Quote from: the mole on March 28, 2011, 07:09:53 PM
You need to ask yourself why you want to change your swingarm. ie. what do you know that the Suzuki engineers who designed it didn't know?

statements like this are ridiculous and willfully ignorant

Quote from: werase643 on March 31, 2011, 05:07:05 AM
make it handle like a fat 1992 TZ250 and you will be happy
the number crunching is almost a waste of time
this is thomas edison light bulb design 101, fab a different SA onto a gs and see what it does
then yo can make the measurement points and plug it into your program to determine if it is ideal

then what determines what is ideal squat for a gs?

I use a much different methodology then persistent trial and error, and the opposite of what you suggest.  I find it saves a lot of time and money to first make ballpark calculations to see how to modify the suspension, nothing needs to be exact or ideal just yet.  Then when you know the parts can provide satisfactory results you modify and install.  

For example, instead of just buying a new front fork set-up and installing it only to find out it is much to short and has drastically increased the rake, first verify that it is going to be a reasonable length then purchase and install.  Of coarse rake is a mfg. published number and the fork length is a simple measurement.  It gets a little more difficult when you start to swap shocks with different spring rates or when you alter rear linkage or anti-squat behavior.

It's not that hard to determine good estimations for these suspension parameters. Then after your parts are installed, you still have to take it for a ride and see how it handles.  Then when you want to make changes you resort back to the analysis to make rational choices.  IMHO, this is a much better method then fab and test, repeat. Of coarse if cosmetics is the only motivation, you can skip the analysis.  Sometimes you get lucky too, other times you can just copy someone's mods (the later assumes that they either did there homework or got satisfactory results).  

Quote from: cd on March 31, 2011, 06:23:50 PM
statements like this are ridiculous and willfully ignorant

That it is a normal response to most out of the box ideas, non-bolt on mods, or any engine related power mods around here. You get used to it.  

Quote from: tb0lt on March 31, 2011, 07:57:39 PM

Quote from: cd on March 31, 2011, 06:23:50 PM
statements like this are ridiculous and willfully ignorant

That it is a normal response to most out of the box ideas, non-bolt on mods, or any engine related power mods around here. You get used to it.  

When you have been around here for a few years like some have and read all the "I am going to  fit FI/a turbo/under-seat exhaust/in line 4 etc etc" threads that show up from time to time, then watch as the poster suddenly vanishes off the radar when the enormity of their idea, the lack of forethought and the practicalities involved in actually making it happen sinks in.......you too may become a tad cynical about such claims when you first read them

Quote from: sledge on April 01, 2011, 01:08:03 AM
When you have been around here for a few years like some have and read all the "I am going to  fit FI/a turbo/under-seat exhaust/in line 4 etc etc" threads that show up from time to time, then watch as the poster suddenly vanishes off the radar when the enormity of their idea, the lack of forethought and the practicalities involved in actually making it happen sinks in.......you too may become a tad cynical about such claims when you first read them

I know it can get tiring when you see stuff like this for years and later realize you got all excited for nothing. Still... if you have nothing positive to add to the discussion or what you say is only going to stifle any creativity and energy in the thread.... you could just watch the thread and not post in it. Believe me, I understand how you feel and I also think the same of some posts... but i'd rather not post an utterly useless reply no one wants especially if it doesn't add anything useful or it is just negative and all I'm doing is adding to my post count (like that means crap). This would be especially true for a technical natured post like the OP. No offense. 

you can design to your hearts content,  but, we are working with given entities.  swing arms are x in length and y in width and the linkage points are set in....weld or cast.  The light bulb methodology actually is skewed.  If you have the ability to make a swing arm, make it to your ideal calculations. 
If you gather data from many different sources, and do trend analysis of the top 10-20 sport bikes in the last 20 yrs.  You will find a set of close majik numbers.  there will be some variances due to some mfgs trying to think outside the box....think rotary shock on the TL-R(how did that work....). 
The formula... bike 350#....600 or 1000 is in that range now therefore if you use the swing arm and stock linkage for a given platform and adapt everything including mount locations....it SHOULD? work just like it was on the other bike except that it is now on a gutless turd.  I don't need cad/calculations to figure that out. 
I have no problem with your approach, but all you are doing is recalculating known data.  If you are modifying a given swing arm to a GS and adapting to GS links.... then your calculations are valid.  The data will then have to be compared to known data from a ideal chassis.  If this is still for bling, you are having fun playing with your expensive cad program, again, kewl. 

