Cracked swing-arm?

[Crasherfromwayback]

Images with the end cap off - notice the direction of the crack. At least it's in one piece still. I feel confident enough to at least ride it to the shop/engineers/etc.

]

Seeing that...I wouldn't even bother getting it welded unless it worsens.

[Ocean1]

Mr ocean, pretty well all Suzuki alloy fabrications are in an air hardening alloy which can be welded no probs at all. can't remember the numbers but the alloy used is very similar to the Italian Ergal ones - and unobtainable here...

Good to know. I wasn't being pedantic without good reason, though, the strength of most extrusions in particular are dramatically affected by welding.

[Ocean1]

Can it be substituted with a suitable similar filler?

Can't go too far wrong with slices from the parent material. If there's none to spare find a wrecker...

[Drew]

Seeing that...I wouldn't even bother getting it welded unless it worsens.

Really?

I'm perplexed as to how it cracked. I imagine a mechanic wouldn't do the axle up without the adjuster spacer in there. But I equally wouldn't expect to see the axle nut with fresh damage, usually caused by using the wrong tool to undo it, or the right tool improperly.

In any case, there's not an easy way to tell. The swingarm is not experiencing it's biggest forces at the axle, but it's still taking a hammering and trying to fight twist back there.

[Crasherfromwayback]

Really?

.

Really. They guy is not road racing it, and it ain't right through the arm. Just keep an eye on it. Not like it's all of a sudden gonna break in half.

[Grumph]

Good to know. I wasn't being pedantic without good reason, though, the strength of most extrusions in particular are dramatically affected by welding.

Oh, quite...What is pretty obvious is that the japs did a lot of research when they started making alloy frames and arms. They came up with a weldable medium/high strength alloy which air hardens post weld - but only to a safe level...Ideal for production line welded fabrications.
Having done that they then secured a source of supply which seems to be restricted to Japan.

More on this family of alloys in The racing Motorcycle Vol2.

[Drew]

If the swingarm was faulty from manufacture, I think it's good for naught but scrap. Whether it CAN be welded or not.

Serious question like, how can the guy be encouraged to ride on something with an obvious flaw as this?

[buggerit]

If you look at the photo of the extrusion you will notice they have created a stress raiser by the way they made the extrusion to
create a slot for the axle end plates to slide in, thats why it cracked where the wedge shape finishes.
I would drill the end of the crack, vee out , tig up and then clean the weld back so you dont create a stress raiser each side of the weld.
I would also weld it up clamped up as it would be in use .
I would pay to have a look at the bottom of the swingarm in the same place and the other side.

[Mike.Gayner]

I would pay to have a look at the bottom of the swingarm in the same place and the other side.

Thanks, did this last night and no signs of cracking - I'll keep an eye on it though.

[Crasherfromwayback]

Serious question like, how can the guy be encouraged to ride on something with an obvious flaw as this?

Serious answer. Keep a close eye on it and see if it stays as is. I'm not saying he should leave it forever. Merely that I'd happily continue to ride it until I found a replacement or had it welded...and if it doesn't get any worse whilst I was doing that...I may do nothing about it. Like I said...he ain't road racing it or jumping off tall buildings. There's every chance it won't change if everything is in place as it should be now.

[Ocean1]

Oh, quite...What is pretty obvious is that the japs did a lot of research when they started making alloy frames and arms. They came up with a weldable medium/high strength alloy which air hardens post weld - but only to a safe level...Ideal for production line welded fabrications.
Having done that they then secured a source of supply which seems to be restricted to Japan.

More on this family of alloys in The racing Motorcycle Vol2.

I made several aluminium swingarms having seen the original factory MX offerings. Still twin-shock but with serious angles. Never got it quite right.

I once picked up a late 90's cr250 frame in one hand and an sx250 frame in the other and wondered why Honda bothered. Especially with all of the bleating about them being "too stiff". Years later I read a piece pointing out that aluminium frames are capable of being manufactured robotically, whereas steel tube frames weren't, (then).

[Mike.Gayner]

Serious answer. Keep a close eye on it and see if it stays as is. I'm not saying he should leave it forever. Merely that I'd happily continue to ride it until I found a replacement or had it welded...and if it doesn't get any worse whilst I was doing that...I may do nothing about it. Like I said...he ain't road racing it or jumping off tall buildings. There's every chance it won't change if everything is in place as it should be now.

I tend to agree but WTF do I know?

I spoke with the mechanic who did the recent work, and he rightly said that he cant really comment without seeing the bike. In any case, my plan of attack for now is to get it V'd and welded soon and keep my eyes open for a decent used swingarm in the near future. I have a good wrecker friend who reckons finding one will be the hard part, but the going rate is only about $100.

[bogan]

Serious answer. Keep a close eye on it and see if it stays as is. I'm not saying he should leave it forever. Merely that I'd happily continue to ride it until I found a replacement or had it welded...and if it doesn't get any worse whilst I was doing that...I may do nothing about it. Like I said...he ain't road racing it or jumping off tall buildings. There's every chance it won't change if everything is in place as it should be now.

Aluminium cracks love to play creepy crawlies; it's a bit huckory, but chucking a decent diameter hole right on the end of the crack stops em moving if it wasn't done cos of operating stress, and provides an easy check mark if it was!

[Crasherfromwayback]

Aluminium cracks love to play creepy crawlies; it's a bit huckory, but chucking a decent diameter hole right on the end of the crack stops em moving if it wasn't done cos of operating stress, and provides an easy check mark if it was!

For sure mate.

[Crasherfromwayback]

I tend to agree but WTF do I know?

I spoke with the mechanic who did the recent work, and he rightly said that he cant really comment without seeing the bike. In any case, my plan of attack for now is to get it V'd and welded soon and keep my eyes open for a decent used swingarm in the near future. I have a good wrecker friend who reckons finding one will be the hard part, but the going rate is only about $100.

Did you say it's in a GSX750F? The one we have here has a steel arm in it.