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18 Apr 2015, 00:16 (Ref:3528389) | #1 | |
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Unexplainable Technology in Modern Cars
1) Stretch Bolts!
If anyone can explain to me logically why a bolt that has been stressed beyond its elastic limits into plastic deformation is better than a bolt working within its stress limits I would be glad to hear about it! Technology of using a heavy component where a much lighter one would do just fine? Anything else anyone has that just plain does not make sense would be good to hear about! |
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18 Apr 2015, 07:59 (Ref:3528433) | #2 | |||
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18 Apr 2015, 09:34 (Ref:3528446) | #3 | ||
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Good expalanation here http://www.gomog.com/allmorgan/stretchbolts.html and they are specifically designed to be tightened such that they go beyond their elastic limit which has a number of advantages explained in the article, particularly for automated assembly and reduced maintenance. |
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19 Apr 2015, 01:02 (Ref:3528756) | #4 | ||
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This is due to the fact that when a fastener is tighten into plastic deformation, it will not change it's effective tensile strength, (and clamp force) by very much over a given amount of elongation, (stretch). So when the pneumatic machine tightens the bolts in your engine, it can vary up to 1/2 turn and still have the same clamp force... at least in theory. At least I know why they are used. I have been substituting the eye wateringly expensive "low grade" stretch bolts with cheap high grade 8.8 Metric bolts for some time now with no ill effects; I do re-torque the bolts though! The spec for these bolts in the article is wrong they min proof load of 85000 psi. Over time the head gasket in such situation will deteriorate to the point where a leak is visible and over-heating occurs. Regardless of how competent the installer is, if the head bolts have inadequate clamp force, the problem will re-occur. The solution then is to install better quality fasteners with adequate strength to meet the demands of the application. Thanks FWD, much appreciated explanation into why the lousy things came into being, and confirmation they are in fact inferior low grade bolts! Last edited by wnut; 19 Apr 2015 at 01:08. |
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19 Apr 2015, 07:13 (Ref:3528802) | #5 | ||
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I recon it's just a ploy by the manufacturers to flog more bolts !!!!!
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
20 Apr 2015, 10:26 (Ref:3529254) | #6 | ||
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fourWheelDrift at least pinned the reason. |
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20 Apr 2015, 10:29 (Ref:3529255) | #7 | |
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Next up Cam Belts - nice idea, lousy in reality, bad reliability and expensive servicing! Massive damage when they break too!
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20 Apr 2015, 10:56 (Ref:3529259) | #8 | |||
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Plus, a couple of cam belt stories: 1. I was told that the original Vauxhall slant 4 (1600 & 2 litre) engines only had a cam belt cover fitted to stop customers worrying, because the belts weren't completely flat, they would move about, tracking back & forth on the pulleys. Vauxhall fitted the cover to stop owners seeing that! 2. Some newer cars now have what I feel is a ridiculous timing belt change period of 125,000 miles or 10 years! Obviously if the belt fails just before then, the car will be well out of warranty anyway, so the owner is left to suffer the consequences! (All done to keep the apparent 'costs per mile' running costs cheap!) |
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20 Apr 2015, 17:19 (Ref:3529370) | #9 | ||
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Yes a lot are going back to timing chains but they still have a life and a recommended change period.
Regards timing belts some cars are worse than others by a long way and will fail if the recommended times or milage are ignored, the Ford Zetec engines will go on for 100,000 miles and eight years or more but some of the breakages are caused by idler wheels and water pumps failing before that, also lots of short runs (heat and cooling cycles) will easily shorten the life. I remember when some manufacturers started to not have any keyways on bottom pulleys, that must have caused a few "problems" for the DIY brigade |
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
20 Apr 2015, 22:10 (Ref:3529493) | #10 | ||
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Another thing I find that is a bit ridiculous in a lot of modern cars is the methods of using the parking brake. Why after years of something that was easy and efficient (on most cars) did somebody decide that an electric handbrake was the way to go with all sorts of problems that will cost a small fortune in the future ? and while I'm at it why bother with rear disc brakes at all ! especially those that are used for parking as when the discs cool down and contract the cars can (and do) run away on a decent hill, whereas a drum will contract and actually get tighter ! and the tiny drum in disc type isn't that marvelous !
Ok performance cars may need massive discs all round but not the majority of "normal" everyday transport vehicles. Climb off my soapbox now ! |
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
21 Apr 2015, 01:10 (Ref:3529523) | #11 | ||
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The cable that is routed down the exhaust tunnel would and would probably contract far more than the disc brake would tend to shrink? |
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21 Apr 2015, 06:07 (Ref:3529573) | #12 | ||
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I had a Citroën BX roll away once. The problem with rear discs us they are not used hard enough in every day driving and so rust/stick frequently. Drums don't do that.
