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RZ350 the 2019 re-frame

16K views 62 replies 19 participants last post by  make that thing forkless 
#1 ·
Forkless is back!

Before I get into the new project, first a quick personal update. I didn't post much last year as I was super busy with a second job. I was hired by an e-moto startup to do the chassis design work for their electric motorcycle project. To date, we've completed a beautiful prototype, but unfortunately the company has now run low on funds and doesn't want to show the bike publicly yet. I was hoping I could share some pics, but those will need to wait.

In the little bit of spare time I've had, a little bit of work has been done to get one of my AK-1s back on the road, and I've gotten my RZ250R out of moth balls and running again. Got two other RZ350 that are getting partial restorations, but nothing really too crazy.

As for some older projects... FOSMC II (Snap-together Ducati) is still on hold. AK-1 (prototype 1) full restoration rebuild is also on hold. And my RZ500 project is still on hold, but I look at it screaming back at me every weekend.

Okay, on to the current new project... Over the years I've had lots of people ask me about building custom RZ350 frames. Some are serious, some less serious, but so far none have made a commitment. None the less, its a project that has always been of high interest (see sketches below). Last year, I decided that I wanted my next Dirtbag Challenge build to be based on an RZ350 so I began sketching some ideas for a chassis with a crazy girder fork design with low mounted dual shocks (sketches below). So kind of a theme here in that for the past few years I've made lots of sketches of semi-trellis framed RZs.

Fast forward to last week and out of the blue a friend sends me this picture of SXR600 race bike with a one-off trellis frame. Holy shit... thats got so many similarities with the frame I want to build! So that was the kick I needed to decide to make this a reality. The plan is to use this year's Dirtbag Challenge as a prototype build (minus the crazy front end), then maybe add the front end for next year's DBC.

More specifically, there are three major flaws with the RZ350 frames that I hope to address. First is the 80s era geometry. At 26 degrees rake and relatively short swingarm there is potential to greatly improve the overall layout. Second is the rear suspension design. Again, the 80s era design relies heavily on motocross technology of the era and results in a linkage geometry that is overly progressive. Lastly is the physical location of the suspension linkage which hangs very low. This is a problem when routing expansion chambers. A design with the shock and linkage positioned higher will result in much better clearance with the pipes.

I think its funny that there have been many attempts by many people to improve RZ frames, but most just end up adding un-needed braces which just adds weight without addressing the real issues in need of improvement.



design sketches for past few years:

[/url]20190303_182636 by andbike, on Flickr[/IMG]

[/url]20190303_182704 by andbike, on Flickr[/IMG]

[/url]20190303_182929 by andbike, on Flickr[/IMG]

[/url]20190303_183018 by andbike, on Flickr[/IMG]

[/url]20190303_181020 by andbike, on Flickr[/IMG]

[/url]20190303_181127 by andbike, on Flickr[/IMG]

[/url]20190303_181149 by andbike, on Flickr[/IMG]




This is the SRX600 that is acting as inspiration (not my bike):

[/url]DSC_0368 by andbike, on Flickr[/IMG]


[/url]SRX_Racer2 by andbike, on Flickr[/IMG]



Stay tuned for more...
 
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#5 ·
Before I get into the next progress update, I want to make a comment about units of measure... professionally I've preferred to design in metric units (as apposed to "stupid units" as one of my co-workers refers to inches). That said, I grew up looking at specs in motorcycle magazines where everything was given in inches. Because of that history, I tend to identify some elements of motorcycle geometry more by inch units rather than millimeters... so bare with me if I tend to use both in the conversation that follows.

This week and for the next few weeks the main task at hand is getting the design into CAD (Solidworks). This process always begins with an overall geometry sketch. This will drive the construction of the model. So things like wheel base, rake and trail, swingarm angle, etc. are laid out and major components will later be mated parametrically to this initial sketch.

I have a few generic parts already modeled from past project such as R1 forks, triple clamps and clip-ons, some generic tires, and an R6 shock. So I went ahaead and added those to the model. Last week I began the initial modeling of a swingarm, although it isn't needed yet.

The main goal today is to get the rear suspension linkage geometry worked out. I've decided to use a TZR250 3XV swinagrm for my inspiration and to use the linkage geometry. There are several reasons why I chose the 3XV swingam... first, its long at almost 23 inches. As mentioned in my first post, one goal is to move the engine a bit farther forward and utilize a longer swingarm.

