On Friday, 25 March 2022 20:09:31 EDT Chris Albertson wrote: > On Fri, Mar 25, 2022 at 2:02 PM Thaddeus Waldner <[email protected]> wrote: > > I would suggest that you calibrate the xy shrinkage, and z shrinkage > > in your printer slicer, instead of compensating for it in your > > design. > Yes, then you can rotate the part 90 degress and it still prints > accurately. I just ran into this here. I rotated the part and now > the dimensions are different. I think belt tension does it, not > shrinkage. The tight belt has a different tooth pitch. 0.5% over > 200mm is 1mm. I might buy some kevlar belt. Having a broadcast engineering background, I bought kevlar belts in the first place. Thats what Philistran (sp?) guy cable is made from, in diameters that match the strength of the usual steel bridge cables used to steady 2000' towers. Slightly larger, you have to use different figures for wind loading to match what EIA says is an 80 lb tower, meaning it will survive a 125 mph hurricane.
The last such tower I was involved in had steel cable, was rated at 50 lbs by Stainless, Nebraska does not have hurricanes but does have a tornado occasionaly, and the lift on the downwind cables compared to the push on the upwind cable, actually pulled the the top of the tower about 6" into the wind. Panic when I measured it from half a mile away, but made sense once I thought about it. What was even more amazing is that the ice detector and the heaters had both failed, we were off the air due to a trasmission line fire the ice caused VSWR started and the 90 foot antenna itself was wearing about 10 tons of a rhyme ice flag pointing downwind at the time. All we could do is wait for the ice to ablate, about 2 weeks, to get it down to where a climber could get inside it, find the burned up heater cable and splice it. That climber earned his keep that day as the weather 2000' feet up was such that when he arrived back on the ground, his snowmobile suit had around 2" of rhyme ice on it. Probably doubled his weight coming back down the ladder. And indian man/boy from one of the neighboring reservations, I was in awe of the grit in that boys gut. When he got back inside and safe, I turned the deicers on manually and was glad the roof was double t-beam concrete about 24" thick, the remaining falling ice made quite a racket. The rest of the crew left before their vehicle got totalled by the ice. Mine was already in the garage. > > > On Mar 25, 2022, at 3:29 PM, gene heskett <[email protected]> > > > wrote: > > > > > > Greetings all; > > > > > > It has come to my attention that one of the potential failures in > > > my > > > harmonic drive with a loose belt experimentation, which seems to be > > > caused by the unequal shrinkage in the xy direction as opposed to > > > the z direction is at least partially caused by the nozzle > > > diameter. If I attempt to achieve a zero clearance bearing simply > > > by shrinking the> > > dummy > > > > > ball from about .5mm bigger than the bearing, as it shrinks, the > > > wider > > > edges of the bearing groove come into zero or a slight preload > > > > condition, > > > > > leading eventually to a race fatigue split at the center of the > > > races > > > width. Working in openscad, a scale command would fix this by > > > shrinking the bb shape used for clearing that groove, only in the > > > x direction. > > > > > > Th question is how much would it take to transfer the majority of > > > the > > > stresses on the race from being on the outer edges of the race, to > > > be > > > more concentrated on the center of the race, with an eye toward > > > reducing the splitting force on the bearing race. > > > > > > 1% x shrink, 2%, 3%, what would be the ideal amount of shrink to > > > compensate for the printers .4mm nozzle, being used to only lay > > > .12mm > > > > per > > > > > layer? > > > > > > Seems to me there ought to be a way to mathematically predict how > > > much > > > that shrinkage diff there is. Attached, an extra 2 lines to draw > > > that > > > away from the bearing itself, showing how little the difference is > > > for a .97 x shrink. > > > > > > Comments plz? > > > > > > Cheers, Gene Heskett. > > > -- > > > "There are four boxes to be used in defense of liberty: > > > soap, ballot, jury, and ammo. Please use in that order." > > > -Ed Howdershelt (Author, 1940) > > > If we desire respect for the law, we must first make the law > > > respectable. - Louis D. Brandeis > > > _______________________________________________ > > > Emc-users mailing list > > > [email protected] > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > -- > > Chris Albertson > Redondo Beach, California > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett. -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
