Cavechat.org

Everyone is talking about making their own gear...
I have recently acquired some titanium( grade 8 ) 3/4" diameter.

I have enough to make a 5-6 bar rack with a hyper bar.
and I am looking at .260" 6AL-4V Titanium bar for the frame.

6AL-4V data sheet :
http://asm.matweb.com/search/SpecificMa ... num=MTP641

6AL-4V = shear strength of .250 bar is 3917#, yield strength is 5880#, tensile = 6370#

302SS,303SS,304SS 3/8" rod : yield = 4400#, tensile = 9900#

Thoughts??

Metalurgists please chime in...

Hmm, I can't answer your specific questions, but... You didn't say, so I'll ask... Do you have the tools/equipment/knowledge to bend and weld a Ti frame? What about drilling the holes in the bars? If you do, I want one too!!!

The Ti bars that I have seen had hollow aluminum inserts for better heat absorbtion/distribution.

You could email Gary Storrick. He knows a lot about a lot. And he's made racks and stuff before. His web site is Vertical Devices. Ask him to post his answer here.

Scott McCrea wrote:Do you have the tools/equipment/knowledge to bend and weld a Ti frame?

Bending - yes
Welding - NO, I will have to have that done but I may use a mechanical closure for the eye of the frame.

Scott McCrea wrote:What about drilling the holes in the bars?

drill-milling the holes will be time consuming.

Scott McCrea wrote:The Ti bars that I have seen had hollow aluminum inserts for better heat absorbtion/distribution.

I have solid bars and to drill them out would take a couple of hours for each.

Don't know if you found them but if you look under racks on the website Scott sent there are about 8 listed as "Howell-N-Mann" something. These are all Titanium of different types. Might give you some ideas...

I have seen one Ti rack where the bars were really worn. Seems like solid bars might be better in the long run, of course that kind of kills the weight savings.

Hunter

Thank you Scott and hunter

Using the 3/4" bars I have 2 solutions on yield strength.
This material has a 55,000 PSI yield.

1. Using the .250 frame = yield is 5880#, shear:3917#
the yield on the bars is 12,149 per side!
turns out that the slots are exactly 50% of the way through.

2. Using the .375 frame = yield:13250#, shear:8813#
the yield on the bars is 7420# per side
0.26" of the 0.75" bar is not cut through in this solution (arc to chord measurement).


Solution # 2 appears better but 3/4" bars are cut 65% of the way through.

Note: my bar calculations ignores the .09" of material on one side.

hunter wrote:Seems like solid bars might be better in the long run, of course that kind of kills the weight savings.

Actually, it is still a weight advantage :)

Man, I'd pay good money for a titanium copy of my BMS Micro Rack.

Man, I'd pay good money for a titanium copy of my BMS Micro Rack.


I second that, I might even include a little used body part.

I found this on the Vertical Devices web site (mentioned earlier): LINK.

Hank Moon says, "I know that Carroll Bassett of BMS experimented with Ti brake bars for racks and concluded that the abrasion resistance is only marginally better than aluminum."

Not trying discourage anyone from using Ti, just some info I found.

Yeah, I emailed Carroll and it's true that the abrasion resistance of titanium made it unsuitable for bars. However, I'd still like to have a titanium frame for my micro rack... seems like that could be made pretty easily.

i have bobbin with titanium wheels for 4 years. sometimes it's useful. not because of weight, but because mud. this year on the expedition to j2 in cheve area i worn out two aluminum bobbins. with rack was even worst - some cavers worn out bars in one trip. there was a lot of sand in the mud.

but i don't like titanium wheels. descent is not so smooth. it's harder to control descend. at the beginning is hard to start. then you are falling and it's hard to brake. i think titanium is too hard for descenders.

Any thoughts on this drilling method?

<img src="http://img.photobucket.com/albums/v515/Mark620/side2view.jpg" alt="Image hosted by Photobucket.com">

<img src="http://img.photobucket.com/albums/v515/Mark620/sideview.jpg" alt="Image hosted by Photobucket.com">

It will allow for about a 10,000# yield(per side) on the brake bars using the 3/8" frame!

New: 3rd solution

3/4" brake bars with 3/8" frame...see yield strengths above

btw that piece is a test piece...it is titanium and I machined it in about 10 min.

Lava wrote:Yeah, I emailed Carroll and it's true that the abrasion resistance of titanium made it unsuitable for bars. However, I'd still like to have a titanium frame for my micro rack... seems like that could be made pretty easily.

The 6AL-4V titanium rod for the frame(enough for one) is about $70.00 for either .26" or .375".

and no that .26 is not a typo that is the diameter available, while .25 is not readily available.

What's the diameter of the hole? Looks like it should work. This hole only holds the bar to the frame. No real stress on it. The only down side I can think of is the sharp edge on the tips. Potential cutting hazard and it could be annoying if the hooky part gets hung on stuff--gloves, shirt, cow's tails, pack, etc.

Just a thought here, I have no idea but would a 1/4" ti frame be strong enough? Less weight, smaller hole.

Mark620 wrote:6AL-4V = shear strength of .250 bar is 3917#, yield strength is 5880#, tensile = 6370#

302SS,303SS,304SS 3/8" rod : yield = 4400#, tensile = 9900#

Here it is on a 3/8" SMC frame:

<img src="http://img.photobucket.com/albums/v515/Mark620/on375SMC.jpg" alt="Image hosted by Photobucket.com">

<img src="http://img.photobucket.com/albums/v515/Mark620/on375SMC2.jpg" alt="Image hosted by Photobucket.com">