/ New cam design
Pictures can be seen here:
my mum, whose a nurse.... says that would fail due to the lock nut and the slot causing a weak point
how do the cams move?
its actually an effing cool idea but Kong have got a cheaper to manufacture alternative
Is there a reason why we dont use bigbros in this country?
I thought it was that Trango have never paid for them to be tested to CE standards, so they can't be sold legally in the EU. I think some slip through the net from time to time, I know a number of Finns who have some though they might have all got them from the States. A shop in Sweden was selling them once IIRC.
The cam is made with off the shelf parts and stuff I had kicking around.
The cam lobes would be spring loaded, it does work, I have fallen onto it!
That Kong thing is a good idea, they are an interesting company.
A really interesting looking idea which ever way. Well done on actually building the thing!
The cam lobes will be spring loaded to fit to the undulations in the crack. In this prototype the lobes hang loose so sometimes don't contact with the rock. Mark 2 is under construction.
What Deacondeacon said. This would be a faff to place if you were particularly pumped, which is when I am normally slapping at my rack for a cam.
It works by the lobes contacting the rock at the narrowest point and locking into that position. When a load is applied it rotates the lobes in the same way as a standard cam.
Its a prototype, so elements like the stem would be stronger!! Although I have tested this model with a static load of 250kg.
Yes, unfortunately this is a down side to the design. However I have an idea to make the locking nut follow the bottom of the arms so you just have to twist, not screw up and down.
The rigidity of the stem is critical (looks like one of yours has already bent) and the adjustment mechanism also needs to be slicker, some sort of ratchet would be great.
As a one off toy made with carbon I-beams, a ratcheting lock and some friend 2 lobes it'd be a very cool project :)
Sounds like a good job. But Im a carpenter buy trade so no official engineering or design experience.
Jonny, another possible problem; in a big fall is there a danger of actually stripping the thread off the bolt and unlocking the device?
Yes, there are so many potential problems, But its fun and I enjoy it!
I'd have my money on snapping an arm before that thread goes but you could always beef it up with a bigger thread or a longer nut.
> Yes, there are so many potential problems, But its fun and I enjoy it!
Certainly not knocking your ingenuity; I showed it to a hobby engineer in the office and he was admiring your handywork. To speed up the locking he suggested a sliding, spring-loaded pawl to engage with the thread on the split bolt in the middle. Something like this but with teeth:
It still has potential for slippage on a big fall though.
> Sounds like a good job. But Im a carpenter buy trade so no official engineering or design experience.
Don't let that put you off. Some of the best ideas come from leftfield.
I think the locking nut and thread is the weakest point. Both literally and from a design pov. If you could solve that problem using a different mechanism, you would be well on your way.
I've never used a Big Bro. Never even seen one in the flesh. But my instinct tells me that your design should or could be more stable.
Keep going. It's an interesting idea, even if it doesn't make you a millionaire.
Adjusting the screw to convert it from a number 1 cam to a number 3 cam is a briliant idea.
The increased complexity (6 bolts/axles) and the car jack like structure makes it look weaker so you're a brave man for falling on it. Somehow it looks like the V shape should point up rather than down.
A ratchet reqires a trigger/pawl/pivot/spring which is yet more complexity and the pawl is safety critical.
As a product a cam needs to have a "place in a panic to get me out of trouble" simplicity which isa big problem for a screw adjuster.
Wouldnt the v shape down from the ends create problems if you spring loaded the cams i.e. how would you get it so the force went outwards equally rather than pulling the cams in because isnt that the principal point of the 4 cams being equaly size/angle?
if the v is pointing down, all the mechanics are above the cam lobes and its bulky, but the principle works better.
After seeing the Valley cams (there huge) I got thinking that the lobes are only that size to fit the larger crack, so I played about with smaller lobes on arms. My idea for this design came from the twin axle, all I did was to find a mechanism that moved the two axes apart in a uniform way.
I love engineering and its possibilities, I guess my motivation came from the Omega Pacific link cam, I wanted to "out do" its range!
The next prototype will have spring loaded cam lobes and a locking/ trigger system.
This is why the locking nut was needed, I made a prototype with a sliding collar but soon realised that when load was applied it rotated the lobes and failed.
