Koga Globetraveller - broken rear fork
#1
Junior Member
Thread Starter
Join Date: Aug 2017
Posts: 23
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Koga Globetraveller - broken rear fork
Hello, I am a proud owner of Koga Globetraveller S You don't see many of them around anymore but it'a a real masterpiece and a joy to travel on. Yesterday I found out that a small bit of rear fork is cracked, to the point where it is almost comes of. This is aluminum frame - 7005 alloy - is there anything that can be done about it ? I work in a company that does aluminum welding ( on a industry scale ) and one of my collegues told me that they can weld it for me, and that this alloy is hmmm weldable.... but he is not a bike expert of course so I am asking you for an advice, is it worth it ?
Thanks
Jan
Thanks
Jan
#2
Dirty Heathen
Join Date: Oct 2015
Location: MC-778, 6250 fsw
Posts: 2,182
Bikes: 1997 Cannondale, 1976 Bridgestone, 1998 SoftRide, 1989 Klein, 1989 Black Lightning #0033
Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 889 Post(s)
Liked 906 Times
in
534 Posts
Well, the frame was welded, to begin with, so I don't see why it couldn't be repaired by welding.
It looks like the 'fork' in in question is the ear where the rack mount attaches, so not a critical structural area.
You're going to lose the paint in that area, but if you're welder's any good, I'd say go for it.
It looks like the 'fork' in in question is the ear where the rack mount attaches, so not a critical structural area.
You're going to lose the paint in that area, but if you're welder's any good, I'd say go for it.
#4
Old fart
Join Date: Nov 2004
Location: Appleton WI
Posts: 24,790
Bikes: Several, mostly not name brands.
Mentioned: 153 Post(s)
Tagged: 0 Thread(s)
Quoted: 3590 Post(s)
Liked 3,401 Times
in
1,935 Posts
Well, the alloy is obviously weldable, since that is how the frame was put together in the first place. You could get it welded, but many (most?) welded aluminum bike frames are heat treated after welding. I'd be concerned about the repair weld not being heat treated, especially since the failure appears to be a fairly high-stress point on the frame.
On the other hand, what have you got to lose? If it fails again, you're no worse off than you are now.
On the other hand, what have you got to lose? If it fails again, you're no worse off than you are now.
#5
Senior Member
Join Date: Feb 2012
Location: Rochester, NY
Posts: 18,096
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4210 Post(s)
Liked 3,878 Times
in
2,315 Posts
Well, the frame was welded, to begin with, so I don't see why it couldn't be repaired by welding.
It looks like the 'fork' in in question is the ear where the rack mount attaches, so not a critical structural area.
You're going to lose the paint in that area, but if you're welder's any good, I'd say go for it.
It looks like the 'fork' in in question is the ear where the rack mount attaches, so not a critical structural area.
You're going to lose the paint in that area, but if you're welder's any good, I'd say go for it.
Look again. The suspension upper link attaches to the stay at the point of cracking. If I were repairing this I might consider a reinforcing plate of some sort as it's obvious that the OEM amount of material (if whatever condition it was after production) wasn't up to the task.
Generally I let riders pick their pleasures. If it's pink fuzzy seat pads or pink poka dot paint that will get one to ride then I'll help one find pink whatever. But this bike is ugly, sorry. Andy
#7
Banned
Metal fatigue happens, that reached a flex cycle limit..
As said above, go to your Koga Dealer, that you got the bike from.
[a hardtail will be more reliable]
....
As said above, go to your Koga Dealer, that you got the bike from.
[a hardtail will be more reliable]
....
Last edited by fietsbob; 02-05-18 at 11:25 AM.
#8
Senior Member
Join Date: May 2010
Location: Bristol, R. I.
Posts: 4,340
Bikes: Specialized Secteur, old Peugeot
Mentioned: 20 Post(s)
Tagged: 0 Thread(s)
Quoted: 663 Post(s)
Liked 496 Times
in
299 Posts
I used to work at a custom yacht builder of aluminum boats up to 70'. Many of the welders at that yard were highly skilled, having worked at New London building submarines where 100% of welds are ex-ray tested. It is customary in boat building to have a celebration of some sort, (beer and pizza) when the shutter plank is installed or in the case of an aluminum vessel, the last hull plate. Some of those guys could weld a beer can to the side of a hull with 1/4" plate. Your bike likely could be repaired by a skilled welder but I'd still look to install extra re-enforcement in some way.
#9
Dirty Heathen
Join Date: Oct 2015
Location: MC-778, 6250 fsw
Posts: 2,182
Bikes: 1997 Cannondale, 1976 Bridgestone, 1998 SoftRide, 1989 Klein, 1989 Black Lightning #0033
Mentioned: 19 Post(s)
Tagged: 0 Thread(s)
Quoted: 889 Post(s)
Liked 906 Times
in
534 Posts
Look again. The suspension upper link attaches to the stay at the point of cracking. If I were repairing this I might consider a reinforcing plate of some sort as it's obvious that the OEM amount of material (if whatever condition it was after production) wasn't up to the task. .....
Now that I've been looking at it, I question the wisdom of having the rear rack mounted to the swingarm, that makes all of the cargo weight unsprung, and acting on those little stub 'chain stays' without the benefit of a full rear triangle, or the spring action of the suspension.
I will agree with you, that it isn't a particularly handsome bike, but if the OP's good with it, then i'll let it go at that.
#10
Senior Member
Jan, You've nothing to lose by welding that crack shut.
In addition I would drill pin holes at each end of the crack, add some re-enforcement extending beyond the "brake bridge", lubing the suspension plate, and determine if the rack is loading upper mounts unequally.
Brad
In addition I would drill pin holes at each end of the crack, add some re-enforcement extending beyond the "brake bridge", lubing the suspension plate, and determine if the rack is loading upper mounts unequally.
Brad
Last edited by bradtx; 02-06-18 at 07:32 AM. Reason: sp