My Suzi T500 Project *It's Alive Video*

teazer

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Re: My Suzi T500 Project

Johnu, That was the point. With different forks and swingarm my 28/29 degree GT750 was sitting at around 22 degrees with the swingarm where I want it and that isn't going to work too well.

I'd suggest you bolt on teh forks and front wheel and slip in the swingarm and rear wheel and then start to raise the center on the frame to get the rear end geometry you are looking for and measure the front end. I suspect you will find that you can reach or pass that objective without cutting the front end of the frame.

Plus the front wheel goes from 19 inches to 17 inches so teh front is much lower and if the forks are shorter the front end will be lower again. Just going 19 to 19 with a one inch drop in teh front end and one inch added at the rear took a stock Gt750 too steep.

BTW, 24 is pretty steep for a bike with a relatively bendy frame. If it comes out to say 5-8 degrees static swingarm droop and say 24-26 degrees of rake it should work, but measure twice and cut once as they say.
 

50gary

Under the Limelight
Re: My Suzi T500 Project

I like the 24 degree rake simply because that's the sportbike norm. The design goal (as I understand it) is to achieve as close to sportbike properties in a tube frame as reasonably possible. Many T500 race guys shorten the standard swingarm to help quicken the steering by making the wheelbase shorter. I think this is backwards to modern thinking, swingarms are now longer and steering head angles steeper. the current thinking is to load the front more if I understand correctly? I did a similar project and had very good results. Plus the challenge is a big part of any project. Two cents.
Cheers, 50gary
 

johnu

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Re: My Suzi T500 Project

Teaser, good call. I have just been playing around with an autocad drawing of the frame, swingarm, forks and 17" wheels and it appears as you say that I may not need to remove the headstock. I don't really like the fact (asthetically) that the engine and chassis rails will be canted by 5* though. However I do like that the rear would be a bit higher with the seat unit angling upward slightly. I'll take your suggestion to bolt up the parts and see what can be achieved and how it looks before cutting anything. My first priority is to get the swingarm pivot brackets tacked in place so that I can do the mock up. If I end up going down the route of not cutting and replacing the headstock I will have to source bearings that both fit the 636 forks and the original headstock, any ideas where I could look for these?

All suggestion are greatly appreciated.
 

johnu

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Re: My Suzi T500 Project

Gary you are correct. I am trying as much as possible to mimick modern sportbike geometry. The fzrswing arm is almost exactly the same length as the original arm. I love doing this stuff, as you say the challenge is a big part of the project for a lot of us. That being said obviously I will not cut off the head tube if other options bring me to the desired geometry.
 

johnu

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Re: My Suzi T500 Project

Did some work on the new swingarm mounting point today. I canted the frame to the spec on my cad drawing which gives me 24* rake angle. The swingarm is at 10* and doesn't look bad. The issue of whether or not to cut off the headstock tube is decided because the Kawi fork pivot tube doesn't quite fit through the original that's on the bike. I will have a new tube made and use the stock Kawi bearings just to keep things easy. Still can't believe how far away the counter shaft center is from the swingarm pivot!
 

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50gary

Under the Limelight
Re: My Suzi T500 Project

Johnu, you're on the right road in my opinion. I like the looks thus far, the Swingarm is indeed along way from the countershaft.
I was thinking simply remove the rear most engine mount, machine the mount off and re-weld another rear mount
That way I could move the S/A pivot forward by 30mm? That would be major but doable. On a more realistic level I would mount the S/A right about where you have the mock up. I have a plan for our T500 that is to remove the pivot plate as you have done and use four new plates, two per side with a welded in steel boss between each pair of plates. I would run the plates up to the new angled tube you have already put in place and down to the original tube of course, fairly thin as then each side of the frame tube would be stressed using chromoly sheet, Also a cross tube between the new angled tubes just above the chain. The other advantage to cutting off the head tube is you can shorten the top tube a bit if need be. I wouldn't think tire clearence wil be a problem, with a smaller diameter tire and a more vertical compression path at 24 degrees. I 'm guess-timating using a 30" fork length as an average you'll save about 2.635" on de-raking alone and another .5" on the triple clamp offset. That will be a huge difference. Did you measure the layout before you took the bike apart? I would measure the overall Wheelbase and the front wheelbase from the axle to the crankshaft and then crankshaft to the rear axle. Just tossing out some ideas, this is very interesting to say the least.
Cheers, 50gary
 

teazer

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Re: My Suzi T500 Project

Another thing to check is the chain run. place a rear hub and sprocket in place and make sure that the chain is clear of the top of the swingarm.

And then check the chain geometry to make sure it creates negative squat at the rear under power - Tony Foale's book or John Robinson's will help there.

Check with All balls for those bearings. check the 636 bearing ID and the T500 OD and see if there's something that will work. The next simple idea is to consider either machining the stem slightly for a smaller lower bearing or making sleeves if the only option is a bearing with the correct T500 OD but larger bore than the stem.

Or have a new stem machined - all easier and cheaper than cutting its head off.
 

teazer

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Re: My Suzi T500 Project

50gary said:
I like the 24 degree rake simply because that's the sportbike norm. The design goal (as I understand it) is to achieve as close to sportbike properties in a tube frame as reasonably possible. Many T500 race guys shorten the standard swingarm to help quicken the steering by making the wheelbase shorter. I think this is backwards to modern thinking, swingarms are now longer and steering head angles steeper. the current thinking is to load the front more if I understand correctly? I did a similar project and had very good results. Plus the challenge is a big part of any project. Two cents.
Cheers, 50gary
Gary, I'm not sure I totally agree. modern bikes do have steeper steering and less offset and much stiffer frames around the steering head. Engines are mounted further forward to shift teh weight distribution forward and that requires a longer swingarm to maintain a reasonable wheelbase.

