j4k3

First time using TPE. Overhangs are pretty rough on a MK3. The rubberiness of TPE is more like a vulcanized natural rubber used on surfaces like conveyor belts. It is similar to bike hoods. That first textured print is still too rough and rigid for a thing like bar tape.

In terms of the part itself, it is a termination point for the handlebar tape so that the shifter body is not integrated into the bar tape and can be removed if needed. I am testing a printed index mechanism, so maybe I am the only real use case.

(Continued from https://lemmy.world/post/43278229 a few days ago...) So, I tried fully removable for the index, but that is impractical as far as the size, space, and complexity. I can't see a way of maintaining concentricity.

Next I tried making various hollow spaces where the main pawl slaps the index with every shift. I wondered if it would sound or feel any different, but no dice. Printed pawls (don't last long) sound very different. The index tooth shapes sound a little different, but messing with the spring preload makes more of a difference.

I spent way too long trying to get a side screw mount to clear the shift lever arm. It is super challenging to mess with two angled vectors pointed across a Cartesian coordinate system and then adding two rotational components of a round object while locating a screw head and square nut around a central shaft... and thinking about print orientation. I broke my rigid sketch based linear workflow to make that one happen. I had to model separate bodies, then use assemblies to layer the coordinate systems.

Then I decided to stop screwing around and simping for big hardware. Obviously the curved shape of the removable index is a printed spring. I guess I was passively thinking I needed to avoid that flexibility or loading. It took me rotating the side bolt from center-ish, to as high as possible before I saw a good way to limit deflection while keeping a snap fit. The fit is actually too good now. I need to make an easier way to remove the thing and alter a bit of geometry to make more removal clearance.

One of the problems with removal of the index from the body is that the pawls need to be in the highest gears to access the location where there is space to slide it out. This makes the screw retained version want to fly apart once the screw is removed. Then omg it is a pain in the ass to get the thing back together with the index back under the pawls. So to solve this, I made an extra index address at the very end where the pawls can park outside of the removable section. This works fantastic, but creates a new problem. That location will be blocked by the RD high side limit screw on the bike. I have a few ideas of how to remedy the issue, but I think the best one is to make a little barrel limit device that sits on the exposed section of the RD shift cable at the RD, between the clamp bolt and housing termination. That could be removed to give access without altering the RD/cable. Another way, but much more involved design, is to create a release mechanism into the barrel.

I've been wondering if I could somehow add a small amount of adjustment to the whole index by changing the distance between the barrel and central axle by a millimeter or so. I had been thinking of simple ways to create such a variance, but adding a bunch more complexity, it might be possible to add the ~3mm of extra shift cable travel needed to get the pawls past the RD limits without releasing the RD cable.

For the rear cassette, I have plenty of room between an 11 speed 11-28 that I typically ride and my spokes. I wish I could find HG 10t cogs or a 9t built into a lock ring. Alas it is easier to extend the big cog side. While I cannot make a regular cassette cog fit, I can easily create a dished carrier for mounting a small chainring at the spoke side. Pretty silly to me as I never even use the 28t, but it would be funny to joke about the marketing of ""12 speeds"" and how my chainring on the back is smaller than many mountain cassettes now. I have a bunch of 38-42t inner chainrings I could use.

On another tangent... all of the 3d printed brake hoods I have seen are hideous. Still, I wonder about TPE as a replacement for bar tape and maybe even hoods. What if it was more modular. What if it was made so that the print creates ribbon like strands and these are braided on the bars. What if nice bar tape equivalent could be removed without damage. What if it was washable. What if the whole road bike system is made to be serviceable piece meal instead of all or nothing.

Then it occurred to me today, with my index measurement tool I made, all anyone needs to do is measure and print their own tuned spacers between the cogs of the rear cassette and every combination is possible. That is the Occam's Razor of solutions. All the fuss and marketing boils down to the size of those little rings of plastic between the cogs.

Had to make the cable pull measuring jig and get it repeatable. Then had to model the interior of the shifter to know where cable contacts the pulley in order to fully understand why the pulley is eccentric and not round. The only valid reference surface is the main pivot shaft and the cable housing stop location is blind.

Then it was a matter of understanding the pawls and their mechanics. This is the oddball 2012 SRAM Red 10 speed stuff that was unique from all the rest. It turns out that the pawls mechanism is designed for the 10 speed 0.120" index standard. On this system, that is around 15 degrees of rotation per index position.

My present 11spd Ultregra 6k8 stuff is very worn out but it pulls around 0.100" of cable and is more consistent than this SRAM Red in factory form, as measured.

I was thinking about burying an adaptor in my bottom bracket shell on my frame. I have space for it internally. However, actually fixing it in the index or barrel sounded more satisfying.

Someone else already made a replacement barrel model and shared it on printables/thingiverse. I printed it and measured it, but the metal index gears protrude into the cable path and disrupt the index at 5th gear. Plus, if you look up ~1.1mm stranded steel cables, they all have minimum pulley sizes that are even larger than the factory original. I've snapped cables inside the shifter with SRAM Red, so this is not my favorite method either.

