Alternative metals

[element180]

Ok so maybe I have no idea what I'm talking about (which is probably true ) but I had an idea.Is there anyway a cam and crank made out of titanium would stand up to the abuse steel cams and cranks live with?I was told...I don't know if it's true or not thought...that the surface hardness of titanium is greater than steel but what about the torsional strength?Is any of this even possible?Obviously cost would be a major factor but if it were'nt...would a titanium cam and crank survive the environment of an internal combustion engine???

[rocketman]

titanium rods have been used along time in the racing world.but the problem with titanium rods is they stretch.i had a circle track motor with them and every 500 laps they have to be replaced,so they dont have great lifespan.i billet core cam is the best choice for a cam,plus the cost to build a titanium motor would be outragious.in racing were engine parts are replaced offen the titanium would prolly work,but not the street.

[DB Z28]

Why do they have them in the New LS-7 427. It turns 7000rpm?

[Blown353]

Speaking of alternate engine materials, if you have about 5K laying around I can hook you up with a good deal on some beryllium pushrods...

Remember, titanium has rather poor frictional properties and is very prone to galling. Structurally it's a great material (if you treat it properly) but using it a application where it is subject to frictional/sliding movement (i.e. a camshaft) is usually a bad idea. Surface treatments and special lubes usually only postpone the inevitable.

I am not aware of any cam or crank being done in Ti for just that reason. Doesn't mean they haven't been experimented with though.

There are some other goodies too being played with that I've dinked with at a friends shop... beryllium, Albemet (aluminum/beryllium), aluminum-lithium, both Al and Ti MMC (metal matrix composites), ceramic lifters, etc. There's a lot of cool stuff to play with when you have deep pockets. Some of it lives, some doesn't, and now that they have enacted composition requirements and minimum component weight requirements in the class he runs he can't run a lot of the uber-exotic stuff anymore. Makes it cheaper, that's for sure!

titanium rods have been used along time in the racing world.but the problem with titanium rods is they stretch.i had a circle track motor with them and every 500 laps they have to be replaced,so they dont have great lifespan.i billet core cam is the best choice for a cam,plus the cost to build a titanium motor would be outragious.in racing were engine parts are replaced offen the titanium would prolly work,but not the street.

Ti rods stretching? Are you sure you don't mean aluminum rods? Titanium is pretty darn good when it comes to high temperature creep properties (try gas turbine applications, both structural and usually compressor section blades) and I can't see having to replace Ti rods every 500 laps. Aluminum rods most definately have a very short service life, but I'm not aware of any service life limitations on Ti rods.

[rohrt]

http://www.schubeckracing.com/index2.html
had to throw this in.

[rocketman]

Ti rods stretching? Are you sure you don't mean aluminum rods? Titanium is pretty darn good when it comes to high temperature creep properties (try gas turbine applications, both structural and usually compressor section blades) and I can't see having to replace Ti rods every 500 laps. Aluminum rods most definately have a very short service life, but I'm not aware of any service life limitations on Ti rods.[/quote]

yeah they stretch,they are awesome lite but in stock car racing,i found they last 500 laps,which is what they recommend changing.

i know ls-7 have them,i am waiting to see what happens in these motors have they get some in the service center,with rod slap.

[rocketman]

Why do they have them in the New LS-7 427. It turns 7000rpm?

i hopin they work good.i no the previous exp,i have wouldnt have put them in a street motor.and i have one of the crate engines going in a street rod.

[ProStreet R/T]

I'll 2nd what 353 said, in an application where there will be constant repetative friction titanium could be the very worst material to use. It will never be seen in a cam, lifters, crank, gears, etc.

As for rods it would be fine, and it actually acts very similar to steel in regards to flex/stretch. There wouldn't be any problems with it at all, other than the massive expense.

My main question is why bother? You aren't going to lose much weight with a ti cam over a standard gun drilled 55mm roller.

Same with a crank

[element180]

Hmm.Found this bit of info

When properly done,a titanium rod can be as strong as it's steel counterpart (assuming one's using the correct steel alloy) and do to the nature of titanium,they tend to be a little easier on bearings than steel rods.

I believe that an honest engine builder should be the one to determine if the use of these expensive rods is necessary or not.

