I am having trouble defining a task constraints.

I have multiple tasks for one individual to do that has multiple interruptions - see below:

Task 1 - Design widget, duration 1 week, completed by resource 1

Task 2 - Manufacture widget, duration 2 weeks, completed by resource 2, to follow task 1

Task 3 - Test widget, duration 1 week, completed by resource 1, to follow task 2

Task 4 - Redesign widget, duration 1 week, completed by resource 1, to follow task 3

Task 5 - Manufacture redesigned widget, duration 2 weeks, completed by resource 2, to follow task 4

Task 6 - Design crate, duration 12 weeks, completed by resource 1, to be worked on during down time when resource 2 is doing supporting work (task 3 and 5) - how do I make these constraints flow into one task to create an overall timeline?

Thanks,

Jamie