Discussion Topic |
|
This thread has been locked |
August West
Trad climber
Where the wind blows strange
|
|
|
Jan 30, 2017 - 03:59pm PT
|
^^^
For some climbs you can scramble to the top to set up a toprope, but others you can't.
My original motivation for getting VGs was to be able to yard/aid my way up Indian Creek cracks to set up topropes so I could learn to climb wide cracks without pro. I would push a VG above me and place an occasional Big Bro (for whatever it might be worth in sandstone) as pro.
That strategy basically worked.
|
|
Clint Cummins
Trad climber
SF Bay area, CA
|
|
|
Jan 30, 2017 - 05:25pm PT
|
Tom,
Thanks for explaining the lateral loading problem.
The Kuate I've used definitely has that problem!
 Clint
|
|
Matt's
climber
|
|
|
Jan 30, 2017 - 05:33pm PT
|
i'd be interested in a #8.
best,
matt
|
|
edavidso
Trad climber
Oakland, CA
|
|
|
Jan 30, 2017 - 08:07pm PT
|
Nutstory, thanks for compiling the list. Looks like I better start building cams!
Tom, thanks for posting and sharing all of the experience you have making, testing, and using large cams. You are, of course, exactly correct about the lobe buckling failure mechanism of large cams. I have seen this in some of my testing of compromised cams (pre-bent lobes). I have not yet tested any #10's to failure but I'm sure buckling will be the first failure mode. I have attempted to address the buckling problem in this design by using a wide double axle, where each cam lobe is supported laterally at both axles. I run FEA for buckling but should probably run some cases with eccentric loading to closer match what is likely to occur on real rock. However, it will remain the case with my cams and any other large cams (and many small cams for that matter) that if you put one into a constriction that does not allow rotation in the direction of pull, then it will fail at a much lower than rated load.
There are methods to decrease weight without sacrificing strength. One obvious example is to just use a stronger material. My stem, for example, is made from stainless 17-4 H1025, which is about 1.5X the strength of stainless 18-8 wire rope. There are also straight-forward methods to do this with geometry. Using hollow axles is one example. A solid axle will be stronger than a hollow axle of same diameter but a hollow axle of slightly larger diameter will quickly overtake the solid axle in strength and weigh less. It is less obvious with the lobe geometry but between iterations I was able to decrease the weight while retaining the same strength and buckling resistance by shifting around material to the higher stressed areas. Since most cams are rated for somewhere between 9-14 kN, I found no reason to make mine stronger. As Tom stated, Valley Giants are most likely more robust against off-axis loading scenarios.
jsj, good question on cam stability. Larger cams are going to be less stable in this regard (becoming lopsided) than smaller cams, or at least the effect is more obvious given their size. My cams perform similar to camalots.
|
|
nutstory
climber
Ajaccio, Corsica, France
|
|
|
Jan 31, 2017 - 12:35am PT
|
Edited list; sorry matty ;-)
1. thebravecowboy 1 #8
2. nutstory 1 #8
3. Moof 1 #8
4. Alexey 1 #8
5. Studly 1 #8
6. Jaybro 1 #8
7. Rhodo-Router 1 #8
8. couchmaster 2 #8’s and 1 #10
9. matty 1 or 2 #8
10. WyoRockMan 1 #8
11. go1dens4 1 #8
12. Trashman 1 #8 and 1 #10
13. Raafie 1 #8
14. Clint Cummins 1 #8
15. Werd 1 #8 and 1 #10
16. Naitch 1 #8
17. lifeguard 2 #8 and 1 #10
18. karabin museum 1 #8 and 1 #10
19. haleyd 1 #8
20. jsj 1 #8
21. OlympicMtnBoy 1 #8
22. Matt’s 1 #8
|
|
Tom
Big Wall climber
San Luis Obispo CA
|
|
|
Jan 31, 2017 - 05:42am PT
|
edavidso,
I just heard from a frequent user of wide cams, of different types (including mine) who said that the single stem design of some other cams was inferior to the U-loop of the VGs, because they tended to bend and break off. This person is, perhaps, the expert in the field at this time.
Just saying.
If your WC6, or other cam, is hard to push up a crack without the head turning sideways and snapping open, you can replace the flexible, mini-cable trigger wires with solid spring wire, and it will cure the problem. The solid trigger wires are what make the VG cams so stable to push up a crack. You can get the spring wire as music wire at hardware stores (and it will rust) or you can find stainless steel spring wire at mcmaster.com in small quantities. I use 0.049" wire, but 0.063" (1/16") would be OK, too. Anything thinner might not be OK.
You'll want the trigger wire to be able to slide through the trigger bar, to accommodate flared cracks.
|
|
edavidso
Trad climber
Oakland, CA
|
|
Tom, thanks for sharing your experience. I wanted to use a single stem design for my cams because I like how they handle and it also made the trigger lock easier to accomplish. It can also result in more weight savings. If using identical material, the double stem will be stronger due to more area and will be less likely to bend about one axis. For my cams I'm using a solid single stem made of 17-4 hardened stainless. It is semi-rigid in the sense that it is very springy. At the handle, you can deflect the stem by about 2.5 inches in any direction before seeing any permanent deformation. During use you will occasionally get a slight bend in the stem and you can just bend it back straight. 17-4 is an amazing material in fatigue and even with it's high strength it still has a good amount of ductility. This means you can bend it back and forth (with permanent deformation on each cycle) hundreds of times. Due to its ductility, you can also bend it over a full 90 degrees and it will not crack or fail under load. I have purposefully done this, bent it back to straight, load tested it, and it still held full strength.
