window springs

Constant Force Window Balance Springs

As the world leader in constant force spring technology,
John Evans’ Sons (est. 1850) has produced well over 100 million
high performance window balance products.

The following innovations are the result of John Evans’ Sons unparalleled experience and technical expertise.

Patent Information by product series HERE.


        …the most technologically advanced Drop-In balance system for hung windows.

              drop-in series constant force balance system logo & graphic

        Offers the following:

              • low cost and a reduction of on-hand inventory
              • quiet operation with low operating forces
              • superior cam strength & reliability
              • higher weight AAMA qualified springs
              • Patents: see link above

Drop-In Balance System

1/2" & 3/4" Series Drop-In Balance System Intro.

Drop-In (di-500) 1/2" width Demo

Four Step Installation Instructions

1/2" Drop-In Series

di-500 width Drop-In Fabrication Instr.

1/2" Drop-In Series

di-500 Series Spring Load Chart

1/2" Drop-In Series

di-500 Series Spring Selection Guide

3/4" Drop-In Series

di-750 width Drop-In Fabrication Instr.

3/4" Drop-In Series

di-750 Series Spring Load Chart

3/4" Drop-In Series

di-750 Series Spring Selection Guide

SideLoad™ Constant Force Balance System

          …a better option for side load windows.

                SideLoad logo & graphic

          Our SideLoad™ Constant Force Balance System uses AAMA qualified springs and is a simple conversion from block & tackle.

          Compared to block & tackle, the SideLoad™ Constant Force Balance System offers:

                • a lower price
                • significantly reduced operating forces
                • a substantial reduction of on-hand inventory
                • dramatically smaller space requirements
                • a tighter fitting sash
                • Patents: see link above

SideLoad Balance System

SideLoad Balance Intro.

SideLoad Balance System

SideLoad Installation Instructions

SideLoad Balance System

SideLoad Spring Selection Guide

SideLoad System Sash Cam

Sash Cam Dimensions & Mounting

SideLoad Balance System

Slot Milling Instructions

SideLoad Balance System

One Piece Sash Guide Instructions

SideLoad Balance System

Two Piece Sash Guide Colors

SideLoad Balance System

Spring Carrier 2-Stage Lock System

SideLoad Balance System

Field Installation Instructions

SideLoad Balance for WOOD

SideLoad for WOOD Intro.

SideLoad Balance for WOOD

SideLoad for WOOD Installation Instructions

the SideLoad™ Balance System Demo

        the NEW SideLoad™ Sash Cam Demo

the SideLoad™ Balance Sash Guides & Sash Cam Component Review

SideLoad constant force balance system demo video
SideLoad Balance with NEW sash cams
SideLoad Balance Sash Guides & NEW Sash Cam Demo

Constant Force Balance Springs

          Today’s window requirements demand quality and consistency. Springs need to pull their weight…and no less.

                Constant force spring characters lifting weights

          Our AAMA qualified springs do just that, no matter how high the rated load.

                • ½” Series: 3 lb. through 10 lb.
                • ¾” Series: 3 lb. through 13 lb.
                • ⅜” Egress Series: 4 lb. through 7 lb.

Constant Force Balance Spring

Info Sheet

Constant Force Balance Spring

1/2" Spring Selection Guide

Constant Force Balance Spring

3/4" Spring Selection Guide

View all related products

Got A Question? Consult our Experts.

Our experts offer a depth of expertise to assist you with all parts of the process. We are ready to answer your questions in a timely manner and will help you define what you need. We produce custom springs for all purposes, and we are here to work with you on any of your customization needs.