Dutch 500AF Conversion 250KXF 2009

[Jos197AF]

So I know I'm sounding like a broken record here (what is the modern phrase for that?) so I'll bring this up one more time and shut up about it.  You really  need to take a second look at 7075 on the frame.  I've had field failures with product using 7075 because of the smallest surface scratches from machining which promoted SCC.  This has nothing to do with welding, machined parts in 7075 can fail under pretty benign conditions.  7075 needs to be in the T7 temper for this application but you might very well anneal the rest of the frame too much by doing so.  You need to look at the aging curves of all the alloys involved and see if a compatible process exists.  If you don't you could end up in the hospitol or under ground.

Maybe it's a good idea to install one extra head mount, on the front of the engine. Just in case. Then always investigate the suspicious parts on cracks after riding the KX5.

I have done some research. Know your point know. But besides, the alloy is often used in the aircraft industrie, and there are also welded mountainbike (or other bicycle) frames made of this alloy. 7075 has good properties of tensile strenght and dynamic tensions. But if I understand you the right way, there is a chance the combined alloys can provide stress in the material, which can lead to cracks (stress corrosion cracking).

If I make an extra head mount, the suspicious parts can fail by cracking, but the chassis will stay together. Or al the four points (now it has three points) of mounts has to fail at the same time.

When i have some time, I wil make an extra Y part, made of another alloy. So when it's neccessary I can replace the Y part easily, it will take me a few hours to re-weld the frame when the engine and the other parts are removed.

Very interesting case... I'm curious about how the frame will stand under charging the KX5.

[motopunk]

that was one of the reasons to make my steel-frame-conversion...  the 2. was that i had this frame laying around and realy like the ergonomics of the 93 kx 250 ... 3. the aluminium-welding is little bit more dificult than on steele and  4. nowhere was an aluminium-framed bike with a blown engine to find... 
but if i will find an al-bike i plan to build the worlds first kx360af ... 

[hulkteam476]

Hi,
The ideal (or the best, I used this) for me is, alloys 6061 t6... or (6063)...better flexibility...
simply, the 7075 is realy rigid. Good aplication for to make the linkage or triple clamp but,
too rigid whit the other part of you'r frame.

THX..

[Jos197AF]

Hi,
The ideal (or the best, I used this) for me is, alloys 6061 t6... or (6063)...better flexibility...
simply, the 7075 is realy rigid. Good aplication for to make the linkage or triple clamp but,
too rigid whit the other part of you'r frame.

THX..

Too rigid? The E modulus of 6061 is 69 GPa, the E modulus of 7075 is 71 GPa. Not a big difference.
I think too rigid is not the problem. 7075 contains more zinc and magnesium.  Stress corrosion cracking is the issue to watch out for.

Applications 7075: aircraft fittings, gears and shafts, fuse parts, missile parts, regulating valve parts, wormgears, keys, aircraft/aerospace/defense applications, bike frames,  atv sprockets

[hulkteam476]

You know I told you this but you do whatever you want my friend.
Just, as you passed spectrometer, your original frame?
I say "simply" not to go into details.
In addition be warned that you have the machined part (7075) in full.
The 7075 does not manage at all the same constraints: bending, vibration ... compared to the 6061 or 6063... for this application. You also have to know that the 6061 is much better for welding performance and is also used in aeronautics.
This said, you were right to try. After testing you can give me your feedback.
Thx

[Jos197AF]

You know I told you this but you do whatever you want my friend.
Just, as you passed spectrometer, your original frame?
I say "simply" not to go into details.
In addition be warned that you have the machined part (7075) in full.
The 7075 does not manage at all the same constraints: bending, vibration ... compared to the 6061 or 6063... for this application. You also have to know that the 6061 is much better for welding performance and is also used in aeronautics.
This said, you were right to try. After testing you can give me your feedback.
Thx

Don't get me wrong. All information is welcome. My English isn't that good, I don't understand everything what is written about this.
I know its risky, and maybe I replace the Y part before I'm going to ride the bike. One evening work and the job is done. But I am also curious about how it will stand. Before I've ordered the 7075 I've got some wrong information about 7075. We have got years of experience with welding aluminium, but usualy 6082 or just cast engine cases for reparation for example. Not special alu alloys.
Whats the best option to use for the chassis? 6061, 6063, 6082, 7005?  Or which one else? Which heat treatment? T6, T651,...?

[hulkteam476]

for me the best: 6061 with T6.
Read This (sorry in french)

http://www.aubertduval.fr/uploads/tx_obladygestionproduit/6061_FR.pdf
Thx

[jBernard]

JFabs rails are 6063 and i talked to him about them. 6061 is T6 full strength heat treated, 6063 i think is not fully treated or not at all. so his idea is that to bend a rail thats more malleable, will induce less stress to the metal than one that is hardened and more brittle. He said he never had a rail breakage on his 6063 ones and he doesnt HT. pretty surprising.

[mxaniac]

6063 has a much lower yield strength in comparable tempers than 6061.  If you're going to heat treat afterwards 6061-O would have the benefits of being softer for forming, then when you precipitation harden it you'll get your desireable strength back.

I still think 7005 is a great choice because it is so easy to heat treat which is why it is so widely used on frames.  It's probably what Kawasaki used in the first place.

[jBernard]

who did your HT and how much was it?

[mxaniac]

I did it myself.  Here is a point of reference you can review: http://www.eastoncycling.com/bike/wp-content/uploads/2010/04/fab_instructions-7005_6061.pdf

[jBernard]

ha, ive read that pdf a few times before, funny you mention it.
did you do 7 series on your rails and just age? or do you have access to an oven that can do solution?

[mxaniac]

Well since my frame is broken perhaps I ain't such a smart feller afterall but I just artificially aged my frame in an oven at work.  The ovens at work won't do solution treatment.  I would recommend waiting until your wife is out of town if you want to try and do it at home.  I'm assuming that Kawasaki also used 7005, I'm not positive on that but there is plenty of speculation that it is.  I'm pretty sure I could identify the alloy with our FTIR at work but it never occured to me to do that at the time.

[ToomanyKaws]

Nice build.      I am having a second frame modified now.  Was at the guys shop yesterday and asked the guy about the alum you are using.   He said you can't.   Will break.  Doesn't want to be welded.   Its ok for a static part.  A bracket, etc.   Not as a structure.    This guy is old and has been machining and welding metals for 50 years.     Then he pulled some alum out of a box he is making stilts out of.    Like you see the characters walking around Disney on.    He makes them for a company who sells them to all of the Disney parks in the world.    Also showed me a few other grades of alum on the rack and what each types strong points are.   So atleast I asked and learned.

[hulkteam476]

Well,
when I putted my frame crf 450 2004 spectrometer I had not removed the "alumine" layer chemically, but the composition was close to the 6061.
To enter into details: When you weld the 6061 t6, it loses itscharacteristics and becomes close to the "t0", so you should make a quenching and an income, particularly by gravity or projection by dropping your piece into water after bringing it to a temperature of 529 -540 ° C max. Normally this heater must be homogeneous, so in an oven. For me, oxyacetylene torch.

Something else: the physical composition of the 7005 is close to the 6061 so it is a good alloy for this application (frame) which has a slightly higher density. But the 7005 does not have a temper and regains its normal state in the open air, they have (the 6061 and 7005) an excellent welding behavior unlike the 7075 which is not weldable to me (heresy). Test weld a piece out of your frame and makes a stress test ( tensile ) has your welding.
Thx