Author Topic: Rockerblock engine--something a little different--  (Read 4845 times)

Offline Brian Rupnow

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Rockerblock engine--something a little different--
« on: April 22, 2017, 06:59:07 AM »
And I do mean different. I want to machine something---but--Something I haven't seen or done before. This is destined to become a water-jacketed engine, 1" bore x 1.125" stroke. I have been casting around for something new to build, and I thought this up last night while fighting off my insomnia. A couple of hours spent on the CAD system this evening just to see if it could be done, and yes, it can. There will probably be many redesigns and changes along the way, but basically this is the overall framework I will stick to.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #1 on: April 22, 2017, 07:00:39 AM »
And yes, I'm even toying with the idea of water-jet cut flywheels.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #2 on: April 22, 2017, 07:03:41 AM »
Well Sir, This is getting exciting. I love it when a plan begins to come together.


Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #3 on: April 22, 2017, 07:04:27 AM »
Now my engine can breath in and breath out. Another hours work and it will have ignition.--And yes, it does even have pushrods.--Little short ones at that, with little swivels where they attach to the rockers to take out any binding.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #4 on: April 22, 2017, 07:05:05 AM »
I almost got caught. Look at the creative carving I had to do on the bottom of that water jacket to clear the revolving crankshaft.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #5 on: April 22, 2017, 07:05:42 AM »
Pete--There is no pressure in the water reservoir. As long as it doesn`t cut thru and leak water, there isn`t any problem. Speaking of the water jacket, my plan for sealing the jacket to the o.d. of the cylinder is shown in this section view of the water jacket. An annular groove cut at each end, just slightly shallower than the cross sectional thickness of a .094 Viton o-ring. Hopefully an o-ring in each groove will seal any water leaks. I will be able to get two or three bolts thru from the flange on the cylinder  into one end of the water jacket to keep it from turning on the cylinder.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #6 on: April 22, 2017, 07:06:24 AM »
Well Hot-Dog!! I even managed to sneak an ignition cam and my old stand by Chrysler ignition points in behind the offside flywheel.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #7 on: April 22, 2017, 07:07:06 AM »
There. That's a solid 8 hours playing. I have to dwell a bit on whether or not I have the crankshaft counterbalances on the correct side of the crankshaft or not, but other than that and a gas tank, the engine design/modelling is finished. Now I have to go shovel out the end of the driveway. We got 5" of April Fools last night. Yuk!! I was hoping we were done with that white stuff!!

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #8 on: April 22, 2017, 07:07:44 AM »
I always think it sucks to design a nicely proportioned engine, and then stick a gas tank on it. Gas tanks don't leave you with a whole lot of options. They have to be near the carburetor, they have to set below the carburetor throat (but not too far below), they shouldn't block any other equipment which needs frequent adjusting, and they shouldn't be directly in line with the exhaust. That being said, you just do the best you can and hope it doesn't ugly things up too much. This is not an improvement over the normally configured gas engine. It's just a different, artsy fartsy way of doing it.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #9 on: April 22, 2017, 07:08:59 AM »
--I've been trying to wrap my head around your concept of reversing the crankshaft counterweights. I have three books here that deal with balancing of small engines, and they are all rather vague. In a vertical cylinder engine, if you remove the piston rings and assume no friction whatsoever, then when the piston is at mid stroke, the counterweights on the crankshaft should, theoretically balance the piston and connecting rod perfectly so that the piston doesn't fall any farther under the influence of gravity, and so that the weight of the offset in the crankshaft doesn't cause the piston to raise back up in the cylinder due to gravity acting on the offset weight of the crankshaft throw.--When you have a horizontal cylinder, then a lot of that reasoning goes out the window, because gravity isn't really acting to move the rod and piston one way or the other, although it still acts on the offset weight of the throw on the crankshaft.  Indeed, the biggest job of balancing that the crankshaft counterweights have is to balance the con-rod journal and the portion of the "throws" that support it on the far side of the crankshaft centerline. In a perfect world, if you set the crankshaft alone on a pair of knife edges, it should be perfectly balanced with no tendency to roll one way or the other because of a "heavy" side. If there is a heavy side to the crankshaft, or due to the weight/drag of the piston in the cylinder, the twin flywheels should compensate for that. The fact that the engine is intended to be a "low speed" engine also does a lot to nullify any great "out of balance" issue. The bottom line is that I don't really know. I'm just running my mouth here. I know that the counterbalances make the crankshaft "look better" to my eye anyways. I think in the end the only way I'm going to know is to build it and run it, and then perhaps I'll know. I always bolt my engines down before I fire them, so even if it is out of balance, it won't run off the end of my reference table and fall on my foot.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #10 on: April 22, 2017, 07:09:29 AM »
I ended up having to angle both the exhaust and the carburetor out 12 degrees from centerline to clear the gas tank. I could have squeaked by with leaving them "in line" but it would have been severely crowded, and since I have to make the yellow "elbows" anyways, I might as well do this and buy a bit of room.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #11 on: April 22, 2017, 07:10:02 AM »
Has anybody used this type of con-rod connection at the crankshaft? I'm pressed for room where my rod attaches to the one piece crankshaft, and this would get me out of trouble. I think the actual hole for the rod journal would be the last step in the fabricating operation so everything would run true. I haven't used this before, but there's a first time for everything.--Brian

