Building a 1933 Harley-Davidson VL: Baffle Repair

As you can see from the above picture, the front baffle on my right engine case had a nice size hole in it.  This appears to have been cause by a piece of debris getting caught between the flywheel and the backside of the baffle which punched out the hole.  This also caused a spiderweb of cracks to form, which were not visible until the baffle was heated for welding.  In the end, I TIG welded both sides of the baffle to ensure that all cracks were repaired.

When welding aluminum, you always want to start out with the cleanest material possible.  I had already cleaned the outside of my cases, so I jumped to the next step which was preheating.  The case was placed in a small parts oven (not a kitchen oven!) and heated at 400 degrees Fahrenheit for about 45 minutes to ensure that the entire case had been warmed equally.  This process was repeated multiple times during the repair.  After doing a pass, I would allow the case to cool to room temperature before heating it back up in the oven for the next pass.

While I was waiting for the case to heat up in the oven, I fashioned a piece of  1/4" thick copper plate to fit over the hole in the baffle.  Aluminum will not weld to copper, so this allowed me to fill in the hole from the backside of the baffle.  I used clamps to hold the copper plate in place during the welding.

Once the hole was filled, my main concern was repairing the cracks which radiated out from it.  Between welding up the cracks and filling holes left from sand casting, I basically welded the entire baffle on both sides.

Now came the fun part.  The excess weld on the backside of the baffle was ground down using a small flap wheel on a hand drill.  I traced the curvature of the baffle from the left side case to make a template to help insure that I ground down the backside of the baffle to the correct shape.

The top of the baffle was much harder to access, so I made a custom tool to do the job.  I started with a 1/2" 4 flute endmill and made a sleeve bushing out of aluminum to cover all of the cutting surfaces leaving 1/4" of teeth exposed on the end.  Then I epoxied the sleeve bushing to the end mill so that the end mill would not rotate inside the bushing and cut through it.

I made a custom end plate for my router out of acrylic which allowed it ride on top of the cases without falling off.  I also fabricated an aluminum engine stand which I could clamp to my work bench to make sure everything was held rigidly in place.

The next step required a steady hand and a lot of patience.  I made many passes over the baffle, cutting about 1/32" of the excess weld with each pass, lubing the surfaces with Teflon lubricant before each pass and cleaning out the chips after.  I was able to use the intact baffle on the left side of the case to set my heights for the different sections of the baffle.  In the end, the results were excellent.

With the bulk of the work done by the router, very little sanding was needed to finish out the repair.  Next the cases will get a thorough cleaning before moving on to coating the insides with Glyptal.

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