RZ350 re-frame... classic 2-stroke gets modern upgrade

[Frame Maker]

Its called back spot facing and it is common enough that there are a variety of tools available for doing it. I happen to have these in two different sizes, so I guess I've done it a few times before. Its kinda cool I gotta say.

Here's a fancy CNC version. Watch how the cutter retracts!

https://www.youtube.com/watch?v=NU-LnZAv2bw

 

[auntiebling]

it's been almost 2 months since i had a chance to catch up on this thread and it's always fascinating!

julian i wonder on the head tubes why you don't leave the bores ~.010 under size to allow a full cut to final size after welding?

 

[Frame Maker]

julian i wonder on the head tubes why you don't leave the bores ~.010 under size to allow a full cut to final size after welding?

Good question. Kinda asking myself the same thing. The short answer is history, skill (lack of), and confidence (lack of in my skills).

The long answer goes back 20 years to my AK-1s. When I built those frames I had the bearing cups machined to be a light press fit. After welding distortion the cups became the tight press fit. Maybe even a bit too tight. At the time I didn't have the confidence in my machining skills to do it any other way. I just smashed the bearings in and off to the races. We ended up winning lots of races so all was good.

At the time the AK-1s were built I had lots of extra bearing cups made so I've continued using the same parts with the same outcome. Of course I've seen pictures of other frame builders machining their bearing cups to size after welding, but never tried it myself. I just kept smashing the bearings in and never had any issues.

With this current batch of frames I'm still using the same bearing cups I had made 20+ years ago, only now I feel more confident in my ability to do some semi-precision machining when needed. Add to this the fact that the first frame was shipped to prominent engine builder so I started feeling like I should improve my build quality in anticipation of his possible scrutiny. And I just want these frames to be nicer fit and finish than frames I was building 20 years ago.

Having now done the post machining on a few complete frames with out any shop drama, and now that I've depleted my batch of bearing cups, the next batch may very well be made under size per your suggestion.

 

[auntiebling]

desogns and skills evolve for sure, thanks for the answer!

 

[Frame Maker]

Its probably time for another update, so here's more progress on swingarms. With the machined parts done, it was time to prepare the tubing. The process is fairly similar with each piece of tube... rough cut, then bend (or leave straight), and notch the ends.



Started with the main side arms...

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And some check fitting...

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Then moved on the the hoop...

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Next were the diagonal bracing (between the pivot tube and the hoop)...

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The big notch at the pivot side was easy since it is perpendicular to the tubes...

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The smaller notches for the hoop were tricky and required some trial and error to get the location and angle correct. I used a scrap of plate and some square blocks to create a location fixture while I got the notching dialed in. Then created a fixture on the mill so that they could easily be repeated...

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4 sets of diagonals notched at both ends...

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But wait, these still aren't ready...

 

[Frame Maker]

There is a third notch required because of overlap with the main side arms. This required even more trial and error to get it just right. Then paper templates were used to transfer the notch profile to each tube for repeatability. Then more test fitting and fine tuning of each tube for good fitment...

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With all of the tubing cut, notched, and test fit, I could begin tack welding the first swingarm together. Not too fast though. The pivot tubes need to be fully welded since there would be weld joints covered by tubing and the top hoop needed an area welded that would be difficult to get to later in the process...

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Okay, now ready to clean everything including sanding off as much mill scale as possible, then ready to tack weld a swingarm together. Ya, this is a lot of work!

But worth it when it starts coming together arty...

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So why is the swingarm in the fixture and in the back of my truck? Well, as mentioned earlier, this is going to be a mono-shock version of the swinagrm so it will need a bracket designed for the shock linkage to attach to. Easiest way to design the bracket is to model in CAD. Then print to paper and test fit to the swingarm. Since the bracket needs to not only fit to the swinagrm, but also locate to the correct location for the pivot, I would leave the swinagrm in the fixture witch has the locating riser for the pivot location in place.

So the swingarm and fixture come home together and paper templates are made. Again, lots of trial and error to get the fit as close as possible.

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A few days later back in the shop with the tacked together swinarm there are still the little vertical tubes to make. These are pretty straight forward. Rough cut, then notch each end, test fit, repeat...

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Don't forget, each tube needs a vent to the the outside world so that hot air doesn't cause pressure to build up and blow out during welding...

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Finally the first gen2 swingarm tack welded together and looking good. I'm starting to really like how these swingarms are going to look. I also weighed one and its a few pounds lighter than the TZR250 swinarms I've been using. I still need to add the linkage bracket, so might be the same weight when done, but I'm okay with that. Just don't want it to be heavier.

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Next installment I hope to have the linkage bracket installed and maybe get a test fit on the rolling chassis. So stay tuned!