The young in this country will buy anything if it's hi tech (carbon,titanium,computer generated,etc.),so don't fall victom to excessive engineering and sales hype.In most instances,running titanium rods is a total waste of money,and once they're installed,you can't even show then to your friends!Compared to good steel,good Ti is 90%-95% as strong in normal stress with a fatigure limit that is 100%-110%,while being 40% lighter.It stretches twice as much.At higher temperatures it is far stronger than any regular steel and below ~2000 degrees is is one of the most corrosion resistant materials known to man.It is also has really poor notch sensitivity - so no scrathes.

For most applications,the half as stiff part makes Ti really unsuitable.What it is really good for (in theory) is rods and valves.It also makes some pretty good springs (if you can fit them),and I have heard of some people who make ultra light weight headers out of it.

The most outsounding property of Ti is it's specific toughness.In english that means that pound for pound it is the most impact resistant steel.By a long way.If the price comes down,excpect to see bumper frames and seat frames made out of Ti,cause they are excellent applications

Speaking of alternate engine materials,if you have about 5K laying around I can hook you up with a good deal on some beryllium pushrods...

Everything I've read says beryllium is very brittle but I've also heard of some drag teams using beryllium blocks so I don't know.I know very little about metalurgy and it's no doubt showing

Ti rods stretching?Are you sure you don't mean aluminum rods?Titanium is pretty darn good when it comes to high temperature creep properties (try gas turbine applications,both structural and usually compressor section blades) and I can't see having to replace Ti rods every 500 laps.Aluminum rods most definately have a very short service life,but I'm not aware of any service life limitations on Ti rods.

Along with Ti pushrods and valve springs

[ProStreet R/T]

Everything I've read says beryllium is very brittle but I've also heard of some drag teams using beryllium blocks so I don't know.I know very little about metalurgy and it's no doubt showing

Where have you heard of people using beryllium blocks? I'd like to see that in action.

Have fun in the event you ever need to weld it, done improperly you might just die... literally.

[element180]

It figures.Now I can't find anything about them.I guess that's what I get for bringing it up...sheesh

[Sparky67]

Here is some good info about titanium rods. Here is my source...http://www.hotrod.com/techarticles/82378/

Titanium
Got a huge wad of cash burning a hole in your wallet? Then you’ll want to know that titanium rods offer the highest strength-to-mass ratio of them all. A well-designed titanium rod is about 20 percent lighter than a comparable steel rod. Titanium is the most abundant element in the earth’s crust, but it must be alloyed with other metals before it has the properties needed for the manufacture of connecting rods. The most common alloy is called “Titanium 6-4” because it has 6 percent aluminum and 4 percent vanadium to improve machineability.
Like steel and aluminum rods, titanium rods can be forged or cut from a billet. Given a choice, titanium rods are most durable when manufactured by the forging process. This is because the grain size of even the best aerospace grade titanium is less than steel. In a Richter-esque grain-sizing scale where a 6 rating is twice as tight as a 5 rating, titanium rates between 5 and 6 while high-carbon steel is far more cohesive, rating as high as a 9. To offset the possible negative impact on strength, a fully machined forged titanium rod is the best type thanks to the improved grain structure around the big end versus a cut-out true billet titanium rod.
Though raw titanium costs five times as much as raw carbon steel, the average retail cost of a set of titanium rods is “only” about twice that of steel. The increased consumer cost reflects the fact that titanium becomes “gummy” when machined and requires specialized tooling and slower feed rates. Titanium expands at about the same rate as steel and is resistant to work hardening, so you could run ’em in your street car with no problems as long as your wife never sees the credit card bill. So where do titanium rods really shine? In any all-out racing effort where an approximate 15-percent reduction in ultimate tensile strength is an acceptable trade-off for an approximate 20-percent reduction in connecting rod weight. As for ultimate power capacity, know that they’re used in everything from 9,000-rpm NASCAR motors to a handful of 6,000hp Top Fuel motors (though most teams use aluminum). With the right communication between you and the manufacturer, they’ll handle anything you can throw at ’em. Just be sure not to scratch them! Titanium is very “notch sensitive.” Small surface imperfections caused by rough handling must be polished immediately, or they can grow quickly.



