Position sensor problems

I was doing some trial fitting after downloading CAD data for the smallest MTS linear position sensor I found at this point in time. At first I thought it would be too big but I am going to spend some time trying to tweak it into position to see if that is the case before deciding to not use this sensor. If I can make it work out, the pushrod will be a part of the actuator itself. Increasing the bore for the position sensors also created clearance problems for the caps that will seal the actuator bore. This problem can be remedied easily but I can see that this entire area will be problematic to the water jacket plates regardless. I will try contacting MTS to see if they offer a smaller sensor. If they do not, hopefully I can get this one to work.

 

Position sensors and hydraulic solenoids

I found this position sensor made by MTS last year while working the original design. I really like them because of the accuracy, response time, and durability. This is a non contact sensor so wear over time is not an issue and it is easy to calibrate and recalibrate as necessary to compensate for thermal expansion as the engine is running. MTS will actually custom make sensors for companies, but I do not have the money to pay for this luxury at this point in time. The major problem with this sensor is its size. It will require a cavity about 2 inches in diameter. I would have to move the bore centerlines which means that the push rods would be drastically angled. I thought about using an offset on the actuators to line the push rods back up with the rockers, but I am not happy with the added mass to the actuators required. Getting this system to operate at at 6000 RPM minimum is already going to be a challenge so adding weight to the reciprocating assembly is not a solution I will accept. I checked out the MTS product line again and found this position sensor. It has a diameter of 1.1 inches which I can squeeze into place by increasing the bore and adding a little material for support.

I am having doubts again about where to place the hydraulic solenoids. I am thinking about mounting them in the valley again. Having remote mounted solenoids would be ideal but that creates more problems than it solves. Having 16 separate hydraulic lines running into the engine block adds too many potential leak points, adds unnecessary clutter in the engine compartment, and complicates the way fluid is routed internally. These lines would also interfere with the accessories at the front of the engine and the bell housing at the rear.

My next major obstacle is going to be a crankshaft position sensor. Accuracy to the half degree would be perfect but, I am going to need something that is at least accurate to the degree. I have quite a bit of work to do before I really have to worry about this so I will just see what's out there for the time being.

Getting close

The block design is getting close to done. The only major piece of the puzzle missing is the main web thicknesses. I have the bolt hole locations but without the thicknesses, there is absolutely no way a Chevy crankshaft would properly fit. I found that SEMA members have access to GM CAD data. It will take me quite a while to save up the money to pay for a membership and get a hold of this information. I have searched for hours trying to find this information on the internet with no luck as well. For the time being, I will ignore the fact that the main webs are not correct. I also need to add bolt holes, oil passages, skirt the block, add the water jacket plates, and add water/steam holes to the deck. I can then add and remove material where necessary for strength and weight reduction and begin FEA and CFD. The next major piece of the puzzle will the the hydraulic manifold and solenoids. This will be fairly simple to complete. The hard part is finding the right solenoid. I have not received a positive response from any company I have contacted yet. Next on the agenda will be high resolution position sensors.

Fluid routing

Routing the hydraulic fluid for the valve actuators through the block is taking a lot longer than I expected. I wanted to keep the solenoids out of the valley and away from the heat and vibration. This would allow me to service/upgrade the solenoids without tearing into the engine as well. The downside is that instead of one pressure and return line going into the block, I have to have a line for each intake/exhaust valve going into the block. I spent a few days trying to come up with an efficient way of doing this and came up with a bolt on piece that looked similar to the valve body in an automatic transmission. I decided to ditch this because it bolted on. Expansion, contraction, and flexing would affect the mating surfaces and numerous seals and gaskets would be required. This introduces to many opportunities for leaks in the system. Any failure in this system would be catastrophic so I want to eliminate as many possible ways for it to fail as I can. This will also be cheaper since I will not need a separate piece machined, o-rings, gaskets, bolts and washers. Judging from the many designs on paper, I will most likely have to play around with the actuator locations in order to have these hydraulic fluid passages machinable. Looks like stock pushrods might not be possible. Here are a few screenshots of the block. I have not done much since the last post. I have spent most of my time drawing different possible solutions on paper.

Coming into focus

I have been tweaking the block design to get it as efficient as possible in CAD format. I am working on a five year old laptop so I need to keep things as simple as possible in order to FEA and CFD analysis on it in a reasonable amount of time once I get to that point. While tweaking the design and dimensions I decided to factor in the water jacket plates last because I found myself working around them when there is absolutely no need for me to do that at this point. I got a hold of the dimensions for the main bolt locations which will give me an idea of where to place the main webs, but I am still going to hold off on adding them until I have all the dimensions I need. Here is what it looks like so far:

It doesn't look much different from the last update but there have been many changes made. I will be working on the actuators themselves today. Once a rough draft done, I will place them in the desired positions in the valley area and begin to add the necessary support structure for them to the block itself. These will be similar in design to linear hydraulic actuators. The biggest challenge will be for me to place them in this area along with the hydraulic fluid pressure and return bores, have them communicate with the main oil feed (in order to lubricate the cylinder heads via the pushrods), and making sure the hydraulic fluid and engine oil remain separated. I will be using the spreadsheets I have been working on to get an estimate on the necessary fluid passage diameters. Hopefully everything will fit with no problems and allow me to still use stock length Chevy pushrods.