A lot simpler than the solder method I have seen. The bushing is locked in place very nicely due to its ovality and of course the locktiteUsing a softer bronze is a good suggestion, I do have some softer Bronze that I have designated for use in making the valve guides. I had some bronze bushings laying around and thought I would give them a try. It requires some special attention when machining. Below are a couple of snaps of my second attempt.
View attachment 137577
View attachment 137578
I am please with the design changes to the connecting rod. The bronze bush is thicker and the cap looks substantial enough. I also was very careful when machining the bronze. I used lots of oil and stepped up one drill size at a time.
This conrod blank is ready for the outside "cosmetic" machining.
That material looks a lot like oil lite bush material ? which is a sintered material and difficult to get to very thin wall due to the particle size so bits fall offOffy – Conrods Part 1
I am going to try something different with the connecting rods. I want to install a bronze split bushing in the big end. It will be secured with Loctite and brass taper pins. As a warning, my first attempt was a failure as can see below:
The bushing is too thin and the material is very brittle and hard to machine. I want the cap screw holes to clear the bushing, but the distances are really tight and the resulting bushing is too thin.
To back up a bit, the following images are of the desired connecting rod. It is not symmetrical as can seen in the side view due to the geometry of the crankshaft with respect to the pistons–the big end is offset from the piston center.
Below is the material squared up and ready to go, fortunately I only make one to start with.
I drill a clearance hole in the work piece to facilitate CNC machining.
Then I turn the bronze bushing to size.
The big end profile is machined:
The hole is reamed and the bronze bushing is installed with Loctite.
The end cap has the cap screws holes drilled/tapped and countersunk.
A slitting saw is used to separate the cap. I use a 1/32″ thick saw blade.
so far, so good.
The surfaces are wet sanded and then the cap is screwed into place.
I then drill and ream out the big end hole. This is where things went awry. Perhaps the drill was not sharp enough, I got too aggressive, or the design was simply poor not allowing enough bearing material.
The gudgeon pin hole was drilled and reamed.
And again the end result:
So I redesigned the Conrod. I moved the cap screws outward to allow for a thicker bearing and I added some material to the con rod cap.
Below is the beginnings of a second try. Here I have completed all of the above steps to the point where I am letting the Locktite cure–that will be over night. The bronze bushing diameter the first time around was .4385″, the second attempt is .499″. The ID will be .375″, so I will have more meat in the bushing, but less in the cap.
So, I am now waiting for the Loctite to cure. I will report back after the rest of the conrod machining is complete.
Ron Colonna used Loctite (don't know which variety) but told me he had issues with his exhaust valves coming loose. When I did mine, I used Loctite 620 and for safety pinned them in place with steel pins. Steel wasn't necessary and will make them more dufficult to remove should the need ever arise. Care is needed to secure them at their edges without actually penetrating their interiors. - TerryFantastic work! I wonder how you are going to secure the valve guides in the head? I have used Locktite stud setting formula and still had some leaks.. The problem was solved with the wicking threadlocker Locktite This is a very useful product and its ability to creep into places is fantastic, sometimes too much so!
I am still formulating my soldering strategy. My thought is to solder the feeder tubes to the flange first, then the cross tube to the feeder tube and the carburetor tube last. Jewelers often use different formulations of silver solder that have slightly different melting temperatures that allow them to stage assembly of a piece. They use the higher temp solder first, the idea being they do not need to raise the temp of the piece as high for subsequent solder operations and not disturb previous work. The single roll of silver solder I have nearly broke the bank, so I am not going to be purchasing additional types.
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