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Q: How Does an Axel Work? ( Answered 5 out of 5 stars,   4 Comments )
Subject: How Does an Axel Work?
Category: Science > Physics
Asked by: subey-ga
List Price: $13.13
Posted: 03 Oct 2006 11:07 PDT
Expires: 02 Nov 2006 10:07 PST
Question ID: 770501
I can't figure out how an Axel works...

Looking at my bike I see that my weight is transfered to the fRAMe and
then to the rear axle. The axle visually has 2 major components. The
fixed portion where my fRAMe attaches, and the moving cylinder that
goes round and round.

My problem is that my weight once transfered to the fixed part of the
axle then has to be transfered to the bottom part of the rotating
cylinder somehow.

Now if I translate this up to say a truck with a 10 ton weight, why
doesn't the friction between the fixed and non rotating part cause
serious problems. Ball bearings seem to be invovled but I can't figure
it out :D
Subject: Re: How Does an Axel Work?
Answered By: denco-ga on 03 Oct 2006 14:28 PDT
Rated:5 out of 5 stars
Howdy subey-ga,

Indeed, bearings are involved to transfer the weight on the frame of a bicycle
and a truck to the wheels.

If you will scroll to the bottom of this "Bikes Not Bombs" manual, you can see
a basic diagram of a bicycle hub and axle set.

Note there is a set of bearings on both sides of the hub that handles the
transfer from the frame to the axle.

Friction is always a concern when it comes to bearings.  Modern bearings are
lubricrated and sealed.  New designs, like this one from Zipp, are made with
friction in mind.

"Most bearings utilize a brass waffle retainer within the cartridge to ensure
the balls remain evenly spaced throughout the cartridge, this also keeps the
balls from rolling against each other, but it does introduce a point of wear,
heat buildup, and friction, as the ball is forever rolling against a metallic
element. Zipp was the first company to spec a plastic retainer made from Teflon
so that each ball is properly located in the cartridge, but the balls never
have any sliding contact with any metal components."

Zipp has some very nice diagrams of bearing cartridges in the above document
that you should examine.

Bicycles use a "cup and cone" style of bearings, but the newer models use the
cartridge style, shown in "Sheldon Brown's Bicycle Glossary" as presented on
the Harris Cyclery website.

"Bearings used in bicycles are usually of the cup-and-cone type, but many newer
bicycles use cartridge bearings."

There is a nice picture on the above page that illustrates the two types.

Cars, and it follows, trucks, are no different, except the sealed bearings are
just larger.  Here is a diagram of the rear axle of a Porsche 944, as seen on
the AutomobileAtlanta website.

The part marked with a "5" is a ball bearing and the part marked with a "7" is
a cylinder roller bearing.

There are some larger images on the DRIVEWIRE website of the cylinder roller
bearing type mentioned above.

Please note that these don't use ball bearings, but rather cylinder bearings.

Timken is a large manufacturer of automobile, truck and other axle bearings.

They make the "Wheel Boss" wheel end system for heavy trucks.

"The WHEEL BOSS line includes an adjusting nut, a patented HDL? grease seal,
a non-vented hub cap and Timken tapered roller bearings. Each WHEEL BOSS
component supports longer bearing life, greater fuel efficiency and reduces
maintenance costs."

Note that the above system uses a tapered roller bearing, and the above page
has an image of one of this type.

A better picture of a tapered roller bearing is shown on this Timken page.

"With our P90 bearings, we?ve taken the concept of power density ? increasing
the bearing capacity-to-weight ratio ? to provide you with a lighter, more
fuel-efficient solution for your axle designs."

You should browse the Timken website in detail for more on the manufacturing
process, as it shows that with higher load demands, so the materials used to
manufacture the bearings have to improve.

Better steel and surface treatments are used to ward off the wear that is
encountered.  Roller bearings are used to spread the load across a wider
surface, and tapered roller bearings are used to handle increased torque.

But, even on ball (cylindrical) roller bearings, the contact surface is an
always changing one, so the theory is that wear is spread, hopefully evenly,
across the entire surface of the bearing.

If you need any clarification, please feel free to ask.

Search strategy:

Google search on: bicycle bearings

Google search on: truck bearings

Referenced the Timken website.

Looking Forward, denco-ga - Google Answers Researcher

Clarification of Answer by denco-ga on 03 Oct 2006 16:09 PDT
Howdy subey-ga,

I agree that it is sometimes tough to visualize the workings of a device
without having a sample right before you.  Here are a few more links to
hopefully aid you in this visualization process.

Dan's Motorcycle - "Roller Bearings"

NHBB - "Exploded view of ball bearing"

Brenco - "Exploded View of BRENCO Tapered Roller Bearing"


Looking Forward, denco-ga - Google Answers Researcher
subey-ga rated this answer:5 out of 5 stars and gave an additional tip of: $6.00
Thanks for the explanation. I understand it intellectually, but it
refuses to gel in my mind for some reason. I think I have to see one
working in front of my own eyes in order for the concept to solidify
in my head.

I am now off to petition the dictionaries of the world to rename
bearings catrings, thanks again.

Subject: Re: How Does an Axel Work?
From: denco-ga on 03 Oct 2006 16:12 PDT
Much thanks for the 5 star rating and generous tip, subey-ga.

I would suggest you go to a local bicycle shop as well as a automobile parts
or repair shop.  They might have an old set of bearings you can examine.

Looking Forward, denco-ga - Google Answers Researcher
Subject: Re: How Does an Axel Work?
From: markvmd-ga on 03 Oct 2006 18:41 PDT
He writes a few licks for Slash and then puts some words to them. Duff
lays down a beat and they go from there.

Oh, I thought you said Axl.
Subject: Re: How Does an Axel Work?
From: redbelly98-ga on 05 Oct 2006 07:00 PDT
Short answer:

Bearings involve surfaces rolling against each other, rather than
sliding against each other.  This greatly reduces the friction.

Look at a diagram, or take apart an actual bearing, to get a better
picture of what's going on.
Subject: Re: How Does an Axel Work?
From: helpfulperson-ga on 10 Nov 2006 12:41 PST
Just to confuse the matter, think about how rollers work as depicted
by Hollywood!  In reality they don't.  An axel is needed to avoid
friction by allowing rolling.  Rollers just slide.

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