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Recent content by NickJ67

  1. NickJ67

    Progressing cavity pump - unusual rotor corrosion - why

    Got to work with the options the manufacturer provides. Neither of two major German manufacturers I've worked for have ever showed any interest in 17/4PH. 304 or 316ss are the mainstream, with or without hard-chrome plating. Duplex in 22% Cr form is also semi-standard, but pricey. 25% Cr is...
  2. NickJ67

    Progressing cavity pump - unusual rotor corrosion - why

    Yes, that's our working theory - though exactly what remains a mystery. Your Br or F maybe. Nobody is very keen to pay for analysis. Pumps will be opened and inspected week after next. Reckon the tool steel rotor will be done by then. It will be replaced by 316ss/hard-chrome plated. Curious...
  3. NickJ67

    Progressing cavity pump - unusual rotor corrosion - why

    Yes, 8.6 is the pH of the slurry. Yes, 1045 class carbon steel. Simple induction hardening where the machined item is passed through an induction loop heating to approx 850 - 900ºC. I don't have any detail on this. It's our typical selection for general waste-water and slurry work where...
  4. NickJ67

    Progressing cavity pump - unusual rotor corrosion - why

    Hi, Long time no post - and first post in the Corrosion area. Needing advice on some rather unusual corrosion on the rotor of a progressing cavity pump. I've been working with these more than 20 years now (applications support, tech sales and some service work) and not seen anything quite...
  5. NickJ67

    Some of the worse designed engines?

    Been a number of deeply suspect engineering decisions in the engine departments of VAG and BMW in the last 15 years or so. Insufficient piston ring tension margins giving huge oil consumptions at low mileages. (Also Toyota though) Ridiculously complex timing-chain arrangements with...
  6. NickJ67

    Lead substitute additives and O2 sensors

    Hi, Slightly unusual situation here in that we have a couple of 60s Triumph car engines running aftermarket fuel injection, with wideband O2 sensors for tuning and trim, but no catalytic converters. One of these does not (yet) have hardened exhaust valve seats fitted and has started to...
  7. NickJ67

    Interpretation of fuel analysis

    Some years ago I briefly ran my C4 Audi A6 2.5TDI on biodiesel. Car already had c.200k miles at that point, all done on regular diesel. I was warned that filter clogging might be an issue and was advised to carry a spare. According to the bio supplier, the clogging risk was due to the bio...
  8. NickJ67

    Mercedes GLC "tyre hop"

    Well..... thanks Cibachrome. Those pics explain alot I reckon. (unforeseen)Packaging problem leading to geometry compromise. The car did get to the dealership this week and they changed the "steering knuckles", which I'd call track-rod ends. Apparently this has all but cured the problem...
  9. NickJ67

    Mercedes GLC "tyre hop"

    Thanks to all for your thoughts. It was supposed to be with the dealer today for attention - not sure whether that actually happened though. Things are strange just now...... I will find out. I did find some text online, allegedly of MB origin, suggesting that the front diff position meant...
  10. NickJ67

    Mercedes GLC "tyre hop"

    Gentlemen, This is a fair bit out there on this subject on the net already, but much of it low level and questionable. In discussion with a colleague yesterday regarding his just-purchased 2019 Mercedes GLC. Something like 10 months old, less than 8000 miles. Former owner, the Mercedes...
  11. NickJ67

    Brake caliper seal design

    Mint Julep - that little trick had passed me by - thanks for pointing it out and re-posting the pic. djhurayt - rotors/disc are to the left - I should have marked it on the sketch. gruntguru - anti-knockback valves are an option, but shouldn't be needed. I've not seen the spring approach...
  12. NickJ67

    Brake caliper seal design

    My question concerns the now rather old Girling type 16 series of brake caliper used on many UK-built cars in the 60s and 70s. It's a robust and reliable (if rather heavy) cast iron design with two opposing pistons of 54mm diameter. The pressure seals are simple, rectangular section rubber...
  13. NickJ67

    What´s maximum static compression ratio appliable to LPG?

    My feeling on CR is that it might just live (for a while at least) at 11:1 without boost, but adding boost will kill it very quickly. To run even moderate boost Ivymikes' numbers look much more realistic. Then there are the very valid points raised by Gruntguru. I wouldn't sell this engine...
  14. NickJ67

    What´s maximum static compression ratio appliable to LPG?

    Interesting thread. Seems like the mechanical aspects of the "conversion" haven't been very thoroughly thought out! The only diesel engines I've come across running lpg without significant mechanical modification (usually different pistons to lower the CR and loose the swirl bowl), have been in...
  15. NickJ67

    Diesel Driven Fire Pump

    Probably better in the pump engineering section? Do you have control of the discharge pressure and if so, are you saying that you have to back the pressure off (open snubber valve or whatever) in order to get the flow to come up to 5,600 l/min @ 1,900 rpm? If this is the case then I would...
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