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #12 on: April 22, 2017, 07:10:47 AM »
Dang, this thing is like a big chocolate cake!! All the pieces look so good, I don't know where to start. The beauty is in the simplicity. I shouldn't get so excited about my own work. Every time I do this I swear to myself that I'm going to take it easy, there's no rush, I'll just work on it in my spare time. Then it takes over my life and making another part is all I can think about. Good wife is away at her job in the local library, and won't be home until 3:00, so I think I'll make gears today. Gears are always fun. A bit intimidating, but fun, nonetheless.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #13 on: April 22, 2017, 07:11:26 AM »
The only real bad dancer I had was the first "Rupnow Engine" which was a horizontal hit and miss single with a set of flyball govenors. It had full diameter brass discs for crank throws, and they were heavy. Since I always bolt or clamp my engines down, I never realized how badly out of balance those full discs made it. A guy from Australia built it and posted a video of it "walking" across his fathers living room floor. He hadn't bolted the engine down when he started it, and they were all amazed to see an engine take off and try to walk back to Canada by itself.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #14 on: April 22, 2017, 07:12:00 AM »
What good is a build thread without "in process" shots? This is my 50 tooth gear, emerging from another "chucking stub" left over  from making a cast iron cylinder. It was barely, barely long enough. I hate doing really short stubs, because if you get to close to those hardened chuck jaws with the gear cutter you can kiss $80 goodbye. The 25 tooth gear which I will do next is on a comfortably longer piece of 1045 steel that was left over from a customer job.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #15 on: April 22, 2017, 07:12:29 AM »
So--Today we made a start. I like cutting gears. I especially like making gears from left over bits and pieces that I have laying about. I always drill a pair of holes the calculated distance apart in a piece of scrap and fit the gears to shafts which set in the reamed holes. It is much better to do it this way and correct any "tightness" in the mesh, rather than trying to do it in a partially assembled engine. These gears seem to be "just right", although that is never a certain thing.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #16 on: April 22, 2017, 07:13:02 AM »
The crankshaft is a much more convenient place for the points. True, you get a spark with every engine revolution, but so what? There is nothing in the cylinder to burn on the exhaust stroke, so it doesn't matter. This is known as a "waste spark" ignition.  Almost all of my single cylinder engines are built that way.--Brian

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #17 on: April 22, 2017, 07:13:36 AM »
I think that to make the con rod a two piece like I'm thinking of, two separate pieces would have to be machined and bolted (and possibly dowelled) together as shown in the first picture. Then after they are firmly bolted and possibly dowelled together, the hole gets put in as shown in the second picture. The sides would have to be match marked to make sure they went back together the same way they came apart. Then they could be separated and put back together around the rod journal.


Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #18 on: April 22, 2017, 07:14:05 AM »
Here is a cross section thru the centerline of the engine. You can see how tight it gets between the rod cap and the underside of the water jacket. Of course, since it is a pressed together crankshaft, I could use a conventional closed rod end and assemble the rod when the crankshaft is pressed together. there's just something about doing that that makes me quiver all over----

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #19 on: April 22, 2017, 07:14:47 AM »
Nope, flywheels won't drag. Won't clear by very much, but won't drag either.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #20 on: April 22, 2017, 07:15:36 AM »
Okay--Back to business. Immediately after I had machined the gears my phone rang about 5 times in a row, each time with a customer I couldn't turn down, and each customer wanted to be looked after "right now". Being a slave to my bank balance, I said yes to all of them, and haven't had time to play "small engine" since. I have discovered one thing, and I'm not sure yet whether it is really a problem or not. When I make built up crankshafts from 3/8" diameter stock, I ream the holes which I am pressing shafts into with a 0.3735" reamer. I use 3/8" drill rod for the shafts, which always seems to come in at .0005" oversize. This gives a VERY hard press fit, with .002" interference, and I have never had one "slip" after the fact. I don't use 3/8" cold rolled steel because it comes in at about .0005 to .0001" undersize, and though it does give a press fit, it is quite a light press fit, and it WILL slip after the fact. Last year I purchased a 0.4985" diameter reamer in case I wanted to make a crankshaft using 1/2" nominal shafting. The problem is, that I just stopped at my metal supplier today  and micrometer measured all of their "01" drill rod, and it all comes in exactly at 0.500" diameter. So--I will only achieve a .0015" interference fit. I have to think on this a bit before I proceed. ---Brian

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #21 on: April 22, 2017, 07:16:11 AM »
What to do--What to do??--Well, we'll make a little test. I drilled and reamed a 0.4985 hole in a piece of 3/8" mild steel, and I turned a very slight "lead" on the end of a piece of 1/2" drill rod, and I pressed it to see what happens. This type of pressing can not be done on a manual arbor press. It gets done in my vice. This was tight, but not "Oh my God, I've just given myself a hernia" tight. (That's the way it is with a .002" interference.) So, to farther quantify the results (We're getting really scientific here), I put the piece of plate in the vice, clamped my vice grips on the 1/2" round stock, and gave it the old "Reef your guts out" test.--And it slipped---Just like I thought might happen. The fit is tight enough to withstand moderate abuse, but not exceptional abuse such as backfire, pre-ignition, or nuclear Armageddon. I do however, think it would work fine if the components were cross drilled and pinned. Probably with .094" (3/32") dowel pins.


Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #22 on: April 22, 2017, 07:17:05 AM »
I've been thinkin', Lincoln---if I do get the flywheels waterjet cut, why not do something fancy? so, I got my old Philip Duclos  book out and using the information in it, created curved spoke flywheels. I think it adds a lot of "pizazz" to the overall engine.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #23 on: April 22, 2017, 07:17:39 AM »
I just ordered Jerry Howells gas valve plans and components to run this engine on propane, and ditched the gas tank. There is just too much beautiful "monkey motion" in those long rocker arms to cover them up with a gas tank, in my opinion. Also, if I do get the water-jet cut flywheels, there will be a relief machined in both sides to accentuate the spoked area.

Offline Brian Rupnow

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Re: Rockerblock engine--something a little different--
« Reply #24 on: April 22, 2017, 07:18:28 AM »
Running the engine on propane is not going to let me mix a little two cycle oil with the gas to keep the viton o-ring lubricated. The simple fix for this is to add a small oil cup with a very small "dribble hole" of about 0.030" diameter to the rear of the cylinder, tucked up tight against the back of the cooling water reservoir.  This will let enough oil onto the piston skirt with each revolution of the crankshaft to carry oil thru the rest of the piston stroke and spread it throughout the cylinder while the engine is running. This was very common on the old hit and miss engines.