search  current discussion  categories  forms - misc 

ivor: hump in middle of platters

updated wed 1 dec 04


Cindy on mon 29 nov 04

So Ivor,

Does this mean one should make the bottom of the platter flat and of even
thickness right out to the rim? I'm not absolutely certain I've understood
you, and I have had this problem. That said, my more recent plates and
platters don't seem to have the hump/bump problem. Maybe that's because I've
just gotten better at making them uniform.

Best wishes,
Cindy in SD

----- Original Message -----
From: "Ivor and Olive Lewis"

> If the cross section of a plate or platter is treated as an
> engineering problem which can be solved using principles of Mechanical
> Physics the solution comes from appreciating this structure is a
> Double Cantilever Bridging System supported on Piers.
> Strength of the various parts is dictated by the distribution of Mass.
> If Mass is assymetrically allocated then there will be movement when
> the ceramic becomes pyroplastic. This motion will be aggravated by the
> distribution of accumulated residual stresses develped during
> throwing, trimming and drying.
> Excess mass at the extremes of the cantilevers will create a turning
> force. If the interior of the well rise you get a "Hump", if it falls,
> a "Spinner"
> Do Intellegently designed plates and platters really need an interior
> footring?
> Remember what Mel tells you about Science.
> Best regards,
> Ivor Lewis.
> Redhill,
> S. Australia.

Ivor and Olive Lewis on tue 30 nov 04

Dear Cindy,
I will have to send you a diagram which illustrates the principle.
May take a few days as I am transferring files to a new computer.
Best regards,