GT380 ground up build

themotoworks said:
got some sketches back from Jeremy, I am really liking the concept, can't wait to finish the mechanical part of the build and start fabricating the pretty stuff.


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I love the sketches. What are you going to do about the exhaust?
 
the expansion chambers I designed will probably be a bit longer, but the exhaust isn't the first thing my eye goes to, so I feel like changing from the pictured design in that area won't alter the overall design much
 
Those sketches look great - I love the look of that front fairing, and the lines make the bike look like it's doing the ton standing still. Very nice!
 
Just curious, as the pictured exhaust looks like something off a new FZ07 or something. The chambers on a triple can be one of the coolest aspects of these builds.
 
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finished the head tube and bearing cups, total pain in the butt, had to machine, weld, then finish machine to make sure welding didn't warp the bearing holders (it does way more than you'd think!), but they came out round and .0005" under bearing OD, the bearings went in with a small hammer and aluminum drift, nice and snug but not too tight. going to set up the engine and a way to clamp my mount plates to the frame jig, then start finishing the frame, probably another day on it
 
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almost done with the frame, you can see where it attaches to the aluminum subframes at the rear, also a pic of my cutting setup, does real nice work, if I design a frame in SW I can notch all the tubes within a few thousandths, putting the frame together leaves no gaps to fill, a bit time consuming to get all the data from the computer, but definitely worth it
 
Could you elaborate on your thinking regarding the decision to create the aluminum brackets? I realize there is a lot going on in this area, and can see machining the aluminum potentially being simpler than creating a steel fabrication, but don't reckon there to be weight savings. This wouldn't be my preferred location for a bolted connection, but as you have obviously put a great deal of thought into your choices it would be helpful to hear how you arrived at some of them. Lovely work all around! I also am a big proponent of building a virtual model and creating parts directly from it - excellent fitting parts become a function of layout skill!
 
it had a lot to do with aligning the engine, swingarm, shock linkage and steel frame with less work than trying to do the same with a weldment, with a weldment I'd be looking at multiple jigs and probably finish machining of the welded assembly to guarantee alignment of the components, this saved all that work and might actually be a bit lighter than the steel spiderweb that would be the result otherwise, the plates are actually pretty light
 
Bimota frequently used steel trellis with aluminum swinger plates. The MV augusta Brutale's have this construction as well.
 
yeah, oil in the cross tube and gas in the main tube, it adds another .75 gallons, so the fuel cell under the bodywork can be smaller
 
Very nice. Reminiscent of the EGLI frames
 
finished machining the axles for the swingarm, they do double duty and hold the rearsets as well, thus the smaller outrigger bearings, most of the rearset force winds up on those bearings and the rearset hanger is kept from rotating by a screw going into the rear aluminum plates... kinda involved but when it's all laid out well it goes together pretty easy, also finished the rear rocker, still waiting on getting the rocker bearings in but they should be here tomorrow and I can start putting the rear end together, will start machining swingarm parts today too


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That is going to be a slick set up - hope you will provide a thorough description of how all the bits are fixed in place. Tapered rollers are pretty unusual for a swing arm pivot, though I have often thought of doing this myself as it would seem the optimal means to eliminate lost motion in this very important pivot. Love the rollers for the foot controls, I have built rear sets doing this very thing (though not coincident with or part of the swing arm axle) and never fail to be pleased with the still perfect and zero play precision motion after many years of use! Lovely old school fab work on the rocker as well - after seeing the aluminum frame plates I expected you would carve up another block for this part. I personally am partial to the "built by hand" look of fabrications like this which seem to becoming scarce with so much CNC work being so prevalent - nice!
 
I think I might actually switch back to ball bearings, having the swingarm mounted the way it is due to the engine mounts being waaay off to one side made things very complicated and the sealing system for the thrust bearings is probably going to fail in service, ball bearings are way simpler and still handle the anticipated loading, but with less margin than the tapered ones, but if the thrust bearings leak grease and pick up road grit asap, then that's no good either... good thing there's mcmaster, swapping to ball bearings is just a day away. love those guys
 
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got some more sketches, the design is getting a lot closer to 100% done, starting to convert the bodywork to actual shapes now, kinda interesting working from an artists renderings and to figure out how to make an actual shape that conforms to what the various views are showing...
 
Going to be a good looking motorcycle. As I think someone else mentioned, don't underestimate the exhaust - it will take up a very large piece if visual real estate not present in the renderings!
 
Perhaps I missed the discussion, but have you decided upon material and construction method for the bodywork?
As jp said, pretty bike. The rendered muffler placement really fits aesthetically, but seems impossible packaging for a two stroke no?

Good stuff in any event.
 
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lots more stuff done, basically a rolling chassis now, just need to grab some hardware for the rear linkage setup, still waiting on an ohlins shock so I grabbed a used on on ebay for fitup. going to get the pegs and bars on in the next day or two
 
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