CAD model of a BD camalot number 1

FUCK! Lol, ok I am retarded. Sorry for wasting your time, but thank you for your explanation. I'll go stand in the corner now.

You owe everyone on this topic $5...

Do you think I'll have trouble marketing the elephant cams?

Here is my question to the group:
If you were able to place a cam and then load it internally(the rope is not pulling on the cam it has some sort of internal mechanism stronger than the current springs) do you think it would eliminate or greatly reduce walking?

Yeah, you would just have to manually resist that during placement. So cams are a balance between placeability and pull strength of lobes. Guess you could make a trigger that you release, effectively locking the cam afterwards, think, those new fancy camming derailers that lock in place on top of regular derailer spring.

Here is my quesiton for the group, yet still over my head.

Since we can understand cam lobes as an exponential equation let's say. And we can understand that their are equations, to the x^4 power. Could you design a cam to operate as such that the logarithmic spiral was a factor of the outer logarithm and an inner one. For instance the stacked axle is a primitive rotate about this, rotate about that. Now could you do stacked logarithmic spirals?? Anybody see what I am getting at??

Bigger range????

OP - very nice job on the model.

The springs are probably the trickiest part of DIY cam manufacture.
Making springs from scratch with a jig can be dangerous. Finding identical right hand spiral and left hand spiral springs ready made with the appropriate diameter is difficult. I ended up using right hand spirals on both sides by bending the business end back over the helix to the start side to still allow for a 90° rotation. Stacked axle might simplify things with how the springs are anchored.

springs for a big double axle cam

Tom Sherman wrote:FUCK! Lol, ok I am retarded. Sorry for wasting your time, but thank you for your explanation. I'll go stand in the corner now.

No worries, i'm just glad you finally got it!

Kyle Cobbler wrote:Here is my question to the group: If you were able to place a cam and then load it internally(the rope is not pulling on the cam it has some sort of internal mechanism stronger than the current springs) do you think it would eliminate or greatly reduce walking?

Just off the top of my head, I'd say it depends.
If the crack has undulations. Then yes it would be harder to compress the lobes to fit into a tighter space.
If the crack is perfectly parallel and I mean perfect. Then still yes because it would be harder to slide the lobes along the rock.

Tom, are you talking about stacking the stacked axles?? if so, it would be a really great way to get a lot more range, but there would be a lot more moving parts. You'd have to have a 'third' axle for the double axle to pivot around, and there would have to be another set of springs (stiffer than the lobes) that you would then pull through. You'd also have to incorporate the rotating axles into the lobe design or you would have interference preventing the lobes from staying oriented correctly.

Another concern of this would be; when pulling into that smaller range, the cam would be maxed out. I don't think this would be too big of a concern if the camming angle stays the same throughout the entire lobe, but I would be nervous to how much actual pressure is being directed outwards with that many moving parts..

"How shall we inscribe his tombstone?" -

"Just write, he made his own cams" -

:) While interesting and all, I compare this problem to back when I considered running my very own Bio Diesel reaction. Spend $700-$2000 to start up, and to brew 40 gallons, spend $30-$50 on supplies, using 20-30 hours to complete a batch. Just not worth the hassle IMO.

Also, this guy seemed to be onto something...

Clicky

Eric, sorry words are so hard to describe this.

The cam is about maintaining a tangential constant point of friction while variably increasing overall width. So this is completed by a logarithmic spiral, which I am assuming to be some basic exponential equation. Call it x^2. Could we redesign based on x^4 and maintain a constant tangential point of friction. Both outer lobe and inner recipient would be logarithmic spirals, except that designed in consideration to equate to an equation of x^4. For smooth expansion, etc. So everything the same, except, the inner would be rotating around, essentially, a cam lobe, as opposed to a circular axle.

Does that make sense, comprehensible, thoughts?

Tom Sherman wrote:Eric, sorry words are so hard to describe this. The cam is about maintaining a tangential constant point of friction while variably increasing overall width. So this is completed by a logarithmic spiral, which I am assuming to be some basic exponential equation. Call it x^2. Could we redesign based on x^4 and maintain a constant tangential point of friction. Both outer lobe and inner recipient would be logarithmic spirals, except that designed in consideration to equate to an equation of x^4. For smooth expansion, etc. So everything the same, except, the inner would be rotating around, essentially, a cam lobe, as opposed to a circular axle. Does that make sense, comprehensible, thoughts?

Good thought, but unfortunately it wouldn't work due to the fact that lobe and the "logarithmic" axle wouldn't be able to rotate around each other since there would only be one point on each of their logarithmic curves that would properly mate. Once you move away from this position the radius of curvature changes and they will bind.

Tom, I see what you're saying now, but I'm going to agree with ^^^ in that it would bind. I can't see it working, but pictures seem to help :) I personally like them to include elephants

In case anyone is still confused by the stacked axle thing, here's how it works.... Dual axles won't work in small sizes due to the need for the axles to overlap, which would prevent the lobes from rotating. However, since the diameter of the axles has no effect on the rotation you can enlarge the one axle to the point of it completely enveloping the other one, thereby obtaining two centers of rotation on a single axle.

stacked axle

This isn't the only solution, BTW. There's an alternate approach involving eccentric bearings on a single axle, but I can't find the patent number at the moment.

EDIT- Found it. google.com/patents/US6042069

Patent 6042069

eccentric bearings essentially do the same thing right? they are just bearings with different centers of rotation..right?

Yup. The eccentrics offset the center of lobe rotation from the center of the axle. Interesting patent, and leads to some fun stuff involving the center of rotation of the log spiral not actually having to be within the physical confines of cam lobe. Easy to get expansion ratios of 2.5:1 on a single axle cam this way, but the springs are a bitch.

would it be possible to make a spring whose tension could be adjusted? like you could put it on low tension to place then increase the tension to reduce walking? if that was possible, it would sell like wildfire

OK Kyle, let's get this thread back to something useful - the coffee mug that we now all want!!!!!

Mock up looks great but the handle should come off one of the angles so when you hold it, you'll drink from a flat. Love the carabiner handle idea. This needs a kickstarter campaign!!!! I'm in for 25.

Don't forget to drill the holes for the sling :-)

John O

I am definitely going to 3D print one of these cams with ABS. Maybe even a pull test, for curiosity's sake. Thanks for the beautiful model!