# bpm_to_stroke()

Hammer stroke from the blow rate of a free-falling ram.

Usage

[Source](https://github.com/lornearnold/driven-pile/blob/main/src/driven_pile/inputs.py#L14-L36)

``` python
bpm_to_stroke(bpm)
```

## Parameters

`bpm: array_like`  
Hammer blows per minute.

## Returns

`ndarray`  
Stroke (drop height), ft.

## Notes

The ram is in free flight for the time between blows, rising for half of it and falling for the other half, so `h = g / 2 * (t / 2)**2` with `t = 60 / bpm` seconds.