Spitfire 1980 pressure differential switch

[Pete Lewis]

i said earlier there are two diameters  as kevin suggested google there are plenty out there 

try this https://www.ebay.co.uk/itm/183906072383?chn=ps&norover=1&mkevt=1&mkrid=710-134428-41853-0&mkcid=2&itemid=183906072383&targetid=1280441980521&device=c&mktype=pla&googleloc=9046046&poi=&campaignid=12126078219&mkgroupid=120032726582&rlsatarget=pla-1280441980521&abcId=9300480&merchantid=101717694&gclid=EAIaIQobChMIteWRovSN8gIV0NPtCh3MdwACEAQYAiABEgKFQfD_BwE

[SpitFire6]

On 30/07/2021 at 10:00, Pete Lewis said:

no the shuttle should close off the pressure lost line as its moved across by the pressure difference to arrest any more fluid loss 

Pete

 

 

Hi Pete,

I believe you are wrong in your assumption. It does not function as you believe it does.

When you understand how it functions, please let me know.

Sincerely,

Iain.
 

[Colin Lindsay]

I've been doing a lot of reading on PDWAs due to this thread and never having had one actually fitted to a Triumph myself (I have rebuilt them, though) I can only go by what I've read - it seems there are certainly two types, one with two pistons and one with a single piston, but this post on another forum is interesting:

The PDWA came in a number of different configurations. One of them has a set of sleeves that will slide with the piston during pressure imbalance, and almost completely blind the low pressure line. I have that PDWA on two of my 1980 Spitfires. 

This seems to point to a system that blanks off the side that is losing fluid; 90% of the other posts / forums and articles state that it's a warning system only, and all it does is activate the warning lamp. That one came from

https://www.tapatalk.com/groups/spitfireinformationexchange/brake-master-and-pdwa-component-and-poor-brake-per-t4519.html

[DVD3500]

Well I am picking up a US spec 1500 on Wednesday and I will be tearing it apart and I am planning on transplanting its braking system... I will take a good look at it...

 

[Pete Lewis]

if it doesn't close the lost circuit its a waste of time  never played or found one that does not protect the braking that left 

in all my years in manufacturing 

agree there are two designs   i said that right at the beginning 

Pete

[AlanT]

Well I’ve ordered new seals from simplybearings.co.uk 

As a late car mine has the two sleeves. Be good to get this right rather than bodge it since the entire braking system is being replaced +pretty much every other mech part on the car! 

[Pete Lewis]

im sure a good clean and new seals will be fine 

Pete