[AT] OT WoodPro wood chipper clutch

[Richard Walker]

You probably nailed it, Steve O, thanks!

Measured the water displacement of one existing shoe.  Then measured 
weight of that one shoe (Zamak?) as 12 ounces.  Calculated weight of a 
shoe if aluminum would be 4.2 ounces. So everything jives within the 
ballpark range of relative densities for Zamak and aluminum.

I'm doing more web research into use of Zamac for centrifugal clutch 
shoes.  Seems to be used a lot.  But most employ a thin bonded friction 
facing.  A disc could probably be cast from a 4-pound Zamak billet 
($13), then machined on a lathe like Steve W. suggested, then cut into 
four pieces to replicate the shoes I need.

Two wild cards remaining are whether there was a friction facing 
originally installed on the shoes that got burned away; and if the 
bearings got ruined because of the high heat.  I plan to pull the clutch 
this weekend to check.

And thanks for the links to new clutches, Thomas.  Trying to avoid this 
route because of high cost, but might be a last resort.


- Richard


On 4/23/2021 7:01 AM, Stephen Offiler wrote:
> I have to wonder if it's zinc (or Zamak alloy).  I can't say I've ever 
> seen aluminum used in a friction application.  It just seems that it 
> would gall and wear rapidly.  Zinc has much higher density than Al and 
> you did mention that it seemed heavy.  Finally, zinc melts at a lower 
> temperature, roughly 700F vs. 1200F and you mentioned that it melted.
>
> If you look around the 'Net you'll find various ways to determine 
> whether it is Al or Zn/Zamak. Oven cleaner is one trick.  That stuff 
> is lye-based and will aggressively attack aluminum but not zinc.
>
> SO
>
> On Fri, Apr 23, 2021 at 3:01 AM Steve W. <swilliams268 at frontier.com 
> <mailto:swilliams268 at frontier.com>> wrote:
>
>     Richard Walker wrote:
>     >
>     >> Those wouldn't be that hard to turn on a lathe. I'm guessing the
>     >> originals were cast aluminum alloy, then final machined. Could
>     turn a
>     >> solid piece with the step and slots for the springs. Then cut them
>     >> apart and finish the ends to size. If I had my lathe still set
>     up I'd
>     >> do it.
>     >
>     >
>     > Thanks, Steve.  Already considered that as one option, have
>     lathe and
>     > large hunks of aluminum round in my scrap bin.  Springs could be
>     > generic, guesstimating the original tension by wire gauge and coil
>     > diameter.  The wild card is whether the type alloy used is
>     critical to
>     > the clutch's proper operation - its friction against the cast
>     iron outer
>     > drum.  The shoes seem noticeably heavier than what I'd expect
>     typical
>     > aluminum to weigh.  At the worst I'm out an afternoon's
>     machining to try
>     > this approach.
>     >
>     > Wet pine needles got lodged between the chipper disc and its
>     housing,
>     > which ultimately bound it up.  As this was in progress, the
>     centrifugal
>     > clutch started slipping and heating up, which I didn't notice at
>     first.
>     > Eventually heat totally melted one of the four aluminum shoes.
>     >
>     > Been the best mid-size chipper I've ever used.  Billed as an AV
>     (All
>     > Vegetation) unit by Vandermolen, it will literally chip and shred
>     > practically anything.  First by the four knives in the disc,
>     then into a
>     > hammer-mill chamber with swinging flails.
>     >
>     >
>     > Richard
>     >
>
>     It could be some odd alloy but I would think it's a 300 series
>     casting.
>     Unless they used a slug of something inside the casting.
>
>     -- 
>     Steve W.
>



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