The springs would be to locate the lobe against the rock, because of the locking nut the arms could not rotate inwards, but the lobe could rotate locking the unit into the opening. I think!!!
Big bros can be a bit fiddly to get them to sit properly on real rock but in cracks that wide you are usually stable when you place them (knee bar or body jam). I prefer monster cams but big-bros go bigger and I have used mine a few times where I was glad to have it. Purchased in the US on holiday but shops like Desert Rock Sports in Vegas will post stuff.
They can be sold but not as PPE, which means that shops won't touch them, despite UIAA testing. It's an example of where CE marking falls flat on its face and creates a trade barrier which there should be no need for one - all the CE standards are based on UIAA standards anyway...
Your design may not be practical (yet), but it's bloody clever!
Off topic but…….
Having checked out your website, you’ve made some really cool stuff. Should I ever have a garden big enough for one of your creations, I’ll be phoning you up for a commission!
Thank you very much, I just like making things, anything! Climbing and making things are my passion, so maybe I need to set up a new gear business.
perhaps you should open-source this idea to protect it from being picked up by a large company and manufactured for profit. google open source engineering for more info.
Thats interesting, I just quickly googled "open source engineering" and it came up with stuff about open source software.
Is the principle that you acknowledge that you are putting the idea in the public domain?
I have another climbing idea that is possibly going through the patent procedure soon. However with the cam idea, I don't think there is much profit to be made from it. I just wanted to get feedback from people as although I enjoy the making of the prototypes I do want a functional, aesthetic product, eventually.
Blimey thats posh.
I think you have to lock the axle some how. And yes theres a lot of bulk going on above the cam lobes. I think the key to the design of the unit is A. making everything strong and B the locking mechanism. If these could be overcome I think Id be well on the way to have a suitable piece of kit.
Ah, I see climbingjoca beat me to it...
Search for the Anti Cam in Google, a climber from Squamish made something that could grab a flake.
Oh, no he didn't; I thought his spring was a threaded central member. His spring will just stretch if the device is loaded and the cams start to engage an exert an inward pressure, and will fall out...
Oh yes, good point. If you get a standard wine bottle opener you can get a good idea of the mechanical principles, just imagine lobes in the arms.
I spent ages looking at one before coming up with the above design.
Climbingjoca looks like he has designed a compound cam similar to an Omega Pacific link cam: The sliding scissor linkage in the middle is just turning a vertical movement into a horizontal outward pressure, like a cam.
you think? I would limit the movement i.e put stops so there is only a limited travel for the spring on the shaft this in a way wouldn't be to much different to the springs on standard cams only used to hold the cam in place, once loaded the caming forces would take affect and really grip the crack.... well as I see it ha
I have said before in this post, before I had a locking nut, when the device was loaded the lobes rotated out, pushing the axle down and popping out. I think this would happen with your design.
I think the problem comes when you have two different systems with different degrees of mechanical advantage. If your cam lobes exert more force than the linkage then it'll fold up, you want comparable forces from both. I think a 13.5 degree cam angle gives about 7x mechanical advantage, so you need your levers to have comparable advantage (will require trigonometry and thinking).
That makes sense, so if locking one direction of movement is the only way round having so many variables, its just thinking up a way to replace the locking nut with something quick and usable with one hand, so back to square 1 haha o well,
how about having some sort of linear ratchet on the main shaft? or when you think about just having a handle like an ice screw, problem with that would be holding it in place while winding it up, duno food for thought.
Believe me, I have spent many hours thinking about this problem, its the crux!!
Ha yeah would help it work, and probably kill the aim for saving space and weight haha however problem solved. :) sorted ;)
> But Im a carpenter buy trade so no official engineering or design experience.
Think more along the lines of a small motorcycle steering damper than a JCB :)
Sprung one-way valve with thumb-push release in the stem. Main expander spring within the ram body... It could be very neat indeed.
Of course it'd need far too much maintenence/inspection for it to be a commercially viable design but it'd be a cool home-workshop project and much better than spinning nuts.
Your going to have to draw it out!
i've previously spent a lot of time redesigning the cam for greater range and your design is incredibly close to what i ended up with though lacking the key element.
impressive stuff. How about having the V pointing up into the crack and the pulling force in the opposite direction . you would need to flip the cams around. That way when you loaded the unit it would try to expand and there would be no need for it to be locked?!?
or maybe just an umbrella with some cams around the rim!
