Could you explain this chart a little better? I may be the only one dense enough not to understand, so if you'd humor me I'd be grateful.

GO

The chart just shows that as the coefficient of friction between the cam and the other surface decreases, you need a smaller cam angle in order for the cam to hold. The green line is "inside" the purple line because the coefficient of dynamic friction (which is what you have after the surfaces have begun to move against each other) is always smaller than the coefficient of static friction.

Curt

Sure, that's all clear, and nothing new. The question is what do the two light blue boxes, the one dark blue box, and the white box represent? I thought they were adding something to the discussion.

GO

I think those just show the sort of "normal" ranges for coefficients of friction and the corresponding cam angles needed.

Curt

I guess I don't see the point, Jay, as the results from a bunch of other cams are back in the OP of this thread. I didn't measure the angles for them as they're all really close to correct and most likely within the error induced by the photos and Cam Fitter software.

Gotcha, and I think you have a very good point about the info being too spread out. I'll see about adding a summary in the OP.

Yup, that's what I meant. Formatting here in the forum sucks so I'll do it up in Excel and post a screenshot of it.

Sound good?

Gotcha, and I think you have a very good point about the info being too spread out. I'll see about adding a summary in the OP.

Sounds really good.

Except not a screen shot of a spreadsheet - you mean attaching it or linking to it, right?

Aric, every time I look at results like this, the first question that pops into my head is, "How do these compare with other brands of cams?" I honestly think that it is imperative that each time you present results for Aliens, that you include results for other brands, as a control—at a minimum, include a link to such results. Otherwise, you are essentially presenting the results of an uncontrolled experiment. The reader has no way of knowing whether these results are unusual, or not.

i just did an initial trial of photos, and found that i was getting very different results between photos of the same lobe. i standardized it by making a tracing of my camera (canon sd1000) on the white paper, and marking the center of the lense, and putting a tiny plumb line on the corner of the camera.

i put the axle on top of the center-lense mark ont eh paper. put the plumb over the corner of the tracing. then aim the center of the focus reticle on the camera at the center of the axle. my results are now precise, but not necessarily accurate. my rock empire cam (which i have never heard of problems with, and had heard of being spot-on in this or another similar thread) has waht i woudl consider a significant axle deviation. (i dont know if this is due to camera problems, or me problems, or whether it is insignificant, or what, but its consistent between four photos)

Besides having the camera lens centered on the center of the cam axle, the aim of the camera must be in line with the cam axle. So, if either the cam or the camera is tilted (but not at the same angle), then the measurement will be off.

im pretty sure that my system (at least theoretically) controls for tilt and axle-lense axis. however, with these short distances im sure that even little errors compound to big discrepancies- its just i dont know whether they matter.

edit: two plumb lines (from different corners) would make it even more accurate, but im confident that plane is easy to eyeball and woudlnt make a big difference in results.

so- are the fitted photos the data-submission mech of choice?

To be honest with you, I don't see data submission as a collaborative effort. I'd rather see Aric produce all the data.

an excellent way to standardize the data!

Well, standardization is kind of the whole point.

But this is important, so I'm more than willing to do it.

FWIW mine were all hand held. I balanced the camera on something solid (pint glass, nalgene, whatever was handy) with one hand and then lined up the cam with the other. And by 'lining up' I mean centered the axle in the frame with it out of alignment and then rotated it whichever direction was necessary to get the sides of the head/nut to disappear (which would indicate proper alignment due to how the lens sees the image). Only issue I ran into was making sure that there was enough light to allow for a somewhat fast shutter speed to make sure there'd be little blur from holding the cam by hand.