Aluminium tubing: 6061 - 7020?
Luc Gorissen
I was thinking about buying a new bike for racing, and I was looking
for an aluminium frame. Like in the 'Is reynolds any good'-thread,
I would like to ask what aluminium tubing is good. I understand that
they are designated by numbers like 6061 or 7020 tubes, etc.
Can somebody enlighten me and tell me what those numbers stand for?
Bye,
Luc Gorissen
Gary Hennigan
The numbers refer to the alloy. I haven't seen any frames that are
pure aluminum 1XXX group. The 6XXX group is an alloy of aluminum with
Magnesium and Silicon. The 7XXX group is an alloy of aluminum with
Zinc. You can get a complete description of what the different groups
are, and more specific information on each number via the BikePro WWW
site. Take a look at:
http://www.bikepro.com/products/metals/metals.html
They have a nice table that gives the frame designation and what
exactly the alloy it is made of consists. It also has a decent
explanation of the characteristics of each alloy group.
Gary
(ghen...@NMSU.Edu)
Kolbjørn Halvorsen
[snip]
>Take a look at:
>
> http://www.bikepro.com/products/metals/metals.html
>
>They have a nice table that gives the frame designation and what
>exactly the alloy it is made of consists. It also has a decent
>explanation of the characteristics of each alloy group.
The table describes the 7xxx series as "high strength", while the 6xxx
series is desribed as "moderate strength".
Then why is it that some manufacturers, such as GT, use 7005 tubing for their
middle-of-the-range bikes, but use 6061 for their high-end products?
anyone?
--
Kolbj=F8rn Halvorsen k.hal...@norskeris.simis.com
Shon Shampain 301-949-0484
: middle-of-the-range bikes, but use 6061 for their high-end products?
Some thoughts:
The only source I've found for 7005 (and granted I haven't looked too hard)
is via Easton. They make an Elan, Elite, and MTB tubeset.
6061 is commonly available, espescially thru non-bike sources (ie industrial
tubing suppliers). 7005 is not.
a) 6061 is *much* cheaper
b) If you are working with 7005 you are constrained to the limitation of the
Easton tubeset, whereas you can pick and choose 6061 tubes (based upon
diameter or wall thickness) to build your frameset with different
properties (which may or may not be advantageous if you are doing things
like ovalizing, etc).
c) 6061 is commonly used for many ancillary works, ie airplane, race car, etc.
There exists an airplane leading edge made from 6061 that I plan to incorp
into a TT frame as a down tube. Therefore, spin-offs from other
industries may be useful.
Just some food for thought.
Regards,
shon shampain sham...@shampain.com 301-949-0484
------------------------------------------------------------------------
shampain engineering Custom 7005 Bicycle Frames (in the near future)
[ 1 ] Prototype(s) on the road, and counting! (Gotta start somewhere)
------------------------------------------------------------------------
When the only tool you have is a hammer, every problem you encounter
tends to look like a nail.
James Carroll
depending on how they are manufactured. 6061 T-6 tubing is often
considered easier to weld and therefore had result in stronger welds,
which is the most likely place for a frame to weld. 7xxx series alloys
also vary greatly in strength. Easton (which I think is 7075) is better
than generic 7005 because of the trick butting and carefull manufacturing
processes. But there are great differences between the alloys. I once
saw a frame made of 7020 on the showroom floor that already had a nasty
crack in the middle of the seat tube. This is probably evidence of poor
quality control and improper heat treating. Needless to say I'm avoiding
7020 alluminum.
If you want the real lowdown on this ask Mr. Helfrich. He posts here
pretty often and has probably forgotten more about metals than most
everyone else here knows.
--
James Carroll | Live to ride,
Buc...@imap1.asu.edu | Ride to live.
Composites Lab
Shampain 301-949-0484) wrote:
> c) 6061 is commonly used for many ancillary works, ie airplane, race car, etc.
