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By Aric Datesman
Jul 22, 2012
Ok Folks, finally got a chance to run some numbers and think on it some, and here's what I propose.... I still don't like the idea of edging in on Tom@VG, so the price will be $175 for a 9" cam, same as Tom's. He's got some sitting on the shelf, and knowing just how much time and money he has tied up in it I'm not all that inclined to undercut him for a similar design. I've got a couple improvements in mind that up the manufacturing costs (mostly in the proof of concept/testing area), so if the higher than expected price is a turn-off, sorry. Tom's got several sitting, so give him a holler if a proven design is more your speed.

That said, what I have in mind is an open-source custom-made cam made to whatever basic layout you all decide upon. Improvements I have in mind are much, much larger diameter axle to help prevent buckling, a quasi-log spiral on the lobes to exchange holding power for expansion range in the last 25% of rotation (proven concept and used on the SuperCam, in case you weren't aware), and a couple weight saving tweaks to the stem and trigger system. I'm still not convinced one way or the other on the single vs dual axle thing, so I'll leave that all up to you. If I get 4 people to commit, I'll make them. Mind you, delivering 4 will involve making 6, of which 2 will be pulled to failure (one at 25% expansion, one at 75% expansion). And to be honest, I'll probably make 8 so I get one and can send one to Stephane at the Nuts Museum, but I'll eat those costs.

Thoughts / comments?

-aric.

FLAG
By NC Rock Climber
From The Oven, AKA Phoenix
Jul 23, 2012
tanuki
Aric.

Props to you for trying to fill a void in the market or at least add options. Also happy to see that you are going to test your product before sending it out to the field. Given your passion for gear and engineering, I am sure that you will research and test this well beyond what is required.

I don't have any use for a monster cam at this time. I also don't have the spare cash to spend $175 on a piece of gear that would spend most of its time in my gear closet. If I did have the need and cash, I would order. I am sure that if you do this, you will do it right.

Best of luck with your venture!

Edit to add: The one Valley Giant cam I held was a real work of craftsmanship. My positive response to Aric making big pro is in no way a negative reflection of Tom and the Valley Giant cams.

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By mattm
From TX
Jul 23, 2012
Grande Grotto
Aric Datesman wrote:
Ok Folks, finally got a chance to run some numbers and think on it some, and here's what I propose.... I still don't like the idea of edging in on Tom@VG, so the price will be $175 for a 9" cam, same as Tom's. He's got some sitting on the shelf, and knowing just how much time and money he has tied up in it I'm not all that inclined to undercut him for a similar design. I've got a couple improvements in mind that up the manufacturing costs (mostly in the proof of concept/testing area), so if the higher than expected price is a turn-off, sorry. Tom's got several sitting, so give him a holler if a proven design is more your speed. That said, what I have in mind is an open-source custom-made cam made to whatever basic layout you all decide upon. Improvements I have in mind are much, much larger diameter axle to help prevent buckling, a quasi-log spiral on the lobes to exchange holding power for expansion range in the last 25% of rotation (proven concept and used on the SuperCam, in case you weren't aware), and a couple weight saving tweaks to the stem and trigger system. I'm still not convinced one way or the other on the single vs dual axle thing, so I'll leave that all up to you. If I get 4 people to commit, I'll make them. Mind you, delivering 4 will involve making 6, of which 2 will be pulled to failure (one at 25% expansion, one at 75% expansion). And to be honest, I'll probably make 8 so I get one and can send one to Stephane at the Nuts Museum, but I'll eat those costs. Thoughts / comments? -aric.


I'd be interested Aric. I have a VG#9 and it's great so, like you said, if people "want the wide" now, hit up Tom for a proven product.

My thoughts on "Big Cams" and my low mileage usage of them on some OW. I'm by no means an OW guru.