 

[augustiron]

Maybe I missed this elsewhere, but why do you prefer eccentric axle adjustment over linear on your builds (seen it on a a bunch/most of you stuff iirc)?

I understand that it also changes ride height, swingarm angle and rake in addition to just chain tension also, but...
Why?

 

[Maddevill]

If I had half your schmartz I'd be a fartsmeller.

Mad

 

[Frame Maker]

Maybe I missed this elsewhere, but why do you prefer eccentric axle adjustment over linear on your builds (seen it on a a bunch/most of you stuff iirc)?

I understand that it also changes ride height, swingarm angle and rake in addition to just chain tension also, but...
Why?

I guess if this is the only thread you're following it may seam like I prefer eccentric adjusters, but truth is I've only used linear adjusters on all of my previous projects. These are just a few examples...

20171008_182128 by andbike, on Flickr

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Anyway, to your question, I'm always interested in trying new things. When planning this project three years ago I came across this bike and I really liked how the CNC machined adjusters looked so I decided to use that style adjuster with my new project...

DSC_0368 by andbike, on Flickr


I guess it was just an aesthetic choice and simply something I wanted to try. So that's the "why".

I don't really have a good engineering answer. You are correct that eccentric adjusters will have an effect on ride height, although it is very minimal within the normal adjustment range. Further, the eccentrics can be flipped for an intentional ride height (effective SA angle) change if needed.

Thanks for the question

 

[Frame Maker]

If I had half your schmartz I'd be a fartsmeller.

Mad

When I was about 12 years old I figured out how use a microphone with my parent's tape recorder. The first thing I recorded was a commercial I came up with for "bottled farts". So I guess great minds think alikearty

 

[Lonster]

If I had half your schmartz I'd be a fartsmeller.

Mad

When I was about 12 years old I figured out how use a microphone with my parent's tape recorder. The first thing I recorded was a commercial I came up with for "bottled farts". So I guess great minds stink alikearty

FIXED!

 

[Frame Maker]

oh how I love BARF!

 

[kpke]

Thanks for the update Julian. A lot more beautiful fabrication work. I am looking forward to more.

 

[Frame Maker]

Thanks Ken. Glad you're enjoying the updates.

 

[Frame Maker]

- NEWS FLASH -
SPY PHOTOS REVEAL FLORIDA MAN BUILDING CUSTOM FRAMED RZ350!

664132198 by andbike, on Flickr

This is from the shop of Tony Doukas Racing. As mentioned previously, Tony (and team) will be track testing and providing valuable feedback. I always enjoy seeing how someone else approaches building one of my frames. Details coming soon.

 

[IL8APEX]

^^^ That looks like a party I'd like to be invited to! I can't wait to see some action shots. This is the coolest.

-T

 

[bobl]

Always interesting. Thanks for taking the time to post.

 

[motoprotocol]

Holy Smoke!

WOW! By far the best thread I've ever seen. You've got school years worth of knowledge in this post. There's fabrication techniques in here that most people will never attain let alone conceive. I am humbled and honored to be around for this. Your tube mitering skills alone, parallel some of the best builders I've seen. This is some legit work, yo! That Tony Doukas build looks gorgeous, btw.

On a side note, I think I can take your TiG game to the next level. Give me 2 hours and a six pack of Stella, and I'll have anybody with (minimal to advanced) TiG experience laying down rainbow stacks in no time.

Here are some samples of my work. I'm open to doing a small class of 3 or 4 people if anyone is interested (no charge, just beer). All you need is a decent hood and some experience, not much. I'll teach you all the tricks I learned from the experts when I was a journeyman TiG welder. Arc manipulation, rod feed timing, pedal usage and perfect machine set-up to name a few.

 

[Frame Maker]

Adrian, first off thank you for the great compliments. Much appreciated.

As for welding tips, absolutely I'd be up for a few hours of professional tutoring. I have a good friend who I'm sure would also be interested. Although I have to say we might disagree over the beer selection. I have a preference for good Mexican lagers so a six pack of Modelo Especial might be my counteroffer

I'm admittedly a novice, even though I started welding nearly 40 years ago after taking one college class, and that was mostly stick. Aluminum I tried once and never got the hang of it. So all of my aluminum goes to Dennis at Norman Racing. As for steel, I could use some help. Lets make it happen. That would be amazing. arty

 

[RalfL]

Beautiful work you are doing! It's such a shame two-strokes died out. The RZ350 was the only motorcycle I owned when living in the US: one from 1986 to 1990 and the second one from 2000 to 2000. I currently have a 1988 TDR250, which is a lot of fun, but an extra 100 ccs would be nice.