You're taught not to leave a car in gear during your driving lessons these days. |
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21 Apr 2015, 07:54 (Ref:3529602) | #13 | |||
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As most of us know in the motor trade there are some cars that only just pass MOT standards on parking brake efficiency when they are new and after a bit of time and miles are rubbish ! |
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
21 Apr 2015, 08:56 (Ref:3529622) | #14 | ||
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I'll take notice on the handbrake implications of drum brakes. I must admit that I have not had a drum brake on anything since I spent a lot of time effort and money removing said drums from a Mini; good for one stop then made absolutely no difference at all, scary scary things! |
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21 Apr 2015, 09:25 (Ref:3529627) | #15 | ||
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I suppose the "powers that be" regards leaving the car in gear think we are all going to start it and crash into something, however a lot of cars now have an isolator switch on the clutch pedal.
I once got fined for parking without "wheel chocks" in San Francisco ! |
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Balls of steel (knob of butter) They're Asking For Larkins. ( Proper beer) not you're Eurofizz crap. Hace más calor en España. Me han conocido a hablar un montón cojones! Send any cheques and cash to PO box 1 Lagos Nigeria Africa ! |
21 Apr 2015, 11:38 (Ref:3529652) | #16 | ||
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We've got drums on the back of the wife's Focus 1.6 Zetec and there hasn't been a moment's trouble with either stopping or longevity. My MGZS 1.8 on the other hand has been through two pairs of discs and two seized calipers. Same with my Peugeot 406 estate, the discs took so little use that they rusted away quicker than the pads wore down! When I had the 405 Estate with drums once again there was no problem at all.
You malign drum brakes based on experiences with a 60 year old design LOL. Discs on the back of ordinary cars used for ordinary family life are a fashion item. I will admit that when using the ZS on a track day then discs were very good :-) |
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21 Apr 2015, 13:49 (Ref:3529693) | #17 | ||
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The move to rear disc brakes was partially to improve pedal feel with ABS systems. When pressure is released from a disc brake the pads move back a tiny amount, 0,1mm or less, whereas on a drum brake the shoes move back a relatively big distance, resulting in much larger pulsations at the pedal. It's also more difficult to match the fade characteristics of disc brake pads & drum brake linings, which makes optimising ABS settings more difficult.
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21 Apr 2015, 15:59 (Ref:3529724) | #18 | |||
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Quote:
My Landcruiser has drum in disc handbrake and the only time they work is the first pull after I've adjusted the shoes, then the cable stretches a bit more and they don't work any more. |
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21 Apr 2015, 19:02 (Ref:3529789) | #19 | |||
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We have a store in the US called Fastenal that I source most of my bolts from. It's pennies compared to manufacturer pricing. For low stress or low risk applications I will reuse TTY bolts with threadlocker. I torque to specification plus a quarter turn. |
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21 Apr 2015, 23:02 (Ref:3529853) | #20 | ||
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TTY bolts they are from now on for me! "I torque to specification plus a quarter turn" Don't they start to neck? They have reached the plastic deformation zone the first time they are torqued beyond the elastic limit, and subsequent installations will just plain stretch them. Have you had trouble removing the large TTY bolts, seem to require huge amounts of torque to undo; probably why they are good without nuts; then often just break clean off! P.S. I use threadlocker low strength on just about everything, stops corrosion in threads and requires the same amount of force to undo. |
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29 Apr 2015, 22:57 (Ref:3531989) | #21 | |
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Gearboxes and Differentials that have no drain plugs to renew the oil!
When the oil wears out the component wears out - not acceptable in my book. "Sealed for like" - EXACTLY - the life of the oil! |
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30 Apr 2015, 04:52 (Ref:3532044) | #22 | ||
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The automatic transmission in my 2002 Ford Falcon was "sealed for life". A mate who is a mechanic specialised in automatic transmissions, he said that's crazy. He had the same model and he replaces the fluid every 100,000km by dropping the pan off.
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1 May 2015, 09:32 (Ref:3532456) | #23 | |
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I'd never buy a used automatic which has no service records telling me when the fluid (+filter if there's one) has been changed. I change manual transmission fluid as well. It may not be so essential as with automatic but just by looking at the magnet on the drain plug it's easy to say it should be changed.
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5 May 2015, 10:07 (Ref:3534278) | #24 | ||
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5 May 2015, 11:38 (Ref:3534301) | #25 | ||
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VW Dealers charge something like $500 for a DSG gearbox service, required every 60,000km. The oil must come from NASA, as it forms a good proportion of that cost. And is independent of any other logbook servicing, as an addition.
I had two oil drops in under 8,000km, under warranty, as the gearbox decided to fail mechanically, electrically and electronically at different times of its life. Imagine buying a used one? (shudders) |
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