What are ' straight cut gears' ?
 

as the title really. what is a straight cut gearbox / straight cut gears ?

dan

Everything you need to know about gears :)

http://www.askautoinfo.com/discuss/c...50/page_1.html

Banny

They are Noisy.

dipster

reverse gear is usually straighcut -- hence the wine

Rally cars used to use them, not sure these days, as they are supposed to be stronger. A mate of mine had an Imp with these in and it was unbearably noisy... not for road use unless you are totally deaf.It is all to do with the angle of the spiral cuttings of the gears, road cars have gears that are cut helically when made that make them quieter and easy to use but straight cut gears are cut without a helical component.

See here...

straight cut gears - Google Images

Ive got a PPG straight cut gear set on mine and dont think its that loud

i,m sure I read a report somewhere recently debunking the view that they were autmatically a stronger alternative to helical cut gears

soemthing to do with stress distribution i think -- better on helical cut gears

People usually run straight cut 1-4 and UK 5th, why is this? Why not all straight cut?

What does it cost?

:)

5th gear has the least strain on it so it doesnt need to be straight cut :)

Tony:)

buy a ppg box dan and give the 6 speed to me :thumb:

leads me to my next question.........................what is a ppg gearbox ?

dan

dont old minis and metros have these hence the noise?

PPG - The Performance Gearbox


read

now buy one and try and break it lol :D

I read some where that it has nothing to do with them being stronger at all, in fact helical gears are stronger due to the increased contact area between the gears.

The main advantage is less mechanical drag due the the smaller contact area on straight cut gears.

if im wrong shoot me down!

no -- although you could get "competition" straight cut gearbox's for them

yep -- i think that was what I was getting at

ppg gearbox kits like in mine are not that bad i use mine as every day car,do get the old remark like "that dont sound healthy" and "that wont last long" etc etc but then fellow petrol heads no that if you have best part of 4k worth of gearbox you must have a decent amount of power to warrent having it lol

Some 'interesting' remarks regarding Spur gears (straight cut) and Helical gears here. We manufacture both for WRC,Rallyraid,GT1,GT2,ALMS,Veron,Ford gt ect ect ect. For a given size of gear, the spur gives a stronger tooth that is more resistant to shock loading. Noise and wear issues are a down side though due to less contact area at any given time.

For the record, All Motorsport transmissions/transaxles we supply use spur gears, this includes F1 teams and prototype leMans one of which is high rpm low (ish) torque the other is low rpm but very high torque levels. The gear tooth thickness and lead lengths are much different but spurs non the less.

Pop back in here, I would like to point out that my mates imp was stripped out, everything including all sound proofing so a car in standard road trim my well be bearable, but it will be noisier in all probability... ask your self do you need these gears? How far are you going to mod the car... rallying or motor sport or massive power?

tbh i don't find mine too loud at all, got a uk 5th in it for motorway cruising, but 1-4 is straight cut ppg.

def louder outside the car compared to inside

Is the noise bearable in daily driving or more suitable for a weekend blast / track days only?

TX.

You tune it out after a while and it does not bother you but passengers will find it annoying lol

Banny

I have a helical cut PPG 5 speed box in my car and absolutely love the whining noise it makes, only thing I don't like about it is the dodgy 3rd gear but apparently that is common with PPG boxes.

OK it sounds like a rally car ... will it involve regular gearbox rebuilds like a rally car too?

TX.

No, they are the same as an OE gearbox for servicing if treated correctly

Main issue I just found yesterday is that the PPG uses a std 5th gear
So guess what gear went on a mapping session
and then guess what - the whole gearbox seized up
Not a happy bunny

I fitted a set of Jack Night straight cut transfer gears in a 1340 Mini I used to road rally. The standard idler gear was helical and the thrust bearing/washers used to go due to increased power thorough them. Answer was straight cut and so no more 'thrust'.

I loved the sound. Course, i was 19 at the time so didn't mind the noise.

must have been running some mega power to break the 5th gear.

you can get full 5 gearsets, but people prefer to have a quiet 5th for motorway work.

will have it stripped at some point and see what the issue is/was if thats possible - sounds like a bag of spanners.......
Not sure what power its running - its quite'fast' at the moment ;-)

lol, my guess would be theres something else gone wrong with it