Custom frame design comments/concernces/constructive criticism

What has changed in the last 20 years really depends on the motorcycle brand that is being considered, BMW for example is doing really well in racing right now but their current hot bike is worlds away from the bikes BMW built in 1989 up to ~2004. The Foale book series was most recently updated in 2006 so I would expect that most recent version to potentially contain considerably more current info.
lol Ya we are getting old and the older you get the faster time fly's, the give away should be "book" printed paper is near obsolete because information changes faster then it can be printed and bound into books. UniHalf needs to be designing innovative motorcycles for the future for his efforts to be worth anything, otherwise he is just re-inventing the wheel and anybody can do that.

... not to suggest that lots of people aren't getting rich by re-inventing old technology or copying other peoples iPhone, but it's the innovators that are in demand and remembered for their contributions to advancement.

TrialsRider said:

...the give away should be "book" printed paper is near obsolete because information changes faster then it can be printed and bound into books. UniHalf needs to be designing innovative motorcycles for the future for his efforts to be worth anything, otherwise he is just re-inventing the wheel and anybody can do that.

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I SO hope you're kidding, I disagree with this hugely bigly. You've got to walk before you can run and the basics have not become obsolete over the past 20 years. Suspension linkages, spring rates, center of mass, ergonomics, etc. The desired numbers or methods may change but the math is still the same math. A guy who learned how to design a rising rate suspension linkage 20 years ago can still discuss it with the guy who's developing it for his 2018 superbike. Put a 1997 CBR600 next to a 2017 CBR600. Show me the innovations on the 2017 that made the '97 obsolete. Evolution is the rule, not innovation.

Name 3 innovations in motorcycling over the past 20 years that weren't made possible because of electronics. Innovations do not mean things like non telescopic front ends that two companies used for five minutes in the '90s. I mean things that changed the landscape and made previous knowledge obsolete. Which of those 3 has the most impact on a college student building his first frame?

Anyone can do it? Who are the other guys here building frames or that have built frames? If anyone can do it why hasn't anyone here done it? I have a degree in aerospace engineering, I've worked on OEM prototype motorcycles, I was a development engineer for about 30 years in the auto industry, I bought all the books, got the donor bike, had access to pretty much any tool I would need and people with the answers to questions I didn't even know enough to ask yet, and I still never did more than modify a frame and even that was on a bike I will likely never finish. Not anyone can do it, and IMHO a large number of people who think they can likely couldn't. Many have no concept of how much they don't know so it sounds a lot easier than it is.

The PO isn't starting a new motorcycle business. He's not selling anything. He's learning about building bikes. 9.5 of 10 threads here are some kid trying to figure out how to superglue a hockey puck to the bottom of Benelli tank to make it fit his CBwhatever frame. Finally a new guy is trying to learn how to actually build something. It doesn't need to qualify on the front row at any racetrack or make rear swingarms obsolete to be worthwhile.

And for my next trick I'll rant about how "innovation" is nothing more than a buzz word for the major companies, and how the development processes they set up make innovation difficult rather than support it. They don't want to hire innovators. They want to hire newbies they can mold into little minions and will reluctantly invest in innovative technology only when forced into it. Innovators are on their own until they have a marketable product.

DesmoDog said:

Anyone can do it? Who are the other guys here building frames or that have built frames? If anyone can do it why hasn't anyone here done it? I have a degree in aerospace engineering, I've worked on OEM prototype motorcycles, I was a development engineer for about 30 years in the auto industry, I bought all the books, got the donor bike, had access to pretty much any tool I would need and people with the answers to questions I didn't even know enough to ask yet, and I still never did more than modify a frame and even that was on a bike I will likely never finish. Not anyone can do it, and IMHO a large number of people who think they can likely couldn't. Many have no concept of how much they don't know so it sounds a lot easier than it is.

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I'd say anyone with perseverance, willingness to do research, moderate financing and tool access, and basic design / construction skills CAN do it.

I grafted a Hossack front and monoshock rear on a cheap old shaft drive (XJ750 Seca). Its admittedly crude (un-aesthetic and heavy) work, but its now finished an ridable (even well suspended thanks to software help) with over 300 road (not track) miles on it. Would have more, but I finished it in September, then blew and engine, bought put another one in by Thanksgiving, and did short rides until the snow hit. Sounds like I got a bit farther along than you did?

My entire engineering and fabrication background can be summed up as "art school dropout and bicycle mechanic". That maybe gave me just barely enough of a head start (like some crude welding practice) to have a concept of where to do research to find out how much I did not know.

If I can do it, any engineering student worth the name surely can, and most gear heads. Without previous experience, my progress was probably slower and less refined, but I have a decent assurance that it is safe based on actual physical load testing with a stress jig. I'd say that last bit is really the one thing I see most people ignoring; they lack both the knowledge to determine strength theoretically, and the will to establish it empirically (and accept that this will likely give sub optimal construction, or outright destroy the results of your work).

So yeah, anybody (for certain values of any) CAN do it. Most don't. There's some benefit in doing it, because when you re-invent the wheel, you then see a bot of how the wheel was invented.

Back to the original question, as I'm late to this thread....

As many pointed out, the sketches on the first page look quite dated. Unless you are intentionally building a period style item, go back to first principles. You are an engineering student, you know a couple of parallel loops of pipe are not going to result in a good stiffness / weight ratio, right?

One stiff way to connect head tube to swing arm is with 4 bars, making the set of elements an elongated tetraheadron (on edge being the head tube, one the swingarm, the other 4 the bars connecting them). This tends to be awkward from an engine packaging perspective, so you end up bending and then re-triangulating.

Another is with a single fat tube, either a large diameter spine the engine hangs from (maybe filled with fuel) or a moncoque construction everything goes inside of.

Material wise, I'd say plain steel tube (1" or 1.25" x 16g should be more than enough) is fine if your welding is decent. Chromo is stronger, but it is NOT stiffer, and your primary design goal is stiffness. If you go boom tube or monocoque, things change a bit, and maybe CNC cut aluminum becomes attractive (that also can maybe do for a space frame / triangulated structure). Hell, people have built some nice bikes from PLYWOOD - high quality wood is actually not to far off good quality composites.

Personal taste, but I'd look at doing a Hossack construction, since it makes it much easier to have variable wheelbase, rake, and trail (and change just one while keeping the others constant) as well as allowing much more suspension setup (shock positions / linkages) without much increase in cost. Its does mean more work, of course - maybe nearly as double the fabrication compared to just grabbing some commercial telefork.

sebwiers said:

I'm gonna be riding in Milwaukee in late June. Actually in late February as well, but that seems an unfair challenge.

Chicago isn't that much farther. Pick a road. Preferably one with lots of curves and bumps.

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And do what exactly?

My track bike should be back together by then. Just waiting on new plastics and adjustable rake triple trees. Maybe you think you could run rings around a 380 pound gsxr750 supersport around “curves and bumps.”

C’mon.

But, I would not mind reading a ride report if you make it up this way. Listen, kudos to you for building what you did. And props if it can take you on a 500 mile ride. I’m impressed.

But don’t for a second think performance and what you built can be mentioned in the same sentence.

Hit me up in June. I’m just giggling thinking about you trying to drag a knee on that thing.