I'm not bashing you(much)
there are only a hand full of nutter ID10TS that will take on the task of spending stupid $ on a turd entry level bike.
FYI....the mad German spent close to 20k building that orange monster.
so a couple of hundred...for a swing arm to try.....

you will get help if you ask realistic questions.  If you come up with something outside of the box that works.... post it with results.  I thought the triumph sssa bike never would get finished.... that guy did huge mods in a relatively short amount of time with beautiful results.

cheers mate
smoke me a kipper

Quote from: werase643 on April 01, 2011, 08:22:58 AM
If you are modifying a given swing arm to a GS and adapting to GS links.... then your calculations are valid.  

Thanks, I'll take that as a complement.  

Even if I did swap everything over from a modern sportbike, including relocating the rocker and shock mount as you point out, I would still have to relocate the engine so that the sprocket is in the same position.  As chain angle is also a factor in anti-squat.

The CAD program was free, it's an older version of DraftSight which is free to download.  The Fortran compiler was also a free download.

I never considered my self that extreme in the financial investment or custom fabrication of motorcycles.  I've seen plenty of pictures of old CB cafe racers, XS dirt trackers, RD -TZ racers, and chopped Harleys with much greater money invested per performance ratios.  I also know amateur level racers spend large amount of money to support their racing hobby.  I don't think modifying "turd" motorcycles is really that expensive of a hobby compared to anything else.  I think it is fun to make modify things and that it is fun to try to become involved in the design aspect.

My original question was what are the lengths of a RGV or GSXR swingarm compared to the GS.  I included why I wanted this information, i.e. I wanted to calculated anti-squat.  I though including this would show that I'm not new to this.  I though this was a realistic question, buy I am new here so will have to adjust to attitude around here.



 

I'm taking the swingarm to Gerry Piazza of GP Frame and Wheel today to have a few parts measured and spacers built. I'll see if I can get parts measurements for reproduction.

I had a chance to look at the linkages of both bikes today, and the first thing that was immediately obvious is that the RGV cushion lever is much shorter overall than the GS500 lever. This means that the shock is going to point somewhat more downward than it would with the GS500 lever. It remains to be seen what impact this will ultimately have on the suspension - at this point, my plan is to bolt it on, and work from there.

On the plus side, the bolts are all the same size, and while one of the bushings is shorter, it is a direct swap from the GS500 to the RGV part.

Ken is the daddy when it comes to this sort of thing but you need to be aware that this forum is populated in the main by humble spanner-wan**rs of varying ability and opinion. Not designers or specialists or even individuals familiar with the level of questions you are asking.

With this in mind can I suggest you post the question and ask for advice in here... http://www.eng-tips.com/threadminder.cfm?pid=668 instead.

They just love this sort of thing and you stand far more chance of finding the info and answers you need on your level you are looking for 

We dont need no shteenkin swingarm, ish jusssh for looks.
Cool.
Buddha.

Please keep me updated burning1, I am working on sourcing a RGV SA and will post my measurements when I can.

I will check out the eng-tips forums, thanks for the suggestion.  Crossing my fingers that a few members are GS500 owners.

give or take 1-2 inches

nothing really huge in difference between them   mostly how they attach to the frame.

