal, but then switched to a rounded HSS cutter as I got close to final dimension. This gave me a much nicer finish. I turned down to about .006” over and switched to emery cloth – 320 grit to start with. This removed material and gave a nice finish, but was taking too long. So, I went back to the round nose HSS cutter and took the stem down to .003” over. I also worked from the tail stock toward the head stock turning just enough for me to get the micrometer in there to measure the OD. As I worked my way toward the headstock I had to move the cross slide out a thou at a time to maintain the constant stem OD. I marked the stem up with a sharpie and used a fine file to knock down a couple of high spots that formed from the different cutter depths. I went back to the 320 emery paper and took the OD to just under .001” over, then switched to 600 and finally 1000 to get a really nice shine. Then I used the round nosed HSS cutter to cut the radius between the stem and the valve top. I then rotated the cross slide to 45 degrees, locked it into place and cut the 45 degree angle where the valve seats into the valve seat/guide. Finally, I used a cut off tool to cut the groove for the retaining clip and started to cut the valve at the thick end, but not all the way through. I used a Dremel cut off wheel to separate the valve from the extra material. Ground the stem to length, then put the stem in the lathe and faced off the top of the valve to size. The valve guide was much easier as it is simpler and the Bronze cuts really nice.

 

[Eccentric]

I have been working on a few odds and ends. I turned the fly wheel and mounted it, but did not put a pulley on the front. I am now thinking I will machine a pulley as I would like to use the engine to do some work, don’t know what yet, at least a generator or magneto. I have returned for a second go at the rockers. I cut the shape from mild steel then mounted it on the lathe to create the side profile. I rather free handed it so the two rockers will probably look a little different, but perfectly functional(I hope).

 

[Richard Hed]

Thanks everybody. It took me four tries before I had an acceptable valve, but then I made one this morning and it turned out better than the first. Using the advice given here I did several things different. First, I turned it with the top of the valve toward the headstock in the lathe. I center drilled the end and used a live center to steady the work.

View attachment 123639

I turned the section of the valve head, .375” in my case, to size, then began turning the stem down toward .125”. I started with larger cuts, .015” off at a time and as I got smaller, I move to .010” cuts, then down to .005”. I used a live center on the stem end of the valve and noticed that the OD near the headstock was smaller than toward the live center. I assume this is due to some side play in the live center. So, as I got close to final dimension, about .030” away, I switched to a dead center and this helped a little but did not totally eliminate the OD difference between the two ends of the stem. I also used a carbide cutter for the majority of the material removal, but then switched to a rounded HSS cutter as I got close to final dimension. This gave me a much nicer finish. I turned down to about .006” over and switched to emery cloth – 320 grit to start with. This removed material and gave a nice finish, but was taking too long. So, I went back to the round nose HSS cutter and took the stem down to .003” over. I also worked from the tail stock toward the head stock turning just enough for me to get the micrometer in there to measure the OD. As I worked my way toward the headstock I had to move the cross slide out a thou at a time to maintain the constant stem OD. I marked the stem up with a sharpie and used a fine file to knock down a couple of high spots that formed from the different cutter depths. I went back to the 320 emery paper and took the OD to just under .001” over, then switched to 600 and finally 1000 to get a really nice shine. Then I used the round nosed HSS cutter to cut the radius between the stem and the valve top. I then rotated the cross slide to 45 degrees, locked it into place and cut the 45 degree angle where the valve seats into the valve seat/guide. Finally, I used a cut off tool to cut the groove for the retaining clip and started to cut the valve at the thick end, but not all the way through. I used a Dremel cut off wheel to separate the valve from the extra material. Ground the stem to length, then put the stem in the lathe and faced off the top of the valve to size. The valve guide was much easier as it is simpler and the Bronze cuts really nice.

View attachment 123640

View attachment 123641

How many of these valves do you need? It's looking good but sounds almost like a nitemare to do. Have you checkt your tailstock offset? I had a problem where I had to shim the tailstock up a thou or two once.

 

[Eccentric]

Richard,

Thanks for the suggestion. I will google "tail set offset". It would be great if my problems could be solved by an adjustment to the lathe. It is a really inexpensive, small 7" X 10" and I would not be surprised if something were off. I am thinking aloud, I could put a long piece of known round stock between centers and run a dial test indicator in the carriage and run it up and down the rod looking at the top and the side to see if the tail stock is off. Or, I could buy a nice, larger lathe

P.S. Yes, the engine only has two valves, but I am hoping to build more valves in the future. This engine building is fun, addictive and very challenging.

 

[Richard Hed]

Richard,

Thanks for the suggestion. I will google "tail set offset". It would be great if my problems could be solved by an adjustment to the lathe. It is a really inexpensive, small 7" X 10" and I would not be surprised if something were off. I am thinking aloud, I could put a long piece of known round stock between centers and run a dial test indicator in the carriage and run it up and down the rod looking at the top and the side to see if the tail stock is off. Or, I could buy a nice, larger lathe

P.S. Yes, the engine only has two valves, but I am hoping to build more valves in the future. This engine building is fun, addictive and very challenging.

