{short description of image}Engine Case
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{short description of image} This is what your new case will look like. The case comes with studs installed to hold the case together but I removed them to do the machine work.
{short description of image} The first thing I did is drill and ream for a 1/4" dowel. When the case is cut in half, one of the installed dowels goes away with the scrap. The location doesn't really matter as long as you try to put it as far from the other dowel as possible. You can see where I drilled if you enlarge the picture.
{short description of image} I purchased a complete VW aircraft engine on ebay that I am using parts from for this engine. The engine I purchased came from Team 38. It was brand new but when I tore it down I found some pitiful machine work on the case. I wouldn't put that case in a car let alone an airplane. The rest of the parts were very high quality. It came with a Scat 78mm crank and Scat individual heads which is why I wanted it in the first place. The crank came from Great Plains because it has their Force One hub with a 1/2-20 bolt. The hub is probably overkill for this engine but since I already had it with a crank machined for it I figured what the heck. This is the setup I used to bore the front bearing bore.
{short description of image} Great Plains instructions on their web site for installing the Force One hub say to bore the front bearing bore .001" smaller than the hub bearing measures. Here the bore is finished and I am checking it with a Sunnen dial bore gage. If you enlarge the picture you will see the needle exactly on zero. I cheated with the reading. It ended up .0001" under nominal. I had to make you think I'm perfect. By the way, if you are in the market for dial bore gages, buy Sunnen gages. They are the best.
{short description of image} This is one case half after machining the bearing bore for the hub bearing. The cast magnesium machines real pretty.
{short description of image} The next step was machining for the 94mm cylinders. This is the setup I used. It was just clamped to 4 1-2-3 blocks.
{short description of image} I circle interpolated the bores on the CNC with an end mill to finish the bores. They didn't need to be as accurate as the hub bearing bore so I didn't use a boring bar. I machined both cylinders on this case half because I wanted to practice on the rear cylinder bore first in case I programmed it incorrectly. I wish I hadn't now because I have to block this rear cylinder bore off after I cut the case and It would have been easier with the stock bore. Live and learn.
{short description of image} After machining, I checked for proper cylinder fit before removing from the machine.
{short description of image} Once the cylinders fit the case I could check for clearance of the rotating assembly. Here the crank is in the case with the main bearings installed and one rod, piston and cylinder. According to Great Plains, you should check each cylinder for clearance individually. Check it with both case halves and a piston without rings. Rotate the crank to make sure nothing hits the case. I am using Scat I-beam rods which are already clearanced for a stroker crank. With a 78mm crank, the Scat rods don't hit the case anywhere in my engine. I will be doing more checking later, but for now I am happy I don't have to do any clearance work to the case. If I was using stock rods or an 82mm crank, it wouldn't clear.
{short description of image} When I was checking clearance I had to stick in another cylinder to see what it looked like. Pretty cool!
{short description of image} It's always fun putting expensive parts in a saw and cutting them in half isn't it? Check your measurements 5 or 6 times to make sure you aren't going to screw up. I cut mine long so I had plenty of room to face it to length on the mill. None of the plans I purchased gives a good measurement for where the crank ends and the case ends for proper location of the mag. You get to figure this out yourself. I'll be waiting till later to do some measuring before I finish the back of the case. I'll have to allow for the plate on the back, make sure my engine mounts will work, and allow for a mag drive on the crank and mag mount on the back plate. I'll let you know what I do.
{short description of image} This is the case in the saw after the rough saw cut. I sawed it very long. I will have to machine a lot of material off.
{short description of image} Here is the case out of the saw after being cut. The pieces removed weigh 7 pounds. The information I found before I decided to go this way lead you to believe that only 5 pounds are removed by cutting the case and you add it all back with a back plate and engine mount. I'm thinking some of these people just want to sell their plans. We'll see when I'm done. There are advantages to both methods of conversion but I think I'll save weight by using a mag instead of a stock ignition with a battery. I am planning to make a back plate out of 3/4" aluminum. I will be removing most of the material by machining pockets in the plate where the strength is not needed leaving thin webs for strength. Doing this I can have engine mount locations in the same place as the Mosler engine and I can build a motor mount per the plans. Right now I am just talking and I haven't designed the thing yet so I don't know if it will work. I'll keep you posted.

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