pedal grinder design refinements

The pedal grinder worked pretty well last fall, to the point where it seemed worth going over the design in an effort to produce a more durable, corrosion resistant, and user friendly version implementing the same basic functions.  The main issues with the current implementation are:

  • Construction of plywood
  • Steel bearings exposed to apple pulp
  • Difficult to clean without tearing down the entire assembly
  • Chain assembly is a bit noisy
  • Some shaft-sprocket connections are insecure and tend to slip

I’ve taken a first pass, as indicated in the Solidworks snapshots below.  Key aspects are:

  • Frame of T slot extrusion, protected from apple pulp by side plates
  • Side plates and diagonal chute plates of polypropylene
  • Thin curved lower shrouds (of lexan or acrylic) contain flying pulp and give a view of the action
  • Side plates, cutter drum, and secondary crusher drums remain in place; diagonal chute plates and lower shrouds easily removed for cleaning
  • Key elements of drive train unchanged (and not shown yet) – I looked into switching to timing belt for the 3x speed increase between the jackshaft and the driven drums, but the sprockets for timing belt are quite expensive at McMaster compared to the amazingly economical 40 pitch roller chain sprockets that we have been using from Burden Surplus Center.  So the current plan is to get some spare sprockets and turn them down on the lathe to fit bike chain (pitch is the same, but standard 40 pitch chain is much wider than bike chain).  I suppose we could get bike sprockets and fit them to shaft collars, but that would probably be more expensive and more work.  We’ll still have the old chain as a fall back
  • Easier to tension drum drive chain by moving jackshaft bearings in T slot
  • (not figured out yet) Integrate a standard derailleur to tension the bike chain and allow shifting gears
  • (also not figured out yet) – cam or other reciprocating mechanism for operating an automatic feed wedge – this probably won’t be a high priority at least while there are friends around who are happy to force the apples in with a wooden plunger, but it might be nice to have the interface figured out in order to add features while machining the side plates.

new-grinder-assembly

new-grinder-assembly-oblique-view

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