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Custom frame design comments/concernces/constructive criticism

9851 Views 66 Replies 10 Participants Last post by  sebwiers
Alright, y'all. Not sure if this belongs here or in technical, but I'm assuming this is okay.

I've got an ambitious project in the works currently. I'm a Mechanical Engineering major in my junior year at Ohio State. I've done a lot with suspension and carbon fiber molding with the Formula SAE team there so I'm not entirely out of my depth here, but we'll see how it goes. I've got an internship in Pennsylvania so over the next 8 months I'm going to start designing and building a motorcycle. First step is drawing up a 3D model of the frame. I'm posting the first draft of the design here because you all have way more experience building/modifying bikes than I do. I'm curious to get your opinions.

Does my design have any glaring errors that I'm missing? What could I improve here? Be harsh if you want, I want to make my design as good as possible. I'm mostly going to be setting it up for road racing/street driving. Good handling and feel is one of my top priorities here.

Diagram Technical drawing Design Drawing Plan

This is my recent iteration.

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Better yet, sportbiketracktime has dates in June to go to autobahn racetrack. I’m already signed up.

Want to come?
What exactly? Well, you were the one talking about meeting the standards of cafe racers, so I kind of figured there would be a cafe and maybe jukebox and road involved...

I have no illusion re power / weight ratio vs a modern sportbike (or even a retro where that was a goal). Commercial construction and modern water cooled engine design are amazingly good, and it began life as a flipping parts bin designed SHAFT DRIVE bike. But again, you compared vs cafe racers. Those don't usually have plastics or water cooling (or efi or ABS or traction control). Maybe you have something appropriately vintage?

I dunno about dragging knee, but it's pretty easy to get the pegs or exhaust to touch the ground - its not like it lost the ability to lean because I built a heavy front end with steep rake. If you're paying for track time, I'd be happy to get laughed at. Assuming tech allows it on in the first place (damn unlikely, but who knows).
I might have some 'just for fun" vids from indoor flat track and / or ice track in a couple months... I'll see what I can do about that knee for yah. ;)

But again, out of respect to OP, maybe better to put such things in a different thread. My intro one is fine by me, it's a designated hater target anyhow.
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I’m not the one that brought up your bike in this thread. Remember that.

I built and rode this at the track last year. It did fine... and it was shit slow compared to real bikes
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Honestly though I don’t think the OP will have an update for a while.
These posts just keep bumping his thread up to the top.
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Hopefully OP is moving forward. Wasn't my intent to bring up my bike, just my experience as a unschooled builder. In my case, progress was VERY slow, but eventually ended at something rideable. I think somebody in school for engineering can do the same or better. I've seen full time students go much, much faster, with better fabrication to boot. God speed, OP!
I'd say anyone with perseverance, willingness to do research, moderate financing and tool access, and basic design / construction skills CAN do it.
Well, yeah, with enough qualifiers "anyone" can do it.

No offense but grafting a front end/monoshock on an existing frame is not the same as designing/building a frame, but none of that was the point of my post anyway. The point was, saying "anyone can do it" is dismissive of what it takes to do and anyone who has never attempted to do it likely has no realistic concept of what it takes to do it.

I really haven't paid attention to the thread on your 750 so can't say much. Sounds like you did get farther than me but "crude, unaesthetic and heavy" doesn't sound much like a track bike, so it would appear our goals were significantly different. FWIW my dad was part of the construction plan, and the project died when he did. That was 20 years ago and the frame building bug still hasn't returned.
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Fair enough; the qualifiers are what separates people who can (and might still fail) from "anyone". Sure, there's a lot of people who assume its easy (per Dunning Kruger). Hopefully they aren't in engineering school.

And yes, my project has different goals from a track bike. The load demands placed on a track bike and drive so save weight certainly do further limit cases where building one would be a good idea, requiring both more design refinement and demanding more fabrication skill (or lowering the margin for errors in both). I may have missed the OP's intent to build a track bike and assumed the goal was a "cafe racer" in the common sense of a street machine with moderately decent (by modern standards) performance and ergonomics that allow spirited riding.

Sorry about your dad, there's certainly a lot of reasons to set projects aside beyond impatience / technical challenges. In fact, I'd say that is almost the larger challenge (if you don't set the technical bar at competetive levels) - simply not having life get in the way.
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