Sure do but in order to work harden aluminum you need to stress the material beyond elastic limits..


http://www.totalmateria.com/page.asp...ite=ktn&NM=163


The original statements was that any stress/ strain would eventually cause the part to fail.

 

 

I agree but what I was actually referring to was the more load bearing members of the airframe like the wing box and the main spar, longerons etc. If they can make those things as strong as they do, and able to take repetitive stress like they do then engineers should be able to make a safe motorcycle frame out of aluminum.

I think I'd still prefer steel though...

Its funny because the bicycle industry has already been through this very argument. I still ride an Italian made steel road bike but the racers moved on to aluminum in the 70s and then onto carbon fiber in the 90s. Of course there are still teams out there using aluminum but most of them went to carbon.

And the aircraft industry is moving towards carbon fiber. Boeing's latest planes are mostly carbon fiber and an Italian manufacturer has already made an entirely carbon fiber light cargo plane.

The materials argument is persistent... aluminum bends and breaks easier than steel, carbon fiber gives no warning and just shatters when it gives way, etc. etc etc.

There are motorcycles out there with aluminum frames that are doing just fine. Heck, there are motorcycles out there where the engine block is a structural member of the frame and they're doing just fine. There are even some exotics out there with carbon fiber frames. I really have no idea how well they're holding up.

I think if the MoCo wanted to make an aluminum framed bike they could do it safely. Their main problem would be selling it. The main Harley buyer like me kinda likes vtwin engines and steel frames.

 

Here's a wikipedia article explaining the aluminum fatigue issue:
https://en.wikipedia.org/wiki/Deform...#Metal_fatigue

Most comments regarding aluminum fatigue are correct to some extent. It is true that the conventional view of metal stress is that if you kept the stress within the range of "elastic deformation", where the metal will return to it's original shape when the stress is removed, then there is no wear. Stress a metal beyond that into "plastic deformation" and it will not be able to return to it's original shape and will fail (break) in a certain number of cycles. So, aircraft were design to never be stressed beyond elastic deformation. HOWEVER, when planes started experiencing parts flying off them, engineers realized this view was incomplete and with enough cycles, even staying within elastic deformation can fatigue metal and cause failure. Hence, stringent aircraft inspections even for planes that don't exceed the flight parameters.

FYI I'm an engineer and took materials science at Kansas State, but I think I only learned the conventional view there and found out about elastic fatigue subsequently.

 

Which comments? The one that aluminum will fail under any stress? One thing to note is that it applies to all ductile materials so it's not any different than different ductile steels. There are no special properties that aluminum had that making it worse.. The link simply states that any ductile material can fail even if the stress/strain is not in the plastic ranges.

 

auto manufactures have been doing it for a while of course for more profits thru standardization + of course we would like a lighter bike but anything that costs HD money is slow to come!

 

The frame was the first thing Harley changed, in 2009. They just finished changing with the new engine.

 

I was getting excited about a new frames and all that until you started bringing the Sporty into the mix. Now you've gone to far!
lol
Seriously, you can save 10 lbs by removing the passenger pegs on this pigs! What the heck.

 

Sorry, i just scoff at the claims that the weight is beneficial in winds. I came from twenty years of BMW where even myself combined with my motorcycle (K1300GTs, R1200RTs, and others) didn't add up to weight of my Road King. Never had a lick of issue with side winds or what not except when I got silly and tried to ride into a hurricane headed for Florida.

As for fitting the M8, why does it have to retain the same CC when expanding across the line? Regardless of that a new frame that is lighter can be done stronger as well all without messing up the styling. If anything I really was hoping HD would be serious about Ducati because they might learn how to make an engine that is lighter weight.

I am mostly curious about two possibilities, first being what did they trademark Sport Glide for and will they improve their Boom audio to the point it natively supports BT headsets. Drop a hundred pounds of the RGU and I would be hard pressed to not trade up

 

they don't have to retain the engine sizes across the lines but historically they have. I imagine it simplifies their manufacturing process quite a bit. Especially since they do their big twin manufacturing in one plant and then ship engines out to two different manufacturing plants in the US and a couple overseas (I've read that some, but not all, of the overseas plants get their engines from US plant).

Also, I really doubt you're going to see a sub-800 pound RGU anytime soon. The M8 has added weight to the touring line as compared to the twin cam.