This could be useful for anyone who wants to soften the ride.
I got a set of 'porch swing' springs from one of those warehouse style home improvement stores. About 8 1/2 bucks. They come with a set of 'drawbar' springs inside. But those are easily removed.
A few carriage bolts, some fender washers and nuts will run a few dollars more. All told, the thing can be built for about 10 bucks.
Sprung seat 01.jpg
Sprung seat 02.jpg
Sprung seat 03.jpg
I got it finished this morning and my test rides, so far, have only amounted to a couple of miles. Still, it feels like it's probably trustworthy. And it's definitely softer. Not as soft as, say, a motorcycle with true rear suspension. But it feels as if I'll be delivering fewer shocks to my rear axle, the chainstays and my lower back.