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Discussion Starter #8
Yep, it's for my XT500 engine.

Needs a lot of machining yet, I can do some at work where I have
access to both CNC mill and lathe, whereas shotpeening and perhaps
grinding or lapping of the bigend bearing race will have to be done
by another workshop.
I'm not yet sure whether to chose I-beam (easier to machine) or H-beam
(smoother transfer of forces from ends to shaft) design, but there's
enough of the sheet left to cut another core...

Best regards
Sven
 

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Discussion Starter #9
Yep, it's for my XT500 engine.

Needs a lot of machining yet, I can do some at work where I have
access to both CNC mill and lathe, whereas shotpeening and perhaps
grinding or lapping of the bigend bearing race will have to be done
by another workshop.
I'm not yet sure whether to chose I-beam (easier to machine) or H-beam
(smoother transfer of forces from ends to shaft) design, but there's
enough of the sheet left to cut another core...

Best regards
Sven
 

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forgive my ignorance.....but what is the advantage of titanium?

before you say stronger and lighter (the no brainer answer), let me rephrase it - I know steel con rods are preferred because of the ductile properties of steel, and aluminum rods, though lighter, are less prefferable for an engine that changes direction a lot (like a street engine vs a race engine) due to their propensity to crack, so why titanium that is both less ductile than steel and aluminum?
 

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forgive my ignorance.....but what is the advantage of titanium?

before you say stronger and lighter (the no brainer answer), let me rephrase it - I know steel con rods are preferred because of the ductile properties of steel, and aluminum rods, though lighter, are less prefferable for an engine that changes direction a lot (like a street engine vs a race engine) due to their propensity to crack, so why titanium that is both less ductile than steel and aluminum?
 

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Discussion Starter #12
Good question...

from a technical view, titanium has two very favorable properties
that qualify it as material for dynamically stressed workpieces:
first of all the high strength:density ratio that allows the rod
to be lighter than one made of steel, secondly its superior fatigue
resistance compared to aluminum. Drawback is a low coefficient of
elasticity that requires high webbed big and smallend to keep them
round.

But that's not why I started this project. I had this sheet lying
around in my workshop for years and the rod inside screamed: "Get
me out of here!"

Best regards
Sven
 

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Discussion Starter #13
Good question...

from a technical view, titanium has two very favorable properties
that qualify it as material for dynamically stressed workpieces:
first of all the high strength:density ratio that allows the rod
to be lighter than one made of steel, secondly its superior fatigue
resistance compared to aluminum. Drawback is a low coefficient of
elasticity that requires high webbed big and smallend to keep them
round.

But that's not why I started this project. I had this sheet lying
around in my workshop for years and the rod inside screamed: "Get
me out of here!"

Best regards
Sven
 

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quote:Originally posted by sven

Good question...

from a technical view, titanium has two very favorable properties
that qualify it as material for dynamically stressed workpieces:
first of all the high strength:density ratio that allows the rod
to be lighter than one made of steel, secondly its superior fatigue
resistance compared to aluminum. Drawback is a low coefficient of
elasticity that requires high webbed big and smallend to keep them
round.

But that's not why I started this project. I had this sheet lying
around in my workshop for years and the rod inside screamed: "Get
me out of here!"

Best regards
Sven
in a motorcycle engine are the forces great enough to actually round out the big end on a Ti con rod?

didn't know about the fatigue...good to know.
 

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quote:Originally posted by sven

Good question...

from a technical view, titanium has two very favorable properties
that qualify it as material for dynamically stressed workpieces:
first of all the high strength:density ratio that allows the rod
to be lighter than one made of steel, secondly its superior fatigue
resistance compared to aluminum. Drawback is a low coefficient of
elasticity that requires high webbed big and smallend to keep them
round.

But that's not why I started this project. I had this sheet lying
around in my workshop for years and the rod inside screamed: "Get
me out of here!"

Best regards
Sven
in a motorcycle engine are the forces great enough to actually round out the big end on a Ti con rod?

didn't know about the fatigue...good to know.
 

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stupid question #2: what's the flareout on a machine that has enough strength to cut Ti with just a jet of water? I have to imagine you are in the 10s of thousands in terms of pressure....how far off is the backside from the front side?
 

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stupid question #2: what's the flareout on a machine that has enough strength to cut Ti with just a jet of water? I have to imagine you are in the 10s of thousands in terms of pressure....how far off is the backside from the front side?
 

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Cool. I think an I-beam is a better design from an engineering standpoint. What are you going to use to between the rod/crank sides? Maybe leave the outer bearing race wider than the rod?
 

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Cool. I think an I-beam is a better design from an engineering standpoint. What are you going to use to between the rod/crank sides? Maybe leave the outer bearing race wider than the rod?
 

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Discussion Starter #20
quote:Originally posted by Geeto67
in a motorcycle engine are the forces great enough to actually round out the big end on a Ti con rod?
An XT500 piston is about 1lb, revving 8000rpm causes some 4000g
acceleration to it at tdc, i.e some 1.8kN inertia force is created
("the piston pulls with almost 2 tons"). Everything flexes, titanium
more than steel, so both big- and smallend tend to ovalize under this
load which may cause trouble in terms of seized wrist pin or bigend
bearing. Webs help to minimize this deformation without adding too
much weight.

quote:didn't know about the fatigue...good to know.
Yep, in this regard Ti6Al4V behaves similar as a good tempering steel.

quote: what's the flareout on a machine that has enough strength to cut Ti with just a jet of water? I have to imagine you are in the 10s of thousands in terms of pressure....how far off is the backside from the front side?
Though this machine works with some 3000bar (over 40,000psi) and a
.014 jet, water alone can only be used to cut soft materials as steaks
(no joke, afaik waterjetting has its origins in the food industry),
rubber or plasics. To cut metal an abrasive similar to the one being
used for sandblastig must be added.
The machine itself looks like a swimming pool with a steel grate at
the surface of the water where the workpiece is put on. A kind of
beam hoist carries the jet, which is put down close to the upper
surface of the workpiece and then driven with little feed (depends
on what is being cut of course, we had some 2inches per minute) along
the contour. Doesn't sound much different than a high pressure washer.

Best regards
Sven
 
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