# Building a Flat Twin



## Rdean33422 (Oct 23, 2020)

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.



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.



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

Next up is the crank case.
Thanks for looking
Ray


----------



## Rdean33422 (Oct 23, 2020)

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.



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.



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


----------



## ironman (Oct 23, 2020)

Looks good.


----------



## teeleevs (Oct 24, 2020)

Rdean33422 said:


> 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
> ...


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.


----------



## Tom 1948 (Oct 24, 2020)

You are on your way to another fine looking build Ray. I am looking forward to seeing/ hearing it run.......Tom


----------



## Rdean33422 (Oct 24, 2020)

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 (Oct 24, 2020)

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.



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



.


See it does fit inside.



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.



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 (Oct 25, 2020)

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


----------



## Rdean33422 (Oct 25, 2020)

Bored the holes for the cam shaft bearings.



This is the cam shaft and the bearing blocks.



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.






Thanks for looking
Ray


----------



## teeleevs (Oct 25, 2020)

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


----------



## Rdean33422 (Oct 27, 2020)

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




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




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




Thanks for looking
Ray


----------



## teeleevs (Oct 28, 2020)

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


----------



## lathe nut (Oct 29, 2020)

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 (Oct 29, 2020)

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 (Oct 29, 2020)

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.


----------



## Brian Rupnow (Oct 29, 2020)

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 (Oct 29, 2020)

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 (Oct 31, 2020)

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



The other cylinder and liner.



The connecting rods will be next.
Thanks for looking

Ray


----------



## Rdean33422 (Nov 1, 2020)

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




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.



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 (Nov 2, 2020)

"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.






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

Thanks for looking
Ray


----------



## teeleevs (Nov 3, 2020)

Looking good


----------



## teeleevs (Nov 3, 2020)

Looking good, here are some shots from my day yesterday, photos 1 and 2 burying the patterns 3 get the furnace going, 4 open the Christmas parcel 5 ready for the shaper,  have video of shaper trueing up the crankcase half an hour after pouring metal.
Thanks for watching 
Ted


----------



## Rdean33422 (Nov 3, 2020)

I disassembled the engine yesterday and made the top and bottom plates.  The top has a cutout inside for the cam gear.  I also painted the plates last night but since it has been a little cooler here I didn't expect the paint to be cured.  I have a toaster oven in the shop I use for different things but never tried to cure paint in it.  I set the oven to 200 degrees for 35 minutes and laid the plates in on the rack.  When the oven shut off I just opened the door and let the plates cool by them selves.  This is a process I will be using in the future as the paint is rock hard with a very nice finish.  I would not try this with freshly painted parts only ones left overnight as who knows what might happen.
I cut the crankshaft end to length, shortened the cam shaft, and drilled holes for the valve lifter bushings.  
I left the rear end of the cam shaft long as I haven't decided if I will make a distributor or not.

Front view



Rear view



I also roughed out the 4 cam lobes.




Thanks for looking
Ray


----------



## teeleevs (Nov 3, 2020)

That's a good start when everything moves as it should, with a flat twin both pistons reach top (full compression in one and exhaust in the other ) so ignition only needs a twin lead coil fireing every time around with only one magnet or cam on the crankshaft, some COP Car coils run 2 plugs and will run on 4 volt can't say which but early Mazda or Ford badged Mazda models is a good try. 
Ted


----------



## Brian Rupnow (Nov 3, 2020)

On the twin that I built, I ran a pair of automotive points off the crankshaft. That gave me a spark on each crankshaft rotation. I used a coil from a two cylinder snowmobile. The coil had two sparkplug wires. It fired both sparkplugs on every rotation. The cylinder under compression would fire, the other cylinder would be up on exhaust, so even though that plug fired, there was nothing in the cylinder to burn. The path that the electricity followed was crazy--It came out one wire, fired the plug, ran thru the block to the other plug and fired it, then ran back thru to the coil on the other plug wire. It worked great, but if you pulled either sparkplug lead, the engine would quit because you had totally broken the circuit. No distributor was required.---Brian


----------



## Rdean33422 (Nov 4, 2020)

That's interesting Brian I had never heard of that configuration.  
I am contemplating several different scenarios for this build.
One is to use a distributor with one ignition module and one hall sensor.   I kind of like the idea of designing and making a distributor and it is a long time proven design with many millions of examples.
I could use two ignition modules each with it's own hall sensor firing just one plug each.  
I could use an ignition module that is designed to fire two plugs which are 180 degrees apart.

I just haven't decided on any one type yet.

Ray


----------



## teeleevs (Nov 4, 2020)

Hi Ray, the ignition system Brian wrote about above is used in most v6 & some 4s car engines today.  But going back into the 1970s Honda motorbikes used the system.   Henry Ford had 4 Trembler (Buz) coils on the T Model and never realised he only needed 2, one of his greatest problems was to have his suppliers deliver him 4 Buz coils every 3 minutes.  A few days ago I Posted pictures of a model Railway trolley I built, so here is the full sized one. Picture 1 & 2 a closeup of one side of the engine, it is 2 cylinder, it had a similar system to energise the 2 Buz coils as Fords T Model but Buz coils were invented for the overland telegraph system about 50 years before Fords first car. I used a set of points on the camshaft with 2 flats on the cam inside the round box, running a Honda twin lead coil.


