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Not what it seems!


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If you read the excellent mag "Race Tech", it's full of the latest wheezes to make your race car lighter, faster and more powerful, and how to prove that it is so, by measurement.    The latest issue includes an article about the conversion of an old railway tunnel into an alternative to a wind tunnel.   https://edition.pagesuite.com/html5/reader/production/default.aspx?pubname=&pubid=b515eee0-42a6-4eec-9cf0-72e1fc49f47f&utm_campaign=Get the latest RACE TECH April 21&utm_source=emailCampaign&utm_content=&utm_medium=email  

That it's straight, nearly three miles long and is excess to requirements  for the successors to Britsh Rail all seem reasonable, but when I read that the test cars will be driven down it, turned around on "automated turntables" to make the return trip,  my credulity switch tripped.     I turned to the front page and sure enough, it's the April edition!

Ho, bleeding ho!   Nice one, chaps! Nearly got me there!     As for the 'leaders' of the motorsport industry  who are part of this 'project', I bet that "Hiroshi Shimoyama" and "George Howard-Chappell" are fictions - their names are just too good!    Look them up so I can write a knowing Letter to the Editor!

Oooops!    The two gentlemen are indeed leading motorsport gurus!  And the Catesby Tunnel really does exist as a car testing facility!   There is even (as if that were proof positive, but I'm back in credulity mode now!) a website devoted to the tunnel: https://catesbytunnel.com/

After that, there's got to be an April Fool in Race Tech!   If only I can find it!

JOhn

Edited by JohnD
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Aye, the Catesby Tunnel (interesting history behind this by the way) was featured on C5 (I think) by the bloke who was walking Britain's lost railways. Series ran end of last year/start of this if I recall?

Anyway, he visited, and cycled the tunnel!

Phil

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Posted (edited)

Further to my list of things that don't reflect well on my judgement is a device I bought online last year.  It's a pressure regulating valve (circled) said to be good up to 140psi, that I bought for the Lucas Pi set-up on the Vitesse.     It had the added bling of its own pressure valve, which made adjustment easier, as I didn't have to get my head out of the boot to do so, and provided a check on the dash gauge reading as well.

image.thumb.png.708b66a50acaecd20211477b255ee306.png

It worked fine, but yesterday, commissioning the car for this season I started it up and was happily fiddling with the idle and so on when I noticed a big damp patch under the car, and that fuel was pouring out of the valve!   Doors and windows open, it was blowy day, so I hadn't noticed the smell but work stopped unti it was blown away.    The fuel was coming from under the gauge, the dial was full of liquid (it's not oil filled) and the plastic (?) disc that carried the graduations for the gauge was all puckered and warped.  Fuel was clearly getting where it shouldn't.

I dismantled the gauge, and sure enough the Bourdon tube was broken.     Or rather, the very fine tube that conveyed pressure from the fuel to the Bourdon was broken.     And I fear this is no surprise, as this length of 2mm copper pipe was the only anchor for the Bourdon!  

Bourdon-tube gauge | instrument | Britannica

As this diagram shows, the fixed end of the Bourdon should be anchored to a block fixed to the casing.   There wasn't one.    The guage was from China, and was more an example of how they can do clever cheap engineering, rather than the clever, good quality work they can also do.

My solution has been to fill the connector that carries the fine tube with plastic steel, and use that as a plug where the gauge was.    I'll manage with the dash gauge!

John

PS  The guage was supplied by the Guangzhou Xinyisheng Trading Co.Ltd, Guagzhou City, Pt.No.254993.   There seem to be many similarly named companies, none of which share the address I have from the packaging, but I've written to them in the hope they will improve thier product.

Edited by JohnD
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You should at least be able to buy a replacement gauge though, John? 

A quick check says 140PSI = 9.6 Bar, so you want a gauge that's rated to 15 Bar (or 210 PSI). Check what your connection threads are, and where the connection is (either bottom or rear).

I say 15 Bar here, because good practice is to always go 50% over your max working pressure. I can't see in your picture very clearly, but it looks like the gauge fitted to your PRV is only 10 Bar (black numbers on the inside), so not only have you got a cheap gauge, but they haven't allowed for any safety margin either!!

Phil

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As Phil says.  Might also be worth getting a glycerine filled gauge as not only does this damp pulsation/vibration of the needle, but it damps internal vibration generally and helps stop them falling apart.

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I have fuel regulators for the Webers. With the possibility to screw in a gauge. After checking and adjusting the pressure I allways remove the gauge and screw in a Plug. I fear the vibrations of a car are no good for the Chinese gauge.

Cheers

Martin

 

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Posted (edited)

No argument with Phil (would I dare?  He is a proper engineer!)    But Lucas Pi runs at 100-110psi, so while 140ps isn't +50%, it's pretty near!

