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Thread: Modern designs that drive you nuts

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  • #102
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    ....with a different bent on topic line....


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    Ahhh, I really like this twist

    WW2 aircraft engine service... time for an oil change ? Nah not worth it let's just change the engine.

    That was not a joke with my all time favourite aircraft:

    After 10 hours of use, the jet engines needed replacement.

    Guys, if you are only a fraction of a nutter like me for technological details and break throughs, wiki reading goes far beyond any YT videos.
    A link like above will cover my entire evening as the internal links just send you deeper and deeper with 100's of browser tabs opened.

    Anyhow I am currently building an Me 262, well it is only 1:18 scale (actually quite large for a display mode) only with the difference that I am re-engineering to become fully functional, well not the weapons of course.

    Immediately when I laid out the wing pieces I had the feeling I was building a modern passenger jet, this thing was that advanced.
    Like a lot German WW2 tech, this aircraft had significant fundamental breakthroughs.
    Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
    Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
    Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...

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    John Deere 6170m serpentine belt routing...





    The belt..... 2991mm long, $260AU genuine part...same for idler pulleys....double that for tensioner pulley....FFS...

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    Quote Originally Posted by wotnot View Post
    John Deere 6170m serpentine belt routing...





    The belt..... 2991mm long, $260AU genuine part...same for idler pulleys....double that for tensioner pulley....FFS...

    What a hideous monstrosity that makes no sense.
    Although I am inclined to say that for almost all ICEs, with the exception of aviation radial engines.
    They are purely a work of art.

    No silly fan belts here:




    ...just a 'few' nuts to drive
    Last edited by Uncle Fester; 24-11-22 at 11:01 AM.
    Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
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    When it comes to large capacity engines, my favourite is the , 18 cylinder, 36 opposing piston 2stroke uniflow diesel. It was based on a Jumo 'diamond' configuration but they couldn't get the crank phasing to work - one of the Napier engineers figured out that with a 'delta' configuration with 3 cranks, would achieve proper crank/port phasing, if one crankshaft rotated in the opposite direction than the other two. With less than half the moving parts of a comparable 4stroke diesel, the power to weight ratio is higher, but even though lighter and more efficient, they still use more fuel/hr in service than a 4stroke turbo...clever engine though, they had a turbo-compound unit of a test bed making 5000hp from a 88litre deltic @ 1500rpm... they have a unique engine note...

    Aero engines have a different life, tuned to prop speed/reduction box limitations, with a narrow operating rpm band, and disassembly/inspect/repair/reassembly routines, that make normal road vehicle engine maintenance schedule look like I joke =) If you applied aero engine maintenance schedules to car engines, they'd last a hell of a lot longer....but....some more modern engines shouldn't be disassembled at all ~ you just replace engine...they're like Bic ball point pens ; if the ball gets damaged but it's still full of ink and the pen body is ok, stiff shit ...buy a new pen.
    Last edited by wotnot; 24-11-22 at 11:01 PM.

  • #108
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    Quote Originally Posted by wotnot View Post
    .but....some more modern engines shouldn't be disassembled at all ~ you just replace engine...they're like Bic ball point pens ; if the ball gets damaged but it's still full of ink and the pen body is ok, stiff shit ...buy a new pen.
    The Toyota v8 diesel is a perfect example of this, cams running directly in the heads, no cam Bearings....

    Sent from my CPH2305 using Tapatalk
    FTTN, 400m line length, bit faster now with 2x100/20 connection via load balancing.....


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    Quote Originally Posted by hoe View Post
    The Toyota v8 diesel is a perfect example of this, cams running directly in the heads, no cam Bearings....
    Yeah, that's common practice these days, with the entire system wholly reliant on good oil pressure/distribution, and a regular oil change interval that's very short... I remember decades ago when that woeful overhead cam in alloy head housing arrangement appeared with the Honda single cylinder in bikes ...you just looked at it and shook your head ; zero serviceability ...if the cam(s) wear out the alloy caps/seat, stiff shit, buy a new head. You get -any- hard debris in the oil between cam journals and these alloy surfaces, we are done ..

    Other stuff is just diabolical, I'm helping a mate sort out a Nissan KA24DE engine...but this is a particular KA24DE build that Nissan put together so they could fit this engine in the limited engine bay space at the front of a Largo van. What they did was get the longitudinal/rear wheel drive block out of a 240SX, and grafted on a head from a front wheel drive car using the same engine type (Altima etc), and they fitted the combined crank angle sensor and HT distributor assembly to the rear of the intake camshaft, driven by a dog and keyed slot in the end of the cam. This puts the 'crank angle sensor' 2 timing chains and 5 sprockets away from the crankshaft itself...(and if you're into engine you should be giggling now ; what could possible go wrong...right? =)

    I'll tell you what can go wrong ~ engine blows a head gasket, perhaps suffering from slight overheat in the process and cylinder head distortion/warp, and so it's removed and resurfaced by someone unknown, and it looks like they took 0.686mm/0.027" off the face of the head to get it good. The service limit here as stated by Nissan, is you can take no more than 0.20mm/0.008" off the interface between head and block...ie; you can take 0.10mm off the block and the head, or 0.05mm off the deck & 0.15mm off the head. This isn't a lot of 'margin' to play with typically speaking, but either way whoever has taken roughly 0.50mm more off the cylinder head face than the stated service limits. Just take it as read here, this has bumped compression ratio a little bit....but wait, there's more!....

    .....because there's 2 timing chains with an idler gear between them (the idler gear accomplishes the 2:1 reduction wrt crank), and the idler gear mounting shaft is bolted to the cylinder head, the resurfacing of the cyl head has brought the idler sprocket 0.686mm closer to the crankshaft sprocket, thus introducing slack in the torsion side of the lower chain. As a result, the spring loaded chain tensioner on on the relaxed side of the lower chain, pushes in further to take up the slack, which results in the idler sprocket rotating a few degrees anticlockwise wrt crank @ TDC. This small counter rotation, gets transferred to the camshaft sprockets, which in turn puts camshafts/valve timing a few degrees retarded wrt crankshaft ....not where they should be...

    ....it gets better....because the crank angle sensor/distributor is driven from and mounted to the back of the intake camshaft, it's -operational- direction of rotation is anticlockwise wrt the crankshaft, and because the sensor itself is based on photo-electronics and a slotted 'chopper' disc which is keyed to the distributor shaft, it ends up signalling the ECU where the camshaft is, not where the crankshaft is wrt TDC......ie; it thinks piston in cyl 1 has reached TDC a few degrees -before- it actually has...

    ...to finish off a nice piece of what happens with this design and geometry..... and ppl working on it who don't understand.... once all this is so, and one connects a timing light to cyl #1 spark plug lead as the trigger, the ECU generated spark event that fires the timing light, is likewise a few degrees out wrt the timing marks on the crankshaft pulley and the marks on the timing cover...so in effect you're trying to set timing when the ECU doesn't actually know what the crankshaft position is.

    Absolutely stoopid setup really, but it's why the service limits are tight ~ we'll try modding the camshaft sprockets first to put them back where they should be wrt crank TDC, which will correct the CAS/dizzy error....and hopefully it won't ping like a mad thing =)

    Old (retired) mate who did his apprenticeship/worked at a Nissan dealership, said the service limit of 0.20mm/0.008" was the point where the altered geometry resulted in 1 degree error at the cams/CAS.





    Pop quiz =) ...look at that chopper disc ... there are 4 datum points wrt crankshaft being top dead center, cylinder 1, compression stroke ... can you see them?
    Last edited by wotnot; 25-11-22 at 01:36 AM.

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