Allis Rake Tedder - Float Springs?

 Your idea of putting a spring in the lift chains is a great one.  If I still had one I'd go to the McMaster Carr catalog and pick out a matched pair of extension spring to do what you did.  

I won't deny some of my fields are exceptionally rough, but I'll try and justify it by saying up here in the rough & rocky Canadian Shield, tillage takes on a whole new dimension. It's hard to maintain smooth fields when you're pulling up boulders the size of smart cars every 100 yards, and when the frost heaves the ground in crazy ways every spring. My grandfather also had the general rule (which still holds approximately true) that every day spent with a tillage implement results in a week's worth of stone picking, so I'll often forgo an extra pass with the discs or cultivator if I think it's smooth enough, and if I want to give my back a break. And a few of my fields are so steep, that every time you till and it rains you're likely to lose some topsoil in runoff.

I remember the first time I tried plowing at a friend's down South in some beautiful flat clay: I couldn't believe how easy & smooth it was. Plowed for a whole morning and only turned up a few grapefruit-sized rocks. I was tempted to sell my farm and move right then.

I'm glad you think the extension springs are a good idea: I ordered a matched set last night. Even so, it's a massive improvement to the rake with the ones I've got in there now. I wish Allis had thought to do this from the factory. For a couple of dollars worth of springs it really transforms the rake, and I'll bet a lot more of these rakes would have survived if they'd been like this since new.

Another thing I did was flip all my teeth around backwards. I only use these rakes for tedding (I have rotary rakes for raking, and would never go back). Flipping the teeth  ensures they're all bending the 'correct' way when tedding, so they don't break off so frequently. Before I did this, I'd loose a few teeth every year. New teeth for these Allis rakes are still available, but I'm not sure for how long.

The ones I ordered are McMaster Carr Part #3630N424. We'll see how they go. They have an 85# preload and 249# maximum capacity. Their spring rate is about 130# per inch. If my guesstimate of basket weight of 350# is correct, they should stretch a little over 1" when taking the basket weight. That equates to about 2 to 3" of basket float with the geometry of the Allis lift mechanism.

If you're giving it a go, when cutting out a section of the existing chain (or rod), you'd have to cut out a little more than the spring's stock length to account for the stretch it will have lifting the basket.

I'll let you know how the new ones work when I get them on there. Won't be for a couple of weeks unfortunately - I'm off to Georgia for work.