> There exists an airplane leading edge made from 6061 that I plan to incorp
> into a TT frame as a down tube. Therefore, spin-offs from other
> industries may be useful.
We've been looking for aero tubing (streamline tubing in the aircraft
world) for potential use in some of the bikes we've designed here. Steel
streamline tube is relaitively common, while aluminum is somewhat less so.
However, the streamline tube only seems to be available in a thickness to
chord ratio of 42%. We were looking for something about half that. Has
anyone seen streamline tubing in anything but the "standard" 42% ratio?
The sources I have checked: Wicks (CA?), Aircraft Spruce & Specialty (CA),
Levine's (Toronto, ON), Grasroots Aviation (Oshawa, ON).
Thanks,
Phil White
Phi...@mecheng.lan.mcgill.ca
Gary Helfrich
: : Then why is it that some manufacturers, such as GT, use 7005 tubing for their
: : middle-of-the-range bikes, but use 6061 for their high-end products?
Here is the simple answer: The real life durability of 6061 is better.
The 6061 bikes had far fewer warranty problems than 7005 bikes of the
same weight and tube configuration. Entry level bikes can afford to have
the weight penality imposed by the lower durability of 7005. The 7005
mid range GT bikes are in no way less durable than the high end 6061
bikes, they are just a bit heavier.
: Some thoughts:
: The only source I've found for 7005 (and granted I haven't looked too hard)
: is via Easton. They make an Elan, Elite, and MTB tubeset.
There are other sources for 7005, but due to an idiotic (on the part of
Alcoa) agreement between Alcoa and Easton, Alcoa cannot sell any 7005 for
sports applications. Alcoa is not the only producer of 7005.
: a) 6061 is *much* cheaper
Only if you go through Easton. Eliminate the middleman, and there is
very little difference in price. The equipment to heat treat 7005 is
significantly less expensive (by an order of magnitude) than the
equipment needed to heat treat 6061. This is why you will see small
companies like Yeti use 7005 and big ones like Cannondale use 6061.
: b) If you are working with 7005 you are constrained to the limitation of the
: Easton tubeset, whereas you can pick and choose 6061 tubes (based upon
: diameter or wall thickness) to build your frameset with different
: properties (which may or may not be advantageous if you are doing things
: like ovalizing, etc).
There are several companies like Tubex and Vari-Wall that can do anything
with 7005 that Easton can. Even small companies like Santana use this as
an approach to get around the problems of working with Easton.
: c) 6061 is commonly used for many ancillary works, ie airplane, race car, etc.
: There exists an airplane leading edge made from 6061 that I plan to incorp
: into a TT frame as a down tube. Therefore, spin-offs from other
: industries may be useful.
Sounds cool.
Gary Helfrich
Arctos Machine
Derek Anderson
: ghen...@ampere.NMSU.Edu (Gary Hennigan) wrote:
: [snip]
: >Take a look at:
: >
: > http://www.bikepro.com/products/metals/metals.html
: >
: >They have a nice table that gives the frame designation and what
: >exactly the alloy it is made of consists. It also has a decent
: >explanation of the characteristics of each alloy group.
: The table describes the 7xxx series as "high strength", while the 6xxx
: series is desribed as "moderate strength".
: Then why is it that some manufacturers, such as GT, use 7005 tubing for their
: middle-of-the-range bikes, but use 6061 for their high-end products?
: anyone?
: --
: Kolbj=F8rn Halvorsen k.hal...@norskeris.simis.com
Yeppers... They use 7005 on their lower end bikes since the lower end
bikes are made in LARGE factories in TAIWAN! The taiwanese factories know
that the demand is for 7005, so that is what they build from. The 6061
bikes are hand made in the USA, and might therefore have a better
construction quality. I read a comparison between a team RTS and a
PANTERA and apparently, the quality of the welds was cleaner on the
tawanese made 7005 bike, which might translate into the frame on the
cheaper bike actually being better, but I wouldn't bet on it.
ME!