Second, its a relatively wide swingarm at 238mm (inside width) and slightly asymmetric (more space on the sprocket side). This will allow for a good variety of wheels to fit. I did a check fits (see photo) with a CBR600 F2, SV650, and a Husky supermoto wheel. All had ample space to fit, although the CBR wheel is pushed all the way to the left and the SV wheel will use a GS500 cush-drive hub.

Third, the linkage location is very high. A stock RZ350 shock linkage dangles around 5 inches below the swingarm. The 3XV linkage is maybe an inch and a half below the swingam. This frees up around 4 inches for expansion chamber clearance if (most likely) I decide on GP style routing (left side crosses under to exit on right side).

Here are a few of my target numbers for geometry (some are subjetc to change)

- wheel base: 56" +/- 1" (variable with chain adjustment and rake angle)
- rake angle: 22.5* +/- 1.5* (I plan to use an adjustable head assembly with adjustable rake angles of 24*, 22.5*, 21*)
- swingarm angle: 8*-9* (with unladen weight of bike)

Most of today's CAD exploration was to model the 3XV linkage and start getting an idea of how the geometry with play into rising rate cures and final shock (spring rate) selection. So far without a lot of refinement it looks like the 3XV linkage has a fairly flat rising curve. So it's not overly progressive. This is also an advantage over the stock RZ350, so I'm very happy with what I'm seeing.

Okay, enough talking, here are a few pics...

[/url]20190302_155417 by andbike, on Flickr[/IMG]

[/url]20190302_160108 by andbike, on Flickr[/IMG]

[/url]20190311 image 1.2 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190311 image 1.05 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190311 image 1.1 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]
 
#7 ·
isn't 9 degree swingarm angle fairly flat? you know way more than I do about geometry, just thinking to when I've had Gerry Piazza measure bikes for me.
 
#8 ·
I kinda remember we had this discussion once before (maybe over on BARF?). I recall the conversation going something like... "blah, blah, blah, Gerry Piazza said, discussion over". I think you said that Gerry measures swinagrm angle with the bike completely un-weighted or lifted off the ground... which has relevance to nothing. Anyway, 8-9 degrees is good from my experience.
 
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#9 ·
Ha ha, no worries. I was the one who ended the conversation once GP's name was mentioned. I have some opinions which I'll keep to myself.

Back to your question... for base line swingarm angle I like to make the measurement with the bike on the ground (weight of the bike supported by the suspension, but without rider). Using this method, 8-9 degrees seams to work well. Maybe a little more on a bike with softer suspension. Again, this is just the base line that I like, and then adjust from there.

Now is see you deleted your last post... no worries. I'm happy to continue the discussion. Its all good.
 
#11 ·
Forkless is back!

Sorry for the long delay, but I got blocked by two work related trips to Suzhou, China and then a few weekends working on putting this little race bike back on the road...

[/url]20190502_145554 by andbike, on Flickr[/IMG]

Anyway, I finally had some time to jump back into the RZ350 frame project. Put in some more effort on the CAD model. My focus was on getting the swignarm further developed. I added the right side main tube which will have an arc for pipe clearance. Also started adding brace tubes and modeled in a chain with 10mm offset from the stock position. This should allow clearance for using stock off-set or the 10mm off-set chain line. As mentioned in my previous post, the linkage and geometry is modeled off a TZR250 so the goal is to have options for either swingarm in the future. Here's some updates of the CAD...

[/url]20190404 image 1.0 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190404 image 1.1 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190404 image 1.2 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190404 image 1.3 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190404 image 1.4 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]


In addition to the CAD work, I've also started collecting parts...

Engine is actually a 350 Banshee, so essentially an RZ350 minus the powervalves. Since I plan to build this bike for this years DirtBag Challenge, I need to keep the budget close to or under $2000. So a Banshee engine will be plenty fun and this one was only $500 on CL. It came with an extra head and both were pretty beat from loose debris (likely a failed bearing cage), so my friend Brian Turfrey hooked me up with some machine work to surface the head and re-cut the combustion cambers, now with slightly higher compression. The engine was missing the carbs, so found a great deal on carbs, with manifolds, pod filters and boost bottle on eBay.

The cases are broken in a non functional area so I could use as-is, but I've got some RZ cases I'll swap and then be able to run a tach. I've also got boxes of side covers, so should be able to easily assembly a complete engine. I'm probably now at around $750 for the engine.

