Custom frame design comments/concernces/constructive criticism

9859 Views 66 Replies 10 Participants Last post by sebwiers, Jan 13, 2018

UniHalf

Discussion Starter · Dec 31, 2017

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.

Thoughts/comments/concerns?

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XB33BSA

· #4 · Dec 31, 2017 (Edited)

welcome you are doing it kinda wrong,actually you could not do it more wrong if your instructor in school said "do this the perfect wrong backwarsds doomed to fail way that you can come up with "
building a frame from scratch gives you many good advantages
but just penciling in a structure with nothing else being comsidered is like being the last man on earth with a beautiful fertal woman and then cutting off your dick and balls ,never to save the human race
but it is typical im patience that you have ,put that aside
there is a huge amount of work to do before you design the frame
mayb e you can figure out what must be done first before the frame
you really should know this i speak of

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XB33BSA

· #5 · Dec 31, 2017

if building a motorcycle from scratch as you are the frame is the very last structural hard part to be designed not the first

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XB33BSA

· #6 · Dec 31, 2017 (Edited)

UniHalf said:
Stupid mistake #1 that I've just discovered going over these photos: the rear chassis brace between the rear engine mounts would block me from putting a chain on.

this is a joke right ?good god you are looking at a chain as though it was a rubber band or an average drive belt, for fucks sake
this is what CAD has done to the human race, step away from the fucking cad before it completely lobotomises all creative thought and function

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XB33BSA

· #12 · Dec 31, 2017

UniHalf said:
I'm designing the frame around the engine (Kawasaki Ninja 250R) and suspension I have in mind. So the dimensions came directly from my height and the mounting points on that engine.

The CAD is necessary partially because it just is the standard for mechanical engineering at this point. It'll also let me do FEA on the tensile strength and fluid dynamics of the end product.

Criticise the CAD all you want but I get paid partially to know how to use it so it's still to my benefit.

I have engine, suspension, swingarm, steering, fuel tank, battery mounting points that I'm working with on the design. A few of those still need to be e added. What is it that I'm completely missing here that makes this a bad starting place?

oh so now you tell us you are in possesion of a donor
the plan then is an exact geometry replica ?to cover exact details like woodsman retorts
the frame you show is terrible ok ? for one thing only somebody who knows zero about structural tubing design would use such small diameter trame tubes \
the only practicle app for small dia tubing is in birdcage space frames trellis like deals
do not try anything radical unless you can spend a hundred grand on testing and a frame scrap pile
copy the best frames made for the type of racing you are doing
you absolutely wil;l not build anything viable on your own ,i can see that by looking at the tubes and steering neck i am embarassed for you it is so bad
you do not understand design and are relying on a machine to design for you
the computers do have usefullness in engineering the math

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