37 replies to this topic

[Paul Wiginton]

Pedantic *melons*er, lol

Its swings and roundabouts really. If you have SC box, you probably have a powerful motor so youre putting different higher loadings on the bearings, such as the pinion trying to climb up the crownwheel which also bends the mainshaft and exerts a lot of extra force on the small bearing between the mainshaft and input shaft and input bearing. I know MiniWilliams has had a lot of problems breaking 3rd gears with his monsterous power due to this as 3rd gear is relatively unsupported.

Paul

Edited by Paul Wiginton, 03 October 2009 - 04:29 AM.

[TimmyG]

Pedantic *melons*er, lol

Its swings and roundabouts really. If you have SC box, you probably have a powerful motor so youre putting different higher loadings on the bearings, such as the pinion trying to climb up the crownwheel which also bends the mainshaft and exerts a lot of extra force on the small bearing between the mainshaft and input shaft and input bearing. I know MiniWilliams has had a lot of problems breaking 3rd gears with his monsterous power due to this as 3rd gear is relatively unsupported.

Paul

haha, sorry! I'm a sucker for detail! lol
Yeah the pinion bearing has to cope with a hell of a lot of torque in first gear with a tuned engine, or any gear come to that if you have as much torque as miniwilliams!

Tim

[george91]

SC boxes arent stronger than helical. A helical gear has a longer 'root' therefore are stronger than SC, but you still are quite unlikely to break one

Paul

I said that a bit bluntly Paul, i understand what you said that in design helical gears are stronger, as if a straight cut gear and a helical gear were made from the exact same material the helical would be stronger but when you buy straight cut gears they are manufactured from a higher strength steel to match or be stronger than the standard gear.


Another part to consider is that helical cut gears are more expensive to manufacture than SC gears, this is why they don't make double helical gears which would be even more expensive again, but mini93 is right they would solve both problems, firstly although they have thrust loading it is in both directions which in term cancels out any side loading which is the reason for SC gears, and due to them still being helical the load is transfered gradually making them the strongest option.

That is whats wrong with SC gears, the load is transfered immediately which basically allows the gears to mesh and come into contact with each other harshly, this causes the signature whine you get for SC gears.

Sorry for the techy reply this is my understanding of gears in general, however i don't know much about gears/gear box's in cars specifically.

Edited by george91, 05 October 2009 - 01:14 PM.

[project mini chris]

What would a SCCR Box be like in a mild road 998? Advantages/ Disadvantages?

Cheers...

[phoenix1]

What BHP  ( I know its also torque ) would you expect a pre A+ gearbox stand. I was reversing into the garage when a tie rod gave way and the wheel went back into the wheelarch .It wont now select reverse without major crunching or select 1st and third. I think when it happened the engine must have moved back somewhat. The engine has approx 120 bhp

[mab01uk]

What BHP  ( I know its also torque ) would you expect a pre A+ gearbox stand. I was reversing into the garage when a tie rod gave way and the wheel went back into the wheelarch .It wont now select reverse without major crunching or select 1st and third. I think when it happened the engine must have moved back somewhat. The engine has approx 120 bhp

 

If the engine moved back it may have bent the rod of the gearchange assembly in the centre tunnel......it is unlikely the gearbox would be damaged internally by what happened.

[Cooperman]

In a fairly mildly modified 998 the very high first gear in the SCCR gear set would mean a very low final drive ratio would be needed unless the clutch was to be excessively slipped when pulling away from rest.
A lower final drive ratio would make 4th very low and restrict cruising speed
So all negatives really.
A really powerful 998 able to rev to well over 7500 rpm and with a 4.3:1 final drive would be fine for racing with a SCCR gearbox.

[MIGLIACARS]

yep. helical are stronger, but you get more transmission loss through them, power is lost as it tries to push the gears to the side. But if you have an engine circa 100bhp this side thrust will push your drop gears through your casing... hence the 'need' for them with high powered engines, no need for a s/c box though.

Its a myth about standard drop gears being no good in high performance engines.

I had pre A plus drops for 2 seasons in my racer. 167atw  no issues ever. Im now on s/c but only as they came in a deal I did.