[/url]20190504_143929 by andbike, on Flickr[/IMG]

[/url]20190504_144046 by andbike, on Flickr[/IMG]

[/url]20190504_144720 by andbike, on Flickr[/IMG]

I also found a good deal on this Toomey Racing filter and jet kit. I probably will run the dual pods to keep my budget lower, but will make sure the frame has ample clearance for the Toomey style filter.

[/url]20190504_144538 by andbike, on Flickr[/IMG]

Next, I'll show a pile of pipes that I'll likely pull a set to chop up later. Second from the left is a set of John Lassak pipes that were given to me, so those are an obvious choice to modify to fit the new frame and not impact budget. On the far right are a crappy set of SpecII pipes, since I have minimal opinions of these, these are also candidates to be cut and modified... but that's a ways away.

[/url]20190504_143948 by andbike, on Flickr[/IMG]

Last, wanted to show the wheels and forks that will be used. The forks are 2001-03 GSXR600. The wheels are DRZ400 hubs (off-road version) laced with 17" Warp 9 supermoto rims. The front wheel will eventually get an aftermarket 320mm rotor.

The wheels and forks were inherited when a good friend passed away a few years back (FUCK CANCER!!!) Eric had started building a KZ400 cafe bike and never got to see it finished, so it will be a nice memento to use this wheels on this bike.

[/url]20190504_143642 by andbike, on Flickr[/IMG]

Thats it for now. Stay tuned for more, hopefully without the long delays:rock:
 
#12 ·
I did a little more CAD work last night trying to decide on how to fabricate the mount for the shock linkage. First concept is a bent heavy gauge sheet metal bracket...

[/url]20190405 image 1.4 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190405 image 1.5 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

Alternative idea is to stay with tubing and bungs. This is a bit more work to fabricate, but keeps the construction method looking more consistent. I'm probably leaning toward this design...

[/url]20190405 image 1.3 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190405 image 1.2 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

Also wanted to see what it would look like with dual shocks. I might do this for the Dirtbag build...

[/url]20190405 image 1.0 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190405 image 1.1 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]
 
#13 ·
A little more CAD progress. Main frame is roughed in. I'm thinking about using inserts for the swingarm pivot mounts so put some circular clamps into the model. Still lots of details to add, followed by lots of fine tuning, but at least starting to look like a motorcycle now...


[/url]201905019 image 1.0 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201905019 image 1.1 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201905019 image 1.2 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]
 
#20 ·
A little more CAD progress. Main frame is roughed in. I'm thinking about using inserts for the swingarm pivot mounts so put some circular clamps into the model. Still lots of details to add, followed by lots of fine tuning, but at least starting to look like a motorcycle now...

[/url]201905019 image 1.1 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

Very interested in what you are doing here, what information do you use to determine the type and size of the tubes to make the frame strong enough, motor mounts are sorta straight forward but what about the other design elements, how many tubes and where?

Many thanks in advance.
 
#17 ·
I imagine that has a lot to do with letting you run different height tires, as different manufacturers are different.

Just a guess though.
 
#19 ·
First off thanks for the comments and feedback. The adjustable swingarm pivots are to satisfy three issues...

- the primary idea is to allow for swingarms of different widths or different pivot shaft diameters without needed for shims or spacers. The inserts can be easily turned to different inside diameter and length. As previously mentioned, the swingarm is based on a TZR250 which is fairly wide at the pivot, however they aren't easy to source. If I end up making duplicate frames and selling a few, this will allow users to easily adapt other swinagrms of different widths if they wish. It might not be needed for this reason, in which case see reasons 2 and 3...

- second is to allow fine tuning of the pivot location (as most comments allude to).

- third is the bling factor... this is also important, right?
 
#22 ·
Another quick CAD update... added cross tubes, head gussets, upper shock mount, and lower linkage mount to the frame. Played with axle eccentrics and swingarm mount inserts. Might do a bit more tweaking with those. Next on the list is engine mounts front and rear. Then lots of fine tuning of the design.

[/url]20190602 image 1.0 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190602 image 1.3 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190602 image 1.1 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]20190602 image 1.2 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]


Also found these golden nuggets on eBay last week for $200. These wil go on the twin shock version.

