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5/6/2019
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Manchester, NH, USA
Edited Date/Time
7/5/2019 10:33pm
Was watching a few Mitch Payton videos about factory sx/mx motors and it got me thinking... What are the odds that factory teams are using titanium for major moving components like the camshaft, crank, etc.? Seems like it would make sense to remove mass from these as long as they can hold up.
Can't imagine how expensive that would be.
Any ideas what crazy materials go into these builds?
Can't imagine how expensive that would be.
Any ideas what crazy materials go into these builds?
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I don't know why the ti crank is a myth, it may just be impossible to balance. Now in a bike a ti crank may work. The ti cam may be just be not worth it because the weight is so small and close to the center of rotation. I assume it ha been tried, so I guess we need to hear from somebody on the inside who has been doing this stuff since the 90's.
In USA I thought (rightly or wrongly) that they must use production cranks and rods?
So, perhaps it is possible to have whatever. But is it practical? Why have titanium this or that and then have to stick a heavier flywheel or counterweight somewhere to make the thing function for a human rider?
Why not polish, fit, debur, coat to make the component(whatever it is) function better?
Rotating mass....I think. Magnesium cases, Ti valve springs, bolts and things like that can be made as light as possible and have nothing to do with the "harmony"(function) of the engine.
Sooner than you know, the challenge will be how to harness high torque/h.p. electric motors for usability. Think about it- 150 h.p. motors. But can a human ride it?
If you want your titanium crankshaft to be as stiff as a steel crankshaft you have to increase the diameter of the shafts by a large amount which is a bad thing for a lot of stuff (overall size, friction, the desired weight savings..).
There are some good reasons why you don't hear about titanium crankshaft.
Titanium cams for a single cylinder engine would probably work. The big problem there would be surface hardness and wear of the lobes.
However, it's intuitive that geometry changes to the crankshaft, cases, and bearings would be made with a Ti crankshaft which would be required when trying to reduce the inertia of the motor.
Basically, anything pre clutch can be heavy and not detrimental, (exception, piston and rod)
The parts you mentioned have there issues using ti, because ti is soft in comparison. for example when making a Ti rod for a 2 stroke you must sleeve the rod for the wrist pin bearing and crank bearing to have a surface hard enough to ride on,
The thing with titanium is that it has a very high specific strength which make it superior to steel in a lot of lightweight applications. But if you look at the specific youngs's modulus, steel and titanium (and aluminium and magnisium fo that matter) are about the same. Steel has a youngs's modulus of 210 GPa at a density of 7.85 g/cm^3 whereas titanium has a yound's modulus of 110 GPa density of 4.5 g/cm^3.
But if you take the geometry into account, it becomes a more complicated. Then you have to take the Young's modulus divided by density squared or cubed into account.
Pit Row
If you want to reduce crank and engine effect (on a motorcycle) you should spin it the opposite direction. My MV Agusta runs backwards and tipping into corners feels like the engine is in N on my other superbikes
https://www.highpowermedia.com/blog/3128/why-not-titanium
Another note: Titanium is approximately 45% lighter than steel. The crankshaft is the heaviest piece in the engine for a reason: torque. Reducing the weight of the crank would change everything about how the engine behaves on a ramp up and down. It would take a host of other changes to make an engine with a TI crank behave in a similar manner to that of a steel crank.
The last WRC motor i was involved with , had a very light bespoke crank, as opposed to the modded road car one, first test was 100 full throttle landings to see it could handle the torque loads.
There is no point to chasing the weight gains of a ti crank or camshaft when easier and less risky areas exist for improvement.
And yes - Ktm factory uses a lot of production parts - if you ever work on a Ktm - they source the best of practically everything, bone stock. I’ve gotten to see some insides of a factory ktm 250f - and it was surprisingly mundane.
Their clutch design can not be lightened or improved - and I’ll bet you the factory bikes run nothing more than a Hinson cover
Now - would I entertain that Honda might be doing something like this - yes. They are 20 lbs too heavy stock, have an insanely deep racing division that is currently motivated to win.
It’s been publicly available from Europe on some titanium rods with some really trick technology in the bearing load areas - the typical problem with ti so let’s just assume since it’s actually a production piece - people use them.
Ti wrist pins I’ve heard too
No way in hell would I run ti valve springs. Never
Ti tranny shafts makes good sense - large part
Ktm already uses aluminum shift drums - super light.
I’d bet the other oems do for racing as well
Ti shift shafts and forks would seem reasonable, but doubtful
Ktm conceivably could do a ti clutch basket, but highly unlikely imho. They don’t need to save the weight.
Honda/kaw/Rm using a ti clutch basket gear - would save a ton of weight
Ti counter balancer shafts - sure
I don’t care for ceramic bearings but you can save weight there
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