Just thought of something.
The way to be sure that compression ratio, and flow, stays the same, is to machine the chamber on 1 side, and dyno engine with this. Then machine the other chamber to match.
Without a flow bench, and a really good way to determine combustion chamber size, this looks like the best option.
Just putting this out there.
You are gaining valuable experience in engineering and communication skills to complete a project not your own.
As an addendum, and to help the next engineer for the coming mods, I would drill the holes to match the rest of the gaskets, or at least those which fall outside the combustion chambers, to help retain the head gasket from moving.
You likely will get by with the girdle approach for the stock configuration. But boost will change the game.
I wanted to comment on this.
The way I did the spacer was knowing that the compression ratio is 6:1, you can simply use the formula for the compression ratio to calculate the volume. You can see the calculations in the picture. Basically, since I 3D modelled the part to then CNC, i was able to measure the resulting volume, ensuring that the combustion chamber volume stays the same.
Still on this, I liked the idea you proposed about offsetting the cylinders to reduce the volume and make the cylinders stay right on top of the valves. However, there were two reasons to do it this way. First, so that the gaskets would align and make the design easier. But the two main reasons were that there was a minimum thickness required to be able to install the spark plugs on the side. We preferred that design to installing the plugs elsewhere. Since the spark plugs were about 18mm in diameter, I had to make the spacer 20mm thick. That's why that centre volume had to be kept to keep the compression ratio and the volume inside the chamber. Also, we wanted to make the cylinders align because that's one of the reasons to better come close to a true opposed piston engine, with a shared cylinder, thus offsetting was not ideal.
Also, the gaskets can be used since the holes align. You can see in the picture. That's also one of the reasons to mount the engines this way.
The previous engine was made another way. Supposedly easier, but the compression ratio took a hit and the only way to ensure a tight seal was to clamp the engines together without any bolts. There were no leaks but since the valves were on the same side and on top of each other, the flow was not optimal, resulting in poor scaveging. That's also one of the reasons I ended up doing it this way.
In fact, one of the engines ended up rotating the opposite direction which also certainly didn't contribute. We decided to go for this design hoping that it would result in better flow. We'll have to see.
The stock cover has a breather it wont be oil tight . Yes add breather .
A pair of small holes on top the vale chamber would be my choice.
Though they should be in oil being at the bottom .
Carbs either way works .
You may have something im unfamiliar with . It needs a vent too atmosphere unrestricted from the crank case up high or at least above the crank in my opinion .drill and tap a nipple in . Or what you have may work . If thats the fill tube and its submerged in oil i do not think it will work . I am used to venting the crankcase via a nipple . To open airor a catch tank to open air . To capture any residual vapor .
The valve spring chamber itself does not necessarily need a vent. In stock form, the entire crankcase vents thru the valve spring chamber.
Remember, the piston displaces the same amount of air in the crankcase as it does in the combustion chamber, during each revolution of the crankshaft.
Also, some pressure will escape past the piston rings into the crankcase. This will need vented outside the crankcase.
The factory setup uses the one way valve to try to prevent air from reentering the crankcase after it has blown out, to try to create a partial vacuum for the piston to move in, in the crankcase.
The factory uses the valve chamber as a vent as it is isolated from the flurry of oil wrapping around the crankshaft while the engine is running.
In your case, leaving the one way valve open on the bottom side will effectively pump oil from that chamber.
Plug hole, and put a nipple that you can attach a hose to, to the upper side of the crankcase. You will lose the benefit of the one way valve, but will allow oil which escapes here to drain back into crankcase.
I would simply make a flat plate cover for the valve chamber.
I'm still undecided about using the stock breather tube in both engines or disabling both and installing a breather plug. I'll discuss it with my professor.
The inclination was exactly what I had in mind. I see you raised the level of oil you anticipated to need. However, that lowered the level of oil not in cylinder bore for the right engine. Probably just better to leave level.
Keep in mind, most of that will be suspended in the air, wrapped around the crankshaft. Which is how the engine gets lubricated.
Isn't our world just full of compromises?
That is true! ahah
I actually prefer to leave them levelled.
Should be able to get your dyno runs done in that configuration. Just watch oil levels between runs. It may be beneficial to come up with a method of measuring oil levels, before final assembly.
Now on to my opinion on a way to further optimize the opposed piston setup.
I like the concept for the head and sparkplug. however, I would align the cylinders and use a dome on the pistons to get to original compression ratio, or raise it even further.
The biggest reason most flatheads do not run higher compression ratios, comparable to OHV engines, is that the only way to make the chamber smaller also restricts airflow. In the search for power, need to get the air in before worrying about compressing it.
In a fully designed engine, a method for securing cylinders to heads would facilitate bolting each half directly together. My thoughts for this utilizing the existing engines is to align bores and use counterbores open to the outside of the engine to bolt each half to the head.
I think having the bores aligned and open to each other would help flow even further.
The design you are using has the benefit of moving the valves closer to the cylinder it is feeding, by putting that air to the opposite engines cylinder. Absolutely should see a large increase in flow.
Right now, not exactly an apples to apples comparison. so, how do you know where the change in power came from?
Any experienced racer will tell you to learn, only change one thing at a time.
You do have the benefit information of the previous test, albeit from a completely different rig.
I think the gear drive setup will net out a loss in power, but an increase in reliability. The belt, or chain will prove less of a power hog, as well as consuming less design and build time. When power levels get high enough, loss in reliability will make the gear drive a necessity.
Injection and turbocharging will both increase torque and power output. but also at higher initial costs.
Like I said, fun to think about.
Can't wait to see the results
Since I want to get a baseline for the stock engine, I really don't want to modify the piston in any way.
I understand what you mean by machining some new pistons with a dome. Maybe that can be done in the future since these projects are always evolving to try and study the impact of different things. My goal is to get the baseline, then compare the performance of each change.
When I'm done, someone in the future will probably install an injection system, turbocharger, machine new pistons, etc. Maybe even a new spacer or more to compare different configurations. And those are all very interesting to mess with! But right now, I can't go down that road, unfortunately.
These belts are actually rated for very high power, high torque and high rpm applications so I don't expect any problems. But indeed further down the road a geartrain may be installed.
One other concern . The dipper on a stock connecting rod is high carbon or spring steel .
those are known to break in a racing application .
if you manufacture your own custom dipper . that may be a concern .
Just a side note Mike Clements came up with an idea to use moving cylinders above the valves .
the design took up extra space in the combustion chamber , without shrouding the valves .
As for the dipper, I'll probably use an aluminium piece bent, similar to the one that is in the pictures I shared previously. I don't think I'll have any problems with it. Worst case scenario, it would bend a little more. And it's lighter and more flexible than steel, so it must have a reduced impact on the rod movement.
That idea is a great idea. However, as I said before, it'll probably not be done for now since the piece is already machined and also for the reasons I mentioned before.
