Why do portal axles always? usually? reduce the gearing?

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whc03grady
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Why do portal axles always? usually? reduce the gearing?

Post by whc03grady » Fri Jun 01, 2018 1:20 am

Why aren't they 1:1?
Ludwig--1974 Westfalia, 2.0L (GD035193), Solex 34PDSIT-2/3 carburetors.
Gertie--1971 Squareback, 1600cc with Bosch D-Jetronic fuel injection from a '72 (E brain).
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sped372
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Re: Why do portal axles always? usually? reduce the gearing?

Post by sped372 » Fri Jun 01, 2018 4:47 am

I would assume that any time you're going to have a gearset it may as well change the ratio... seems wasteful to simply use them strictly for the height advantage. Everything "inboard" of the portals (axles, trans, etc) can be "smaller" since it's carrying less torque, too. Just my thoughts.
1971 Karmann Ghia - 1600 DP
1984 Westfalia - 1.9 WBX

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whc03grady
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Re: Why do portal axles always? usually? reduce the gearing?

Post by whc03grady » Fri Jun 01, 2018 1:10 pm

I always assumed their main purpose was increased clearance, but with a moment's thought after reading your post, it makes sense: Splitties had to do a lot with a little, so reducing the gears means more torque at the wheel, though a lower top speed (and who cares about that in 1961). Increased clearance was a useful spandrel.
Ludwig--1974 Westfalia, 2.0L (GD035193), Solex 34PDSIT-2/3 carburetors.
Gertie--1971 Squareback, 1600cc with Bosch D-Jetronic fuel injection from a '72 (E brain).
Read about their adventures:
http://www.ludwigandgertie.blogspot.com

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Amskeptic
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Re: Why do portal axles always? usually? reduce the gearing?

Post by Amskeptic » Tue Jun 12, 2018 9:45 am

whc03grady wrote:
Fri Jun 01, 2018 1:10 pm
I always assumed their main purpose was increased clearance, but with a moment's thought after reading your post, it makes sense: Splitties had to do a lot with a little, so reducing the gears means more torque at the wheel, though a lower top speed (and who cares about that in 1961). Increased clearance was a useful spandrel.
The reduction boxes on the splitties were totally required for ground clearance with the engine sitting so much higher in the chassis and having only the early technology of fulcrum plates for the axle artickilation. The bays dropped the entire drivetrain a good six inches and used them fancy CVs for the first time.

The ratio of the first reduction boxes was because the early buses used drop-in bug transaxles that had to deal with far greater payloads.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 94,615 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,990 miles

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