[MIGLIACARS]

What would a SCCR Box be like in a mild road 998? Advantages/ Disadvantages?

Cheers...

terrible 

[Avtovaz]

straight cut boxes are stronger, fact.

 

when the power is put into the box, a helical box tries to force the shafts back and forth and outwards. So that puts forces into the bearings, in 2 directions. If you use straight  cut gears the forces are only outwards, so the forces go directly into the gears, bearings and the casing. because of this also, on some boxes you can use a thicker shaft and neadle roller bearings, which are stronger again. Difference between a type 9 clubman and a professional box.

 

If you put a sccr box into a standard 998 motor, with the drop gears, it will last longer than a normal box, as of these forces acting in this way. Putting that box on a 998 also, depending on the ratios you get you may get a long first, you can get not so long ones.

 

 

The best car ive had was a 1500cc lada riva, it had a standard engine, with single 45 webber, tran-x 5 speed, 2.48 first over drive 5th that is too, 4.4 lsd. It was good as you could use all its rev range to make the best of the power. So driving something underpowered to the max is quite rewarding. They are loud, i know, i drove that car later with a 1600 engine in it to czech.. ;)

 

 

 

But , look at what you are trying to build, a rally car or a road car?

Edited by Avtovaz, 17 October 2017 - 07:14 PM.

[MIGLIACARS]

straight cut boxes are stronger, fact.

 

Wrong wrong wrong.   

 

But believe what you will.

 

 

If you put a sccr box into a standard 998 motor, with the drop gears, it will last longer than a normal box,

 

wrong wrong wrong.

 

Ive seen a mini gearbox do over 100000 miles.  There are no s/c boxes out there that can do this.

 

 

sccr boxes are made for motor sport to keep the ratios close for cammy engines.

 

dog-boxes are stronger in the fact that they do not use synchos instead they use dogs.

 

If you think that the cheap sccr gear-kits that mini-spares produce are made to the tolerances and of a better quality steel than the factory cars you are again wrong.

 

I find it hard to believe that some folks think that the Morris, Austin, rover engineers had know idea what they were making. and that a small company can produce better items.

[Avtovaz]

straight cut boxes are stronger, fact.

 

Wrong wrong wrong.   

 

But believe what you will.

 

 

If you put a sccr box into a standard 998 motor, with the drop gears, it will last longer than a normal box,

 

wrong wrong wrong.

 

Ive seen a mini gearbox do over 100000 miles.  There are no s/c boxes out there that can do this.

 

 

sccr boxes are made for motor sport to keep the ratios close for cammy engines.

 

dog-boxes are stronger in the fact that they do not use synchos instead they use dogs.

 

If you think that the cheap sccr gear-kits that mini-spares produce are made to the tolerances and of a better quality steel than the factory cars you are again wrong.

 

I find it hard to believe that some folks think that the Morris, Austin, rover engineers had know idea what they were making. and that a small company can produce better items.

 

 

straight cut boxes are stronger, fact.

Wrong wrong wrong.   

But believe what you will.

 

=> How can loading the bearings in a box for and aft and out be stringer than just out? I cant understand that ?

 

 

If you put a sccr box into a standard 998 motor, with the drop gears, it will last longer than a normal box,

wrong wrong wrong.

 

=> Again, use the drop gears, your not forcing the gear hard into the casing and as soon as any wear causing back lash and making the slide hammer effect.

 

 

Ive seen a mini gearbox do over 100000 miles.  There are no s/c boxes out there that can do this.

 

=> You dont for example get many old ladies running sccr boxes in their cars, and also they are usally fitted to the more exuberant driver.

 

 

dog-boxes are stronger in the fact that they do not use synchos instead they use dogs.

 

=> No, they give fast gear changes at a cost.

 

 

If you think that the cheap sccr gear-kits that mini-spares produce are made to the tolerances and of a better quality steel than the factory cars you are again wrong.

 

=> i cant comment on these boxes, and i wasnt talking about these boxes, but the logic of straight cut gears over helical, straigh cut wins every day.

 

I find it hard to believe that some folks think that the Morris, Austin, rover engineers had know idea what they were making. and that a small company can produce better items.

