# Automatic compression of springs

I am trying to design something for a friend, but am struggling to come up with the mechanics. Can you help?

So imagine a long extendable pole, like a bow staff. Imagine after pulling out a "peg" the bow staff extends using springs. Now say I wanted to automatically close this extended pole. What would be a good way of doing this?

My idea is a wire/string inside the staff that runs from the top to the bottom. Pulling this wire can compress the staff. In my head, some kind of motor can wrap up the string to compress the staff. My worry is that the motor wouldn't be able to pull against the strength of the springs. Can this be solved through a gear mechanism allowing the motor to be safe from the resistance of the springs? If so, how?

My second idea is to eliminate the motor. Instead, the wire is simply pulled from the bottom to compress the staff. But I wouldn't want to pull the string the entirety of the bow staff. Potentially through some pully or gear system, a semi-short pull of the string can compress the entire staff. Like the string would only have to be pulled out half or a quarter of the distance of the bow staff, but still, compress the entire thing.

Which method is more doable? Is there a better way to automate the compression of the staff?

This is only in the planning stages so springs are not chosen, though their strength will be similar to that of the springs used inside an umbrella. Here is a picture that should provide some basic dimensions. Fully extended, each section is about 13cm. The inner diameters are 9.5mm, 6.5mm, and 3.5mm. I look forward to hearing your answers. I don't have a lot of experience with gears which is why I am asking. Thanks!

• Rough dimensions of what you're thinking of would help. Compressing a spring 4 inches vs 4 feet is a world of difference.
– jko
Jan 19, 2021 at 19:59
• Great point thank you, I updated the question with very rough dimensions. Let me know what you think or if you need any other details!
– Max
Jan 23, 2021 at 1:02
• Older cars used to have motor driven extending antennas. A similar mechanism could work here. Jan 23, 2021 at 2:56