Open Column Twin

[cfellows]

I thought I'd move this thread over here where probably ought to be.

Done with the major machining of the heads and have them bolted on to the cylinders now.

This is the view from the spark plug and intake manifold side:

Here you can see where the intake and exhaust valve guides will fit. You can also see the 3, recessed socket head cap screws that hold each head on:

This view is taken from the push rode side and shows the exhaust ports:

 

[wareagle]

This one is looking great. Keep the pictures coming!

 

[deere_x475guy]

Cfellows this sure is a nice looking engine. Is this one you designed? It looks like the crank was machined instead of built up. Do you build most of your cranks this way? Nice job and keep the pictures coming.

 

[cfellows]

Cfellows this sure is a nice looking engine. Is this one you designed? It looks like the crank was machined instead of built up. Do you build most of your cranks this way? Nice job and keep the pictures coming.

My engine is based on a 6 cylinder model designed and built by Randall Cox. He has displayed his engine at several of the most recent GEARS shows in Portland. I saw it when I was there in 2006. Plans for the 6 cylinder model are also featured in one of the first issues of Model Engine Builder, which the following picture is scanned from. Everything on my engine is pretty close to Randall's design except I machined the crankshaft from solid and I reversed one of the heads to make the exhaust, intake, etc., symmetrical. I made the Crank Throws 180 degrees apart so it will (hopefully) sound like an old, 2 cylinder John Deere.

Chuck

 

[cfellows]

Finished a few more pieces in the past couple of days.

I decided to make the pistons out of cast iron. Mostly because I had some the right size and didn't have any 1" aluminum. Since I intend for it to be a slow runner, I thought the Cast Iron might be more in keeping with the older, slow running engines.

I have to say, I really don't like making Connecting Rods. They are just so tedius! And, I've yet to make one that I really thought turned out nice. Guess it must be time to design a jig to simplify the who process.

Chuck

 

[wareagle]

Chuck, I for one think the rods look nice. You did a great job one them.

The pistons came out very well, also. When you get this engine compete, it will be one impressive model, no doubt about it. Your getting closer!

Keep the pictures and updates coming!

 

[cfellows]

Here you can see I've started cutting the large timing gear. This is a 24 pitch, 54 tooth. I'm making the timing gears kind of big cause I like to be able to seem them when the engine is running!

Turns out I didn't have the right cutter for 27 teeth for the small timing gear, so I had to order it from MSC. Darn those things are pricey! I actually ordered 3 different sizes that I was missing, so now I have darn near a full set for 24 pitch gear cutters. I'm still lacking the 55-134 cutter. I expect that will be the next one I need! I figure I better stock up on tooling before I retire and don't have any money.

This gear is being cut from another piece from the extra-parts bin. You can probably tell from the photo that I had started to make a 6 spoked wheel sometime in my distant past and decided the spoke was too thin, based on the two holes drilled close together. I'm probably going to make this gear six spoked as well, but the holes already drilled will be in the waste part cut out between the spokes.

Chuck

 

[Bogstandard]

Hi Chuck,
Looking good.
I know what you mean about gear cutters, I refurbished an old Myford ML2 a few years back and had to buy some cutters for making change wheels and a new bull gear. I nearly fell off my chair when I was pricing them up.
When I fully retool, hopefully fairly soon, I hope to go for gear hobs, I think they will work out much cheaper, one size does all. Definitely a thing I will have to look into.
I do like the way you have stripped the two cylinders off a six cylinder engine. Are you going to be making the cam out of the solid, or are you going to be building it up? If you get stuck, I have some fairly easy plans for a cam grinder. I have got all the bits to make one, but like most things like that, they are sitting under the bench waiting for the right project to come along where it will be needed, then maybe it will get built.

John

 

[cfellows]

Here's the finished gear. It always gets tense when you get close to the end. It's easy for the mind to drift when you have such a repetitive task and near the end, you wonder if you miscounted or something. It's always a relief when that last cut goes in and the teeth are all even!

Chuck

 

[Bogstandard]

Lovely bit of work.

John

 

[cfellows]

Lovely bit of work.

