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Es gibt da einen interesanten Artikel von - Ich glaube der war's - Keith Calver:

Zitat von Calver

Quit Whining – the truth about straight cut gears.

My recent flag-waving about the amazing performance increase merely altering the gearing gives has fanned the flames of the ‘straight-cut gears are far too noisy’ discussions. Not that I said to use straight-cut gears, but the shortage of new components for the old S/1275GT close ratio conversion – most notably pre-A+ second and third gears – has lead to further discussions on the pro’s and con’s of straight-cut gears. Several close-ratio options are readily available, but not all are suited to most road-going engines. So let’s delve!

Whether the gears produce the pronounced and widely recognised signature ‘whine’ or not is mainly dependant on three areas – where they are located in the engine, their design, and then manufacture.

Location. There are three separate areas where gears work within out trusty Mini gearboxes – the transfer (drop) gears, main gear cluster, and final drive (FD/diff).

Strangely the transfer gears are so called because they transfer drive from crankshaft to gearbox, constituting three gears. Primary gear on the crank, input gear on the first motion gear supplying drive to the gearbox, and idler gear suspended between the two moving drive from one to the other. These are the noisiest of the trio by a LONG way, simply because they aren’t drowned in oil. Consequently, in-built ‘features’ of manufacture and design are amplified.

The main gear cluster makes up the collection of gears, first through to top. Nestling down in what effectively is the Mini’s ‘sump’ it’s constantly running in an oil bath. Consequently the noise produced by the straight-cut teeth is very much damped out.

Giving motion to the car ultimately is the final drive (FD or ‘diff’ as it’s generally addressed). Comprising two gears – the small pinion gear mounted on the mainshaft supplying drive to the much larger crown wheel bolted to the diff assembly – which run partly submersed in oil. The top half on the crown wheel runs in oil ‘splash’ thrown up by the lower half that is submersed. So it’s half way between the other two as far as ‘damped’ noise is concerned.

Design. The original idea behind straight-cut gears (cut at 90 degrees across the gear) was really ease of manufacture. Where limited numbers of gears are made for development – be it standard or motorsport – straight-cut gears are far cheaper and easier to produce. A multitude of gear ratio options being available by ‘correcting’ proper tooth profiles to suit - excruciatingly difficult and not economically viable with helical teeth where very much more expensive tooling’s needed. Other bonuses were reduced loads and drag inherent in the helical (cut at an angle across the gear) design – therefore leaving more power to drive the car. That straight-cuts are stronger than helical gears is a myth. Helical cut teeth run quieter as they’re almost constantly engaged, also eliminating shock loads. They’re stronger through better tooth root design and more load-bearing area – the helical angle increasing overall tooth length and surface area by a small but appreciable amount.

Mini FD gears are a special case. Originally these were straight-cut too, but the very weird size differential between pinion and crown wheel meant problems. To get the sort of ratios suitable for motorsport, it’s necessary to make the pinions very small, necessitating massive tooth profile ‘correcting’. This gave rise to at least premature wear, closely followed by regular failure. To improve matters, a very slight helical angle was applied – so now they’re classified as ‘semi-helical’.

Manufacture. The tooth profiles are literally ‘chopped’ out of round steel billets. Straight-cuts are far easier to produce as there’s no complex angle to set up. This can be witnessed in certain manufacturer’s gears where lines can be seen running across the teeth – almost ‘serrations’. How prominent these are is dependant on how fast the ‘chopping’ machine’s run. The faster it runs, the quicker (cheaper) the gears are made, but the more pronounced these serrations are. This is a bad thing, as they rub against each other in use – promoting both more noise and accelerated wear. Worst problem with this in our Minis is that the metal particles shaved off end up in the oil pump/engine! To avoid this the gear teeth should either be cut slowly or ground afterwards. The smoother the tooth, the quieter it’ll run and the longer it’ll last.

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Und Teil zwei...

Zitat

Quit Whining – the truth about straight cut gears.

My recent flag-waving about the amazing performance increase merely altering the gearing gives has fanned the flames of the ‘straight-cut gears are far too noisy’ discussions. Not that I said to use straight-cut gears, but the shortage of new components for the old S/1275GT close ratio conversion – most notably pre-A+ second and third gears – has lead to further discussions on the pro’s and con’s of straight-cut gears. Several close-ratio options are readily available, but not all are suited to most road-going engines. So let’s delve!

