Group buy interest-MPS Diaphragms, Just a thought. Options

[r_towle]

Try this One for Info

We are such a bunch of loosers...we cant even get a BBQ arranged.....lol

Getting that done was a pipe dream...lol

Maybe the next guy up at the plate will have more success.

Rich

[jk76.914]

I took five MPS apart last year. I brought them in to work and analyzed them using XRF- X-Ray fluorescence- which non-destructively determines alloy composition. I have the actual alloy materials, but I'm off site today. I'll post them this weekend.

Bottom line-
stock- virtually pure copper
aftermarket1- pure copper, 2 pleats, but very nice workmanship.
aftermarket2- stainless steel, otherwise a perfect repro of stock.
aftermarket3,4,5- brass, 3 pleats, very poor workmanship.

The brass diaphrams have bad ripples around the perimeter where they're supposed to seal to the housing. This causes a slow leak. Also, the brass pieces are stiffer and thicker than either the copper or stainless pieces. One of these was from a newly refurbished unit (still in the box with the receipt) from a well-regarded 914 parts supplier. I took it apart because of the slow leak.

The most flexible is the stainless steel one. Interestingly, that unit also had stainless aneroid cells. The others cells were pure copper. The workmanship is so perfect that it makes me suspect that Bosch may have switched to stainless near the end of production to try and reduce fatigue failures. I can't imagine an aftermarket manufacturer tooling the aneroid cells, as they don't tend to fail, meaning any rebuilder would have lots of good used ones from MPS that failed for other reasons.

Other thing I noticed, kinda off topic, is that the aneroid cells contain a partial vacuum. This is contrary to some reports that they are charged to one atmosphere.

Jim