John

Thanks, John. To your earlier question, I am going to build up the cam using the same method that Randall Cox use on his 6 cylinder design. The intake and exhaust lobes for each cylinder is a one-piece affair with a hub in the middle for attaching to the shaft with a setscrew. Here's a picture of his drawing:

By the way, what are you doing up this time of night (morning) Isn't it like 3am over there?

Chuck

 

[Bogstandard]

Thanks for showing that Chuck, it does make life a lot easier when built like that.
Time now 4.45am, long story.
Nearly time to take hound out for a walk.

John

 

[cfellows]

Didn't get too much done this weekend. I finished up the pistons Friday night. Today, made the tapered, split bushings to hold the flywheels on and tapered the bore on the flywheels to match. First time I've ever used this mechanism to hold flywheels on. It's not as hard as it looks. The included angle is 8 degrees, as recommended by Roy Rice. I set the compound as close to 4 degrees as I could from the scale. The angle doesn't have to be precise, as long as you taper the bushing and the flywheel bore without changing the compound angle. You also have to be sure your cutting tool is dead nuts on center height for both the bushing and the flywheel tapers or they won't match.

Chuck

 

[DICKEYBIRD]

Hi Chuck,

Great work sir! I'm interested in the collet style mounting system you're using. That looks like a great way to reduce the runout I always seem to get with flywheels.

I'm familar with the collet/drive washer setup used on many model aircraft engines but with my newbieness, I can't quite grasp what's going on with the system you've used. Got any drawings?

Thanks!
Milton

 

[cfellows]

Here's a drawing of the tapered bushing assembly. The tapered bushing is turned to a sliding fit over the shaft, then split completely through on one side only. The bushing is inserted into the flywheel hub, then the assembly is slide onto the shaft, flange side out. Screws, inserted through the flange of the bushing are threaded into the hub of the flywhee. As the screws are tightened, the bushing is pulled into the flywheel hub, which is taper bored to match the bushing. Further tightening of the screws causes the bushing to be squeezed onto the shaft providing a very secure connection.

With the 8 degree included angle, the just loosening the screws will not free the flywheel from the shaft. A screwdriver, chisel or other bladed instrument will have to be (lightly) driven between the flange and the flywheel to pry it loose. A steeper angle would be easier to free up, but also requires a larger diameter flywheel hub.

 

[Bogstandard]

I don't want to interfere with your explanation of the tapered flywheel setup, but normally what you would do is put two extra threaded holes in the tapered bushing flange. This would allow you to 'jack' the bits apart rather trying to pry them apart. This is standard practice on full sized tapered fittings.
This is a very good setup for flywheel mounting, I used it on almost all my ic. engines.

John

 

[dparker]

Chuck: When I was working with belt driven pumps we used split taper hubs on the sheaves, we had many bushings so that the sheaves would fit different size shafts. If you have room would it be possible to put a couple of "jack screw" holes to remove the bushings by pushing the bushing out if desired? This may save damage from the screwdriver or pry bar on the so very precious parts. Very interesting and nice looking project!
Don

 

[cfellows]

Don and John,

Thanks for the tip on the jack screws - very good idea! And I thought I knew it all...

Chuck

 

[DICKEYBIRD]

(Bowing to the gurus, hat in hand) Thanks, it's perfectly clear now. I'll definitely be using that trick.

 

[cfellows]

I'm now starting to work on the cams. This will be a built up cam using a 1/4" steel rod for the main camshaft. Each cylinder will have an added piece which contains the intake and the exhaust lobes.

The first picture shows the cam unit in my machinists vise. I've just used the blade of the square to mark the center of the middle lobe. This will be drilled and tapped for the set screw. The intake and exhaust lobes will be on either side of the center lobe. The diameter of the pieces is .625".

The second picture shows the vise sitting on my dedicated center drill drillpress. I thought the group might be interested in seeing it. I picked it up used on eBay several years ago, added a DC motor on top and a browning timing belt setup for the drive. When I first got it, it had some kind of funky drill chuck adapted to it. I managed to get it off and found a perfect jacobs taper underneath it all that perfectly fit my little Jacobs 0 - 5/16" chuck. I keep a center drill in it and pretty much use it for nothing else.