Inline Twin Engine Ep. 16

To be able to tension the O-ring belts, I’ll be making a dummy alternator.

For the alternator bracket and tensioner parts, which are somewhat odd shaped, the first side is machined. Then a set of machinable jaws is installed in the vise to machine off the holding stock and finish the second side of the parts.

Inline Twin 247 (800x600)Inline Twin 248 (800x600)Inline Twin 249 (800x600)

Second side being machined in the soft jaws:

Inline Twin 250 (800x600)Inline Twin 251 (800x600)Inline Twin 252 (800x600)

The tensioner parts are tapped, and the slot for the fork is milled.

Inline Twin 253 (800x600)Inline Twin 254 (800x600)

The alternator housing and end bell are machined:

Inline Twin 255 (800x600)Inline Twin 256 (800x600)

Here the finished parts:

Inline Twin 257 (800x600)Inline Twin 258 (800x600)Inline Twin 259 (800x600)Inline Twin 260 (800x600)

The assembled dummy alternator:

Inline Twin 261 (800x600)Inline Twin 262 (800x600)

Installed on the engine:

Inline Twin 263 (800x600)Inline Twin 264 (800x600)

The fan is made from .040″ 3003 aluminum sheet. I used CA glue and masking tape to secure the sheet to a plate. The use of masking tape seems to be popular by a number of YouTube machinist, so I figured I would give it a try. It worked very well. To release, I warmed up the parts until the bond let go.

Inline Twin 265 (800x600)

The fan blade after deburring:

Inline Twin 266 (800x600)

To press the radius into the blades, I 3D printed a die with the required shape. This was an experiment, and it worked flawless. I’m confident this would work on even thicker material.

Inline Twin 267 (800x600)Inline Twin 268 (800x600)Inline Twin 269 (800x600)

The last part was to twist the blades. For this, I used the bending die again, to gripped the blade firmly, while using a protractor to twist each blade the same amount.

The finished fan:

Inline Twin 270 (800x600)Inline Twin 271 (800x600)

The fan installed on the engine:

Inline Twin 272 (800x600)


Thank you for visiting my shop.

If you have any questions about the engine or any of the other projects, please leave a comment below, or email at yogisworkshop(at)

For other projects from the shop, please check out the Projects Page in the top menu.



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