Who else would like to see more wide cams on the market?
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 Sep 1, 2012 Crap. Had a long explanation of where this project is, and the combination of exhaustion and drooping thumbs on a laptop with touchpad lead to losing the whole thing. Sigh. Short version: Thanks for posting your program Brenta. Seeing that, I'm embarrassed to post mine... Clearly I've not even stayed in a Holiday Inn Express, given how ugly my program is. But it does what I need it to do, so all is well I guess. Key bit I was talking about is this... the equation I'm using for the curve is along the lines of: (sorry about the lack or reformatting... its hours past when I should have been in bed) reg[\[Theta]_] = areg*Exp[Tan[\[Theta]reg]*\[Theta] + b*\[Theta]^c + d*\[Theta]^e] where: areg = the minimum size crack the piece can fit, taking into account single or double axle and the axle spacing [theta]reg = the tangent angle of the curve b = first modifier c = first exponential modifier d = second modifier e = second exponential modifier In a nutshell, it's not much different from what I heard was done with the SuperCam (with its second order modifier), but with a slight twist that allows the curve to grow within acceptable tan angles within normal rotation (like what I surmise happens with the SuperCam), and then shoot outwards in the last final bit of rotation. IIRC the formula for the plot I posted earlier was something along the lines of: reg[\[Theta]_] = areg*Exp[Tan[14Deg]*\[Theta] +0.005*\[Theta]^2 + 0.0005*\[Theta]^6] Sadly, after playing with this for longer that I'd like to admit I don't think there's any benefit from going this route for typical single and dual axle designs, as any gains on the tail end are easily met by simply upping the tangent angle a small amount for a regular log spiral (which leads to the usual Metolius vs BD debate). I've not looked at the implications of what happens with large amounts or rotation, so perhaps this is what lets the SuperCam do its magic. Dunno, and frankly have little interest in pursuing this train of though further unless someone chimes in with a compelling reason to do so. So, any thoughts? On a side note, I've been on babysitting duty the past 2 weeks, which means naptime has been spent finally reorganizing the workshop to fit the "new" lathe (1970's vintage Clausing 5900). Which in turn means I'm a big step towards having the milling machine back operational, which means this project is closer to moving forward. Which means anyone with an opinion about what they'd like better start chiming in, otherwise Killis is apparently running the show. Aric DatesmanJoined Sep 16, 20080 points
 Sep 2, 2012 If you are making a large cam with a large hollow axle, then you should ditch the stem completely. Spread the lobes far enough apart that you can fit your fist in the middle. This will increase the torque a bit, but an oversized axle should be able to handle it. The trigger can be a bar and curved slot through the lobes that you simple grab and squeeze. This saves weight and volume, and in my opinion, would make it easier to handle and place. If you want to get extra range, load off the backside of one of the lobes instead of the axle. It's the same principle as the Max Cams (only one pair is offset) and Totem Cams (all lobes get an offset loading). Or do a complete spiral like the Super Cam. Or do both. DannyUncannyFrom VancouverJoined Aug 27, 20105 points
 Sep 7, 2012 All Killer No Filler wrote:I'm running nothing, I'm just up for chipping in so you can push the design envelope. True, but you seem to be the only one chiming in, so by default you're in charge... :-) Been cogitating on Danny's suggestion above re: MaxCam-esque design, and am going to pass on that. I've been sitting on what I think would be a solution to the MaxCam flop issue for a while now (really have to get around to cutting one of my #2's apart to try it...), but my solution won't play well with widely spaced lobes on large sizes due to side loading of the inner lobes. Anyone have any comments re: the increasing cam angle stuff I posted above? Specifically, which would you prefer: a constant 15 deg cam angle or one that increases from 14 to 15 in the normal usable range (66% expansion) and then jumps up to ~18 deg or so for the last bit? Looks to me that there's no advantage to the increasing angle thing range-wise, but it would give relatively more holding power in the usable range. -a. Aric DatesmanJoined Sep 16, 20080 points
 Sep 7, 2012 The flop issue is only because the stem and trigger were up at the offset axle. If you stick with a single axle it's fine. If you simply load a long sling off the back of two of the lobes so that they are equalized, you get very little side load (long sling = less side pull). If you still think it is too much, it would be very simple to add a spreader bar to the sling, to keep it from pulling the lobes together. DannyUncannyFrom VancouverJoined Aug 27, 20105 points
 Sep 7, 2012 So much for being coy about the solution... But given how long the Totems have been on the market I'm not surprised at how obvious it is now. That project has been sitting on the back burner for years, as I really don't want to cut up a cam that's on my regular rack to prove the idea works... Anyway, I'm not sure a spreader bar on a soft good would work as you intend. I played with using roller chain to help constrain things, but didn't like that result very much either. Which brought me back to the belief that extended range cams are a dead end evolutionarily, as they're too wide on the small end and too narrow on the big end. YMMV though, and I'm more than willing to discuss this further. -a. Aric DatesmanJoined Sep 16, 20080 points