[/url]20190602_131608 by andbike, on Flickr[/IMG]
 
#23 ·
How much does distance from countershaft to swingarm pivot matter? I know swingarm angle matters, and closer spacing means you can run a smaller sprocket without having as much rub (for a given swingarm/travel), but does it matter much for handling?
 
#24 ·
In VERY basic terms what you are asking about is amount of squat / anti-squat as influenced by the rear suspension geometry. Swingarm angle (as you mentioned) has the most influence. Next is direction of chain pull force. In other words, how close does the chain come from passing through the center of the swingarm pivot. My understanding, the actual sprocket position doesn't mater so much as where the chain line passes past the pivot center.

Here's an article that does a much better job of explaining the geometry and squat / anti-squat calculations... https://www.datamc.org/data-acquisition/suspension-data-analysis/anti-squat-geometry/

If this is of interest, I'd highly suggest Tony Foale's book and software... https://motochassis.com/
 
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#25 ·
This week made more progress on the CAD model. The main effort was to start the rear sub-frame. Also added foot bracket mounting plates, played with the cosmetic details on the eccentric chain adjusters, and eliminated a bend in the upper frame tubes that wasn't needed. Here are some screen captures, not in any particular order...

[/url]201906011image 1.0 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906011image 1.2 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906011image 1.1 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906011image 1.4 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906011image 1.3 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906011image 1.5 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]
 
#26 ·
In a few hours I'm off to China for yet another work trip (the life of a product development engineer). Anyway, thought I'd post a quick update.

This week started on the engine mounts. I start by reverse engineering the mount locations from an existing engine case. I bolt the case to a mill bed and using the DRO I pick up and record the centers of mounting locations, counter-shaft center, and crank center.

[/url]20190615_143136 by andbike, on Flickr[/IMG]

Those numbers are translated into a sketch in CAD...

[/url]201906016mage 1.7 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

Width measurement are simple to get with calipers, then the CAD model can progress. I did find that I didn't allow enough space for air filter(s), so the top shock mount needed to be moved rearward a bit. Anyway, here are some updated images (in no particular order)...

[/url]201906016mage 1.0 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906016mage 1.1 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906016mage 1.2 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906016mage 1.4 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906016mage 1.3 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906016mage 1.5 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]

[/url]201906016mage 1.6 rz350 frame assembly 2019 by andbike, on Flickr[/IMG]
 
#27 ·
NEWS UPDATE: Dirtbag Challenge is "GO"!

So this changes everything... my original plan (thinking DBC is usually later in the year) was to continue design prep and build the first prototype frame for Dirtbag. But then to many folk's surprise, Dirtbag was announced two weeks ago and unfortunately I'm not far enough along with the frame design.

My original plan was for next year I'd add to the frame with a crazy girder frontend... so with Dirtbag coming sooner than expected, I've changed my plans and will build the crazy girder and the swingarm (as seen in the CAD images) and mount these to a stock RZ350 frame and that will be my DBC bike for this year. Its still and enormous amount of fabrication to pull off in two months, but that's the new plan.

Then at some point later in the year, I hope to come back to the frame development.

[/url]Screenshot-from-2018-04-24-03-22-44 by andbike, on Flickr[/IMG]
 
#32 ·
This post will be more of a personal update than a project update. A few weeks ago I began working on the initial frame fixture design...

[/url]rz350 frame assembly 2019.fixture1.0 by andbike, on Flickr[/IMG]


Then THIS happened!

[/url]8r7HyfCh by andbike, on Flickr[/IMG]

[/url]20191024_113915 by andbike, on Flickr[/IMG]

[/url]20191019_092714 by andbike, on Flickr[/IMG]

[/url]20191026_102252 by andbike, on Flickr[/IMG]

Final score: SXV5.5 - 1, deer - 0, me - collateral damage (broken elbow, broken shoulder, 6" laceration down to bone on my forearm, bruised rib, various bruised internal organs, road rash in a few spots)

Spent a very long night in ER, followed by 4 days in the hospital. I'm now home recovering and very anxious to start a new job on Monday. All in all I'm lucky it wasn't worse, and lesson learned: animals are dumb and unpredictable.

That's it for now. hoping to get my energy level back so I can make progress on this project very soon.

cheers:rock:

PS: - huge props to my friend and fellow RZ enthusiast, Ken for fetching my SXV and getting it returned home.
- and props to my old road race buddy Bill for making the award of "Dubious Distinction and Questionable Honor".:D
 
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