Horizontal Twin

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Weirsdale, Florida
I was doing some shop cleanup and organizing the other day and ran across this crank shaft that I had made close to 3 years ago. At that time I had built a flat twin engine that did run but not very well. After a lot of fiddling around and some disappointments I decided to use some of the parts off that engine for my 90 degree v-twin engine. That engine turned out to be very reliable and a good runner.

I thought maybe I should take another shot at building a horizontal twin engine I can't just throw the crank away.

I found a pair of piston and rod assembles that I had made for a different engine at some time and remade the connecting rod bearings to fit this crank.
IMG_2478.JPG
This might be a good time to experiment on a bolt-together engine. No castings or large lumps of aluminum just flat plates screwed together in a simple way.
Since the crank, rods, and pistons are already made I will have to build around these parts.
I started with a couple of 1/2" aluminum plates and installed a ball bearing in each.
IMG_2483.JPG

So here is the starting point.
1" bore and 1" stroke.
IMG_2486.JPG

Thanks for looking
Ray
 
I had some 3/8" aluminum plate to make the sides from as I wanted the sides to be stiff for the cylinders to mount to.
IMG_2491.JPG

I added a couple of main rails for mounting the engine to a wood base.
IMG_2494.JPG

It looks like I could have made the bearing end plates an inch shorter and still had plenty of room for the crank. I usually don't have enough room and now I have more room than I need. On well it gives it more stability.

Thanks for looking
Ray
 
I took the frame apart, cleaned it up and even gave it a polish.
IMG_2496.JPG

Drilled and bored for the cylinders and spotted the holes for the cylinder mounting bolts.
IMG_2500.JPG

IMG_2502.JPG

The next logical thing for me to do would be to start on the cylinders but the 4ft long piece of 1 7/8" aluminum rod I had is not 6061. I don't know what it is but it does not machine well. Even sanding it doesn't help much so since I need a nice finish inside and out I ordered a piece of 2".
It will be several days for the aluminum to arrive so I will see what other parts I can work on for now.

Thanks for looking
Ray
 
I was doing some shop cleanup and organizing the other day and ran across this crank shaft that I had made close to 3 years ago. At that time I had built a flat twin engine that did run but not very well. After a lot of fiddling around and some disappointments I decided to use some of the parts off that engine for my 90 degree v-twin engine. That engine turned out to be very reliable and a good runner.

I thought maybe I should take another shot at building a horizontal twin engine I can't just throw the crank away.

I found a pair of piston and rod assembles that I had made for a different engine at some time and remade the connecting rod bearings to fit this crank.
View attachment 151194
This might be a good time to experiment on a bolt-together engine. No castings or large lumps of aluminum just flat plates screwed together in a simple way.
Since the crank, rods, and pistons are already made I will have to build around these parts.
I started with a couple of 1/2" aluminum plates and installed a ball bearing in each.
View attachment 151195

So here is the starting point.
1" bore and 1" stroke.
View attachment 151196

Thanks for looking
Ray
This is an IC engine?
 
Hello Richard yes it will be a IC gasoline engine that will look a little different and have some uncommon features new to me.
I don't think I will run into too many gotchas along the way but that is a problem when you don't know what the finished product will look like from the start.

Ray
 
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I have never started on the cylinder heads before I make the cylinders on any of my engines but I just had to do something while waiting on the 2" aluminum to get here.

I spotted the holes for the head bolts, spark plug, and valve cages.
IMG_2507.JPG

On the drill press I drilled the rest of the way through the head and counter sunk for the head bolts..
IMG_2509.JPG

Thanks for looking
Ray
 
All right I have made up my mind to make the twin with overhead cams. I have never tried this before and there are not a lot of home built examples to look at. The cylinder heads are 2.5" in diameter in order to give me some room for the cam brackets.


Here I am taking 0.250 off two sides of the cylinder head to give me a flat place to mount the cam brackets.
IMG_2512.JPG

The intake and exhaust valves are 0.110 offset lower from the center line of the head to allow room for the spark plug above them.
The intake and exhaust valve ports are both on an angle and exit on the lower side of the head.
This shows drilling those ports so they intersect with the valve guide holes.
IMG_2514.JPG

I made up 4 each of the valve guides and valves.
IMG_2522.JPG

Here are the heads with the valve guides installed and the connecting ports drilled through the guides and the ports tapped 5/16 X24.
IMG_2518.JPG

This will be interesting.
Thanks for looking
Ray
 
I studied for some time as to how to get this to work and thought about a small bucket over the ends of the valve stems and keepers. They could be machined to different internal lengths to achieve the proper valve clearance but how to keep them in place. Every idea I came up with involved some sort of guide for the buckets and it would be a pain to work on.

So I went a different course and threaded the valve stems to accept brass stubs that the cams would push on directly. Simple and easy but there is still the matter of side load on the valve stems. I'm going to give it a try.will give it a try.
The side supports will be adjustable to get the valve clearance.
IMG_2523.JPG
This shows one of the supports being cut on the CNC.
IMG_2527.JPG

Thanks for looking
Ray
 
Nice work Ray.
I doubt you will have any problems with side loading of the valves. The valve train forces in model engines are very low compared to larger engines, because the valve weight is small and you don't need much spring force to close them.
Also worth noting that the larger the diameter of your cams, the smaller the ramp angles will be for a given valve lift.
Looking forward to seeing this engine running!
Pete.
 
I turned a couple of shafts for the cams to mount on and I left the ends long for now. They can be trimmed off later when I know where everything goes.
IMG_2540.JPG

This shows cutting one of the cams from 0.400 thick bronze on the CNC.
IMG_2544.JPG

Two of them drilled and tapped with the set screws.
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The heads are complete and ready to install.
IMG_2550.JPG

I was concerned that there may be excessive side load on the valve stems but that won't be a problem as they operate very smoothly.

The aluminum for the cylinders did come in so those are the next parts to make.

Thanks for looking
Ray
 
Thank you Minh.

I had been thinking on the overhead cam for close to a year and rejected the idea of building one as being too complicated for my talents. It wasn't until I had the head in my hands that I came up with this configuration.

I really don't know just what the final engine will look like when I start.

Ray
 
The 2" aluminum rod came in so on to the cylinders.
All roughed out.
IMG_2553.JPG

Holes drilled and tapped with a little shine.
IMG_2554.JPG

Cylinders bolted on the frame and the holes even lined up.
IMG_2557.JPG

I am thinking of painting the flywheel black to give the engine some color contrast.

Anyone, your thoughts on painting and the color?

Thanks for looking
Ray
 
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