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Building a Flat Twin

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Rdean33422

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I have built three different hit-miss engines since this covid thing started mainly to have something to keep me busy. When I started the first build, a Kerzel from plans, I thought maybe I would end up with a display model that didn't look too bad but did not run. Well that didn't happen as all three of my models run very nicely and my building skills have improved with each engine.
Now I am ready for something more complicated and the Upshur Twin caught my eye. I acquired a set of plans but I soon realized that I didn't want to build the engine the way the author had so here is my take on my flat twin.
The specifications of what I wanted for my engine are.
1" Piston
1" Stroke
Ball bearing Crank shaft mains
Ball bearing Cam shaft
One piece crank case
Electronic ignition

I started with the crank shaft making it the same way I had done on the other models but I soon found out that a two throw crank shaft is immensely more complimented that a single throw crank. After several failed attempts I decided to try this method.
GEDC4714s.JPG
It is made of six pieces, three shafts and three bars. These were assembled with a close fit and red lock tite and left over night.
Next day the shafts were further secured using 1/8" pins through the bars and shafts. Next was to cut out the bits I didn't want and do some shaping of the bar ends and a coat of paint.
GEDC4716s.jpg

The crank ended up very true and it even looks nice.

Next up is the crank case.
Thanks for looking
Ray
 

Rdean33422

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I have a block of aluminum about 4 X 3 1/2 X 3 that I will be using for the crank case so I squared it up on all sides.
GEDC4720s.jpg

I then hollowed out the inside of the block leaving 1/2" walls all around. The finished product turned out nice but what a pile of chips and several hours milling. I didn't have an end mill long enough so I had to cut from the both sides to the middle.
GEDC4724s.jpg

It looks like the crank will fit inside and hopefully have enough room for the throw of the connecting rods.
Only time will tell.

Thanks for looking
Ray
 

teeleevs

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I have built three different hit-miss engines since this covid thing started mainly to have something to keep me busy. When I started the first build, a Kerzel from plans, I thought maybe I would end up with a display model that didn't look too bad but did not run. Well that didn't happen as all three of my models run very nicely and my building skills have improved with each engine.
Now I am ready for something more complicated and the Upshur Twin caught my eye. I acquired a set of plans but I soon realized that I didn't want to build the engine the way the author had so here is my take on my flat twin.
The specifications of what I wanted for my engine are.
1" Piston
1" Stroke
Ball bearing Crank shaft mains
Ball bearing Cam shaft
One piece crank case
Electronic ignition

I started with the crank shaft making it the same way I had done on the other models but I soon found out that a two throw crank shaft is immensely more complimented that a single throw crank. After several failed attempts I decided to try this method.
View attachment 120203
It is made of six pieces, three shafts and three bars. These were assembled with a close fit and red lock tite and left over night.
Next day the shafts were further secured using 1/8" pins through the bars and shafts. Next was to cut out the bits I didn't want and do some shaping of the bar ends and a coat of paint.
View attachment 120204

The crank ended up very true and it even looks nice.

Next up is the crank case.
Thanks for looking
Ray
Good job on the crankshaft Ray, I'm going to attempt turning down from round, bolted through the roller big ends.
I'm building an Onan twin from photos, have done flat drawings using TurboCAD, I'm no expert on CAD but it does help me avoid clangers. Started with a box of alloy, done some patterns, the camshaft with governor. Roughly half scale, Honda 39mm pistons . Photo 1 grinding the 4mm mixture needle, 2 the carby in brass, 3 the camshaft. Was surprised to find all the cams finished up on the same side.
 

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Rdean33422

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Thanks Tom
teeleevs that sounds like an interesting project and the best of luck turning the crank shaft.
What is the size of the crank and the rod throws?

Ray
 

Rdean33422

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Drilled the large hole for the crankshaft and installed a bearing for the other end.
I will probably make the other end the flywheel end.
GEDC4727s.jpg

Made a bearing cap for this end and screwed it in place.
GEDC4733s.jpg

.GEDC4737s.jpg

See it does fit inside.
GEDC4730s.jpg

Now where to put the cam shaft so that the cam lobes have enough clearance to miss the connecting rod ends.
This was an issue I had thought about for several days because the timing gears have to large enough to connect to the cam and the crank. If they are too small there won't be enough clearance and if too large they won't fit inside the crank case.
These are what I decided on for gears a 29 tooth and a 58 tooth Module 1 set.
GEDC4744s.jpg

I screwed upon the first set so I had to make another . These will give me enough height for the cam but the large gear doesn't fit inside the crankcase. I f you look two pictures up you can see how I remedied this by cutting into the side walls. I will have a cover with a trough cut into the bottom of it to cover the part of the large gear that sticks out the top of the crank case.

