Topic: Swingarm question

[squirley]

Quick question here, attached is a picture of an aluminum swingarm with eccentric adjusters.  The arm is supposed to attach with the brace facing down.  
Here's my question, I am planning a monoshock conversion, and would like to turn the swingarm over and use the brace as a point to attach a shock.  Does anyone see a problem with running the adjusters in a flipped posistion? Any help would be appreciated.

[754]

The strongest side of the parts contacting the adjuster is on the top side, turning this swingarm over would put the weaker side up.

I am thinking that you could maybe put the shock thru the swingarm (if there was room), then the mount point is at the front of the brace. They do it on some dirtbikes. It would leave more roomfor aircleaners, oiltank, elrctics, etc... just a thought.

I wouldnt butcher that swingarm, it will only decrease the value. Make a steel one-off, if it  it gets sorted out, then make an aluminum version.

[squirley]

Thanks 754, I felt the same way about the adjusters being a weak link.  It was just a hopefull scenario that would save me a lot of work. 
The swingarm is actually going on an h1 with no electronics or airbox in the way, but I get most of the helpfull feedback on this site. 

[crazypj]

Its always stronger in compression than in tension.
 Shouldn't be a problem with adjusters, just rotate them 180 deg. The pinch bolts underneath would  look nicer
 Unless shock was orientated to sit inline with brace about halfway through travel there is a possibility the 'link' part could fail (as it would be in tension) An extra brace to pivot would probably cure any possible problem though
 I would keep an eye on the welds, they would probably be first failure point
PJ

[754]

I would not bother doing any mods(involving welding) to an aluminum swingarm, with out planning on re heat-treating after it was done..

[HavocTurbo]

Its always stronger in compression than in tension.
 Shouldn't be a problem with adjusters, just rotate them 180 deg. The pinch bolts underneath would  look nicer
 Unless shock was orientated to sit inline with brace about halfway through travel there is a possibility the 'link' part could fail (as it would be in tension) An extra brace to pivot would probably cure any possible problem though
 I would keep an eye on the welds, they would probably be first failure point
PJ

Elaborate for me as I don't quite know what you mean...

He wants to mount the shock on the top of the loop. You are saying that if mounted on the top of the loop there is a possibility of the loop either folding over or breaking completely right?

And to counteract that a support brace would be needed to prevent that?

I've read your post about 100 times and I'm still not sure this is what you mean. Sorry.

[crazypj]

That's right. stress would be along the brace part if turned over, pretty much going directly to axle,  don't know loading on the pivot end but brace would try and lift at certain axle positions.
Now I've though about it a bit more, it would be very similar to early Yamaha mono-shock design which works ok but you really don't want to hit square edged bumps unless you have a real good new style shock (speed sensitive variable, not linear damping) Just about any modern sport bike will have that type though so shouldn't be a problem sourcing something decent
PJ

[squirley]

Ok some clarification/questions

First lets deal with the brace.  when I turn the swingarm over, the position and angle of the shock will try and lift the brace, trying to seperate it from the swingarm through its rotation.  However,  I would brace and add corner brackets connecting the brace to the swingarm in a stronger fashion.  That is not a problem here.

As for the adjusters, I have not had much involvement with them, so my discussion here is based only on what I can see in the pictures.  When the swingarm is turned over, I am now transfering the load from swingarm adjuster portion to that of the adjuster clips.  In the original position, the force of the bike travels into the adjusters that are supported by the swingarm portion of the adjuster retainers; it is all one piece.  The bottom adjuster clips are there to retain the adjusters, but do not see the loads of the swingarm portion.  If I turn over the swingarm, I have changed the roles of the adjuster retainers, now placing the main load on the adjuster clips.  from the pictures it appears that the adjuster retaining clips are just held in by a captured ledge and a pinch bolt.  By turining it over, I am now putting a much larger shear force on the adjuster clip retaining ledge.  (Hope this makes sense).  Am I looking at this correctly?

[coyotecowboy]

I would not bother doing any mods(involving welding) to an aluminum swingarm, with out planning on re heat-treating after it was done..

Hmmm, so if I had a newer alu. swingarm (late 80's GSXR 750 for ex.) and had tabs welded on for shock mounts, it would need to be re-treated?   If so, I'll have to re-think things a little bit.  I like the idea of drilling and tapping even less.

[Edit]  about forgot that my father-in-law is supervisor at a metal finishing plant.  He could definately heat-treat something for me. 

[Retro Rocket]

I had my GSXR1100 swingarm modified by an engineer that builds all sorts of aluminum stuff for bikes and he said if the welding is done properly there is no need for heat treatment, it also depends on the type of alloy.

Mick

[coyotecowboy]

Well in that case, I might have pop-in-law weld it for me too.  He's still certified to weld about anything.

[HavocTurbo]

Ok some clarification/questions

First lets deal with the brace.  when I turn the swingarm over, the position and angle of the shock will try and lift the brace, trying to seperate it from the swingarm through its rotation.  However,  I would brace and add corner brackets connecting the brace to the swingarm in a stronger fashion.  That is not a problem here.

As for the adjusters, I have not had much involvement with them, so my discussion here is based only on what I can see in the pictures.  When the swingarm is turned over, I am now transfering the load from swingarm adjuster portion to that of the adjuster clips.  In the original position, the force of the bike travels into the adjusters that are supported by the swingarm portion of the adjuster retainers; it is all one piece.  The bottom adjuster clips are there to retain the adjusters, but do not see the loads of the swingarm portion.  If I turn over the swingarm, I have changed the roles of the adjuster retainers, now placing the main load on the adjuster clips.  from the pictures it appears that the adjuster retaining clips are just held in by a captured ledge and a pinch bolt.  By turining it over, I am now putting a much larger shear force on the adjuster clip retaining ledge.  (Hope this makes sense).  Am I looking at this correctly?

If it were me...

I would do nothing with the cam adjusters. Just leave them as they are. Even upside down they will still function normally.

As for the loads on the end of the swingarm - Can you get a better picture of the ends? I cannot see the amount of welded material.