Opposed Twin I.C.

[Brian Rupnow]

The problem I see with turning the cylinders over and having the cam shaft and pushrods on the bottom is that it becomes difficult to access the intakes for a common carburetor feed.

[Brian Rupnow]

Chuck--that was my plan--run a single set of points driven by the crankshaft.---Brian

[Jasonb]

Opps posted it on teh other side but will put it here too

Brian, one thing to watch and that I still need to sort out on mine is that the crank tends to throw the oil into the right cylinder and oils it up so it does not fire so well. You can feel the exhaust gas from one cylinder is a lot colder than the other but when it does clear itself it romps away.

Either wants a curved baffle plate in the sump to lessen the amount of oil coming into contact with the crank or some thin plates either side of the cylinder opening in the crankcase to stop most of the oil getting to the bore.

This is why the inverted design may be better as the cams won't throw up as much oil and the plugs will be at the top of the heads not the bottom so won't be affected by flooding.

I have the hall sensor being tripped off the camshaft with lost spark, I have a S/S twin coil ignition which sends a spark to both cylinders at the same time

[Brian Rupnow]

Jason--My intent all along has been to run this thing open crankcase---no top on it. Drill oil galleries down thru from the top to the crankcase and camshaft bushings and just give the cams and con rods a squirt of oil on start up.  This engine will never see long duration runs nor heavy service. I want it to run slowly and use a 6 inch diameter flywheel as shown with vanes cut into the outer inch to act as a fan to blow on the cylinders to cool them. This makes for a rather strange looking base but I need that much height in the base to get flywheel clearance.

[Brian Rupnow]

I didn't like that first base---It looked too much like the clock my grandma had on her fireplace mantle!!!

[Brian Rupnow]

So---This is what I would like to do with the flywheel. The flywheel is 6" maximum outer diameter overall x 3/4" thick, made from either brass or mild steel or a combination of the two. The outer band is 1/8" thick The "blades" as I have shown them are 3/16" thick. The outer diameter of the main flywheel body is 4 1/4", and the bore is 3/8". The recess shown in the sides of the flywheel is somewhat irrelevant (I know how to do that.) Now remember--This is a "best case" scenario". I do not have the capacity to machine it from solid. I do have the capacity to cut 3/16" wide slots x 1/8" deep in the outer diameter of the main body to act as "positioners" for the 8 "blades", but the body would soak up so much heat that it would be a real bear to solder the blades in place as individual entities, and that leaves me having to solder or bolt the outer rim into place.--I want the flywheel to be concentric---I hate flywheels that look like they are "orbiting" the crankshaft. I could probably even use #2-56 s.h.c.s. to bolt the blades on, but that's a lot of tapping with a fairly fragile tap. (The head on a #2-56 shcs is small enough to bury in a counterbore in the 3/16" wide blades.)  I'm open for suggestions!!--Brian

[Brian Rupnow]

I have one last piece of bronze left from the government scale checking weight that I was given a couple of years ago. It measures 5 3/4" diameter x 1 5/8" thick. I am so intrigued by the "flywheel with cooling vanes" that I may try to make the flywheel first. :eek::eek: I will have to cobble up some method of slicing it in half. The guy I buy my steel from has a giant bandsaw that he has been using to slice of 1" lengths of this thing for me to make flywheels from, at $10 per slice, but it is now to thin to hold in his saw vice.

[Art K]

Brian,
This is an intriguing project. I have to admit to having a BMW R90 S it does have the cam underneath but the intake on the back and exhaust in the front. I don't know what the cam looks like though. It looks like you are having fun with the design. Keep up the good work.
Art

[Jasonb]

Brian, to reduce your heating (soldering) problem rather than just use an outer ring have one ring 6" and another say 4". You can then solder the fan blades between the two rings as there will not be a large mass of metal to heat. Then turn your central disc to a good fit inside the inner 4" ring and loctite the two together.

[Ian S C]

Make up the fan as Jason says, then the centre part and hub from aluminium. Allow about .001" per inch over size, put the flywheel in the freezer, warm up the fan section to a bit less than enough to disturb the solder, and pop them together, when it cools it won't move.
Ian S C

[Brian Rupnow]

I've spent the best part of this morning tweaking the model. I had the overlap in the main frame going the wrong direction, so I changed that so the bolts. dowel pins, and crank and camshafts were all in the same plane. I went to a centrally mounted single camshaft, which does indeed simplify things.

[Brian Rupnow]

 I already have an "ignition box" containing a standard 12 volt automobile coil, which is wired appropriately with two leads and a high tension wire. It runs in conjunction with an extra 12 volt battery that I have had for years. Since I have 8 or 10 different engines, all single cylinder, with their own points and condensers, I can "plug and play" whatever engine I want into the "ignition box".  I did this because coils are expensive at about $50 each.  i don't want to buy an electronic ignition nor a special coil. I think I can probably make a "splitter box" out of non conductive material which has the coil wire connected to one port, with two separate ignition leads coming out of it, one going to each sparkplug. I see no reason that wouldn't work. Has anybody done that?

[Brian Rupnow]

Okay---now we're at the "what if" stage.--I'm not likely to do this, but IF I decided not to run the engine with an open crankcase, it would be simple to add a couple of gaskets and a top cover. If I ran a cover, then I would need to run some oil in the base for splash lubrication.--As Jason pointed out, this would lead to other issues, with the clockwise rotation flinging oil into the "down-wind" cylinder and loading it up with oil. Really, at this point I'm just "imagineering".
 

[Dave Otto]

I already have an "ignition box" containing a standard 12 volt automobile coil, which is wired appropriately with two leads and a high tension wire. It runs in conjunction with an extra 12 volt battery that I have had for years. Since I have 8 or 10 different engines, all single cylinder, with their own points and condensers, I can "plug and play" whatever engine I want into the "ignition box".  I did this because coils are expensive at about $50 each.  i don't want to buy an electronic ignition nor a special coil. I think I can probably make a "splitter box" out of non conductive material which has the coil wire connected to one port, with two separate ignition leads coming out of it, one going to each sparkplug. I see no reason that wouldn't work. Has anybody done that?

The voltage will take the path of least resistance; only one plug will spark.

Dave

[ogaryd]

Brian,  I believe your ignition idea will fire the plug on the cylinder W/O compression.              Gary