Some good progress on the L-P the past couple of weeks...
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| Trying out fuel tank fit |
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| Sheet metal and seat in front cockpit |
I also wanted to take a look at how the cockpit sheet metal and seats were going to fit. Fortunately, I have the original pieces and some that Andy had made back in the '60's when he bought the airplane. It was not as much of a puzzle to figure out that I thought it would be. I'll have to fabricate quite a few, but they are mostly simple pieces with just a few bends here and there.
It is quite a luxurious cockpit for the '20s. Much of the interior of both cockpits is covered with sheet metal (painted gray) with a black leatherette material laced on in the open areas. This material, also used for the headrest and cockpit combings, is called a long-grain cobra material which is used on vinyl tops and upholstery on Model T Fords. (more Ford stuff!!)
There is also a decent sized baggage compartment in the rear. I'm focusing on it first. Fitting and fabricating the necessary parts. The frame and compartment are fine, but I need to make a new door. I have the original latch which will be a nice addition. I'll post pictures of it when done.
I also got a good start on the OX-5...
The camshaft goes in first. The fit and bearing clearances are very important. Curtiss had a goofy idea of first sending oil through the camshaft and then to the crankshaft main bearings. Excessive clearances on the cam bearings lead to lower than normal oil pressure at the crankshaft. Manuals call for .0015 clearance between the cam and the bearings with a tight fit of the bearings in the crankcase. Having such a low time engine, my clearances were all within spec.
It works best to slide the camshaft into the crankcase, then install the bearings just before their respective positions, then drive the assembly into position. Doing it this way, you are only driving each bearing into its mounting bore once.
Once the cam is fully installed, you can put the front and rear bearings into position. The number 1 cylinder is at the rear of the engine (tractor configuration) the bearing with the oil pressure regulator is on the propeller end. The fitting shown above the regulator in this picture is where the oil pressure gauge attaches.
Hex-head screws "pin" the camshaft bearings into positions so they cannot move. These screws were not originally safetied. A common mod is to drill the heads and the adjacent web in the crankcase and safety wire them.
The crankshaft goes in next. I bought a new bearing. It's a stock bearing, still made today - identical to the original. Buying this bearing is one of my favorite stories...once I determined the number, I shopped around to find the best price. Believe it or not, Amazon had the best price. I ordered the bearing for a 100 year old OX-5 and the movie The world's fastest Indian - all on the same order. It is amazing how times have changed!
I had to get the rod bearings re-babbitted, but the mains checked out great. The clearances need to be .0015-.002". Mine were all within these tolerances.
When the crankshaft is installed, make sure the timing marks are properly aligned.
Once everything is torqued and secured, the crankshaft/camshaft should rotate with no binding. It's also important to make sure there is clearance between the camshaft gear and crankshaft gear, and that the thrust bearing will rotate in the crankcase. This assures the crank is being supported by the main bearings and not the gears or thrust bearing.
This is also a good time to lap in the prop hub before the key is installed on the tapered portion of the crank. I just use fine valve lapping compound, put some on the hub, and slowly rotate it around . It's amazing how much better the fit is after doing this. This also makes sure the nickel plating I had put on the hub did not reduce its ID any.
Got a few things ready to assembly cylinders too. I had new intake springs made (the exhaust were fine). I measured the load on all the springs to make sure they were in spec. I also made a valve spring compressor to aid installation. For this, I used a broken water pipe/rocker arm support and then made a handle to compress the spring. What's nice about it is I can pull out the shaft that holds the handle, rotate it around, and install the other spring without unbolting the support.
Another mod many people do is to make an exhaust deflector to go under the exhaust spring. The exhaust manifold has a deflector welded on it, but this will not protect the spring from loosing its temper if the gasket blows. You could make these from many different materials. I made mine from .032" 4130 so I could black oxide them. I'll have better pictures to show how this works once the cylinders are assembled.
PHEW! A long post. The next one will probably be more sheet metal work on the airframe and OX-5 assembly. Check back in a couple weeks.
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| Sheet metal and seat in rear cockpit |
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| Baggage compartment |
I also got a good start on the OX-5...
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| New gasket under oil pressure regulator |
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| Cam bearings are a matched set - make sure numbers match |
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| Getting ready to insert cam into location |
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| Cam fully installed showing regulator |
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| Cam bearing retainer screws drilled and safety-wired |
It works best to slide the camshaft into the crankcase, then install the bearings just before their respective positions, then drive the assembly into position. Doing it this way, you are only driving each bearing into its mounting bore once.
Once the cam is fully installed, you can put the front and rear bearings into position. The number 1 cylinder is at the rear of the engine (tractor configuration) the bearing with the oil pressure regulator is on the propeller end. The fitting shown above the regulator in this picture is where the oil pressure gauge attaches.
Hex-head screws "pin" the camshaft bearings into positions so they cannot move. These screws were not originally safetied. A common mod is to drill the heads and the adjacent web in the crankcase and safety wire them.
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| New thrust bearing |
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| Thrust bearing installed and installing lock wire |
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| Main bearing cap |
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| Timing marks on camshaft gear and crankshaft gear |
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| Completed installation with bearing caps torqued |
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| Don't forget the bevel drive gear for the oil pump! |
I had to get the rod bearings re-babbitted, but the mains checked out great. The clearances need to be .0015-.002". Mine were all within these tolerances.
When the crankshaft is installed, make sure the timing marks are properly aligned.
Once everything is torqued and secured, the crankshaft/camshaft should rotate with no binding. It's also important to make sure there is clearance between the camshaft gear and crankshaft gear, and that the thrust bearing will rotate in the crankcase. This assures the crank is being supported by the main bearings and not the gears or thrust bearing.
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| Lapping in prop hub |
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| Finished lap showing good contact the entire length |
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| Valve spring compressor |
Got a few things ready to assembly cylinders too. I had new intake springs made (the exhaust were fine). I measured the load on all the springs to make sure they were in spec. I also made a valve spring compressor to aid installation. For this, I used a broken water pipe/rocker arm support and then made a handle to compress the spring. What's nice about it is I can pull out the shaft that holds the handle, rotate it around, and install the other spring without unbolting the support.
 |
| Exhaust deflectors |
Another mod many people do is to make an exhaust deflector to go under the exhaust spring. The exhaust manifold has a deflector welded on it, but this will not protect the spring from loosing its temper if the gasket blows. You could make these from many different materials. I made mine from .032" 4130 so I could black oxide them. I'll have better pictures to show how this works once the cylinders are assembled.
PHEW! A long post. The next one will probably be more sheet metal work on the airframe and OX-5 assembly. Check back in a couple weeks.
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