- Double Axel is a must IMO. I know people RAVE about the WC #6 but in my experience, the lobes tend to flip or invert on one side. Not good. With rope drag, the rope pushing on the cams and all the all weird crap that happens when you get into the antics of climbing the OW, I've just noticed the WC single axels have more issues than the BD#6 which WILL NOT invert at all. It also seems easier to push the BD#6 along with you as you struggle upwards.
- like the idea of having "extended" range on the wide open side. Often, as you push a cam along and you get into the tipped out area, I'd much rather have just a bit more range than massive holding power.
- Weight and compactness. The VG#9 is a BEAST to carry and deploy. If you carry it in the "closed" position it can be hard to deploy in desperate situations. It would be cool to have some sort of spring activated release on the trigger. Pull and Set in the "locked" position for climbing. When you pull the trigger again the "lock" springs open allowing full cam deployment.
- Have some sort of sling built in. I've hand tied one on my VG but it's bulky and not ideal.

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By TBD
Aug 3, 2012
Hey Aric, are you still kicking this idea around? I'm interested. The lighter the better is my input, a lock-out in the closed position would be cool too.

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By Stone Nude
Aug 3, 2012
When dumb people have disposable income, hilarity ...
Aric, I sent a PM before but to reiterate, I'm in. Sign me up. Also happy with double axle stability, think having a sewn sling would be nice, and am interested in the supercam/extended range idea. For really big cams, I think this idea has even more merit than it does in fist-ish sizes, because you're unlikely to walk a fist piece as far or as often as a monster size.

So that's two of us blowing two bills to advance humanity towards offwidth perfection. Who else is in?

FLAG
By Rob Warden, Space Lizard
From Springdale Ut
Aug 3, 2012
blah
I am tired of soiling myself in zion i am down...

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By Aric Datesman
Aug 3, 2012
Howdy Folks,

Sorry for ignoring this thread for a bit... I'm at the tail end of a year long project restoring a ~1850 vintage schoolhouse and haven't had a chance to follow up on this.

I'm still game, and between the response here and what I've gotten privately it looks like there's more than enough interest. Sounds like a large double axle option is what people are looking for, so I've been spending what little free time I've had lately fixing issues with my lobe-generation program (skipping half dozen versions of Mathematica didn't go as smoothly as hoped... the single axle version is now working, and is the basis for the much more complicated dual axle one that needs to be fixed).

For typical log-spiral cam lobes this wouldn't have been a big deal, but I'm interested in exploring what advantages there are with what John Field did with the SuperCam and the quasi-logarithmic spiral he used to trade expansion for holding power as the lobe rotates outward (IIRC he made mention of this on RC a number of years ago WRT using his Cam Fitter software on the SuperCam). Interesting stuff, and easiest way to explain it is the following pic:



What's pictured is a theoretical single axle cam lobe, with the Red one using a 14 degree cam angle, the Orange one using a 15 degree cam angle and the Blue one using a quasi-logarithmic spiral that closely follows the 14 degree spiral for most of its rotation and then increases to ~18 degree cam angle at the end and ultimately achieves a bit more range than the 15 degree cam angle lobe. I'm still not completely sold on the idea WRT single axle, but need to play with it more once I get the double axle program fixed to see if it makes much of a difference there.

Anyway, once I get the program working again I'll ping everyone for more input and likely start a new thread for this project.

-aric.

BTW, if you're in the mood for a brain teaser, the radial lines in the pic are placed at every 10% of expansion for each curve. Took a bit to get my head around why the angles worked out like that, at which point I really bought into the intrinsic beauty of the log spiral.

BTW x2- then again, looking once more at that pic (which I made 3 weeks ago) I think there's a problem with the angle calculation for each 10% of the Blue curve. The math's not actually that hard; it's more that log spirals are self-similar in rotation and I never quite got my head around working in polar coordinates. So for now kindly ignore the Blue radial lines as I think they're incorrectly placed. And frankly, long story short they were only added to help me work through figuring out the formula to calculate the theoretical maximum range of a cam lobe with an increasing cam angle, so they don't really mean anything anyway.

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By Aric Datesman
Aug 4, 2012
Aric Datesman wrote:
BTW x2- then again, looking once more at that pic (which I made 3 weeks ago) I think there's a problem with the angle calculation for each 10% of the Blue curve. The math's not actually that hard; it's more that log spirals are self-similar in rotation and I never quite got my head around working in polar coordinates. So for now kindly ignore the Blue radial lines as I think they're incorrectly placed. And frankly, long story short they were only added to help me work through figuring out the formula to calculate the theoretical maximum range of a cam lobe with an increasing cam angle, so they don't really mean anything anyway.


