Bracing the headstock on a gs750

[no class]

[Reinhoud]

11 hours ago, gorbys said:

So basically riding any B-road or mountain pass here in Norway then? 

That's why I posted in the first place to get some feedback since all the guides tend to the gsx. 

Anyways, isn't the point of bracing the headstock like this to prevent lateral or twisting motion? 

Than the headstock isn't the problem, the problem is further back..

[Poldark]

2 hours ago, Reinhoud said:

Than the headstock isn't the problem, the problem is further back..

How far back? About an arm's length? 

[Reinhoud]

5 hours ago, Poldark said:

How far back? About an arm's length? 

Depends how long your arm is

Where the 3 tubes go over in 2

Edited February 8, 2020 by Reinhoud

[Poldark]

The part of the frame near the air filters.  There is less material there, but at least most of the forces acting there are compressive and not bending.  Some bending may be induced in the curved portion of those two tubes.  Some the example photos show reinforcement in that area.

The "further back" had me thinking of a reference to the rider being the problem.

[johnr]

ive a kat frame in the shed that was braced for a build intended for one of the monthly bike rags, they built two frames and this was the one they didnt use. bracing is rather nicely done although im not sure how sturdy it would be.

[Poldark]

If it was done for a magazine, it was probably done more for looks than structural engineering purposes.  It is a nice looking frame and it just sits in your shed; please build something on it.

[johnr]

it was done by lucky7 for practical sportsbike mags kat build.
these are the pics of the bracing done to the frame for the build, in fact, these are pics of the frame i have in my shed, the other was used in the mag. it will get built one day, but collecting kat 1000 stuff and yoshi bits is an expensive persuit.
 

 

Edited February 11, 2020 by johnr

[johnr]

its in a queue behind 5 other bikes, all katanas....

[Gixer1460]

8 hours ago, Poldark said:

If it was done for a magazine, it was probably done more for looks than structural engineering purposes. 

You are assuming they used some backyard bodger! Lucky7 used to have a good rep and turned out good work in the 80/90's! As regards engineering, that is pretty good and well thought out - all main elements are connected and braced in multiple directions, sheet is lighter than tube and has greater surface area to resist torsion + its bloody nice welding! That should be stiff as f**k - bastard to paint though! 

[Reinhoud]

On 2/9/2020 at 12:00 AM, Poldark said:

The part of the frame near the air filters.  There is less material there, but at least most of the forces acting there are compressive and not bending.  Some bending may be induced in the curved portion of those two tubes.  Some the example photos show reinforcement in that area.

The "further back" had me thinking of a reference to the rider being the problem.

A cross  in the frame behind the carburetors is probably one of the best spots to reinforce.

Welding brackets in the top tubes at the end, above the carbies, might look like it does something, and it probably does, but the tubes below that are probably not very strong/stiff.

Imo the head stock is about the stiffest spot in the frame..

The places where stiffness can be achieved isn't accessable because of the engine, again, just my opinion.

[Poldark]

Hang on... I never disparaged the work done on John's frame.  I'm sure Lucky7 work is much better than my own backyard bodge jobs.  If it the intent was to be featured in a magazine, the primary goal of the work would mostly be cosmetic because beautiful bikes in full page color photos sells magazines.  Did Lucky7 do frames for professional race teams?  Those examples may tell us more about effective frame reinforcement; in racing, winning, not looks, is the most important.  When it comes to motorcycles, I'm not a professional anything.  I'm a backyard bodger who is into motorcycles as a hobby.  My formal training is in mechanical engineering, so I find this discussion interesting, but I'm not the expert. 

There is 3D modeling software (Inventor, SolidWorks, etc) that can do stress analysis, but loading in all the data points would take more time than it's worth.  If we were going to mass produce something, the analysis is well worth the effort.  

[Gixer1460]

18 hours ago, Poldark said:

There is 3D modeling software (Inventor, SolidWorks, etc) that can do stress analysis, but loading in all the data points would take more time than it's worth.  If we were going to mass produce something, the analysis is well worth the effort.  

And Suzuki more than likely had, and used it - even back in the 80's . . . . . . but 'back yard' bodgers still think they can improve on that - with road bikes - whilst bring totally unnecessary* (unnecessary* - as in no noticeable / appreciable improvement)

[Poldark]

But we can greatly improve on something when we go backyard bodging: we make our bikes uniquely ours.  If one of us really wanted the best engineered bike, go out and buy a late model GSXR.  The engineers at Suzuki, with feedback from the race team and modern manufacturing facilities, can produce a superior motorcycle compared to anything I could put together.  Still, I'd rather build something myself, and have it be uniquely mine.  

"What kind of bike is that?"  

"It's a 19XX GSxxx frame, with engine and running gear from a 20XX....; with all the performance improvements, I had to reinforce the frame...."

"You did all that yourself?"

"Yeah, it's a hobby."

The home-spun skill and creativity is what attracted me to OSS.  Sometimes I read the forums at other places such as TheGSResources, they are knowledgeable but boring.

[bluedog59]

It's true that there may be little point in bracing a stock frame, if you are running a stock engine and stock "period" tyres and suspension. If you start to upgrade tyres and running gear you can exceed the original design requirements of the stock frame.

Case in point. I "hobby race" our old race bike 2 or 3 times a year with a couple of friends. Last season we were allowed to run slicks and a once trouble free bike is now snapping engine bolts and mounts with the extra force being fed into the chassis.