Jeff

[gumbycw]

Slightly off topic but titanium is certainly NOT the most common element in the earths crust. It is oxygen, followed by silicon. I teach this info all the time in chemistry.
Caleb

[element180]

Interesting.Ok so steel rods would be best for longevity in a street engine,but obviously the point of this thread is to reduce rotating mass in the engine.What is the acceptable threshold for Ti rods in a street engine?Would daily driver duty a Procharged LSX at a streetable 6-8psi be too much for them?

[Blown353]

Interesting.Ok so steel rods would be best for longevity in a street engine,but obviously the point of this thread is to reduce rotating mass in the engine.What is the acceptable threshold for Ti rods in a street engine?Would daily driver duty a Procharged LSX at a streetable 6-8psi be too much for them?

What you really need to be asking is:

Will the reduction in rotating mass that Ti Rods offer (at the cost of about $4000-4500 per set) be worth it for a moderate-RPM street application?

I think you'll find the answer is a big NO... unless you just like to needlessly throw money at things for the bragging rights.

I'd strongly suggest you save the $3000 and buy a good set of steel rods-- then use the extra money somewhere else where you can really see a benefit from it, like headwork, a custom intake,
etc.

Remember, titanium's propensity to galling also applies to the bolts holding them together. You usually have to use special Moly-based lubes and even then they may gall up... sending a very expensive rod to the junkpile. I've seen some now where they are using studs rather than bolts to significantly reduce the chance of galling, since you only have to thread the stud into the Ti rod once.

Also, using Ti rods with a stock weight crank would be silly, so then you're out another $4K or so for a good profiled lightened crank from the likes of Bryant or Callies, and then you're onto extremely lightweight pistons and wristpins, and the super-light pistons wouldn't be such a good idea in a boosted application anyways... It's the classic snowball effect.

To sum things up: My friend spent darn near 5 figures per set for his beryllium pushrods back when they were class legal. They were worth, at best, 17hp @ 9800 rpm in his drag application over the runner-up pushrods because at 9800 rpm the mass reduction and additional stiffness kept the valvetrain more stable. On a cost-benefit basis that means he spent about $500 per horsepower. That's the kind of cost-benefit ratio you get to when you start dealing with really exotic parts, you spend ungodly amounts of money for small gains. But in a competitive class it can mean the difference between winning and losing. On the street it really doesn't matter much and there are places where that money will do a LOT more good such as heads.

Also keep in mind the stresses on rotating parts increase as a square of the RPM but linearly in relation to the component weight. Thus the best way to keep stresses down is to limit your maximum RPM. Capping a street engine at say 6500-7000 rpm really keeps stresses at sane levels and reduces the need for exotic lightweight parts. It when you start getting into stratospheric RPM levels that you need the exotic lightweight parts; since you're locked into a specific RPM-range (typcially given engine rules for the class) the only way at that point to reduce the stresses on the internal components is to reduce their component weights or shapes to alter the moment of inertia-- and lighter metals not only allow you to reduce the components overall weight because of their lower density but you can then add additional "meat" where it is required for strength without taking a huge weight or MOI penalty because of that reduced density.

I still want to see a technical article or other concrete proof that Ti rods suffer from such severe creep/stretch issues in automotive rod applications that they require short-term replacement. This just doesn't sit right with my aircraft/aerospace experience where properly done Ti components survive extended lives even in much harsher enviornments than the inside of an automotive engine.

Troy

[element180]

Well when you put it that way I guess it makes alot more sense to me.After reading everything in this thread I guess it would be much more worthwhile to go for strength rather that lightweight and considering some guys are running 800+ hp and close to 900 lb-ft at the wheels on 19-psi boost on a stock crank and forged steel rods such as http://gmhightechperformance.com/features/0602htp_sp/ ,it does seem like a waste of money

[Blown353]

One place I will recommend you try to run light components, even if it is a street engine, is in the valvetrain. Any weight saved in the valvetrain is a good thing (as long as it maintains stiffness) and has the best benefit for the dollar.

That feature article has one thing in it that scares me... CAT rods. Anything from CAT is usually better used as a paperweight!