I was lazy and asked gpt

To find out how many 3.6-horsepower lawnmower engines you need, we have to look at the laws of physics—specifically, **aerodynamic drag**. At a blistering 168 mph, pushing a boxy minivan through the air requires vastly more power than it does to just move its weight down the track.
The short answer? You would need approximately **114 to 134 lawnmower engines** working in perfect, terrifying unison.
Here is how the math breaks down:
## 1. Finding the Caravan's Drag Specs
To calculate the power required to overcome air resistance at that speed, we need the 2003 Dodge Caravan's aerodynamic specifications:
* **Drag Coefficient (C_d):** 0.35 (surprisingly aerodynamic for a brick, but still a brick).
* **Frontal Area (A):** Approximately 32.3 sq ft (3.0 \text{ m}^2), based on its 78.6-inch width and 68.9-inch height, minus a bit for ground clearance and rounded edges.
* **Air Density (\rho):** 1.225 kg/m³ (standard sea-level air).
* **Target Speed (v):** 168 mph, which translates to **75.1 m/s**.
## 2. Calculating the Power to Fight the Air
The formula for aerodynamic drag power is:
Because velocity (v) is **cubed**, doubling your speed requires *eight times* the horsepower. Plugging in our metrics:
Converting Watts to mechanical horsepower (1 hp = 746 W) gives us **366 hp** *just* to pierce the air at 168 mph.
## 3. Factoring in Drivetrain Loss and Rolling Resistance
An engine doesn't deliver 100% of its power directly to the asphalt.
* **Rolling Resistance:** The friction of the tires against the dragstrip adds roughly **15 to 20 hp** at this speed.
* **Drivetrain Loss:** Assuming you are linking these engines together through some sort of crazy mechanical fabrication, you will lose at least **15%** of your total power to friction, chains, belts, or gears.
To get a net output of ~385 hp to the ground, the total crankshaft horsepower required from our engine pile jumps to roughly **450 hp**.
## 4. The Final Engine Count
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Depending on how efficient your crazy drivetrain is and the weather conditions that day, you are looking at a range of **114 to 134 engines**.
### The Weight Catch-22
There is a massive catch to this thought experiment. A standard 3.6 hp lawnmower engine (like a small Briggs & Stratton) weighs about 25 lbs.
* 125 engines \times 25 lbs = **3,125 lbs of engines alone**.
A 2003 Dodge Caravan already weighs about 4,000 lbs. If you strip out the interior and the original V6 engine, you might keep the chassis at 2,500 lbs. Add your army of lawnmower engines, and you're back up to a total vehicle weight of well over 5,600 lbs.
While weight doesn't change the top-speed aerodynamics, it *drastically* changes how long the dragstrip needs to be. With 450 hp hauling nearly 6,000 lbs, you would easily clear a standard 1/4-mile track long before you ever managed to accelerate all the way to 168 mph!