I spent the free time I had last week working on the shifter box design. "Easy" removal of the belts in the box is my main design requirement. Everything I've come up with before now would have required removing the housing to install or replace belts. It seemed like the only way to maintain the rigidity of the housing.
But then I tried designing the housing using sheet metal and bending everything into place. This also gave me another chance to play around with F360s sheet metal tools. This is what I have so far:
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The long tab would be welded to the transmission frame. This would also be how the transmission frame attaches to the vehicle frame. The right side of the box would also be welded to the frame for stiffness. The tabs in the front and top of the box should keep the two pulleys from sliding when the shifter plate moves between them.
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In this setup, the two gears are mounted on the main freewheel axle. There is no direct contact between these two pulleys and the shifter box (except for the anti-slide tabs). Here is the sheet metal flat pattern
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I had to break out some graph paper and scissors to work some of this out. 😅 The slanted part of the box will eventually have a slot for the shifter pole. That is still dependent on what's inside the lawnmower's rear axle.
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