Engine fan blade construction

[gbritnell]

Mosey had started a thread on mounting a chuck on a rotary table. I didn't want it to get to far off topic as there was some comment on building a fan for a model engine.
I am attaching some pictures of the fans I made for a couple of my engines. First up will be the 302 engine. The fan is made in 2 pieces. I took some .032 aluminum sheet and cut out the shape that I wanted. For this one I made a small die to press a rib into the blade for stiffness. The tip was then curved. It is mounted with 4 bolts through the fan and hub into the flange on the water pump. I wanted to replicate a full sized fan as much as possible.
George

 

[gbritnell]

Next up is my Holt engine. The drawings for the Holt didn't include a water pump or fan which is how I originally built it. It didn't take long to find that there was way to much heat in the engine to run without a water pump. With that addition it helped tremendously but would still get warm after a short while. I then added the fan, mounting brackets and shroud to the engine. Being that this was an industrial type of engine I wanted a fan to fit the engine so this was the style that I made. It is cut out of one piece of aluminum sheet. I made a die out of wood to form the curve uniformly on all of the blades. As you can see it the bolts go through an outer flange, the fan and into the hub.
I must say at this point that most fans on small model engines are somewhat cosmetic. With the Holt the engine spends most of it's time running very slowly and the fan doesn't pull much air through the radiator. I even put more curvature onto the blades but it just doesn't pull much air. The 302 is a little different because the fan is a bit larger but it still only does a minimal job of air movement.
If a person wanted to run his engine for extended periods of time I would recommend using a small muffin fan placed in front of the radiator to blow air through it.
George

 

[gbritnell]

Here is one last picture of the Holt with the shroud and fan in place. It does pull air through the hottest part of the rad but not enough for extended periods. Once the water gets warm in the Holt I can run it for about 5 minutes before it starts to spit out of the overflow. How that equates to operating temperature I can't say. When it does this I let it sit for about 10 minutes and then start it back up.
George