HP pipe thread size ?

electrokid · Post by **electrokid** » Tue May 11, 2010 12:04 am

Hi,

Does anyone know the size and thread type of the output port of the HP pump, or the other end of the pipe if they are different ?

Cheers,
Brian.

citronut · Post by **citronut** » Tue May 11, 2010 8:11 am

i think the pipe thread is 8 or 10mm not sure of the thread pitch, and yes both ends are the same size,

why do you ask,

did you find an air box of the corect type

regards malcolm

electrokid · Post by **electrokid** » Tue May 11, 2010 4:36 pm

Hi Malcolm,

Thanks for getting back to me - I now have the info ! ! by a rather strange route...

I had the front spheres replaced this morning so when Andy (Andy's Autos of Woking) dropped the car back so I could take him back to his garage I asked about the thread size. When we got back to Woking he dissappeared into a cupboard and had a rummage in his odd bits box and came out with a pipe - the pump output pipe ! "You can have that"

Brilliant

So I've measured it - max OD is 11.89mm, thread ID is around 10.79mm and the pitch is 1.25mm - so if anyone else needs the info - it's 12mm ISO metric FINE.

And the reason... well you know I'm a bit mad by now

I want to put a tee in the line and fit a pressure transducer (I've found one for 250 bar with a 1/4 BSPP thread) driving a bit of electronics (that's the easy bit for me). I've figured I can switch the rev counter between rpm x100 and psi x100 - then I can keep an eye on the pump without having to guess if it's ok.

Nope - not found the airbox yet - as long as I can do the mod before winter (because global warming isn't going as planned) it'll be fine.

Cheers,
Brian.

citronut · Post by **citronut** » Tue May 11, 2010 9:19 pm

that sounds odd to me, how can the thread be 12mm when the spanner size is 12mm,

regards malcolm

rayfenwick · Post by **rayfenwick** » Tue May 11, 2010 10:11 pm

electrokid wrote:And the reason... well you know I'm a bit mad by now I want to put a tee in the line and fit a pressure transducer (I've found one for 250 bar with a 1/4 BSPP thread) driving a bit of electronics (that's the easy bit for me). I've figured I can switch the rev counter between rpm x100 and psi x100 - then I can keep an eye on the pump without having to guess if it's ok.

Darn it, that's clever! I'd like to see a write up of how that goes, if you'd be willing. Electrickery is my field too, so this would be very interesting. I'm already thinking about expanding the capabilities of the dot matrix display in the XM, and this fits in nicely...

electrokid · Post by **electrokid** » Tue May 11, 2010 11:02 pm

You're right Malcolm - I've got the pipe in front of me - the A/F on the nut is the same as the OD on the thread - clever these French. But then from memory the torque required is quite low for that sized nut because the little rubber tube is the pressure seal so gets better the higher the pressure - you'd normally tighten hydraulic connections until your knuckles match the whitewash

electrokid · Post by **electrokid** » Tue May 11, 2010 11:36 pm

The sensor is fairly standard...

http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... K:MEWAX:IT

and having chatted with the seller it is welded StSt sealed construction so it's well up to the job. The output is 1 to 6 volts. The tacho takes pulses from its sensor (not sure how many per revolution but I'll find out in due course - I'll base the math on the minimum one pulse pre rev) so all that's needed is a voltage to pulse conversion - a 555 timer makes it simple.

From memory the cut-in / cut-out pressures are 145 / 175 bar + or minus 5 bar - which is about 2100 - 2500 psi.

To read '21' to '25' on the tacho a cct is needed that converts the sensor's output at 145 bar (3.9v) and the output at 175 bar (4.5v) to 35 pulses per second and 41.6 pulses per second respectively - it's going to be a linear relationship between volts and frequency but those are the points we need to worry about.

It probably won't be linear down to very low pressures - but then the big STOP light will be on anyway - I always thought that light should say "STOP... if you can"

It may be a bit of a pipe dream (OUCH - didn't see that coming

) but the valver instrument pod I won on eBay (sorry if I outbid any of you guys) has arrived today so I'm about to play with it (the instrument pod that is) so I'll see what can be done.

Switching between rpm and psi should be a simple matter of putting a switch in whatever the tacho uses as an input to divert it to the output of the 555 timer when psi readings are needed.

If it gets done I'll certaily do a write-up - I'm well behind with webbie stuff right now but it will get done - honest.