Bimetalic domes

how about instead of removing material from the flat surface of the dome to remove material around the outside diameter? would that alter the point at which the dome went PING? i was just wondering if the outside edge is constrained in a bezel, if there was more room to expand there if that would alter it's temperature rating?

b.w.

If there were room, one could add a preload spring to change the set point.

Mark Rand RTFM

The use I see them is located fairly loosely in a well in a bakelite disc that is itself located loosely in the bakelite outer housing

I might try that , will require adding a small well for the spring

I remember reading that the process used by the Mint for forming tri-clad coins was invented (patented?) by the company that makes the very good but outrageously expensive All-Clad cookware. I think that their sucess at the coin process led them to introduce the cookware.

Joe

I wonder if one could paint the convex face with fingernail polish as an etch resist and put the disc in an etching solution to thin the concave side? Would the relatively smaller 'concave mass' shift the trigger temperature upwards?

--Winston

Heaven knows, I don't like reinventing the wheel, but unless you can find documentation (such as a patent) that explains in detail how these devices work, and how a particular temperature is set, you're going to have to experiment.

I again recommend looking for one of those interchangeable thermostats. Perhaps ripping it apart will reveal the secret!

The Presto "Control Master" has been around at least 40 years, and Presto is still making appliances that use it. (I don't know whether the internal design or operating principles have changed. The probe part does appear to be longer and narrower in the current version.)

DuPont patented the process of explosion welding that was originally used for the clad coins, but they stopped using the method somewhere along the line and now use some sort of rolling method to do it.

Kaiser Steel figured out the original Aluminum to steel "welding" Was used in the armor plating of tanks. Abrams I think.

Armco steel, (Now A-K Steel) developed the aluminum clad stainless steel used for catalytic converters. It was great for body work, too. :)

I got to tour the Armco rolling mill in Middletown, OH when it opened. One of the more impressive experiences. 50 ton block of steel goes into an oven to get red hot and then sheared off in to manageable pieces. That eventually are rolled out to very long sheets of steel. Those big rolls of steel you see at times.

Wareever pot so it looks like - Might have been electro-spotted in a press. Looks like some heat spots here and there and in a ring.

Mart>> Explosive welding.

I have been waiting for someone to suggest that the temperature at which they switch is controlled by how domed the discs are. At least that is my guess. Suggest you get some rubber and a ballpein hammer. Test what the temperature is that one switches at, and then make in a bit more domed and see if that changed the temperature at which it switches. My guess is that more domed means more change from ambient temperature before it switches.

Dan

I have been waiting for someone to suggest that the temperature at which they switch is controlled by how domed the discs are. At least that is my guess. Suggest you get some rubber and a ballpein hammer. Test what the temperature is that one switches at, and then make in a bit more domed and see if that changed the temperature at which it switches. My guess is that more domed means more change from ambient temperature before it switches.

Dan

I will give it a go with large ballbearing in a cup and a press. But the full range of temp (10 to 220 deg C at least) switches all come in the same size package and the internal spaces and activation pins are the same dimensions including degree of doming, all that changes is the materials or construction within the domes. Normally open for the same temp normally closed is simply just the same dome in, the other way up

I lived near the 'Project 600' plant for 20+ years. The original 'rolling mill' was built in the late 1800s. 'Project 600' was its replacement and the first computerized steel mill in the US. The air was red with rust, until the old mill was decommissioned, years after 'Project 600' was in full operation. It was used to make specialty steels, while 'Project 600' made steel for the big three auto companies and several companies that built major appliances. It also made the steel skin for their 'Armco Steel Buildings' division.

Early pilots used the red cloud as a navigation aid. Some days it could be spotted 100 miles away. The original plant had so much of that fine rust clinging to the inside walls and roof that part of the complex collapsed.

I had a friend who was their analytic chemist. He did all the stack sampling tests, as well as chemical testing of the various alloys. He got me a few pieces of aluminized stainless in the late '80s to repair the sliding doors on my stepvan. That stuff was hard to drill! :)

Another thing to try is local heating and quenching in order to change the distribution of internal stresses in the dome.

It's bimetal; I don't think you want any "unexpected" stresses.

Isaac

I remember seeing a red cloud above some buildings. Was 1968 and I worked for NCR in those days and wife and I went down to tour the plant when they opened it to the public for the grand opening. Was in Dayton for a class. Growing up 10 blocks from San Francisco bay, did not see a lot of rolling mills here.

Pretty difficult to calibrate that change. I'd try mounting a small coil spring so as to work with or against the direction of the snap. A setscrew can then be used to modify the spring preload and adjust the snap point.