My 'field mod', blocking off the gauge connection, and using it as a plug, has worked well.    The PRV itself works fine!   I just can't watch the fuel pressure from the boot, but then I don't drive it from there!    That would be silly, it would screw up all the weight distribution!

John

Edited by JohnD
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1 hour ago, JohnD said:

No argument with Phil (would I dare?  He is a proper engineer!)    But Lucas Pi runs at 100-110psi, so while 140ps isn't +50%, it's pretty near!

My 'field mod', blocking off the gauge connection, and using it as a plug, has worked well.    The PRV itself works fine!   I just can't watch the fuel pressure from the boot, but then I don't drive it from there!    That would be silly, it would screw up all the weight distribution!

John

Ahh, but remember that the 100-110psi is the "downstream" pressure going to the metering unit (if my admittedly very sketchy understanding of the Lucas system is correct). Your pump is obviously producing a higher pressure that (hence the need for a PRV lol), so that is the pressure you need to consider.

It's very much a case of plan for the worst. If your PRV fails, and delivers full pressure to the system, are the fittings and pipework rated for it?

And even ship designers get this wrong! On the current vessel we have 20k boilers (k = kg/cm2, which is roughly equal to bar). The feed water supply system runs at 37-38 bar (it has to overcome 20k of course). However, the numpty who designed the system presumably saw the 20k boiler bit, and specced a 20k feed water piping system, valves, flanges, the lot!! We pray every time we start the feedwater pumps lol.

Phil

 

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4 hours ago, thebrookster said:

We pray every time we start the feedwater pumps lol.

Why does you system need to run 18 Bar over the 20 Bar boiler pressure?  Should be a 1.5 safety factory on your 20 Bar stuff.... but it's not enough and  it ain't the right way to do it!  What do Lloyds / DNV /ABS have to say about that?!

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19 minutes ago, Nick Jones said:

Why does you system need to run 18 Bar over the 20 Bar boiler pressure?  Should be a 1.5 safety factory on your 20 Bar stuff.... but it's not enough and  it ain't the right way to do it!  What do Lloyds / DNV /ABS have to say about that?!

It doesn't need to be 18 Bar over, however pump pressure does need to roughly 10 Bar over Boiler Drum Pressure, else you can't get the water into the drum fast enough! If we run at full whack with two boilers in operation, both feed valves will be approx 85% open. This gives a resultant pump pressure of about 30 Bar, and pumps are something in the region of 40-50m below the boiler steam drums.

We are ABS, and yes, the system is class certified! It's all about knowing the right person..........

Edited by thebrookster
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1 hour ago, RedRooster said:

All bull shit' are still on the go though.

Oh yeah....

If it’s possible to get what Phil reports certified..... they aren’t worth much.

But hey, it’s only a boiler feed system... not as though it’s propulsion/ safety related.... or on a vessel with hazardous cargo....... Oh, wait....... 3 for 3 :ninja:

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Posted (edited)

Ok, Phil, Pax!    YOU are the engineer, and point out my ignorance very nicely.     

I would say that the gauge sensed the downstream pressure.    It was badly (IMHO) designed and failed, which bodes ill for the PRV part of the item.

Two QS, please:

Does anyone know what pressure an unregulated Pi pump would achieve, OE Lucas or Bosch?

And what goes wrong with an OE Lucas PRV?   I tried installing the original one, that I had with the kit of parts I bought, that had given probs before.     The pressure it delivered was all over the place, low, turn it up, goes higher, into acceptable then drops off again with no adjustment.     I think that design operates with just a needle vale against a spring.   Could the spring have weakened, or the valve worn out?

JOhn

 

Edited by JohnD
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Both pump types are positive displacement and will keep on pushing until something gives. If you are lucky popping the supply fuse rather than pipe.

Never looked inside a Lucas PRV.... sounds like something sticking.

Can’t remember whether you run a Lucas pump or Bosch one John? One of the issues with the Bosch ones is that they flow a lot more than the Lucas and more than the original PRV is comfortable with.

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Nick,

My apologies - there are more proper engineers here, and you are one of them, who also has aided my education in the Art!  My thnaks to you too!

Run till it pops, eh?    And I run a Bosch!    The simplicity and apparent ruggedness of the OE valve suddenly becomes attractive,  if I can get it rebuilt/restored.

John

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IIRC, the OE PRV is considered marginal for the Bosch pump flow and gives problems with noise/ resonance and control unless a loop of rubber hose is used as a damper.

https://www.revingtontr.com/product/rtr4456k/name/fuel-pressure-regulator
 

not suggesting you buy this (Neil is never knowingly oversold) but the write up might be informative.

https://www.tr-register.co.uk/forums/index.php?/topic/9148-pressure-relief-valve-noise/

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