To transfer data directly, you'll need to access the Smartsheet API. First, visit the Smartsheet Developers portal and create an account if you haven't already. Once logged in, navigate to the API access section to generate a personal access token, which will be used to authenticate requests to the Smartsheet API.

Log in to your Smartsheet account and open the sheet you wish to export data from. The URL of the sheet contains a unique sheet ID. Note this ID down, as it will be required to specify which sheet data to retrieve when using the API.

Prepare your local development environment to make API requests. You can use a command-line tool such as `curl`, or a programming language like Python with the `requests` library. Ensure you have access to a text editor or IDE for scripting purposes.

Construct an API request to fetch data from your desired Smartsheet. If using Python, you can use the following script as a basic template:

```python
import requests

# Your access token and sheet ID
access_token = 'YOUR_ACCESS_TOKEN'
sheet_id = 'YOUR_SHEET_ID'

# API endpoint URL
url = f'https://api.smartsheet.com/2.0/sheets/{sheet_id}'

# Headers with authorization
headers = {
'Authorization': f'Bearer {access_token}',
'Content-Type': 'application/json'
}

# Make the request
response = requests.get(url, headers=headers)

if response.status_code == 200:
sheet_data = response.json()
else:
raise Exception(f"Failed to retrieve data: {response.status_code}")
```

Once you have the full sheet data, extract the relevant rows and columns. The data returned by the API will be a JSON object containing metadata and row data. Filter the JSON to retain only the necessary information based on your requirements.

```python
# Extract rows and columns
rows = sheet_data.get('rows', [])
extracted_data = []
for row in rows:
row_data = {cell['columnId']: cell['value'] for cell in row.get('cells', []) if 'value' in cell}
extracted_data.append(row_data)
```

Convert the extracted data into a JSON format suitable for local storage. This can be done using Python's built-in `json` module.

```python
import json

# Convert to JSON
json_data = json.dumps(extracted_data, indent=4)
```

Finally, save the JSON data to a local file. Choose an appropriate file path and ensure you have write permissions.

```python
# Save to a local JSON file
with open('smartsheet_data.json', 'w') as json_file:
json_file.write(json_data)

print("Data successfully saved to smartsheet_data.json")
```

By following these steps, you can manually transfer data from Smartsheets to a local JSON file without relying on third-party connectors or integrations.