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above is the fancy new grate shaker addition bear's been working on for the last week or so. for all the datalogged test runs last summer we had a somewhat hacked pulley system to automate the grate, but it wasn't very reproducable (or elegant). so bear has been working on a reasonable regular add-on to do this.
what he's come up with above bolts onto the flange ring at the base of the gas cowling, and uses the same drive motor as the auger. two gears and a chain to move the grate post. it is very simple and very robust. he runs it with a little slop in the chain so he can still manually shake the it if he wants. that is why the grate handle is retained. we find manual access to any automated system makes operation much more flexible.
bear is controlling the timing of the shaky-shake with the gcu. you can either shake on a time basis, or more accurately when you see the pressure drop across the bed rise. there should be a fairly constant relationship between the pressure drop across the nozzles and pressure drop across the bed. (ideally you have sized the nozzles to make this ratio about 1:1) whatever your stable point, when you see the bed part of this ratio increasing, it is time to shake the grate.
here's a little more detail about how it is made.
