Ducati goes all technical.....

[CYCLE_MONKEY]

http://blog.cycleworld.com/?p=2080

While this is a great technology for crankcases, tailsection supports and brackets that are typically die-cast anyways, I definately do NOT like the trend of the big 4 using die-cast frames like they do now. I cast anything, strength being equal, will ALWAYS be heavier than a comparable formed (sheetmetal) or machined part. My '01 is lighter than the newer Gixxers, and most likely stronger too. Why? Because my frame and swingarm are made of sheetmetal and tubing, both formed items. The reason they're going this way is they can make more complicated parts easier and cheaper (fewer welds), not because they're better. You won't see any die-cast frames or swingarms on a MotoGP bike for a reason.

[brennahm]

Before I start - Frank, we all know you were in design for DOD for 15 years.

You talk about strength...what do you mean? The advantages they're gaining from cast parts are vast. First, yes, it is easier/cheaper to do mass production in a cast system. Secondly, you're able to tune the frame to a much higher degree than is possible with other manu methods. By this I mean that lateral stiffness, steering stem flex, torsional rigidity can all be affected much easier than with sheetmetal. And machined parts? You really want to pay for a billet frame? All in all, I doubt your 01 is "stronger" and definitely not where it counts.

The newer bikes hit a wall in the mid 2000's and began increasing in weight due NOT to the frame, but emissions equipment and things like that.

The reason you don't see cast frames in MotoGP is because die casting is only economically feasible on a mass production scale. This would be unnecessarily expensive for the teams. Sand casting and machining are much more economical because they only need one or two parts. Not 5-10 thousand.

It really would be interesting though to weigh some frames. Say Gixxer 1k frames through all iterations. I'm nearly positive however they are lighter and stronger as suspension and tire technology advances.

[Cap'n Crunch]

I don't know as much about mfg. processes as you guys, but hopefully Ducati doesn't start using this process to make beam type frames for their bikes, like the Big 4. I've always liked the trellis type frame that they use - kinda unique to Ducati these days.

[brennahm]

I doubt they will. The article only mentions its use for things that Frank mentioned like subframes or engine casings.

I actually spoke with a Ducati engineer on a plane once, and by his tone the narrowness of their bikes is a major source of pride. A lot of that comes from the steel trellis frame and is, for all intents and purposes, not something they can obtain with a cast frame. I'm with you, I like companies having identities and sticking to them as long as it doesn't hold them back.

[cbrjohnny]

i should check the author of these post b4 i read them lmao

[CYCLE_MONKEY]

i should check the author of these post b4 i read them lmao

It's obvious that you have absolutely zero capability for contributing anything technically worthwile, so it's good you're going to keep your mouth shut.

[MetaLord 9]

It's obvious that you have absolutely zero capability for contributing anything [SNIP] worthwile, so it's good you're going to keep your mouth shut.

If everyone did that, this forum would just be Dirk talking to himself...

[CYCLE_MONKEY]

Before I start - Frank, we all know you were in design for DOD for 15 years.

You talk about strength...what do you mean? The advantages they're gaining from cast parts are vast. First, yes, it is easier/cheaper to do mass production in a cast system. Secondly, you're able to tune the frame to a much higher degree than is possible with other manu methods. By this I mean that lateral stiffness, steering stem flex, torsional rigidity can all be affected much easier than with sheetmetal. And machined parts? You really want to pay for a billet frame? All in all, I doubt your 01 is "stronger" and definitely not where it counts.

The newer bikes hit a wall in the mid 2000's and began increasing in weight due NOT to the frame, but emissions equipment and things like that.

The reason you don't see cast frames in MotoGP is because die casting is only economically feasible on a mass production scale. This would be unnecessarily expensive for the teams. Sand casting and machining are much more economical because they only need one or two parts. Not 5-10 thousand.

It really would be interesting though to weigh some frames. Say Gixxer 1k frames through all iterations. I'm nearly positive however they are lighter and stronger as suspension and tire technology advances.

I've also DONE die-casting research and design, as well as a lot of IM plastic parts.

True, you can add some ribs etc, and true the mass production issue although die-casting might not be cost-effective for 5-10k in that size and complexity, I think there's more made than that, but MotoGP frames are billet and sheetmetal for a reason I'd say. Also, the only things I've ever seen cast on a MotoGP bike are the engine cases, if that. Also, it's easier to weld a gusset on for strength quickly rather than having modify a $100k+ die for each side. I know we and the aircraft industry generally uses forgings or machinings rather than castings, and it's for the strength/pound reason. When I was at NASA, we'd machine a 200lb block of Al just to get a 20lb part. Regardless, the material properties of die-castings, even vacuum die-castings, are far lower than wrought materials, partially due to the voids and porousity, partially due to the working of the material, but also in large part due to the grain structure. I've seen bikes with sheetmetal frames take a serious wreck, and be straightened out without major issue. I've seen a minor wreck on an R1 with a cast frame where the entire steering head just snapped off, and you could tell it was due to the material. We for instance used extrusions for an aircraft control unit that had to be extremely light yet take insane heat and vibration. The PE I worked for, a BRILLIANT guy, was adamant that a die-casting would not work, and I believe him because I saw how good he was and how he did FEA and physical testing on EVERYTHING.

[CYCLE_MONKEY]

If everyone did that, this forum would just be Dirk talking to himself...

Hah!

.....but....what if Dirk already talks to himself?

[CYCLE_MONKEY]

Ok, imagine a frame where the swingarm plates and headstock are machined billet, with extruded tubes connecting them either by welding or fasteners. Then fill the tubes with foamed aluminum. Bird bones particularly (or any bones) are extremely stong per weight. You have a thin strong outer shell to support/resist/absorb the majority of the load and prevent crushing damage to the foam, and a light airy structure inside to prevent buckling. If they could start doing this economically, you'd have an extremely light and strong frame.

http://en.wikipedia.org/wiki/Metal_foam

http://www.isotechinc.com/foamed-aluminum.html

http://www.ergaerospace.com/foamprop...properties.htm



Or, perhaps they could use vacuum die-castings, the use the HIP (Hot Isostatic Pressing) process to reduce porosity, improve grain structure, and otherwise improve the mechanical properties of the castings.

http://en.wikipedia.org/wiki/Hot_isostatic_pressing

http://www.pressuretechnology.com/ho...c_pressing.htm

Of note, besides the MotoGP bikes, almost all of the old Bimotas had billet and extruded frames, and they were usually a lot lighter that the stock bikes from which they were based. Also, the new aprilia has a sheetmetal frame and swingarm.

One of the issues about Ducati frames, is that with that many welds, it seems like there could be a pretty drastic variation in stiffness from frame to frame, or even side to side of the same frame depending on who welded each one, the differences in the effective throat (size) of the welds, the penetration and preparation, etc.