[geeks] food geekery question

[Phil Stracchino]

gsm at mendelson.com wrote:
> On Tue, Dec 22, 2009 at 09:02:16AM -0500, Phil Stracchino wrote:
>> Nylon, by you, is not plastic?
> 
> No, Nylon gears are much stronger, and self lubricating. So while Nylon
> is a plastic, compared to the plastic geared Chinese made mixers I've had,
> it is a very different material.

"Much stronger than what", then becomes the question.  Delrin, for
example, is an engineering thermoplastic with good mechanical strength
and high lubricity.  Polysulfone is extremely strong and has excellent
temperature resistance, making it good for laboratory glassware.

Reading between the lines here, I'd guess that when you're saying
"plastic" as distinct from nylon, you're probably talking about
ultra-high-molecular-weight polyethylene.  Which is a perfectly sound
and quite good plastic ... but not a suitable material for gears,
particularly ones that are going to have to transmit high torque.  It
doesn't have the shear strength for the job.  But then, honestly,
neither does nylon, though you can make properly-designed glass-filled
nylon parts last a fair while.

(Another problem is taking a part designed for steel, brass or bronze,
and simply changing the material to one plastic or another using exactly
the same drawing.  If the part in question is a mechanically stressed
part, it's invariably a recipe for disaster.  You *can't do that* and
expect it to work for long.  You need to redesign the part - and
possibly the entire mechanism - for the new material.)

When Kitchenaid was bought by Whirlpool, two of the first things they
did as cost-cutting measures were to replace the cast-metal gearbox
housing with molded phenolic resin and replace several of the
previously-all-steel gears with nylon ones.  One of those gears turns
out to have to take very high torque, and the word became, "Don't buy
KitchenAid Artisan series mixers, the plastic gears will strip; buy the
Professional, it still has all-steel gearing."  Whirlpool has now gone
back to steel gears across the entire line and cast metal gearbox
housings, and has the metal gearbox housing available as an inexpensive
replacement part if you have a KitchenAid with a phenolic resin gearbox
housing.


>>> Note that my 500 watt Kitchen Aid would not do such a thing, with much less
>>> flour, it would walk across the counter and drop the bowl (it had a lever to
>>> raise the bowl into place,not a drop down motor).
>> I don't think my wife ever got her KitchenAid to "walk".
> 
> Mine used to do it all the time. One time it walked off the counter top. :-(

Wow.  I'll bet that made a crash to wake the neighbors.....


> The Kitchen aid ones are rated 500 watts for the one top of the line model,
> the regular ones, including the "professional" ones are rated 325 watts.
> I'm familar with that because people bring them here to run on transformers.
> At 50Hz, they only put out a max of 250 watts. 

Hmm.  Sounds like they don't take well to the power change.

>> KitchenAid's commercial origins as "KitchenAid by Hobart" - it was
>> basically a half-scale Hobart C-100 commercial mixer, originally
>> designed as a portable demo unit. 
> 
> Bear in mind that has not been true since around 1993 when Hobart sold the
> brand to another company. 

Yes, Whirlpool.  See above.  :)


-- 
  Phil Stracchino, CDK#2     DoD#299792458     ICBM: 43.5607, -71.355
  alaric at caerllewys.net   alaric at metrocast.net   phil at co.ordinate.org
         Renaissance Man, Unix ronin, Perl hacker, Free Stater
                 It's not the years, it's the mileage.