Straight cut gearbox

[Anthony]

Hi,
just wondered but for example, is a sc f20 any stronger than a standard f20 box?
I currently run an f28 as an f20 probably wouldn't last too long with my c20let. However, there is a sccr f20 box for sale up the road from me. Is this a bad idea? or will it be able to take more abise than a standard f20?

Regards

[spuds_own]

Re: Straight cut gearbox

get the sc box mate they are awesome and much stronger than the standard f20 but if its cr then it might be a bit of a waste on the turbo

[DarrenH]

Re: Straight cut gearbox

definately a SC is stronger than a standard F20.

by basic design a straight cut is gear is stronger than a helical cut gear. its not so much because quaiffe or whoever have engineered the gear stronger (although the probably have too)

secondly. its hard to describe in words, but, helical gears (standard) are cut at an angle to each other. so when you put engine torque through the gearbox, you get side loadings down the shaft it sits on, aswell as transmitting drive to its meshing gear

straight cut gears completely remove side loadings down the shafts, also reduces friction on endcase bearings, the gears themselves and syncros, so you also have less transmission losses.

the trade of is noise.

[screamer69]

Re: Straight cut gearbox

sc all the way like darren said the noise is a get on your tits problem but as soon as i have the funds ill be getting one ( just not telling the mrs )

[KEV]

Re: Straight cut gearbox

A couple of years ago I managed to find a company that made a fully sequential straight cut 6 speed box for the XE in FWD applications, I'm sure it was about £6500! It came with shafts and all the change lever gubbins, an awfull lot of money but oh my god how good would that be clicking up the gears BTCC style!

[_SBD16v]

Re: Straight cut gearbox

straight cut gearboxes are not always stronger !!

the gearbox in my submarine is helical and that is rated to over 1million yes 1million ftlb of TQ

the main reason straight cut gears were first used in motorsport was because there so much easyer to make, and because there easyer to make they can be made stronger for the same money with better materials and its easyer to make a larger gear

when i spoke to quaife they said dont use one of there boxes over 300bhp or it will fail

[Anthony]

Re: Straight cut gearbox

when i spoke to quaife they said dont use one of there boxes over 300bhp or it will fail

That may be a slight problem then as i'd want it to be as strong as the f28 i have now currently

A couple of years ago I managed to find a company that made a fully sequential straight cut 6 speed box for the XE in FWD applications, I'm sure it was about £6500! It came with shafts and all the change lever gubbins, an awfull lot of money but oh my god how good would that be clicking up the gears BTCC style!

Now that sounds ideal Group buy lol

the trade of is noise.

The noise wouldn't really be much issue apart from trips to the 'ring where it would probably then get on my tits!

Regards

[ant]

Re: Straight cut gearbox

The F28 gearbox has a 3.72:1 diff ratio and 4th gear is 1:1 with basically 2 overdrives.

You need to ask what the diff ratio is in the sccr f20.

My sccr f16 has a 4.8:1 diff ratio which relates to about 150km/h at 6500rpm in 5th on 50series 15" wheels.

If it is all straight cut including the diff (most are) then the noise will kill you trust me I often have to drive it 95kms to the Autocross track and I have to wear ear plugs.

[kickastra]

Re: Straight cut gearbox

A couple of years ago I managed to find a company that made a fully sequential straight cut 6 speed box for the XE in FWD applications, I'm sure it was about £6500! It came with shafts and all the change lever gubbins, an awfull lot of money but oh my god how good would that be clicking up the gears BTCC style!

Sounds like Sadev.We have one in our MK3 Astra rally car. Almost no noise or whine, and came with uprated inboard joints,shafts and larger CV joints which entailed changing the drive flange.There are three pages worth of gear ratios and tons of final drives.

And yes, they are a joy to drive!!

[Guest]

Re: Straight cut gearbox

I was taught that helical cut gears are stronger and present a greater tooth root area at any one time. When in mesh with its corresponding gear it takes up more back lash when running and gives a sliding edge, as the tooth meshes with its opposite speed wheel, thus making it run quieter.
But because of the the greater rubbing surface, it absorbs more power and generates more heat, that's was why a straight cut gear is preferred for competition, not for strength.
Following the advent of the computer, this has improved the calculation and design of gear teeth.
Before that the auto industry relied on the the genius of Monsieur Citroen[the helical mesh gear] and Dr. Cadillac [the synchromesh hub] .
Just thought I'd chuck in my two bob's worth. lol.

[Joker]

Re: Straight cut gearbox

I think the windy noise sounds mint! I'd have one but don't have 6k lying around lol. I asked quaife about the sequential box for the xe and they said they no longer make them anymore and are trialing a new box which should be out in the next year or so...(don't count on that)

Joker

[ant]

Re: Straight cut gearbox

couple of years ago I managed to find a company that made a fully sequential straight cut 6 speed box for the XE in FWD applications, I'm sure it was about £6500! It came with shafts and all the change lever gubbins, an awfull lot of money but oh my god how good would that be clicking up the gears BTCC style!

Kev have you still got the details about the company that had the F28 sequential setup.

Sounds like Sadev.We have one in our MK3 Astra rally car. Almost no noise or whine, and came with uprated inboard joints,shafts and larger CV joints which entailed changing the drive flange.There are three pages worth of gear ratios and tons of final drives.

And yes, they are a joy to drive!!

Kickastra do you have a F28 in your rally car and do you have contact details for these people that have ratio's?

[steveboyslim]

Re: Straight cut gearbox

All the so called close ratio F20 gearbox is a standard F20 rearbox with a lower(4x4 F20) CWP making the gears seem closer together, giving a lower top speed , they are no stronger or weaker than the usual F20 gearbox using the same sized bearings, internal shafts, gears and casings and can be easily reproduced if the parts from both gearboxes are used.

Steve

[kickastra]

Re: Straight cut gearbox

Kev have you still got the details about the company that had the F28 sequential setup.



Kickastra do you have a F28 in your rally car and do you have contact details for these people that have ratio's?

We have a 6 speed Sadev sequential in our rally car, not an F28.

[KEV]

Re: Straight cut gearbox

Kev have you still got the details about the company that had the F28 sequential setup.

Ant, not seen this till now so sorry for the late reply. I cant remember the company name to be honest, and I've just tried a google search. It wasn't an F28, this was a proper designed and built racing gearbox made with a bellhousing adapter to fit the XE.