Thanks for looking
Ray
 

teeleevs

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Hi Ray, it will be 40mm stroke and the crankshaft will have a lot of weight like a motorcycle crank, the timing gears 30/60 from a Seig lathe set. Photos start with a box, I wonder if that is why they call it a Boxer engine, one of many drawings, boring the holes and timing gears before modifying for the governor balls. Ted
 

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Rdean33422

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Bored the holes for the cam shaft bearings.
GEDC4750s.jpg

This is the cam shaft and the bearing blocks.
GEDC4748s.jpg

I had to cut away part of the crank shaft bearing block in order for the cam bearing block to fit. I also bored the two cylinder locating holes and spotted for the cylinder mounting bolt holes.

GEDC4752s.jpg
GEDC4753s.jpg

Thanks for looking
Ray
 

teeleevs

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I didn't think the camshaft needed bearings, virtually no load, just running it in the alloy, there will be a lot of oil flying around. Photos 1/ this is what I am building in 1/4 scale to run on 7&1/4" track, Giving kids rides, found it parked in a street near my mates place. 2/ cutting the cams, 3/ wood patterns, 4/ opted for polystyrene patterns. Ted
 

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Rdean33422

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Tapped the holes for the cylinder bolts in the crank case and started on the cylinders.

GEDC4757s.jpg

And here are the cylinders done except for the inner liners and head bolts holes.

GEDC4760s.jpg

This is where I are now and starting to look like an engine.

GEDC4762s.jpg

Thanks for looking
Ray
 

teeleevs

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Sorry I didn't say what this thing was, it is a 2 man Railway Inspectors trolley, called a Fairmont Speeder (because it was faster than the 3 wheeled man powered one). The early versions had a 2 stroke engine which ran either way, no reverse gear, the later ones were powered by an Onan flat twin. Photo 3/ My version of the 6 man Gangers trolley powered by a 2 stroke mower engine much modified to run either way, 4/ The real one needing some TLC, 5/ mine doing some real work giving kids rides. Thanks for watching, Ted from down under
 

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lathe nut

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Thanks for the tour and saying what you have going, that is some fine looking work, glad to see that there will be more coming, like the photo's of the build, for a fellow like me who has the machines and don't have all the know how just sometimes on how to hold it to make the cut or the mill, guess this is what I call look and learn, thanks for sharing, Joe
 

Rdean33422

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Joe you are very welcome and as I am still learning every day.
I enjoy coming up with an idea and thinking it through and then running into problems and working them out.

Ray
 

teeleevs

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Me, I have been learning every day for the last 75 years, my first successful engine build was this rideable model of a 1889 Inspectors trolley that was used on the Normanton to Croydon railway line in far NWest Queensland Australia. Thanks for the comments, Ted from down under.
 

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Brian Rupnow

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I built a flat opposed twin a few years ago, very similar to what you are building. The configuration of the engine more or less demands that the sparkplugs end up at the lowest point on the cylinders.---If the engine didn't start right away, it would flood so dramatically that you could crank until hell froze over and it wouldn't clear itself and start. I didn't use ball bearings on my crankshaft---I used bronze bushings. My ignition system included a set of breaker points which ran off a cam attached to the crankshaft. My crankshaft wasn't perfectly 100% straight (few of them are). The fact that it wasn't perfectly 100% straight created a lot of wear on the bushing closest to the cam. This allowed the crankshaft to "orbit" a bit and the fact that it "orbited" meant that I could never get the points set right. The engine ran great when it was first made, but it only ran for a few hours before it started missing and refusing to run properly because of the situation with the breaker points. Some day when I'm really, really bored, I will redo that engine using ball bearings instead of bushings. Surprisingly, ball bearings will tolerate a bit of a wonky crankshaft, but bronze bushings won't.---Brian
 

Rdean33422

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I am very happy with my crankshaft and much straighter than any of the others I have made.
I had planed to locate the spark plug on the low side of the head but not for the reason you mentioned so thank you for the information.
I will be using a hall sensor to trigger the ignition module.

Ray
 

Rdean33422

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Just finishing up one of the cast iron cylinder liners. It sure makes a mess!
GEDC4766s.jpg

The other cylinder and liner.
GEDC4768s.jpg

The connecting rods will be next.
Thanks for looking

Ray
 

Rdean33422

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I finished the connecting rods and most of the work on the pistons.
GEDC4771s.jpg


I should have taken some pictures before I assembled them but I wanted a nice tight fit between the wrist pin and the piston walls. When I test fit the wrist pins they were a very tight fit and I was afraid I might damage the pistons if I tried to remove them.

I painted the crankcase even tho I have many more holes to drill in it and the chances of damaging the paint is high.
GEDC4772s.jpg

I found that I am more careful in all of my building if I have a shiny painted part to protect.

Thanks for looking
Ray
 

Rdean33422

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"Even a blind squirrel finds a nut sometimes"

Well some times things just work out as planned.
All of my concerns about the cylinders lining up with the crank, enough clearance for the rods, the length of the connecting rods and clearance for the cams have been put to bed.
EVERYTHING FITS and MOVES as it should


Very pleased with this trial assembly.
GEDC4777s.jpg

GEDC4783s.jpg

Now to take it all apart and finish the cylinders and cut the main and cam shafts to length.

Thanks for looking
Ray
 

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