Actually, scratch that. The angles are in fact calculated and plotted correctly. The radial lines are plotted for every 10% of expansion, not 10% of rotation and for some reason I was thinking the rotation should be similar between the lines, which is incorrect for the variable cam angle curve.

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By brenta
From Boulder, CO
Aug 4, 2012
Cima Margherita and Cima Tosa in the Dolomiti di B...
Unless I misunderstand what you mean by 10% expansion, there is a problem for all the lines. A logarithmic spiral with a pitch of 14 degrees expands by 10% every 21.9 degrees of rotation. If the pitch is 15 degrees, it takes 20.38 degrees to expand by 10%.

There are too many 10% expansions within 90 degrees in the figure, even if one looks at 10% of the smallest radius, instead of the current radius. (That is, if one takes the sequence of expansion factors to be (1 + n*0.1) instead of (1.1)^n.

Moreover, the orange rays should always occur for lower angles than the corresponding red rays, and the blue rays should be in between the others until the blue spiral becomes the largest.

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By Aric Datesman
Aug 4, 2012
Hmm... I suspect I'm simply explaining it poorly, but as I mentioned earlier I have trouble thinking in polar so perhaps there is an error there.

It gets funny with the quasi-log spiral, so let's get on the same page with traditional lobes first. Here's a new plot for just a 14 degree cam angle lobe and a 15 degree cam angle lobe, both of which are centered in a 100mm wide crack and touching both sides (thereby giving the theoretical maximum size lobe possible in that configuration). From my perspective, 0% expansion is where the lobe is touching both sides of the crack and 100% expansion is where only the very tip of the lobe is touching the crack at it's tangent angle (there's a bit more range available as the lobe fully opens and the tip passes the tangent angle, but I'm ignoring that since bearing loads on the tip go way up and the material will likely yield before it comes into play).



Equations for the curves are:
RedCurve[Theta] = 50 * Exp[Tan[14Degree] * Theta]
OrangeCurve[Theta] = 50* Exp[Tan[15Degree] * Theta]

Other variables involved are:
RedRotation = Rotation of the unit curve to get it to fit the 50mm minimum
RedMaxAngle = Rotation beyond RedRotation to get where the curve intersects the other side of the crack
RedRangeRed = RedCurve[RedMaxAngle] - RedCurve[RedRotation]

OrangeRotation = Rotation of the unit curve to get it to fit the 50mm minimum
OrangeMaxAngle = Rotation beyond OrangeRotation to get where the curve intersects the other side of the crack
OrangeRange = RedCurve[OrangeMaxAngle] - RedCurve[OrangeRotation]

From there I have the program solve for the rotation needed to fit the curve to:

RedCurve[Theta + X] = RedCurve[Theta] + RangeRed * .10
RedCurve[Theta + X] = RedCurve[Theta] + RangeRed * .20
RedCurve[Theta + X] = RedCurve[Theta] + RangeRed * .30....

And so on.

For the 14 Deg lobe I get the following: (sorry for the lack of formatting)
% Range / rotation degrees from tan angle / % total rotation
10% / 14.1 deg / 12.5%
20% / 27.3 deg / 24.3%
30% / 39.9 deg / 35.4%
40% / 51.8 deg / 46.0%
50% / 63.1 deg / 56.1%
60% / 73.8 deg / 65.6%
70% / 84.1 deg / 74.8%
80% / 94.0 deg / 83.5%
90% / 103.4 deg / 91.9%
100% / 112.5 deg / 100%

Perhaps that clears things up? I hope? :-)

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By brenta
From Boulder, CO
Aug 4, 2012
Cima Margherita and Cima Tosa in the Dolomiti di B...
Why not

RedCurve[RedRotation + X] = RedCurve[RedRotation] + RangeRed * .10

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By Aric Datesman
Aug 4, 2012
Because I basically slept through all of my Mathematica lab classes 15 years ago and didn't want to diverge from the FindRoot[] examples too much? :-)


Edit- crap. More like 20 years ago. :-(

Edit x2- also the equations above are a simplified version of what's actually in the program to make this discussion easier. The program acutually allows for non-coaxial lobes (dual axle and single-axle approximations of dual axle), defining of minimum amounts of material around the axle, clearance on the opposite side of the crack when fully retracted, quasi-log spirals and a bunch of other things. It grew kinda organically as I added features, and i never went back to simplify things like that which were basically equivalent and already working.

