So last week I found some issues with shaft sizes and gearboxes, and generally just went down the rabbit hole of too many design options without clear advantages. This lead me to try and source some alternatives for cheap gearboxes. In the course of this search I found a great source: Worldwide Electric. It looks like princess auto, motion, and omega.ca distribute some of their models so getting appropriate ones should be easy enough.
I was also posed the question this week of: why don’t you put your sprockets next to the bearings? You will bend your shaft if you put the load closer to the middle. The reason was the lower gearbox (shown below) for controlling the wall angle got in the way, pushing the chain at least 4″ from the bearing. But trying options from a different vendor we can mount the lower gearbox flush to the main channel, getting that distance down to 2.5″. Which is about as close as we can get before the mounting flanges on the chain get too close to the channels.
Using a larger gearbox at the top means we can use a bigger drive sprocket, skipping the extra idler. This larger gearbox has a thru shaft and can handle the overhung load so we can skip the outside bearing there and the need for a coupler. The larger gearbox also takes a 1″ shaft so the issues from last week are kinda moot now.
At first glance I really like the look of this approach, it is much simpler than some other options, and I think I will charge forward with it. The larger gearbox and thru shaft options cost a little more but that is offset by savings elsewhere. Unless anyone would care to point out something else I have overlooked.
Oh! there is a disadvantage to the larger sprocket that I haven’t discussed. It requires a bit more head room. So for a given ceiling height you get a smaller wall, but that seems pretty minor when our primary design goal is to do this as cheap as possible.