Bill_qaz wrote: ↑Thu Sep 24, 2026 8:34 am
Thanks Stephen for the information
There's actually a chronology to the different centring systems, I've never been able to get dates, or even the year of change.
I was on the phone to Burlen a few years ago, asking about the differences as I'd ordered a repair kit illustrated with nylon devices and it came with brass rings. In the course of conversation, I asked why they had gone back to Brass Rings and apparently the Plastic/Nylon devices they tried just didn't do the job well enough.
So the original design had
9 brass rings to centre the the diaphragm assembly as on my photo below; but then at some point,I'm guessing in the 60s/70s, they switched to the single piece nylon assembly as per my photo and the exploded view they still use on the website.
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- 20260924_105238.jpg (809.28 KiB) Viewed 294 times
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But sometime later, they switched to the Figure 8 Nylon devices as still illustrated in some of their overhaul kit images...
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- Figure 8.JPG (39.92 KiB) Viewed 294 times
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In more recent years, they have moved to using
11 Brass Rings, as shown in some other kit images ....
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- Rings 11.JPG (42.89 KiB) Viewed 294 times
I only discovered this difference in ring numbers when I opened up a very old pump I'd brought for £1 at the National Rally, the one in my first photo.
So the rings must obviously be different sizes, but I haven't got a newer pump to compare with at the moment.
Perhaps there is a difference in the size of the recess between pre and post 1985 Coil Housings?
When I find out, I'll make a new post about it.