Load Testing a Web API

I am attempting to load test a web API I have created. Now normally I would use visual studios handy load and web testing projects to do this easily but at the moment I cant afford to use that so have to test this out manually. Its a unique little problem, does anyone have any ideas of how to best achieve this?

Essentially I want to call a particular method on my API, maybe something like 10 calls in the first minute, then in the next 20, then 50 , the numbers dont have to be that exact the more important thing is the increased load getting bigger.

The recording of results is already being handled, I log from the API calls so can see the response times and fails etc, I am really just looking for any ideas on how best to continuously call a web api while increasing the number of calls per minute.