SLABBY SWINGARM LENGTHS

[wassuck]

Just whipped out my arm and it measures 61cm end to end near enough.  Could any helpful OSS tell me what the same dim is for a 750 G or H? They are apparently longer (25mm) but was the measurement end to end or centre to centre? Could really do with the info so thanks in advance guys.

Edited May 1, 2016 by wassuck
Ham fists

[wassuck]

I'm answering my own question, that's what I love about OSS!

Anyway in my search for dimensions I have discovered the following using my trusty tape measure:

GSXR750 F = 550mm centre of pivot to centre of chain adjuster slot

GSXR750 G/H = 570mm centre of pivot to centre of chain adjuster slot

Of course the reason why I was so interested in finding the dimensions was because everyone wants a later 'arm to avoid the infamous shimmy in cornering. Now that Slabbies are being raced again, this makes the later and longer swing arm desirable. Unfortunately, as I didn't have the measurements I couldn't identify an earlier 'arm from a later one as well as an 1100. After research I found the above measurements, which were then backed up in the flesh when I lucked out and bought a later 'arm from fleabay. A huge difference between early Slab 1100 swing arms and 750s is in the construction of the shock linkage (cushion) mountings. On the 1100, they are a lot more substantial ('box' type) whereas the 750 is essentially welded aluminium plate. Anyway, I hope this helps and doubtless many of you already know this but there are some who might find it useful especially as parts become rare and sellers don't really know what they are flogging. The diagrams will explain what my words fall short of......I hope....

[Swiss Toni]

Shoulda left the original short arm in. Makes it more...'interesting'.

[wassuck]

Actually it's got no arm in it as I'm bracing it. I've had a few moments with the  shorter arm but nothing to brag about so it's a motorised wheelbarrow at the moment t:D

[clivegto]

Early r1 brace welded on, what bracing is in your plan.

[wassuck]

That's really pretty. I'll be looking at this ahem, privately for inspiration over the next few days. Actually not sure about the bracing yet, been looking around but sorting measurements has been a huge task and learning curve and that's just been on getting the right if scabby 'arm. The moment you move away from standard its a different world of conflicting advice and minefield of potential mistakes. How the hell is your swinger looking so good? Did you strip it?

[wassuck]

BTW yours is a G or H 'arm isn't it?

[GSXR400man]

Much appreciated in confirming the 1985 slabside dimensions.  Wanted to check the 85 arm I bought was indeed an inch shorter and it was  !

:)

[Sandman]

On 5/12/2016 at 10:05 PM, clivegto said:

Early r1 brace welded on, what bracing is in your plan.

 

This type of bracing may look cool, but contributes almost nothing to torsional stiffness or flexural stiffness of the swingarm. It only contributes to increased weight.

 

[clivegto]

On 11/27/2020 at 9:58 PM, Sandman said:

 

This type of bracing may look cool, but contributes almost nothing to torsional stiffness or flexural stiffness of the swingarm. It only contributes to increased weight.

 

Worked well enough on a 260hp turbo slabby. 

Edited November 29, 2020 by clivegto

[Sandman]

It want make the swing arm any stiffer, even if you have 750 hp.

[Dezza]

Kevin Schwantz had similar so they are good enough for most people on here

[Ted M]

16 hours ago, Sandman said:

It want make the swing arm any stiffer, even if you have 750 hp.

I'm curious. Why isn't the bracing contributing to torsional or flexural stiffness?

[coombehouse]

26 minutes ago, Ted M said:

I'm curious. Why isn't the bracing contributing to torsional or flexural stiffness?

To have any effect, the bracing needs to be connected to the pivot tube. Have a look at a 750 srad arm & you'll see what I mean.

[Ted M]

@coombehouseI see what you mean by attaching to the pivot tube but if you look at the K1 and K2 GSXR 1000 and 750 the bracing stops short of the pivot tube. I'm not convinced that the bracing has no effect at all.

[Sandman]

But K1/K1 and R1 swing arm have a box that gives the stiffness to the structure. The bracing on the swing arm in the picture only supported by a flimsy alloy sheet, almost without any stiffness. 

[coombehouse]

On 11/30/2020 at 1:51 PM, Ted M said:

@coombehouseI see what you mean by attaching to the pivot tube but if you look at the K1 and K2 GSXR 1000 and 750 the bracing stops short of the pivot tube. I'm not convinced that the bracing has no effect at all.

You need to have a better look at the gsxr1000 arm. It's connected to the pivot with a very stiff chunk of ally as @Sandman says

[clivegto]

On 11/30/2020 at 11:13 PM, Sandman said:

 The bracing on the swing arm in the picture only supported by a flimsy alloy sheet, almost without any stiffness. 

8mm plate isn't without stiffness. 

[Ted M]

7 hours ago, coombehouse said:

You need to have a better look at the gsxr1000 arm. It's connected to the pivot with a very stiff chunk of ally as @Sandman says

As you can see the bracing stops short of the pivot. Agreed it is a stiff chunk of ally but it doesn’t go all the way to the pivot tube. 

[coombehouse]

5 hours ago, Ted M said:

As you can see the bracing stops short of the pivot. Agreed it is a stiff chunk of ally but it doesn’t go all the way to the pivot tube. 

 

Agreed though it's close & it's not just a flat bit of plate is it. 

From 2005 onwards the design was changed & it does extend to the pivot though it was a casting rather than a fabrication. 

The 750 srad extends to the pivot too

Edited December 2, 2020 by coombehouse
Info

[Ted M]

I’ll have to bow to your knowledge there mate. I’ve got a k6 swing arm at home and the stiffness in that is phenomenal. But I still reckon that clives bracing will offer more stiffness than as standard especially in the side to side plane

[Sandman]

The design of swing arms for K1/K2 is far from optimal. SRAD swing arm is stiffer, but much heavier. K6 is more up to date. Look at a swing arm for a KALEX chassis in MOTO2. It is a piece of art. The picture of the braced swing arm shown above for the slabside is made by an amateur. Take a course in advanced structural engineering and FE analyis and you will understand what I try to tell.

[Sandman]

Here is a picture of a Moto2 KALEX chassis for 2020-season.

[clivegto]

I now run this Metmachex swinging arm in my Turbo Slabby bike. I do belive the one I made about 4 years ago in a shed in North Yorkshire must have more strength than the standard one. Obviously there are stronger arms available. 

Edited December 2, 2020 by clivegto

[Sandman]

Do the math and descover that your homemade swing arm is not considerable stiffer than the stock one.