Edit x3 (so I can stop thinking about this and get some sleep)- Actually, what you propose is what's in the program... Looks like I did a crap job of fixing what the MP post interface did to the Mathematica code, and my only excuse is that I was in keeping a 2 year old occupied while doing it. And then the subsequent edits while watching the Olympics. Sorry about that, should have given it my full attention. The actual code from the program is as follows, with regang1 being the angle at 10%, "\[Rho]reg" the rotation constant for the unit curve to touch the minimum expansion, regrange the range of the lobe and angle1 being 0.10 (for 10% of the range... the next lines have angle2 as .20, angle3 as .30, etc...)

regang1 = x /. FindRoot[reg[x + \[Rho]reg] == reg[\[Rho]reg] + regrange*angle1, {x,0 Degree}];

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By brenta
From Boulder, CO
Aug 5, 2012
Cima Margherita and Cima Tosa in the Dolomiti di B...
All clear now. Thanks. I've been able to replicate the numbers and the graph.

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By Aric Datesman
Aug 5, 2012
Cool. Thinking on it more last night I think the disconnect was that I'm looking at the expansion linearly rather than logarithmically, which means the rotation per unit goes down as the rotation increases. Or to put it another way, I see where you're coming from. Hopefully the blue graph above makes sense now, given the screwy-small amount of rotation it needs to get the same amount of linear expansion as the earlier sections of the curve.

Ok, back to work on the dual-axle program. Anyone have an idea what I was using the Delta variable to track? Been staring at it for hours, and frankly have no idea what it was for since it was zeroed out later on.

Sigh. I need to learn to document better, as while I never expected to let the program sit for 2 years, that's exactly what happened. I seem to recall it having something to do with half the axle diameter plus clearance of the tip of the lobe on the opposite wall plus the amount of material left on the lobe around the axle, but don't remember why that was important.

Crap.

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By Will S
From Joshua Tree
Aug 6, 2012
A question:

Why do you need larger dia axle(s)? Is this because the head width will be increased?

I'm interested in acquiring one, assuming double axle and a range that runs roughly 5.5 - 9.1


Basically I'd like to see the added range partially on the small end (i.e. it goes a little tighter than 5.7) rather than solely on the wide end.

Do you have a ballpark estimate for finished production?

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By Aric Datesman
Aug 6, 2012
Will S wrote:
A question: Why do you need larger dia axle(s)?


It's not so much 'need' as 'want'... One of the prime failure modes for big cams is buckling of the lobes, and I think a larger diameter axle will go a long way towards reducing the lever arm that causes the buckling.


Will S wrote:
Do you have a ballpark estimate for finished production?


I believe I said a while back they'd be the same as Tom charges for a 9 VG. Once I firm up the design I'll have a better idea of the costs and will give a hard price then.

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By Will S
From Joshua Tree
Aug 6, 2012
Interesting. Changing the lever arm, at most say 1/2" over a ~5" span, call it 10%, will be effective in reducing the propensity to buckle?

I meant estimated timeline, not cost.

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By Gregger Man
Aug 6, 2012
gg
Aric -
Since the one I built is somewhat similar to this idea, I could probably convince Wally to let you borrow it for a while if it would help you work out your design (learn from what I got right/wrong.) And/or I can send you my CAD files if that might help.

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By Aric Datesman
Aug 6, 2012
Will S wrote:
Interesting. Changing the lever arm, at most say 1/2" over a ~5" span, call it 10%, will be effective in reducing the propensity to buckle?


Dunno, that will shake out as the design is finalized. FWIW, I'm mostly thinking along those lines for a single axle, not double, since the double can have the lobes supported by the plates on the end terminations.

Will S wrote:
I meant estimated timeline, not cost.


Oops. Gotcha. Short answer: not terribly soon and if you're in a hurry give Tom@VG a call. I figure it'll take a couple iterations to get everyone on board on a design, followed by making and breaking a sample or two, revising, another sample or two and then running a batch of final version. I'm currently tied up with finishing renovations on a circa 1850 schoolhouse we bought last year, so don't have much free time for anything beyond design/modeling until that's done (at the moment what little free time I have is spent with my wife&toddler, and design/modeling I can do while they watch a movie). I figure I'll be done with that project in the next 4-6 weeks, at which point my schedule gets a lot more flexible. So maybe year end?