What you are seeing on race bikes (apart from copy cat type imitation) is shorter swingrams to make for a more agile bike. The idea is that a shorter wheelbase is more beneficial than the adverse effects of shift in weight distribution. Longer shocks and slightly shorter front forks cuse the bike to be more nose heavy, so overall it works.

On this bike we have shorter forks, much less offset and stock swingarm, so we have significant forward movement of CofG and less trail and rake. Once it's mocked up it will be possible to measure CofG position and compare that to stock.

Should be a nice bike, but I would be wary of simply trying to paste modern geometry onto an old bike without making the frame a lot stiffer than stock in th vertical and horizontal planes. I'l leave some lateral flex in there.
 

johnu

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Re: My Suzi T500 Project

50gary said:
Johnu, you're on the right road in my opinion. I like the looks thus far, the Swingarm is indeed along way from the countershaft.
I was thinking simply remove the rear most engine mount, machine the mount off and re-weld another rear mount
That way I could move the S/A pivot forward by 30mm? That would be major but doable. On a more realistic level I would mount the S/A right about where you have the mock up. I have a plan for our T500 that is to remove the pivot plate as you have done and use four new plates, two per side with a welded in steel boss between each pair of plates. I would run the plates up to the new angled tube you have already put in place and down to the original tube of course, fairly thin as then each side of the frame tube would be stressed using chromoly sheet, Also a cross tube between the new angled tubes just above the chain. The other advantage to cutting off the head tube is you can shorten the top tube a bit if need be. I wouldn't think tire clearence wil be a problem, with a smaller diameter tire and a more vertical compression path at 24 degrees. I 'm guess-timating using a 30" fork length as an average you'll save about 2.635" on de-raking alone and another .5" on the triple clamp offset. That will be a huge difference. Did you measure the layout before you took the bike apart? I would measure the overall Wheelbase and the front wheelbase from the axle to the crankshaft and then crankshaft to the rear axle. Just tossing out some ideas, this is very interesting to say the least.
Cheers, 50gary
Removing the rear engine mount is pretty ambitious! I too would have liked to create the double sheet metal mounting plate you describe, however my swing arm is wider than the inside of the frame tubes. I do plant to go up and attach to the new bracing though. My original wheelbase was 58.75" on my cad drawing the new wheelbase should be 56.25".
 

johnu

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Re: My Suzi T500 Project

Teaser, what suggestions do you have for stiffening the frame?
 

johnu

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Re: My Suzi T500 Project

Ok guys, not much to report as I've been busy on other things like work and such! I made a cardboard temp for the swingarm mounting point but that's about it. Nothing scientific about the design but I think it looks right. I think I am going to try and mock up the forks in the stock head tube as on my cad drawing it looks like with how I have canted the frame it will work out to about 24* of rake.
 

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johnu

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Re: My Suzi T500 Project

Ok I changed my mind! I am now going to go with 16gauge formed sheet for the swingarm mounts with bosses weld through the sheet. I was going to use 5mm plate as the mounts.
 

50gary

Under the Limelight
Re: My Suzi T500 Project

Good, more like a race bike. Remember, overkill is good. With the plate mounted S/A the rigidity is limited to the strength of the steel plate not supporting geometry.
I would weld the formed sheet only on the sides of the frame tubes, not on the curved surface of the tubes. I think that creates a stress riser? Any engineers out there?
Cheers, 50gary
 

johnu

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Re: My Suzi T500 Project

You are correct about not welding the parts that contact the round part of the tube. In all the books I have on frame building they suggest this. I've seen examples of how the frame cracks if you weld this area. Funnily enough though I think if you bronze weld the parts it's not an issue.
 

Erskine

New Member
Re: My Suzi T500 Project

50gary said:
Remember, overkill is good.
I like the cut of your jib!:)
The GT500 I had back in the day was made out of rubber.
In fact the steering damper I put on it acted as a stressed member.;)
 

zooke581

New Member
Re: My Suzi T500 Project

johnu said:
Ok I changed my mind! I am now going to go with 16gauge formed sheet for the swingarm mounts with bosses weld through the sheet. I was going to use 5mm plate as the mounts.
I was going this route but the pieces I cut off the GS500E frame to use would have put it outside my frame rails and I didn't want to modify those. So I will use the plate with a pivot and use the motor to stiffen it as the factory did.
 

johnu

Active Member
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Re: My Suzi T500 Project

Ok guys a little more progress! I got the swingarm pivot mounting brackets made out of 16 gauge. Had to hand form everything and it seems to have come out pretty well so far. Hope to get them welded in this week some time.
 

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zooke581

New Member
Re: My Suzi T500 Project

Those are nice and actually look like they would work on my setup. Especially as they fit towards the outside as mine have to. Will they incorportate the rear engine mounts as well?
 

50gary

Under the Limelight
Re: My Suzi T500 Project

Good job, that's just about what I thought. I might have gone one gauge thicker on the material 14? I'm watching to see how you are going to make this S/A pivot square with the world? I consider the Swingarm pivot the most important piece, being the center of any bike. This is fun stuff.
Cheers, 50gary
 

johnu

Active Member
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Re: My Suzi T500 Project

zooke581 said:
Those are nice and actually look like they would work on my setup. Especially as they fit towards the outside as mine have to. Will they incorportate the rear engine mounts as well?
Indeed they will incorporate the engine mount, that will be added one the parts are welded in place.
 

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