Most of us work with what is in front of us.  I used to run to the salvage yard with a tape and a caliper and measured many swing arms.  Did I save that data... no.  I wonder if anybody considered installing a buell swing arm.... it was a v-twin...so the arm should be narrow at the pivot....
ooooo, under-mount shock working in expansion......

nope, i don't need no more projects

so do you have data for the GS?
any other bikes?
GSXR?
R6?
ZX6?

what is your baseline data?
what is considered bad numbers?
how does the GS compare?

when I was modding
swing arm angle was important 9-13 degrees (i think, been a few yrs)
getting everything to mount was important
making sure the chain didn't saw into the swing arm was important
and an adjustable shock was important

whatever swing arm went on was off of a similar weight bike....therefore, close enough to be able to make adjustments and ride around any problems.

with your calc's, will you make new parts to solv problem or just use info to determine what will not work?

dog bones are easy to fab
rocker links are probably $$ due to the cad/cam required to fab one out of billet.
shock theory....buy a fox/ohlins/penske/elka/....and get it re-valved after you determine what problems are.
after that, you either fab a different swing arm with different mount points or start hacking the mount points off the frame and re-locating them.

good luck, 
we will help if we can
but most us us are dum hicks

I am sorry, I do not have the info on the RG-V SA....I'll try to get it this weekend.
what year GSXR swing arm do you want info on
600/750/1000/1100
what year?1985-2011
many variables
old skool 1100's were 1-2 inch longer than same year 750
I have some 86-87 SA's  but the linkage on them is weird.

if you get to the point where you have to move the engine.... don't waste your time/money using a gs lump.  KTM DUKE/KL-R/DR650(DR800)/XR650L/Raptor 660
and build a frame to go around a worthy power-plant and go with the ultimate SOS bike(drool...) and build around the 225# goal.

RG-V 21.25-22.5 inch
87 GSXR11 22.25-23.5
87 GSXR7.5 21.75-23

chain adjusters will make a slight difference in the calcs

Well... I had the RGV spacers machined up this weekend, and mounted the RGV swingarm to the bike during lunch at my trackday. Best I can tell, is that the braced RGV swingarm isn't really a direct bolt on. I had very limited time to investigate, by initial impressions is that the RGV dog-bones may raise the rear end way too high. Never managed to bolt things up, since the swingarm would not clear the shock, no matter what link I used.

Major issue with the RGV double braced swingarm is that the linkage is not based around a couple of easily machined bones like the GS500. It uses a set of bones that are welded together at the swingarm end, similar to the linkage used on newer GSX-Rs.

http://www.cmsnl.com/suzuki-rgv250-1993-p_model14009/partslist/FIG54A.html

When I have more time, I'll mock up the swingarm to confirm. *If* this issue can be resolved using new linkage, and *if* I can find a set of cheap compatible links I'll try proceeding. But right now, I think the best approach may be to trade my braced swingarm with someone who has an older bananna swingarm that uses traditional links.

FWIW, my overall feeling on this project is "don't bother." I'm pretty deep into the hole on this one, and I'm going to be very surprised if the performance advantage is worth the cost and effort.

03 gsxr 1k arm that i just scrapped....22 - 23

I made some progress on my swingarm swap and analysis.  I'll keep this short as I'm sure most people don't care about engineering principles or modifying turd motorcycles.

The RGV VJ22 swingarm fits will little trouble.  The RGV swingarm pivot bolt is 20mm, the GS is 14mm.  The RGV SA pivot length is smaller so you need to add ~ 5mm spacer on both sides.  The GS rocker will work fine with the RGV dogbone is you trim the metal sleeve for the dogbone bearings, about 1.25mm per side.  The dogbones are really close to the the rocker, but it is fine. The RGV dogbones are too short, as already noted.  For my setup they needed to be about 6mm longer.

As for the analysis,  I did measured the GS frame and rocker, along with my other suspension parts.  I'm not using GS wheels, GS forks, GS rear damper or the same gearing, or even drive sprocket location so little can apply to the stock GS.  However it does show some trends. It also provides direction to further modification.

I am showing two plots below.  The first shows the wheel force as it varies with suspension displacement.  You can see the suspension maintains a progressive nature (i.e. slope deviates from 45 degrees).  The second plot shows the anti-squat behavior.  Where squat ratio is the ratio between the tangent of the load transfer angle and the tangent of the squat angle.  Both look like they need a little adjusting.




I welcome any discussion.

I'm still a little unclear as to what kind of suspension progression is ideal. What I'm seeing now is that 0-15 percent is a pretty typical range, but... Not entirely sure. I really should pick up Tony Foyle's book. I have a copy of Motorcycle Dynamics by Vittore Cossalter, but it didn't seem to have a really in depth discussion on suspension design.