57 replies to this topic

[wolfie]

I use mine as a daily too... although that is with a 3.1 diff which tames it a bit...

the missus will quite happily got to sleep in it on long journeys, (and short ones)

Wow...thats quite something

not really............ shes deaf

Edited by wolfie, 10 January 2010 - 06:57 PM.

[gregh55]

I use mine as a daily too... although that is with a 3.1 diff which tames it a bit...

the missus will quite happily got to sleep in it on long journeys, (and short ones)

Wow...thats quite something

not really............ shes deaf

LMAO. . . .Legend!

[mini13]

PMSL!

[leaky]

I love the sound of straight cut gears. And would love to fit one to my car but 2 things. One how much does one cost? And two is it even worth fitting one to a 998? I'll defo be fitting one to my 1380 when I get it.

[Ethel]

With a bit of rough rounding off the speed of sound is 300m/s and, for ease, say an idler gear has a circumference of 30cm; that means the gear's gotta do 60,000rpm to get supersonic. Of course that doesn't take in to account the effect of any squishing between the teeth on the oil or air so I guess it depends on whether that could amplify things by 20:1 or more. What's different between a helical and straight cut is where I think we should be looking. An involute gear must alter speed slightly as it meshes, that might cause vibration unless 2 sets of teeth are meshed at once which might cause some slipping of the contact area, a constant speed and possibly even some harmonic damping like double valve springs ???

You get 1.2khz for teeth meshing at 3000rpm which seems in the right ballpark for the tone.

[Pauly]

I love the sound of straight cut gears. And would love to fit one to my car but 2 things. One how much does one cost? And two is it even worth fitting one to a 998? I'll defo be fitting one to my 1380 when I get it.

Mine cost about £190 for the drops. Are they worth fitting to a 998? If you love the noise then it wont harm it fitting them, and they will reduce transmission loss, just make sure you get the shimming of the idler right. Its your engine at the end of the day.

Edited by Pauly, 10 January 2010 - 08:21 PM.

[mk1leg]

Mk1leg, what brakes are you running?

I'm using KAD 4pot with grooved 10" disc setup..................

[liirge]

Mk1leg, what brakes are you running?

I'm using KAD 4pot with grooved 10" disc setup..................

ahh.......nice!

[stormintrooper]

The ratio changes the pitch of the noise........

The actual noise is caused by oil shear, which is oil under extreme high pressure escaping under extreme high speed. The noise is the oil breaking the sound barrier

Im not so sure that is the case as straight cut gearing systems that rely on grease, make much the same noise. Take for instance a high end electric raidio controlled car

IMHO straight cut sounds exactly like an RC car...especialy when u let the joystick go and the electric motor slows the car down..couldnt be dealing with it personaly..and i think the noise of when u take your foot of the gas is horendous

[TimmyG]

I have straight cut drop gears on my 1293 mini, i think and occasionally get told that it sounds like a motorbike, i love the noise, especially at over 6k, things can get a bit loud and annoying on the motorway though, i use ear protectors, lol

how far away is lordswood from ashford, ill come and find you, well after the minis been to the doctor for a new wing, so you can hear for yourself.

Its about 15-20mile's matey...

Thanks for alot of these replys..so ive listened to all these videos, Im getting the impression that they are good fun and great noise at low speed (around town etc) But going on motorways is a no no as they tend to take there tole on the ears...

Is there anyone to get a good cruisning speed with not this hi pitch on motorway?

As long as you don't fit the straight cut drop gears aswel, the SC gearbox on it's own will barely make anymore noise than standard in 4th gear as the drive goes straight through the mainshaft to the final drive, so only loading up helical cut gears. A little bit more noise than standard might be emitted from the non loaded 1st, 2nd and 3rd gears that are in constant mesh but are not loaded in 4th gear. So to summarise, straight cut gear whine in 1st 2nd and 3rd (when you most want it) and none in 4th (when you least want it) Happy days!

[cooperdan]

I have straight cut drop gears on my 1293 mini, i think and occasionally get told that it sounds like a motorbike, i love the noise, especially at over 6k, things can get a bit loud and annoying on the motorway though, i use ear protectors, lol

how far away is lordswood from ashford, ill come and find you, well after the minis been to the doctor for a new wing, so you can hear for yourself.

Its about 15-20mile's matey...

Thanks for alot of these replys..so ive listened to all these videos, Im getting the impression that they are good fun and great noise at low speed (around town etc) But going on motorways is a no no as they tend to take there tole on the ears...

Is there anyone to get a good cruisning speed with not this hi pitch on motorway?

As long as you don't fit the straight cut drop gears aswel, the SC gearbox on it's own will barely make anymore noise than standard in 4th gear as the drive goes straight through the mainshaft to the final drive, so only loading up helical cut gears. A little bit more noise than standard might be emitted from the non loaded 1st, 2nd and 3rd gears that are in constant mesh but are not loaded in 4th gear. So to summarise, straight cut gear whine in 1st 2nd and 3rd (when you most want it) and none in 4th (when you least want it) Happy days!

That is the best reply i have had on this, too the point, Only whine's in 1st 2nd and 3rd Not in 4th...

So i will be getting one now, knowing i can put it in 4th on motorway and happly cruise along...

Thank you VERY much

[pantera2075]

SC gear noise is mainly due to the gears hitting each other as they mesh. This system introduces a miniscule speed difference between the gears in the period of demesh/remesh meaning the driving gear has to hit the driven gear at every mesh to equalise the velocities through the meshed period.
Helicals are such that the gears are never out of mesh - as one pair demeshes, the next pair is already meshed - so the gears always run at identical velocity and hence no velocity induced impacts.

In a perfect world we'd have double-helical dog boxes.

[cooperdan]

SC gear noise is mainly due to the gears hitting each other as they mesh. This system introduces a miniscule speed difference between the gears in the period of demesh/remesh meaning the driving gear has to hit the driven gear at every mesh to equalise the velocities through the meshed period.
Helicals are such that the gears are never out of mesh - as one pair demeshes, the next pair is already meshed - so the gears always run at identical velocity and hence no velocity induced impacts.

In a perfect world we'd have double-helical dog boxes.

Thank you very much

This really good info, and its helping with my concerns...