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Home > Beginners Tech > Sc gears and helical drop gears

fixitphil2

116 Posts
Member #: 10945
Advanced Member

scarborough/ northyorkshire

hi ,can someone explain why it's ok to run a sc gear box with helical drops or vice verser, I'm building engine and box to take 150 bhp reliabley with mini spares clubman sc gears but using standard drop gears, cheers


wil_h

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9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

Correctly shimmed drop gears of the later A+ type (larger idler bearing) are perfectly capable of way over 150bhp, ask Robert.

A helical box is on it's limit at 150.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


minimole23

4300 Posts
Member #: 1321
Post Whore

Wiltshire

I would also ensure the bush in the primary gear is not worn too.

On 7th Oct, 2010 5haneJ said:
yeah I gave it all a good prodding


fixitphil2

116 Posts
Member #: 10945
Advanced Member

scarborough/ northyorkshire

there is a bit of play on the primary gear bush but not got a new one to compare,i had 9 thou on idler when i stripped it will be setting to 4 thou,il have to find internal diameter of a new one


fixitphil2

116 Posts
Member #: 10945
Advanced Member

scarborough/ northyorkshire

hows fitting sc drops helping a helical gear box tho,is it the combination of the side loads from both at the same time the problem,as alot of people have just sc drops


stevieturbo

3569 Posts
Member #: 655
Post Whore

Northern Ireland




On 16th Jan, 2016 fixitphil2 said:
hows fitting sc drops helping a helical gear box tho


it isnt.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


minimole23

4300 Posts
Member #: 1321
Post Whore

Wiltshire

When you compare the section thickness of helical drops there is probably at least 50% more contact patch/section thickness compared to the gears in the box, hence why those are the ones that need uprating.

Edited by minimole23 on 16th Jan, 2016.

On 7th Oct, 2010 5haneJ said:
yeah I gave it all a good prodding


wil_h

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9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

A primary gear too tight is worse than it being too slack in my experience (within limits of course).

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

On 2nd Jan, 2013 fastcarl said:

the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.


apbellamy

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16540 Posts
Member #: 4241
King Gaycharger, butt plug dealer, Sheldon Cooper and a BAC but generally a niceish fella if you dont mind a northerner

Rotherham, South Yorkshire

If you run s.c. drops with a helical gear set, the rest of the box needs to be in tip top condition.

We did this in the metro van on a used box with about 150 bananas and found the first motion roller bearing collapsed when we pulled it apart. More than likely caused by emergency starts on the strip..

On 11th Feb, 2015 robert said:
i tried putting soap on it , and heating it to brown , then slathered my new lube on it

*hehe!*


Cables123

6 Posts
Member #: 11097
Junior Member

i did the same as apbellamy with less than 150bhp using standard drops and gearset with a 1380, TWICE! I rebuilt the 3rd time with straight cuts throughout, i really dont want to splitting the engine again to fix the box


BENROSS

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9812 Posts
Member #: 332
Resident Cylinder Head Modifier

Mitsi Evo 7, 911, Cossie. & all the chavs ...... won no problem

Take it from me, helical drops and minispares clubman set will take what the engine produces, fit new bearings all around and your sorted.






Turbo This..

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1767 Posts
Member #: 9165
Previously josh4444

Australia, brisbane

imo its all about how much it gets abused i broke the bearing cage on the dubble roller a timken bearing by the way on a stock 1100 + mild cam if your rough on it then nothing will last but as ive lerant if your kind to it youll get away with more


stevieturbo

3569 Posts
Member #: 655
Post Whore

Northern Ireland




On 19th Jan, 2016 Turbo This.. said:
imo its all about how much it gets abused i broke the bearing cage on the dubble roller a timken bearing by the way on a stock 1100 + mild cam if your rough on it then nothing will last but as ive lerant if your kind to it youll get away with more


Certainly on the metros...cant recall the number of balls in them. But one type used, every single gearbox I took apart that had it, the cage was always broken. Didnt matter what age or mileage or engine size, they were all broke.

If you replaced it with the alternative which had either 1 ball more or less ( cant recall which ), they never really broke

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

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