🥚 Egg Beater: step-by-step build

Turn the handle and two whisks whizz round in opposite directions.

Before electric mixers, cooks used a hand egg beater — invented about 150 years ago. You turn a handle sideways, and a corner gear sends the spin DOWN to the whisks. Two gears side by side make the whisks spin opposite ways, so the eggs get beaten from both sides. Yours stands on a table over its own "bowl" — no eggs needed!

• Level 2 of 5 (easy)
• About 20 minutes
• 12 steps, 38 parts
• Powered by: Hand-crank
• Series: Mechanical Wonders

What you will learn

• Bevel Gears: Around the Corner: Slanted gears send spinning power around a corner.
• Idler Gears & Direction: A gear in the middle flips the direction back.
• Gear Ratio: Fast or Slow: A big gear turning a small gear makes it spin faster.
• Frames: A frame is a ready-made strong rectangle.

Build these first

• 🌬️ Bevel-Gear Windmill: Turn the handwheel at the bottom — the sails spin at the top! (level 3 of 5, about 25 minutes, 16 steps)

Parts you need

• 1 × Open frame 5×11
• 4 × Axle 8
• 9 × Half bush
• 1 × Open frame 5×7
• 5 × Bush
• 2 × Knob wheel
• 2 × Cross block
• 2 × Axle 7
• 2 × Small gear (16 teeth)
• 1 × Corner gear (12 teeth)
• 2 × Blue long pin
• 2 × Split pin block
• 2 × Red axle-pin
• 1 × Beam 5
• 1 × Corner gear (20 teeth)
• 1 × Hand crank

Steps

1. Lay the 5×11 frame flat. This is the bowl stand.
2. Stand three 8-long axles in the stand: holes 5 and 7 of the left side and hole 7 of the right side. Push a half bush down the right column onto the stand.
3. Slide a half bush down each column until it is one hole below the top.
4. Press the 5×7 frame down onto the columns until it sits on the half bushes. This is the gear deck. Lock it with a half bush on top of each column.
5. Right whisk: hold a bush under the 4th front hole of the deck, then a knob wheel and a cross block below it. Push an 8-long axle down through the deck and all three.
6. Left whisk: the same through the 2nd front hole with a 7-long axle, and the cross block's arm pointing the other way.
7. Slide a 16-tooth gear onto each shaft, on top of the deck. Their teeth must mesh. Lock the left one with a half bush.
8. Put a small corner gear on top of the right shaft and lock it with a half bush.
9. Push a blue long pin up into the 3rd and 5th holes of the back end of the deck. Press two split pin blocks onto them, one on top of the other.
10. Push a red axle pin into the middle of each block, pointing forward, and press a 5-hole beam onto them: the crank post.
11. Hold a bush against the front of the post, and another bush and the big corner gear in a row over the small gear. Push the 7-long crank axle through the 3rd hole of the post and all three.
12. Lock the corner gear with a bush on the front end of the axle, and put the red crank on the back end.

Play time

Turn the crank slowly and watch which way each whisk spins. Now crank fast! Count: one turn of the handle makes the whisks go round how many times?

Real-world inspiration

Rotary egg beater (1870s patents) — https://en.wikipedia.org/wiki/Egg_beater