Titanium Dog Bones

[aviationfred]

I have received some Titanium bar stock to cut into dog bones.

Here are some photos of a stock 1991 dog bone with the weight displayed, then a photo of the Titanium bar before trimming to size and drilling the holes.

The Titanium bar stock is 3/16th of an inch thick. Real close to the stock thickness.


Fred

[fj1289]

How do the material properties of titanium compare to steel?  I'm thinking elongation of the holes or how susceptible to stress risers? 

I know titanium is supposed to be stronger than steel for the same size, but don't remember much about the other properties - ductile vs brittle, how it reacts to machining, etc.  Guess I have some googling to do...

[red]

I have received some Titanium bar stock to cut into dog bones.  Here are some photos of a stock 1991 dog bone with the weight displayed, then a photo of the Titanium bar before trimming to size and drilling the holes.  The Titanium bar stock is 3/16th of an inch thick. Real close to the stock thickness.
Fred

Fred,

Sure is light.  Sure is strong.  Now, before you do that, you should know that titanium does not work and play well with some metals, aluminum being one of the worst.  Depending on the type of steel being used also, there may be other problems as well.  Any two dis-similar metals can act like a battery when touching, and Galvanic Corrosion is the result.  Here is one Galvanic List (there are others, better and worse).  The farther any two metals are apart on this list, the more rapidly they will corrode on contact.  Click the link, and scroll down:

http://www.corrosion-doctors.org/Definitions/galvanic-series.htm

To me, titanium is for racing, where things get dis-assembled, inspected, and replaced often.  Not sure I'd want that stuff in an out-of-sight place like the rear suspension.

Cheers,
Red

[Country Joe]

I would think that powder coating the dog bones would be sufficient isolation from the swing arm. I'm tearing down the rear suspension of my FJ today or tomorrow, I can check the amount of side clearance between the dog bones and swing arm.

Joe

[FJ_Hooligan]

Hey Joe,
What' wrong with the suspension?  I greased the linkages on a regular basis.

I believe the dog bones are held slightly off of the aluminum parts by the steel collars.

[Country Joe]

Hooligan,
There is nothing wrong with the rear suspension. The bushings and bearings all are clean and well greased. I am just putting on my new shock, YZF600 rear wheel and FZ1 swingarm. I just loved the difference the 17" rear tire made on my old FJ.

Joe

[aviationfred]

It has been awhile. I have finally installed the Titanium dog bones.


Fred

[CutterBill]

I'm sure Fred is well aware of this, but for the newbies who perhaps don't know... saying "Titanium" is no more useful than saying "Aluminum".  One must know the alloy you are looking at before any meaningful parts can be made. Grade 2 Ti is only about the same strength as 6061-T6 aluminum, roughly 60K psi Yield.  But Grade 5 Ti is up around 128K psi, much stronger.  And there are other alloys (which names escape me) that have insanely high strengths, up around 280K psi Ultimate.  My point being: don't go down to the surplus metal store, grab something that is just labeled as "Titanium" and start making parts.  You better know what you have.

And don't even get me started on "Military-grade" aluminum or "Billet" aluminum...   
Bill

[FJmonkey]

This stuff would work really well for dog boones Domex/Strenx. I worked with it at a prior job. Quite amazing, strong, can be bent and welded. I may have a few dog bones laser cut from this stuff kicking around. 

[CutterBill]

This stuff would work really well for dog boones Domex/Strenx...

It yields at 100K but breaks at 110K?  Weird stuff.  Strong, but brittle.

[FJmonkey]

Not that brittle it can be bent to 1.6T or 1.6 of its own thickness.

[aviationfred]

I believe the dog bones are held slightly off of the aluminum parts by the steel collars.

Hooligan is correct. The relay arm and pivot boss on the swing arm do not come into contact with the dog bones. In the relay arm and the swing arm boss are a set of roller bearings that are pressed in. A steel sleeve is installed through the bearings and is slightly wider than the relay arm and swing arm boss. The bolts clamp the dog bones to the steel sleeves. The key function is to capture the steel sleeves with the torque of the bolts and then allow the sleeves to rotate inside the bearings when the shock moves.

Another important item to note is the diameter of the dog bone hole is critical. As Chris mentioned, you want as little play in the bolt to hole. The perfect hole size for the 12mm bolt would be a 12.5mm hole. 12.5mm drill bits can be found. Instead of ordering one. I used a 31/64 drill bit (this size is actually a tad bit smaller that 12.5mm) that is found in most 1/16-1/2 inch drill indexes. There is very little play left in the dog bone


Fred

[CutterBill]

Not that brittle it can be bent to 1.6T or 1.6 of its own thickness.

Yeah, I saw that.  I'm thinking the posted Ultimate figure is a mistake.  Otherwise that stuff would be glass.