A hydrospring or hydro-spring is a spring damped by hydraulic fluid (typically oil) being driven through holes in a piston, as the piston moves in response to a force. The spring is often made of rubber. Inside a rubber hydrospring there are hydraulic viscous damping systems which damp movement in all three directions but require very few parts. Even the slack adjustment may be integrated into the element.^[1]

Hydrosprings are used mainly as shock absorbers in applications such as damped suspension in railway bogies, bulldozer blade shock absorbers and as recoil absorbers for artillery.

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  A railway type rubber hydrospring^[2]
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  A railway type rubber hydrospring in compressed state
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  A railway type rubber hydrospring in relaxed state
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  Hydro-spring recoil system of British WWI 60 pounder gun, with working explained