I am looking for an alternative/improved visual warning device that will indicate the status of the vacuum braking system on a Leyland PS1. At the moment (in typical 'less is more' LT style) the only warning of a looming braking issue is a small illuminating slot cut into the face of the speedo casing, the bulb is ON when the effective braking pressure is available.

I was thinking about the RM stop flag, does this work the same way? ie does the servo pull the flag up when brake pressure is available, and are the status lights OFF when all is well?

Also, if this could work what are the chances of finding an RM brake/gearbox warning stop flag unit for sale?

Thanks

The RM flag works electrically with pressure switches on the gearbox air supply and the hydraulic pipes.

I suppose you could wire one in to the light bulb circuit on the Leyland so when the light comes on it energises the solenoid and the flag raises.

The GS works the same way round. when vacuum is created, the light comes on; it also doubles as the speedo light!

The RT/RF flag relies on air pressure to raise the flag, so not suitable for a vacuum system!

Presumably the Leyland is vacuum on the front, and vacuum/mechanical on the rear?

My bus number (if any): RML2532

Try RS Components for an adjustable vacuum sensitive switch, a light or buzzer and a gauge. You will have to illuminate the gauge however.

I bought two 4" Vacuum gauges from them last year in order to diagnose a vacuum problem.

The safe limit for MOT is 10" to 12" vacuum.

Many thanks Roy's you've given me a few ideas now. The easiest thing to do then is look around for an RM stop flag, failing that I have a scrap RT/RF type flag unit that could be modified to work like the RM type with a push/pull solenoid from the RS Components website (plenty of 24v DC units at sub £20 !!).

I hope to use an original Smiths vacuum gauge as fitted to the 'normal' Leyland Tiger, a magnolia gauge would be nice but I doubt one will ever turn up. There are a few black Smiths gauges on Ebay at the mo, they go up (or is it down?) to 30".

Not sure about the vacuum brakes layout.....

Cheers

There are several specialists overhauling automotive gauges, I am sure that one will be able reproduce a magnolia face if required. It will be important to observe return earth insulation for the gauge lighting if required by the vehicle circuit.

Vacuum brakes are bad news for obtaining MOT efficiency even though the reputation seems to be that AEC vacuum brakes are better than Leyland air brakes for vehicles of that era. Everything has to be in practically tip-top condition in order to obtain a pass. It is helpful to know what in/hg reading is obtained at the auxilary servo motors for full brake application.

I expect you have already tried Ray Trigg or Bernie Smith for the guage ?

My bus number (if any): RML2747

I wonder whether you may regret using an RM or RT stop flag at a later date when one could be required for the correct type of vehicle. The existing red light could be retained, but linked with a buzzer, both wired to operate (in reverse from its existing arrangement)from the vaccuum switch when assistance drops. A lit gauge would act as indication of the reason for the warning.

I'm still working through the theory at this stage so i want to keep costs down to a minimum, a higher quality quage can be sourced if the concept is sound.

Roy I do agree about the use of an RM stop flag, even if I could find one! The RT/RF units I have are u/s, plus I've had them in stock for over 15 years. The problem I have is this bus (TD) is very basic in the cab equipment dept, it has a speedo with a bulb that acts as both illumination and vacuum warning (same as GS), that's it. I am converting to square speedo and adding oil pressure and vacuum gauges (so far). I need to install a buzzer for the emergency exit, a warning light for the passenger door, a high beam light and a 'winker' light (again so far!). Adding more dash lights and/or buzzers might lead to confusion, I think the stop flag is by far the best attention getter up there in the drivers view.

Also the RT type flag has the added bonus of a contact switch that will effectively reverse the vacuum switch (wired independent) for me.

Is this TD going to be used as a psv? there may be some breaking news in the next few weeks regarding the position regarding CoiFs for old vehicles but I can't say too much just yet.

Why fit high beam warning lights? they're not a legal requirement. As for passenger door warnings, take a conductor with you! But, refer to my comment above. :)

I once had an MoT examiner who asked about the warning on the emergency rear window on our RML; I told him it was crew operated, then he asked where the conductor was! I then had to tell him inspecting the conductor was not in the psv test manual.

My bus number (if any): RML2532

Perhaps a sharp spike that comes up through the driver's seat!

Modern vehicles have plethora of warning lights but drivers still manage, although their abilities may be debatable. Even coaches from the 1980s/90s had numerous warning lights and switches, BUT they were marked to indicate their function.

If you can get an RT/RF flag unit to work then it may be your best solution. However, forgetting LT's idiosyncratic approach and terminology, if the driver has even the most basic level of competence he should be able to interpret that a green flashing warning light is for the indicators, and a blue light refers to main beam (although as said not required if never fitted originally).

He should also be able to realise that a regular tick in time with a green flashing light refers to the indicators and that a constant tone or rapid bleeping refers to a fault which requires investigating, or that he has selected operation of a system.

As far as actual warning lights go, sheer size can be used to signify importance, 8mm lenses for warning and 20 mm for STOP.

Is this bus a post war PS1 or a pre war TS? The pre war may well have vacuum hydraulic braking with the rather feeble telescopic wheel cylinders.

Talking to someone the other day about COIFs, he quoted RT1; they fitted flashing indicators as a safety issue. the nearside lens utilised the side light lens on the nearside bulkhead. the Certifying Officer didn't like it because it was too far back. Had the bus not been fitted with flashers, it would not have been a problem. Why fit stuff you don't need?

My bus number (if any): RML2532

None of this is up to me, it's customer requirements. Personally I couldn't agree more.... if it wasn't needed in the 1950's why is it needed now?

I'm not sure about future psv usage, it is probable though and that's where the passenger door comes in (originally open steps), I'm just guessing here but a conductor on a 31 seat bus may be uneconomical? I do intend to follow the universally accepted warning light colour codes, it makes life simple for everyone. I dismantled an RT flag unit today and with the valve and spring out it's almost ready made to fit a solenoid, the flag is actually quite light on the pivot pin so it should work out ok.

It's a post war PS1... vac front/vac mechanical rear, 25-30 in/Hg.

I've only had one indirect encounter with the COIF (Condescending Oaf Incites Fury) test. On an RF ten items were cited as grounds for failure and only one was legitimate, six were laughable, two were debatable and one more was a consequence of a lack of knowledge on obsolete tech.

I've had battles with the COIF officer on Rt tyre sizes, RF emergency door valve position, height of RF steps..

Like I said earlier, watch this space for COIF news.

My bus number (if any): RML2532