 Sep 8, 2012 My input would be 15 degree constant angle and as light as possible without sacraficing too much durability. A mechanism to hold the cam retracted would be great but possibly also a liability... TBDJoined Dec 27, 2001500 points
 Sep 10, 2012 There are some SMART folks on this thread... LockerFrom Yucca Valley, CAJoined Oct 13, 20021,635 points
 Sep 10, 2012 Well the real question is: Who wishes there were more wide cracks out there???? :-) Princess MiaFrom VailJoined May 22, 200630 points
 Sep 10, 2012 haha and the thread comes full circle. Greg GFrom SLC, UTJoined Oct 3, 2008523 points
 Sep 13, 2012 DannyUncanny wrote:If you are making a large cam with a large hollow axle, then you should ditch the stem completely. Spread the lobes far enough apart that you can fit your fist in the middle. This will increase the torque a bit, but an oversized axle should be able to handle it. The trigger can be a bar and curved slot through the lobes that you simple grab and squeeze. This saves weight and volume, and in my opinion, would make it easier to handle and place. Certainly a cool idea for the interface BUT Problem with that is the length of the pull needed to retract huge lobes VS the "length" that your hand can open / squeeze. That's why the stems on larger cams are larger. Sure you could come up with mechanisms for solving that problem but that'd just add complexity and weight to the design. Wish I could commit to buying one of whatever gets produced, but school saps all my time and \$ NorCalNomadFrom San FranciscoJoined Oct 6, 201155 points
 Sep 13, 2012 After the 15th of this month I will be able to afford one. I'll chip in Killer boy. 175 I believe was his price. Unassigned UserJoined Dec 31, 19690 points
 Sep 13, 2012 Ranar wrote: Certainly a cool idea for the interface BUT Problem with that is the length of the pull needed to retract huge lobes VS the "length" that your hand can open / squeeze. That's why the stems on larger cams are larger. Sure you could come up with mechanisms for solving that problem but that'd just add complexity and weight to the design. Wish I could commit to buying one of whatever gets produced, but school saps all my time and \$ I dunno about you, but I can squeeze a hell of a lot harder with a fist than I can pull on a trigger with 2 fingers and an awkward bend in my wrist. That means a shorter pull with a higher force. I would bet even a weak person could fully retract a cam with only an inch or so of pull if they could use their full fist to squeeze the trigger. DannyUncannyFrom VancouverJoined Aug 27, 20105 points
 Sep 13, 2012 DannyUncanny wrote: I dunno about you, but I can squeeze a hell of a lot harder with a fist than I can pull on a trigger with 2 fingers and an awkward bend in my wrist. That means a shorter pull with a higher force. I would bet even a weak person could fully retract a cam with only an inch or so of pull if they could use their full fist to squeeze the trigger. You're missing this part. Sure you could come up with mechanisms for solving that problem but that'd just add complexity and weight to the design. NorCalNomadFrom San FranciscoJoined Oct 6, 201155 points
 Sep 14, 2012 Having a different amount of trigger pull doesn't take any additional mechanism. With regular cams it is only a function of the location where the trigger wires attach to the lobes. With the squeeze thing I'm talking about it is a function of the curve you cut your slot at. These are all basic features that you need regardless of whether you want long trigger pull or short. DannyUncannyFrom VancouverJoined Aug 27, 20105 points
 Sep 15, 2012 Danny let's see a drawing of your design! I can sort of picture it, but am still having trouble grasping the full package. Greg GFrom SLC, UTJoined Oct 3, 2008523 points
 Sep 17, 2012 All Killer No Filler wrote:What's the status, Oh Great One? How close are we to banging out a final design? I thought it was mentioned a couple posts up that the thread has come full circle, like Finnegan's Wake? Kidding aside, I don't know I've seen opinions one way or the other on the expanding cam angle thing, so that's still up in the air as far as I'm concerned (in spite of my vote against it). Also, with the wide-mostly-used-for-TR-as-you-go I'm coming around to the MaxCam-esque design. I've got quite a few MaxCams and thinking on it more most of my issues with them are easily avoided with the push-the-gear-as-you-go-TR-the-wide approach. I mentioned there being an issue with off-axis loading earlier, but that's easily solved by me simply getting thicker material... And frankly, I'm much more excited about doing a quasi-MaxCam (with the aforementioned change to single-axle, loaded on a lever thing) than a larger BD knockoff, so I guess that's where my vote is. Simply the more I think about it, the less concern I have about larger sizes getting over-square (to steal the car engine term) and getting tippy, since they're generally not left as pro and instead pushed ahead on TR. Aric DatesmanJoined Sep 16, 20080 points