 

=> I can see what you say, and was teh argument over not putting DTA on my bmw over the standard ECU, bmw spent millions on developing it so keep it, and you take it to someone like wayne chip wizard to get mapped.. and it works.

 

BMC produced a very good box > for road use < short first to pull up any hill, second for light traffic, etc etc...

 

You find a mk2 escort, nova, or mini that is into motorsport that needs a strong box, they all will be sccr.

[MIGLIACARS]

 

straight cut boxes are stronger, fact.

 

Wrong wrong wrong.   

 

But believe what you will.

 

 

If you put a sccr box into a standard 998 motor, with the drop gears, it will last longer than a normal box,

 

wrong wrong wrong.

 

Ive seen a mini gearbox do over 100000 miles.  There are no s/c boxes out there that can do this.

 

 

sccr boxes are made for motor sport to keep the ratios close for cammy engines.

 

dog-boxes are stronger in the fact that they do not use synchos instead they use dogs.

 

If you think that the cheap sccr gear-kits that mini-spares produce are made to the tolerances and of a better quality steel than the factory cars you are again wrong.

 

I find it hard to believe that some folks think that the Morris, Austin, rover engineers had know idea what they were making. and that a small company can produce better items.

 

 

straight cut boxes are stronger, fact.

Wrong wrong wrong.   

But believe what you will.

 

=> How can loading the bearings in a box for and aft and out be stringer than just out? I cant understand that ?

 

 

If you put a sccr box into a standard 998 motor, with the drop gears, it will last longer than a normal box,

wrong wrong wrong.

 

=> Again, use the drop gears, your not forcing the gear hard into the casing and as soon as any wear causing back lash and making the slide hammer effect.

 

 

Ive seen a mini gearbox do over 100000 miles.  There are no s/c boxes out there that can do this.

 

=> You dont for example get many old ladies running sccr boxes in their cars, and also they are usally fitted to the more exuberant driver.

 

 

dog-boxes are stronger in the fact that they do not use synchos instead they use dogs.

 

=> No, they give fast gear changes at a cost.

 

 

If you think that the cheap sccr gear-kits that mini-spares produce are made to the tolerances and of a better quality steel than the factory cars you are again wrong.

 

=> i cant comment on these boxes, and i wasnt talking about these boxes, but the logic of straight cut gears over helical, straigh cut wins every day.

 

I find it hard to believe that some folks think that the Morris, Austin, rover engineers had know idea what they were making. and that a small company can produce better items.

 

=> I can see what you say, and was teh argument over not putting DTA on my bmw over the standard ECU, bmw spent millions on developing it so keep it, and you take it to someone like wayne chip wizard to get mapped.. and it works.

 

BMC produced a very good box > for road use < short first to pull up any hill, second for light traffic, etc etc...

 

You find a mk2 escort, nova, or mini that is into motorsport that needs a strong box, they all will be sccr.

 

If we are talking sccr not dog box,they are used in competition cars because they have hairy cams, If these engines fall off cam it will not clear itself very well.    so they use sccr boxes so when you change gear it will drop straight back into the power. In minis and old escorts the factory never really produced a close ratio box good enough for the big cammed engines. That is the main reason sccr boxes are used. 

Also the helical boxes take some engine power from the wheels. 

 

Ive also used the helical box in my car The only issue being the synchro mesh system which is the same setup as the sccr.

 

The gears in a mini gearbox are extremely strong its a myth that there weak.

[nicklouse]

 

 

You find a mk2 escort, nova, or mini that is into motorsport that needs a strong box, they all will be sccr.

 

i will not try and laught to loudly. they will have a SC box if they cant get a suitable ratio as SC gears are cheaper to make.

 

and no they are not.

[Spider]

straight cut boxes are stronger, fact.

 

 

If your thinking is open (and I suggest that's a good thing), then can I ask you have a good read of this thread, it was discussed at length and with some proven facts;-

 

http://www.theminifo...ears-beginners/

 

Of course, I'm all ears if you disagree, but I'll ask you to read that thread and then come back.

 

I do love an open, frank and most important, respectful discussion, but I'm not interested in arguing any points.