4 ms·

Why are train wheels connected with an axle? Is it structural? If the wheel pairs were independent then it wouldn't matter how fast each wheel in a pair rotate

Why are train wheels connected with an axle? Is it structural? If the wheel pairs were independent then it wouldn't matter how fast each wheel in a pair rotates.

Lammy 5y ago
> Is it structural? Yes, the cars' weight rests on the end of each axle via a "bogie" that holds the suspension and brakes and such, and then the multi-axle bogie itself rotates on a center pin: https://en.wikipedia.org/wiki/Bogie#Components https://en.wikipedia.org/wiki/Bogie#Components https://en.wikipedia.org/wiki/List_of_railroad_truck_parts#Axlebox https://en.wikipedia.org/wiki/List_of_railroad_truck_parts#A...
- CRConrad 5y ago
  But that doesn't explain why the wheels are rotationally fixed to each other by an axle.
johnwalkr 5y ago
They are, and for non-driven wheels, the bogey and train cars basically sit on top. There's only a few minor things like brake hardware that need to be removed to remove a wheel. When there is a derailment, many of the wheel sets fall off. The axles are tough. Each axle weighs about 1 ton if I remember correctly. Each wheel can be reworked on a lathe several times (either with the wheel set removed or in situ on a drive-through floor-mounted lathe). After a few years, the diameter of the wheel is out of spec, and new ones are pressed on the axle. Axles can last about 75 years.
twobitshifter 5y ago
On some low floor trams they are independently rotating such as the Siemens avenio. https://en.m.wikipedia.org/wiki/Siemens_Avenio https://en.m.wikipedia.org/wiki/Siemens_Avenio Technical study https://assets.new.siemens.com/siemens/assets/api/uuid:2dbbe04aeb88674e9b6c332c43d452456b59019e/wheel-sets-independent-en.pdf https://assets.new.siemens.com/siemens/assets/api/uuid:2dbbe...
andbberger 5y ago
If the wheels were independent trains wouldn't be able to turn
- SilverRed 5y ago
  Why?
  - function_seven 5y ago
    Because the differential effect requires the wheels to be rotating in sync, so the conical sections can do their thing. If the wheels could independently rotate at their own speed, then there would be nothing stoping the train from derailing itself (or bouncing off the flanges that you’d have to incorporate)

Why are train wheels connected with an axle? Is it structural? If the wheel pairs were independent then it wouldn't matter how fast each wheel in a pair rotates.

Lammy 5y ago

> Is it structural? Yes, the cars' weight rests on the end of each axle via a "bogie" that holds the suspension and brakes and such, and then the multi-axle bogie itself rotates on a center pin: https://en.wikipedia.org/wiki/Bogie#Components https://en.wikipedia.org/wiki/Bogie#Components https://en.wikipedia.org/wiki/List_of_railroad_truck_parts#Axlebox https://en.wikipedia.org/wiki/List_of_railroad_truck_parts#A...

CRConrad 5y ago
But that doesn't explain why the wheels are rotationally fixed to each other by an axle.

johnwalkr 5y ago

They are, and for non-driven wheels, the bogey and train cars basically sit on top. There's only a few minor things like brake hardware that need to be removed to remove a wheel. When there is a derailment, many of the wheel sets fall off. The axles are tough. Each axle weighs about 1 ton if I remember correctly. Each wheel can be reworked on a lathe several times (either with the wheel set removed or in situ on a drive-through floor-mounted lathe). After a few years, the diameter of the wheel is out of spec, and new ones are pressed on the axle. Axles can last about 75 years.

twobitshifter 5y ago

On some low floor trams they are independently rotating such as the Siemens avenio. https://en.m.wikipedia.org/wiki/Siemens_Avenio https://en.m.wikipedia.org/wiki/Siemens_Avenio Technical study https://assets.new.siemens.com/siemens/assets/api/uuid:2dbbe04aeb88674e9b6c332c43d452456b59019e/wheel-sets-independent-en.pdf https://assets.new.siemens.com/siemens/assets/api/uuid:2dbbe...

andbberger 5y ago

If the wheels were independent trains wouldn't be able to turn

SilverRed 5y ago
Why?
- function_seven 5y ago
  Because the differential effect requires the wheels to be rotating in sync, so the conical sections can do their thing. If the wheels could independently rotate at their own speed, then there would be nothing stoping the train from derailing itself (or bouncing off the flanges that you’d have to incorporate)