Yes, the second solution is probably the better one if you have the room. I have an Enco, 9-20. It's OK for small, non critical things, but if you want precision or turn threads, it is a dud. Doesn't even turn LH threads at all. I could put an idler reverse in it somewhere, but the threads, no matter what, are rather crappy compared to the new lathe I just got in January, which is a Grizz G4003G. It does great threads, imperial and metric. Anyway, your problem.

I'm not sure if you are familiar with the procedure by your remarks. I thimpfk Joe Pi, Blondi, and others have utub vids that show the procedure for checking the alignment of your tailstock. It's not that difficult a test, but getting the thing aligned if it is out, is a bit more need of patience. First get a good rod, putting counter-sink in each end, put it between centers, then cut a swath about an inch on each end, making SURE the crossfeed settings are EXACTLY the same. Measure that and this will tell you whether or not your tailstock is offset . I really hate reading something from someone advising me of something I already know, so I hope this is not preaching to the choir. utub is full of good stuff.

 

[Eccentric]

The last couple of days I have been working on the cylinder head and its associated parts. I drilled, created the counterbore and tapped the spark plug hole. In the first picture you can see the fixture used to align the head at the required 40 degrees on the mill. I really enjoy creating the fixtures that are some times required in the course of machining. These are the unsung components that get fabricated, but are never seen by the casual observer of the finished project. There is often some stunning creativity put into fabricating fixtures.

I fabricated the rocker pillar, which has a very interesting shape. It is threaded into the cylinder head, has a 3/8” round foot tight against the head, then it tapers up at 10 degrees, and flares into a square section where the rockers are mounted. It is crowned with a semi domed top.



The eccentric rocker bushes are fabricated from bronze. They serve two purposes, first of course as the bearing for the rocker arms, but secondly, they allow the adjustment of the valve lash. They are mounted to the pillar through an offset hole that allows them to be turned and provide adjustment to the valve lash. I cut a 5/16” head to allow a tool to be used in the adjustment.

I found some commercial compression springs that would work for my valve springs, but they are $18 for ten springs. I figured I would try to make my own in the spirit of building as much as possible. I found some guitar strings for 78 cents on Amazon that are .022" in diameter. We will see how it goes.

 

[CFLBob]

I found some guitar strings for 78 cents on Amazon that are .022" in diameter. We will see how it goes.

No reason it shouldn't work.

Since I have several guitars, I always have strings around. The first time I made a spring was using a used guitar string. Last time I made some springs I changed strings on a guitar to get some used music wire.

Between having wire, some steel wool, a toaster oven and this, it's all you need:
http://www.deansphotographica.com/machining/projects/springs/springs.html

 

[olympic]

Thanks for the link, CFLBob. I found a brand new 800-foot coil of .020 music wire, still in the box, at the dump, so I am ready to spring into action.

 

[Eccentric]

Thanks for the link Bob, you know what I will be up to today. I have a new spring in my step, I succeded in making an appointments for my Covid vaccine this morning! I got up before six this morning and pinged the vaccination web site until I got in; they go quick. It reminds me of when I was a kid and online was a new thing, trying to get concert tickets before they sold out.

 

[Eccentric]

I am running out of parts to machine so I have started to work on preping for assembly. HereI am sand blasting the aluminum parts to remove the tooling marks as a result of machining. Not such a great picture of the front crankcase half in the blast cabinet, but you get the idea. I am using 80 grit glass beads.

Here are the parts after blasing. They almost look like they could be sand castings.

And Here are a few shots after assembly.

It is very difficult to get the cylinder retaining screws in, I think I am going to use studs in the crankcase and nuts to hold down the cylinder.

I have the carburetor and points in hand. I needs to make the intake and exhaust flanges that mount to the cylinder head, collect the rest of the ingition system and see if she will run.

Thanks everyone, I have learned an awful lot building my first 4-stroke IC eninge. I think I am hooked.

 

[bluejets]

It is very difficult to get the cylinder retaining screws in, I think I am going to use studs in the crankcase and nuts to hold down the cylinder.

Had a similar problem with one of mine and used studs with nuts.
Another option with yours may be to open up the clearance on the holes a little.
You have a lot more room above than I had.

Didn't think of using a 1/4" spark plug ...???
6mm bore carby...might be more suited to something smaller.

 

[mu38&Bg#]

NGK CM-6 is a 10mm plug. A 6mm carb will be plenty, the plans call for a 1/4" throat. The blasted parts look great!

 

[kuhncw]

You've built a very nice looking engine. The bead blast finish really sets it off.

What is the tube with the black cap that is part of the carb?

Chuck

 

[bluejets]

NGK CM-6 is a 10mm plug. A 6mm carb will be plenty, the plans call for a 1/4" throat. The blasted parts look great!

Well aware it's a 10mm plug.
6mm carby may well be too large which is why I brought it up.

 

[Brian Rupnow]

Eccentric---that is a lovely engine. I like the blasted finish on your aluminum parts.---Brian

 

[gilbycoath]

No reason it shouldn't work.

Since I have several guitars, I always have strings around. The first time I made a spring was using a used guitar string. Last time I made some springs I changed strings on a guitar to get some used music wire.

Between having wire, some steel wool, a toaster oven and this, it's all you need:
http://www.deansphotographica.com/machining/projects/springs/springs.html

Thanks so much to Dean Williams for an excellent article on small spring making. a subject I am interested in.
The article was well written with simple explanations and very clear photographs.
Thanks again Dean.
Ron