----------



## teeleevs (Nov 5, 2020)

Todays work on the Onan opposed twin, the fan, made entirely from polystyrene, picture 1, burying it in the clay, 2 turn the box over, 3 ready to pour metal, 4 just enough metal in the pot, 5 open the Christmas box, 6 looks like I might have gotten away with it. It run true in the lathe, a few imperfections but hey, what is paint made for? Would have been very difficult to do this with a wooden pattern.
Ted from down under


----------



## MRA (Nov 5, 2020)

That's really neat!  Did you carve those blades freehand?  Lost polystyrene is one of the things I have not tried yet in my home casting adventures.  The museum where I volunteer needs a thermostat body for an old Gardner diesel engine - it's a very odd shape and I can't work out how to do it with a conventional pattern.  That might be an interesting way forward.


----------



## Richard Hed (Nov 5, 2020)

MRA said:


> That's really neat!  Did you carve those blades freehand?  Lost polystyrene is one of the things I have not tried yet in my home casting adventures.  The museum where I volunteer needs a thermostat body for an old Gardner diesel engine - it's a very odd shape and I can't work out how to do it with a conventional pattern.  That might be an interesting way forward.


I did that in college class.  The one warning I have is if there is a flaw, even a tiny one, it will show up exactly as y9ou see it on the polystyrene.  Also, apparently, there are two types:  one very poisonous which will melt or disolve with a bit of gasoline poured on it, so easy to detect.  and the other which is far less poisonous.  Other than these probs, the stuff is EASY to work with, I mean, the stuff can come out to 5-10 thou if you are careful.  When I get around to foundry work, this technique will be a number one for me to use.


----------



## teeleevs (Nov 6, 2020)

I turned the main circles in the lathe then setup a Dremel machine on the Mill and marked out the blades on the rotary table from there on I used various sharp blades by hand. I often glue pieces together with Aquadhere but the resulting ash can affect the finish as noted by Brian above, so the less gluing the better. It can be cut with a sharp knife, hot wire, or bandsaw, doesn't cost much if lucky enough to pick up a chunk on the side of the road. Casting comes out a bit rough, takes a little more finishing. Give it a try. 
Ted from down under


----------



## teeleevs (Nov 6, 2020)

Sorry that was Richard above


----------



## teeleevs (Nov 7, 2020)

Again today we cast the timing cover, and one of the cylinder blocks. A lot of cleaning up after but it is all good. 
Ted


----------



## teeleevs (Nov 11, 2020)

More pictures of progress on my Onan opposed twin, the timing cover is a bit rough but there is a lot more to machine on it, a friend gave me a Lifan Chinese magnito so need to fit that, it is almost exactly the same as the original Onan one only much smaller, should work fine, it fits inside the fan come flywheel. Last picture the Onan original.


----------



## davidyat (Nov 12, 2020)

*Brian, I had a Honda 160 motorcycle, 4 stroke, that fired on every stroke like that. When I was racing motorcycles in the Mojave desert, my bike had 2 spark plug holes in the head, one being plugged. It was a 2 stroke Yamaha. I mounted the coil on the bike, stuck 2 plugs in the head and found out 2 plugs firing greatly increased the power.
Grasshopper*


----------



## ddmckee54 (Nov 12, 2020)

Teeleevs:

It looks like you're doing lost foam casting in greensand, is that correct?  If you haven't been there yet, you might want to check out thehomefoundry.org.  They've got a forum devoted to lost foam casting.  It might make things a little easier for you.  I'm amazed at some of the stuff that Kelly has cast with lost foam on that forum, his username is Al203.  There are many tricks that you can use to get some outstanding surface quality.

Don


----------



## Richard Hed (Nov 12, 2020)

ddmckee54 said:


> Teeleevs:
> 
> It looks like you're doing lost foam casting in greensand, is that correct?  If you haven't been there yet, you might want to check out thehomefoundry.org.  They've got a forum devoted to lost foam casting.  It might make things a little easier for you.  I'm amazed at some of the stuff that Kelly has cast with lost foam on that forum, his username is Al203.  There are many tricks that you can use to get some outstanding surface quality.
> 
> Don


Don,
Is there another url?  That one doesn't work for me.  I'll search for it.  Thanx

Whoa--the foundry is everything from weddings to church stuff.  The nearest thing I found to this is The Foundry: NEK Vermont MakerSpace  | The Foundry

OK, I found it but my ip address has been banned!?


----------



## ddmckee54 (Nov 13, 2020)

Try contacting an administrator there and explain what's going on.  Otherwise PM me and I'll contact an administrator there and tell them about your problem.

Don


----------



## teeleevs (Nov 14, 2020)

ddmckee54 said:


> Try contacting an administrator there and explain what's going on.  Otherwise PM me and I'll contact an administrator there and tell them about your problem.
> 
> Don





ddmckee54 said:


> Teeleevs:
> 
> It looks like you're doing lost foam casting in greensand, is that correct?  If you haven't been there yet, you might want to check out thehomefoundry.org.  They've got a forum devoted to lost foam casting.  It might make things a little easier for you.  I'm amazed at some of the stuff that Kelly has cast with lost foam on that forum, his username is Al203.  There are many tricks that you can use to get some outstanding surface quality.
> 
> Don


Thanks Don, I tried a couple of different ways but thehomefoundry.org gave me a message that it was a dangerous site? Couldn't think that was right.
Ted from down under


----------



## guyf2000 (Nov 15, 2020)

"thehomefoundry.org" resulted in "Untrusted site".  However, The Home Foundry finally worked.


----------



## Shopgeezer (Nov 15, 2020)

I’m getting junk mail from homefoundary.org. I suspect they have been hacked.


----------