Whether the gears produce the pronounced and widely recognised signature ‘whine’ or not is mainly dependant on three areas – where they are located in the engine, their design, and then manufacture.

Location. There are three separate areas where gears work within out trusty Mini gearboxes – the transfer (drop) gears, main gear cluster, and final drive (FD/diff).

Strangely the transfer gears are so called because they transfer drive from crankshaft to gearbox, constituting three gears. Primary gear on the crank, input gear on the first motion gear supplying drive to the gearbox, and idler gear suspended between the two moving drive from one to the other. These are the noisiest of the trio by a LONG way, simply because they aren’t drowned in oil. Consequently, in-built ‘features’ of manufacture and design are amplified.

The main gear cluster makes up the collection of gears, first through to top. Nestling down in what effectively is the Mini’s ‘sump’ it’s constantly running in an oil bath. Consequently the noise produced by the straight-cut teeth is very much damped out.

Giving motion to the car ultimately is the final drive (FD or ‘diff’ as it’s generally addressed). Comprising two gears – the small pinion gear mounted on the mainshaft supplying drive to the much larger crown wheel bolted to the diff assembly – which run partly submersed in oil. The top half on the crown wheel runs in oil ‘splash’ thrown up by the lower half that is submersed. So it’s half way between the other two as far as ‘damped’ noise is concerned.

Design. The original idea behind straight-cut gears (cut at 90 degrees across the gear) was really ease of manufacture. Where limited numbers of gears are made for development – be it standard or motorsport – straight-cut gears are far cheaper and easier to produce. A multitude of gear ratio options being available by ‘correcting’ proper tooth profiles to suit - excruciatingly difficult and not economically viable with helical teeth where very much more expensive tooling’s needed. Other bonuses were reduced loads and drag inherent in the helical (cut at an angle across the gear) design – therefore leaving more power to drive the car. That straight-cuts are stronger than helical gears is a myth. Helical cut teeth run quieter as they’re almost constantly engaged, also eliminating shock loads. They’re stronger through better tooth root design and more load-bearing area – the helical angle increasing overall tooth length and surface area by a small but appreciable amount.

Mini FD gears are a special case. Originally these were straight-cut too, but the very weird size differential between pinion and crown wheel meant problems. To get the sort of ratios suitable for motorsport, it’s necessary to make the pinions very small, necessitating massive tooth profile ‘correcting’. This gave rise to at least premature wear, closely followed by regular failure. To improve matters, a very slight helical angle was applied – so now they’re classified as ‘semi-helical’.

Manufacture. The tooth profiles are literally ‘chopped’ out of round steel billets. Straight-cuts are far easier to produce as there’s no complex angle to set up. This can be witnessed in certain manufacturer’s gears where lines can be seen running across the teeth – almost ‘serrations’. How prominent these are is dependant on how fast the ‘chopping’ machine’s run. The faster it runs, the quicker (cheaper) the gears are made, but the more pronounced these serrations are. This is a bad thing, as they rub against each other in use – promoting both more noise and accelerated wear. Worst problem with this in our Minis is that the metal particles shaved off end up in the oil pump/engine! To avoid this the gear teeth should either be cut slowly or ground afterwards. The smoother the tooth, the quieter it’ll run and the longer it’ll last.

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Und noch die 'Conclusion' hinterher...

Zitat

Conclusion. Straight-cut gears will ‘chatter’ at idle as there’s no initial load to instigate a stabilising side thrust. Rapid manufacture will increase noise generated via increased friction, and amplify the chatter by excessive lash between the gears. The more oil the gears run in, the greater the damping effect on noise production. So the main gear cluster actual develops very little noise at all. Barely discernable. Final drive gears produce more noise than their semi-submersed situation implies simply because of the area/quantity/design of teeth doing the work. The noisiest of all are the transfer gears – lots of activity and very little oil. The good news then is using a close ratio straight-cut gear cluster isn’t going to make you deaf!

Panel – ‘Recommendation for the road – If the helical S/1275GT set-up proves illusive, use Mini Spares Centre’s ‘Clubman’ kit. Practically the same ratios as the old 3-syncro straight-cut cluster (recognised as probably the best ratios for fast road use) but fits four syncro boxes. Wicked.

