Open Column Twin

[cfellows]

More work done tonight. I finished machining the cams. Probably not quite as good a job as a cam grinder would do, but not bad.

I used the method prescribed by Randall Cox. The cam blanks are mounted on a 1/4" stub arbor which is affixed to the rotary table. The arbor is centered under the mill spindle. A boring head is mounted in the milling spindle with the boring bare turned inward toward the blank. The radius formed by the arc of the cutting tools is about 5/8" in. The boring bar tip is brought up to the edge of the cam blank. The repeated downward cuts are made with the mill/drill handle, advancing the x-axis into the boring bar cutter .010" each time. When one side of the cam blank is milled down to the primary radius of the cam, the x-axis is locked, then repeated downward cuts are made again, only this them, the rotary table is turned 2-3 degrees between cuts. This is continued on around until the the proper cam lobe is formed. After finishing one lobe, the cam blank is turned over on the arbor and the process is repeated on the second lobe. You have to do some kind of tricky calculations to figure out the starting and end positions on the rotary table to get the two lobes at the right angular separation, in this case 110 degrees. And, since the intake / exhaust valve configurations between the two heads are opposite, the two cam one cam segment wants the 110 degrees separation and the other wants a -110 degrees separation. Took me two days to figure out all the starting and end points! Chuck

 

[wareagle]

Chuck, the cam looks great! It looks like a tedious task to machine it that way, but it works! I have never thought of cutting cam lobes in that fashion. I'll have to try it sometime!

 

[cfellows]

Chuck, the cam looks great! It looks like a tedious task to machine it that way, but it works! I have never thought of cutting cam lobes in that fashion. I'll have to try it sometime!

Thanks! It's a little tedious, but not as bad as it looks. Took me a little over an hour to make all 4 cam lobes.

Chuck

 

[Canyonman]

Neat method for the cam.

Did you make that drill? It's Great! I Love It!!!!

But then again I most always like the Odd stuffus!!!!! :

If it ever comes up for sale, EMail Me!!!!!!!! ;D

Take Care, Ken

 

[Bogstandard]

Lovely bit of work there Chuck.
I have never seen that method before, but as they say, there is always more than one way to skin a cat.
For a composite cam I always went with the method described by E.T. Westbury and made a jig and timing disc for making them in the lathe, now that is tedious. But I think your method is very similar, but using the RT instead of the timing disc, and might be a better way to go if ever I get back into ic engines.
I can't wait to see this one running, a real achievement.
BTW have you seen my latest post on the poppet valve engine, I have managed to get it running on three different cycles by making three different pin cams.

John

 

[cfellows]

Well, after a sabbatical of a couple of weeks, I'm back into engine building mode. I finished up the 4 valve guides tonight. Not much of a leap, but tomorrow is my last day of work for two weeks and the "General" is going to Austin to visit the kids for a week, soooo... lots of uninterrupted, quality shop time ;D. I hope to get a lot done by the time 2008 rolls around! Chuck

 

[Bogstandard]

Lovely work again Chuck, brass or bronze?
This is turning into a really informative project. It is nice to see how an engine gradually comes together, especially from a modified planset.


John

 

[cfellows]

Thanks, John. A little more progress today. I finished the valve lifters and the valve Lifter Guides as you can see in the photo. I've got to get started on the distributer soon. I can't do much else with the Camshaft until I figure out the distributer design and placement... Chuck

 

[cfellows]

I got the valves pretty much finished today. I just need to cut them down to the proper length. They were cut from 3/8" hot rolled steel and the stems are 5/32" in diameter. The brass pieces in the picture are the valve guides.

Chuck

 

[Powder keg]

I really like how this engine is turning out:O) Keep up the good work.

 

[cfellows]

A few more pictures for your viewing pleasure. I spent two days making the rocker arms, rocker arm posts, and valve spring retainers. These are all niggling little bits that require a lot of time and patience. I'm about finished with all the mechanical parts except for a few retaining rings, setscrews, etc. Next are the fuel and ignition parts... Chuck

 

[wareagle]

Chuck, your engine is looking great! Just seeing the pictures of it coming together is getting me excited. You should have a very nice model before long. Again, thanks for sharing your build with us! It certainly is an inspiration.

 

[Brass_Machine]

Wow. That is awesome!


Eric

 

[deere_x475guy]

Chuck it's looking awesome! Did you use cap screws and let the pushrods center in the allen hole? Also have you thought about using an electronic ignition system? I know there are several guys out there making the electronic ignition for IC engines. Great work keep the pics coming.))

 

[cfellows]

Thanks, Bob. Yes, the adjustment screws on the rocker arms are just 4-40 socket head cap screws. However, I am going to drill them out with with a ball shaped endmill. Have to buy one first...

I bought the electronic ignition module (TIM6) and exciter ignition coil from Jerry Howell. The exciter coil has two high tension leads, so I don't need a distributer. I still have to figure out where to mount the hall effect transistor. Don't know whether to mount it in the middle of the cam shaft or on the outboard end. And, I have to solder the TIM6 together. Shouldn't be too difficult... I've soldered a lot of circuits together over the years.

My real dilemna at the moment is deciding which carburetor to build. I have plans for Jerry Howell's carburetor as well as the plans in Randall Cox's Open Column 6. I have a few other designs to pick from as well. None of them are exactly what I'm looking for and I don't know enough about Carburetor design to come up with my own.

Chuck

 

[gilessim]

That engine is looking fantastic!, how did you cut that profile on the bottom of the rocker arms?....Giles

 

[cfellows]

That engine is looking fantastic!, how did you cut that profile on the bottom of the rocker arms?....Giles

I milled the bottom profiles using a 1/4" carbide end mill in my mill/drill. I have a small, secondary vise I built which I hold in the jaws of the big vise. The small vise holds the work so I can mill the edges of small pieces. I originally built it to make connecting rods, but I found that it get's used for a lot of other things. Here's some pictures:

For reference, the end mill shown is a 5/8"

Chuck

 

[cfellows]

Finally made some more progress on my Open Column twin. After being stalled for far too long, I've come up with a design for the intake manifold and the carb. I decided on a functional design similar to that used on the Upshur T-Head marine engine. I still have to make the innards for the carb, but that should be pretty straight forward. I also have to solder the manifold together after I get the manifold holes and matching holes in the heads drilled and tapped. And, I have to close up the drilled holes in the ends of the manifold where the carb attaches.

You can also see the aluminum disk on the end of the camshaft that will hold the magnets for the hall effect ignition pick up.

Chuck

 

[deere_x475guy]

Chuck things are coming along nicely it would appear. I always look forward to seeing your progress on this engine, keep up the good work.

 

[tel]

That's a seriously nice engine. After 30 years of building steam engines, I'm still not quite sure that my skills are up to taking on something like that