The semi-rigid stem makes it very easy to place and to push up cracks. So I'm using 3/64" stainless wire rope for the trigger wires to retain independent lobe movement.
I made a bunch of parts over the weekend but still many more to make. Still working on numbers and shaving cycle time off of the machining ops.
|
|
nutstory
climber
Ajaccio, Corsica, France
|
|
Have great fun when making our future monster jewels ;-)
|
|
Oso Flaco
Gym climber
Atascadero, CA
|
|
Please count me in for a #8. These look awesome.
|
|
Clint Cummins
Trad climber
SF Bay area, CA
|
|
Thanks for the update and the shaft material discussion.
It's great news that you're making the parts.
|
|
Tom
Big Wall climber
San Luis Obispo CA
|
|
edviso,
I like the idea of having a spring-steel type single stem, which can deflect and come back. That would seem to be the ideal configuration, because it is light, strong, resilient and reliable.
But, how does that 17-4 stainless react to the silver brazing process? Doesn't the heat create a zone of annealed, soft metal right at the spacer block, where the bending stress is the highest?
If you figure out a really economical way to cut out cam lobes, let me know. I have tried everything from CNC milling, to waterjets, to plasma cutters, and either the cost or the quality, or both, have been an issue.
|
|
nutstory
climber
Ajaccio, Corsica, France
|
|
Tom, what about "my" old-time Excalibur-specification VG7 with undrilled cam lobes... ;-)
|
|
nutstory
climber
Ajaccio, Corsica, France
|
|
|
Feb 10, 2017 - 06:31am PT
|
Marty, it's not worth teasing me... Of course, I know that you have this treasure at home...
|
|
BLUEBLOCR
Social climber
joshua tree
|
|
|
Feb 10, 2017 - 08:09am PT
|
Edavidso, are you taking any more orders? I would love to have a #8 please.
And maybe a #10, how much are they?
PM me for payment arrangements.
Thank you sir!
-Mike
|
|
karabin museum
Trad climber
phoenix, az
|
|
|
Feb 10, 2017 - 08:16pm PT
|
Stephane, You are a great friend of mine. No teasing, just sharing a better picture of the VG 7 cam.
Hmmm....I do notice that Toms VG 7 cams have solid aluminum thumb and trigger bars, where mine has a plastic trigger and hollow aluminum thumb bar....so it is a later but still wonderful version of the VG7.
|
|
edavidso
Trad climber
Oakland, CA
|
|
|
Feb 11, 2017 - 11:18pm PT
|
Nutstory, that's a pretty awesome Excalibur rack!
Tom, good question on silver soldering causing annealing. On one of my early prototypes, I was using strain hardened 304 wire rope for the stem and I did get some annealing at the silver solder joint where it joins the stem end. This is where the cam failed at 10 kN. You would get the same result if you used a solid strain hardened rod or any quench and tempered alloy. 17-4, however, is a precipitation hardening stainless, which means the hardening and softening process is very slow (hours). So the time at temperature for silver soldering causes almost no reduction in strength. I still wanted to eliminate the silver soldering at this joint because it was time consuming and recently was able to do this. I'm now heading the end of the 17-4 rod so that it flares outward. I put a matching tapered hole in the stem end and press them together with a couple tons. So no more silver soldering at that joint but I still have to silver solder where it connects to the handle.
As for the lobes, I've always machined them. I can make two at a time by nesting them side by side. I've got machining time down to a couple of minutes per lobe, which will make them more economical than some of the other parts. I don't think waterjetting or plasma cutting would give me the profile tolerance I need where they connect to the horns so haven't considered them. Per your comments on buckling, I've beefed them up a bit...
Blueblocr, once I have this all figured out I'll set up some kind of website to take orders.
|
|
Barney Rubble
Trad climber
ALAMEDA
|
|
|
Mar 10, 2017 - 03:58pm PT
|
Hi Erick,
What's the latest? Is it too late to get on the list for a #8? Looks like you're going to be busy making cams!!!
Saw someone's post about a prettiest cam contest. If there's a better looking cam than yours out there I haven't seen it. Let's see contenders posted up :-)
Greg
|
|
nutstory
climber
Ajaccio, Corsica, France
|
|
|
Mar 11, 2017 - 12:17am PT
|
1. thebravecowboy 1 #8
2. nutstory 1 #8
3. Moof 1 #8
4. Alexey 1 #8
5. Studly 1 #8
6. Jaybro 1 #8
7. Rhodo-Router 1 #8
8. couchmaster 2 #8’s and 1 #10
9. matty 1 or 2 #8
10. WyoRockMan 1 #8
11. go1dens4 1 #8
12. Trashman 1 #8 and 1 #10
13. Raafie 1 #8
14. Clint Cummins 1 #8
15. Werd 1 #8 and 1 #10
16. Naitch 1 #8
17. lifeguard 2 #8 and 1 #10
18. karabin museum 1 #8 and 1 #10
19. haleyd 1 #8
20. jsj 1 #8
21. OlympicMtnBoy 1 #8
22. Matt’s 1 #8
23. Oso Flaco 1 #8
24. BLUEBLOCR 1 #8 and (maybe) 1 #10
25. Barney Rubble 1 #8
|
|
|
SuperTopo on the Web
|
Let us know!