EDIT- I realize "year end" might sound like a long time out, but frankly I've got my plate more than full at the moment and am only getting into this big cam stuff as a favor to those wanting other options, as I need a break from the house renovation and want to rejuvenate my interest in machining so I can finish off the line of cams I've had out for beta testing for the past year or so. Not interested in a wait, give Tom a call. Don't mind waiting, post up what you'd like and we'll see what we can get a group of folks to agree upon. A few folks here have seen the quality of my work (the aforementioned cams in beta test), but unfortunately the most vocal of the bunch recently left MP so I'm lacking references at the moment.

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By Aric Datesman
Aug 21, 2012
Quick bump to say I've been pondering this project in what little free time I've had and have the dual-axle springing worked out (issue being wanting to better support the lobes for sideways loading than is done in currently-available cams). Looks like I'm on baby-sitting duty the next two weeks, so provided she naps I'll finally have a chunk of time each day to work on this. The program to calculate the optimized increasing-cam-angle curves is ~80% finished (working for single axle), so looking forward to getting this project moving.

will update as there's news....

-a.

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By Stone Nude
Aug 21, 2012
When dumb people have disposable income, hilarity ...
Rad. Psyched that you're into pushing the design envelope. Wondering how close to a honking supercam the end result will be. Sign me up for the first unit!

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By Aric Datesman
Aug 23, 2012
Lots or progress this week thanks to the babysitter being out of town (and me being home instead of working), and it looks like I have the combined/generalized program working (previously had separate programs for single and double axle cams). Need to play with it a bunch more to make sure it's working properly, but it's looking good so far.

So, here's something to chew on for a couple days while I take a break from programming.... I'm not sold on this increasing-cam-angle thing, so will throw it out here for discussion.

In a nutshell, I ran several scenarios with is using curves with a base 14 degree cam angle and limited the increase such that it would be ~15 degree cam angle at 60% expansion and below 18 degree cam angle at the tip, figuring allowing the cam angle to run up at the end would gain range at the expense of holding power. Turns out that the additional range over simply using a constant 15 degree cam angle was negligible, hence me not being sold on the idea. Thing is, those are limiting values I picked kind of arbitrarily and the increase would be much greater if those limitations were loosened up (like letting it run up higher in the middle of the expansion and say, 20+ degrees at the tip). Dunno if I'm thrilled with that idea, but figured I'd throw it out for discussion.

To help make it clearer, here are some graphs and charts of the results:

First up, single axle cam to fit into a 100mm crack. The red curve has a constant 14 degree cam angle, the orange curve a 15 degree cam angle, and a blue one that increases from 14.1 degrees to just under 18 degrees at the tip (the exact cam angles for every 10% of expansion are in the results).



Here are the numbers for it: (Click to enlarge it so it's readable, red arrow is the max range, green arrow the cam angle and orange the overall range and expansion ratio)


Second is a set of double axle cams for a 100mm crack, again with the red curve having a constant 14 degree cam angle, the orange curve a constant 15 degree cam angle and the blue one with an increasing cam angle.



And the numbers:


I'm going to ponder this for a couple days, but please feel free to chime in with your thoughts.

-a.

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By CWood
From SLC, UT
Aug 24, 2012
1.5 cm more range for a double axle cam seems non-trivial to me in this size. I'm just imagining what a large double-axle U-stem cam might look like. Could use some fun equalization system for the two cables or something...

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By Aric Datesman
Aug 24, 2012
Hmmm.. Replied to this a while ago and it's nowhere to be seen.

Anyway, sorry for the confusion... It's going to be double axle; I just included the single axle chart/results because I thought it interesting how the increasing angle thing worked similarly in either case (which differs from the earlier analysis).

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By Will S
From Joshua Tree
Aug 24, 2012
I haven't look at a force v. cam angle diagram in a long time, but my recollection is that using the common coeffcient of friction for rock/aluminum at about 0.35, anything beyond about 18deg is getting pretty sketchy and at 20deg you've reached critical point.

I wouldn't personally use a cam above 18deg. Isn't the Alien design about 17?

FLAG


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