PS: Warum eigentlich die Beschränkung auf so wenige Zeichen? Könnte man die aufheben/vergrößern?

The original idea behind straight-cut gears (cut at 90 degrees across the gear) was really ease of manufacture.

Ergo ist das straightcut billiger...:D

Nils

Kurz und Knapp von einem Laien! Erklärt : Bei einem Gerade Verzahnten Getriebe, greift jeweils Ein Zahn auf den Anderen. Hat den Vorteil das man Weniger Reibungsverlust, zu einem Schräg Verzahnten Getriebe hat. Sprich es Geht Weniger Motorleistung ,durch das Getriebe Verloren. Bei einem Schrägverzahnten Getriebe Greifen Mehrere Zähne Gleichzeitig aufeinander. Was den Vorteil hat,das die Belastung sich Veringert. Und das Getriebe Länger hält,und Deutlich Leiser ist. Wie Gesagt das Ganze ist jetzt "etwas" Grob erklärt.

Hier hört man eins "singen"

Mir gefällts.

Zitat von svenismk2

Kurz und Knapp von einem Laien! Erklärt : Bei einem Gerade Verzahnten Getriebe, greift jeweils Ein Zahn auf den Anderen. Hat den Vorteil das man Weniger Reibungsverlust, zu einem Schräg Verzahnten Getriebe hat. Sprich es Geht Weniger Motorleistung ,durch das Getriebe Verloren. Bei einem Schrägverzahnten Getriebe Greifen Mehrere Zähne Gleichzeitig aufeinander. Was den Vorteil hat,das die Belastung sich Veringert. Und das Getriebe Länger hält,und Deutlich Leiser ist. Wie Gesagt das Ganze ist jetzt "etwas" Grob erklärt.

Hallo,

Sehr grob:D

Der Hauptgrund, gerade Verzahnungen einzubauen ist neben den kleineren Reibungsverlusten, dass keine Seitendrücke entstehen können.
Gerade bei sehr stark getunten Motoren entstehen im Primärantrieb, aber auch im Getriebe selber sehr hohe Seitendrücke, was sich dann öfters mal in eingelaufenen Anlaufscheiben, bzw. zerstörten Zwischenraddeckeln äussert.
Dass sich nur jeweils ein Zahn im Eingriff befindet, ist eher ein Nachteil, da sich dadurch die Zahnflankendrücke vergrössern und deshalb eigentlich breitere Räder eingebaut werden müssten, was aber aufgrund der gegebenen Platzverhältnisse (im Mini zumindest) eher schwierig sein dürfte.

Das Mehr an Lärm beim Getriebe hält sich übrigens in Grenzen. Ein gerade verzahntes Primary gear ist aber schon hörbar...

Gruss
nerd

Hallo zusammen.

Gerade- und Schrägverzahnte Getriebe haben jeweils Vor- und Nachteile.

Das Geradeverzahnte überträgt die Antriebskraft von einer Welle zur anderen ohne seitliche (achsiale) Kräfte und letztendlich dadurch auch mit einem besseren Wirkungsgrad. Dafür erzeugt es ein Geräusch, eben dieses Singen. Rückwärtsgänge sind auch meistens geradeverzahnt und machen auch dieses Geräusch.

Ein schrägverzahntes Getriebe läuft wesentlich geräuschärmer und geschmeidiger. Dafür erzeugt es auch erhebliche achsiale Kräfte auf die Lager, das Gehäuse etc, was bei hoher Leistung (Tuning) in Verbindung mit einem Seriengetriebe (oder seriennahem Getriebe) zu Problemen führen kann.

Das waren jetzt nicht ausgesprochen wenige Worte, aber vielleicht doch ganz gut erklärt.

Gruß. Martin.

Aber was da geweckt hat, das war n i c h t das Getriebe sondern der Primärtrieb.
Geradeverzahnte Getriebe klingen in etwa wie jedes Seriengetriebe 1970 mit 65.000KM Laufleistung.

Aber diese Mär oder dieser Trugschluß hält sich schon seit fast 40 Jahren.

Andreas Hohls
P.S.: Und ein Geradverzahntes Getriebe hat auch in Alltagsautos Vorteile, weil die sportorientierte Gangabstufung kurze Drehzahlsprünge mit besseren Anschlüßen erlaubt.