Does the modification keep the lobes at the top, with nothing else above it, so the unit can be placed in shallow cracks?
I have played around with applying the totem cam direct loading system. So the load wire loops over the top axes and is fixed to the bottom of the arms.
I guess the other issue is that as standard cams increase in size they increase in width.
It's easy enough to describe. You have a linear piston, much like those used on a JCB. Instead of the ram protruding from only one end of the cylinder you arrange it to protrude from both like a motorcycle steering damper, that solves the change in internal volume you get with the single ended ram. You now have a cylinder that can only slide along the ram while fluid is able to pass the piston. Close the valve and it's locked in place. Make it a one way valve the cylinder can only freely travel one way until that valve is manually opened. The valve and or actuation mechanism can be externally mounted on the cylinder or neatly buried in the stem. The cylinder is now doing the job of the nut (plus ratcheting action via the one way valve). The Cylinder can also contain a helical spring in the fluid space which is useful.
Of course the fluid pressure during a fall is potentially very high indeed, a quick reality check of a practical sized piston and realistic applied load suggests ~50kpsi for the configuration I sketched out which isn't the worst case arrangement by a long shot. I don't know much about hydraulics but I can see the design more generally causes significant force multiplication problems at the lower end of its expansion range, that is a problem whatever stem lock you choose.
The contact angle is purely a function of the cam expansion rate. Not all cams use 13.5 degrees, as it's a compromise between range and friction. Wild Country Friends use 13.75, IIRC.
The cam is an equiangular spiral:
r = k.exp(a.theta)
where a = sin(cam angle)
I agree that the structure of the expanding framework is critical; preventing it twisting, bucking, slipping sideways or just plain breaking are interesting challenges.
If your expansion framework only has a spring to keep it in place, it will:
a) fight with the cam springs
b) compress when the cams try to engage and apply an inward load.
b) is how the cams work; you need a sideways force between cam and rock to create a frictional force to prevent the cam slipping. And, given the shallow angle, that inward force is significantly larger than the vertical force (imagine rigging a sling at that angle; you're into Death Triangle territory). The ratio of these two forces gives you the theoretically available limiting coefficient of friction.
You'd need some locking mechanism to hold the framework fixed once it's been placed. Taking design_crisis' comment "If you get a standard wine bottle opener", you might envisage a vertical shaft that had annular notches, like the wine bottle opener, and some mating structure that would swing onto the shaft (and lock in place...) to prevent it moving.
Bonjour, design crisis,
Jean-Paul FRECHIN (The New Alp – Chamonix) worked on a rather similar project some years ago. French Patent n° FR 2 551 981, Jean-Paul Fréchin, 22 March 1985.
If you send me an email, I can forward you a photograph of the prototype.
That is brilliant, just had a look at the patent. He had the idea a year before I was born!! He had the same issue of locking the axes in a user friendly way aswell.
I would love to see a picture of the divice if there is one. My email adress is jbriggs16AThotmailDOTcoDOTuk
Link to the patent
Hi. I developed a prototype along these lines with a similar large expansion range. When I showed it to some suppliers, the opinion was that, despite its obvious merits, Wild Country would take me to court for patent infringment.
Apart from some other problems you will find that the further apart the axles of the cam lobes are the worse the cam walks and it becomes unstable as well. It´s the nature of the beasts!
If I remember rightly (it´s a while since I read the standard) devices such as the BigBro which require user intervention (manual adjustment) to function don´t pass the requirements of PPE so won´t be certified as a frictional device.
Really, that's interesting, I love the patent website, such a good resourse for browsing what people have come up with. There is some right guff on there though.
I did think about the patent for this design but it's not a commercially viable design. Something as amazing as the link cam is inspirational and I would have defiantly got a patent on that idea.
On a slightly different note, awesome carpentry.
As many others have said, it is interesting but I wouldn't trust it unless I knew I was going to fall on it correctly ie, in one direction.
Thanks, I just like making things whether it's structures, furniture or climbing kit.
Yes, one of the flaws is the rigid stem, maybe I'll get working on a flexible one!
I have seen this on the Kong website, it's an interesting piece of kit, would love to see one.
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