yoopertool, the springs come "bare" and you need to make your own hub. The spring in its natural state is coiled tighter than when on the hub, so you are prestressing it a little when you wind it on the hub. The spring generates its force by being straightened from the coiled position, which is why it has linear force. The good news is that your router will have much less travel than the spring is long, so if the spring does break you can just unwind some more, punch a new hole by the end and use a new section of the spring which hasn't been flexing.
Best regards,
Randy |