Cooling Fan Repair

Heinkel Engines have a fan screwed onto the armature that provides cooling across the cylinder fins on the engine. If you get something caught in the fan it is possible to break blades. A high speed spinning fan that's off balance could vibrate excessively.

How do you fix a fan blade? I decided to try using epoxy and then try a test to see if it would hold .

Here's the fan. I'm lucky only one blade was broken. If I had a lot of broken pieces I'd consider buying a new fan, although there are supposedly 5 or 6 different fans and none of them are reproduced by the club.

Heinkel Fan with Broken Blase at Bottom

 Here's my fan. The bottom blade is broken off. My first step was to clean this up so the epoxy fan would stick to it.

Two Part Epoxy in Cross Section

I decided to use a semi-solid epoxy roll that I would mold into shape. You cut a section of glue off of a roll and roll it out to activate the hardening process. After rolling it out I used the existing fan blades to mold the replacement blade to the proper shape. 

Molded Blade in Place on Fan

Once I molded the blade I stuck it into place, and then extended the glue down the side of the stub. It was a lot like a dentist putting a crown on a tooth.

Heinkel Fan Repair from Top

Once the blade was added I let it dry for about 20 minutes before trimming it to shape with scissors.

The next step required some patience. I decided to let it dry for a week or two to make sure it was totally cured. The real test would be to see if it would hold up in real life. A spinning fan is subjected to a lot of force (think of jet engines losing blades and the consequences). 

I decided to test it using a wood lathe.

Testing Fan Repair on a Wood Lathe

On my lathe I can get up to 3000 RPM, and I can shift speeds on the fly. I thought is would be a good simulation as I could move between different speeds easily. Also, since the lathe was electric, I got immediate torque from the engine that probably exceeds what the Heinkel engine would ever produce.

The Result: Passed with flying colors! I think it's a good solution. It's slightly softer and a bit flexible, is more or less the same color as the rest of the fan, and it's pretty easy to do. I recommend it.