Aluminium grades, questions to metal experts

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I'm in the process to get aluminium sheets and tubes to build a frame and I'm now totally confused about the various aluminium grades. I had a contact in the US who said that I might use 5052, 6061 and 7075, depending of what kind of part I have to manufacture (compromise between strenght and resistance to cracking, resistance to corrosion is not a priority). Now Pechiney in France seems to recommend 5086 and 6064 with a preference for the 5086 keeping in mind that this is a motorcycle frame, so fully stressed.

My researches on the web didn't help a lot. Is it confirmed that there is a difference between US and Europe in terms of metal grades? Does 5052 in the US means a 5086 in Europe (and 6061 = 6064) or is it not that simple?...

The welder seems to know his job, however any information too concerning the welding process on all these grades is welcome!
 
jlo

I am building frames for a hobby and have looked into alloy frames for years.... The best alloy  for a bike frame is 7020. Spondon and everyone uses 7020. 7020 Ultimate tensile Strength is about 350 MPa. 6061 UTS is about 260 MPa. 6063 is about 205 MPa. 6063 is what they use for doors and window frames. I have seen a bike they build out of 6061 and it is looking fine. Just use condition T6.
The big problem with this lower grade alloys are tha its not easy to bend it. Say you take a 6061 T6 tubing it will not bend in a short radius. Well it will but it will look crap. So you need 6061 T4... T4 is fine but then you need to heat treat the whole frame when you done one day to get it to T6, and that is not cheap. That is why 7020 is the best one to work with. You can bend it and weld it with no problem. Just remeber to let the frame cool down on its own. (dont cool it down using water). 7075 is not for extrusions. 
Here in South Africa you cant get hold of 7020. Thats why I stick if steel. I have built 3 tube frames and it weighs only 1 kg more than the stock alloy beam frame... (GSXR1100)

Good luck and just do it, Maybe you should build your first frame with steel and then go over to alloy. And if you can get hold of 7020 T6, 38mm round alloy tubing please give me a call. I want 20 meters. :D

Herman
 
Many thanks Herman, the first real understandable reply I've got on the subject!
7020 seems to be rare, at least through the aircraft metal supplyers. They have 6061 ("Alclad" or not) and most of the time they sell them in rod not tubes, I have not seen any 7020 yet, only 7075 T6 in rods only too. Tubes are available in 3003 and 5052 it seems. I'm speaking in US grades and none of them seem to be available in France so my question about the grade correspondance between the european and US reference.

Speaking of steel, as a general rule, what is the best way to join steel tubes to aluminium plates (see picture attached as an example)? Does a welding process available?

Please are you ok to receive more questions from me in the future?  ;)


 

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jean-louis,

according to John Bradley* there are only 4 choices for welded aluminium frames:

"6082 T6 weld it up accept/allow for the reduction in strength due to welding.

6082 in whatever condition suits and heat treat entire structure afterwards.

7020 T6 or T651 which will recover most of its strength after welding.

5083 non heat treatable alloy"

*The Racing Motorcycle,  A Technical Guide for Constructors Vol 2
Chassis materials and construction techniques
ISBN 0951292935.

(Vol 1 is ISBN 0951292927, gearing, geometry, aerodynamics and suspension)

another excellent text is Tony Foale's Motorcycle handling and Chassis Design
http://www.tonyfoale.com/

there's a big difference in making a frame and making a frame that works
the knowledge and wisdom in these texts is worth every penny

7075 is for machining, not welding. use it for plates, brackets, pegs
6061 has a lower strength after welding than 5083 unless heat treated afterwards.

alloy grades are to an international standard but there are variations between standards.
generally the first digit is the alloy class, the remaining digits are the composition of alloys
within the metal

different alloys require different filler (rod) for welding
for 5052 use 5754 rod
for 5083 use 5356 rod
for 7020 use 5356 or 5280

Tigcraft uses 6802 T6 with 4043A filler
Spondon uses 7020
Foggy Petonas uses 5083

my personal choice to build an alloy frame would be 5083 in O condition for forming.
however, given my budget, i'll stick with 1018 mild steel

hope this helps

cheers,
scott

i don't think welding steel to aluminum is an option
bolts, rivets or, perhaps, some kind of structural glue



 
Hi JLO,

a friend of a friend runs BFO Motocycles here in the Midlands of England and recommends/uses 7020 in T6 temper.

http://www.bfomotorcycles.co.uk/

Not much 'new' help, but the more the merrier.

Paul H
 
Thanks all for the reply. What puzzles me is that Pechiney says that 6000 and above all 7000 grades are strong but also very sensitive to vibration, so prone to crack.
I agree that a very good knowledge is required to build a good frame, however I only need a "dummy" frame as a first step.
 
jotacorsa said:
dummy? for modeling how and where everything goes
or a full prototype to r&d under power?
Click to expand...

First option. No need of special metal for that for the moment however I'm trying to look forward  8)
 
Haggis said:
Hi JLO,
a friend of a friend runs BFO Motocycles here in the Midlands of England and recommends/uses 7020 in T6 temper.
http://www.bfomotorcycles.co.uk/
Not much 'new' help, but the more the merrier.
Paul H
Click to expand...

Hi Paul H.

if this friend of a friend uses 7020 in T6 temper, where does he get his material from? I wonder if he would share his material source with your mutual friend? Worth asking.

the Fireblade kit that BFO does looks like a really well thought out kit. Wonder if he would do one for a Laverda triple motor?

Paul LeClair
 
paul, i believe 7020 is commonly available from uk aircraft sources.
i've not seen it available in north america.

http://www.aircraftmaterialsuk.com/data/aluminium/7020.html

note the similar specs listed are to British Standard
just because it is a listed alloy to an international std
doesn't mean its readily available over here  ;)
sort of like trying to get Reynolds 531 steel

BFO does make a pretty neat machine, shame they don't list the kit price
7500 and you supply a blade and get a turnkey bike doesn't sound out of line

i'd bet harris would do you a frame kit...
phil might have an extra chassis for a good home.
then again, you could get a space frame kit from piero
for a period special  :D

cheers,
scott



 
I got a price from aircraft materials last year and the shipping to South Africa was double the price of the tubing...


I know there is a foundry in Italy doing 7020 alloy... Hulliets,the foundry here in South Africa said they can get me 7020 and extrude any shape for me, but I need to buy 250 kg!!!  :LOL: Believe me, 250 kg of tubing is allot of tubing!!  And it would cost me an arm and a leg... Like 40 000 rands = $35k

So I will stick with steel...
 
A bit of a weird question gets a weird response.....

  Triumph , VW. Norton and Vincent used steel tipped push rods and Never had a problem with heat expansion.... WTF
 
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