While reverse engineering the pulley and mechanism, I noticed how it will all work by gravity without the springs holding tension. This counters the intuitive notion that the loads are too high or this is some kind of "tough" thing. It really is not. Almost all of the actual load comes from inside the pawls and how they slide around each other. The index gear is not loaded very much.

I went on a quest to see how much variance the pawls could handle. Like are all the shifters the same and only the barrel changes diameter. That does not appear to be the case. Each unit seems uniquely made. So I started messing with height differences and small off sets to see if I could alter the index pitch with the original pawls and find a combo that still worked with 11+ speeds.

I do not really care about the extra gear. Heck, I am more interested in running dirt cheap 8 speed cassettes and chains that last longer.

Yesterday I discovered the index trick that works. I ditched the gear tooth profile in favor of a more complex tapered and angled triangular ramp. This "tooth" profile works reliably.

Another challenge was print orientation for index tooth details. Printing on supports at a steep angle was the only way the definition was sharp enough. Today I managed to fix that using internal micro structures around each index position and added an assembled part for the spring retainer to get the print orientation optimised. This got me to actual measurable parts in the iterative regime, and it exceeded the accuracy of my mechanism replication jig.

I still want to make the thing removable in whole or part to replace the index without rebuilding the bike. In so doing, I will likely remove the requirement for the road shifting specific cable head, or any head at all. Judging by the wear on cheap prototyping PLA, this will likely last at least as long as a chain(×2)/cassette in printed form. If it can be removed in situ, that is a compromise I am willing to make in order to run any shift system combo or alternative gearing I choose. There is enough travel present to run 12 cogs at 10-speed pitch index, or 14 with 11-speed pitch. It is only a matter of rear clearance spacing... and a mor gearz iz betar disorder I guess. I have several ideas swirling at the moment for how to design an entirely new shifter made for 3d printing. A waffler stack, a bearing detent, or a star ratchet are all possible for a barrel assembly type design from scratch. The cooler option would be a cascading stage compliant mechanism that prints in place and pulls the cable forward instead of requiring rotation. Each index position is only 2.54mm for 11-speed.

I cannot eliminate or make claims about actual accuracy with my little excuse for metrology. I could certainly improve this one with a third iteration. Based on my measurements and comparisons, shifting is only around 5%-10% the same value each time even on factory stuff. I can shift a dozen times and get the same zeroed measured result when shifting back down. But every upshift, the result varies more. Some are clearly bad shifts but most are within a similar margin of precision. I am using ways inserts in the index measurement tool, with mechanisms to control backlash, and three point contact on an internal sled. I also made housing clamps to remove their flex from the equation. Chasing that one... gluing a housing into the ferrule caps would likely make a large difference in shifting performance, especially over time. Motion here has a very substantial effect.

Anyways, that is just my musing on my project so far. I have a 10 speed SRAM Red shifter with 12 speeds of index at an 11 speed pitch. All to avoid the $500+ "proper" (exploding) rear derailleur... again.

Adjective
tendentious (comparative more tendentious, superlative most tendentious)

• (of persons or their words) Having a tendency, written or spoken, with a partisan, biased or prejudiced purpose, especially a controversial one; implicitly or explicitly slanted; biased.

That he was a supporter of the cause was clear, because his reports from the front were tendentious.

https://en.wiktionary.org/wiki/tendentious

From 20 minutes ago... The sonic boom took 8 minutes to arrive.

I don't need useful translation. I need a way to randomize the words across different languages within the same sentence like a noise source where the basic grammatical structure is English but the words are many languages. I need to ensure the translated words are not in a list, then display the rest as a pull down menu or just code to swap the first option.

I was thinking about using the Wiktionary data dump, but if anyone knows a better option, I'd love to hear it.

Not asking for cynicism about clickbait. I feel a degree of emotional blindness about what makes some content creators popular. No one is universally popular. Demographics determine much. What drives a channel like Kurzgesagt or Veritasium over others?

I find it funny that I intuit how think tanks have a popularity formula they are following, but the second I find out about that relationship, I tune them out. The only exception I know of is Dr. Ben Miles. Prager trash was the first one I recall encountering ages ago with their spurious nonsense.

I have no interest in emotional empathy driven stuff. In terms of technically interesting content, I feel totally blind to the popularity rules. Do you know? Please explain them.

1. How are you focused mentally?
2. Do you think about other things at the same time?
3. Are you focused on the lines, the imaginary half line, the staring points, the previous letter alignment, spacing, what comes next, what will fit on the line, the artistic expression of style, or simply the pure minimal effort required to communicate written thought?
4. Do you often find yourself bored and evolving or changing your style of writing as an outlet of secondary creativity along with whatever task is at hand?
5. Are you concerned with the impact your writing style has upon others, or are you only concerned with the expansion of your own short/long term memory and usefulness?
6. Are you aware of the loose correlation between intellect and handwriting? What does that mean to you personally.
7. Are the ergonomics a point of conscious focus?

I like the hacked breadboards so far. I made a sloppy super-breadboard. I should have glued it before soldering but was worried the glue might make it into the slots with the metal contacts. I also broke up the internal rails and labeled so that 8b data and 16b address all exist on the same set of 4 power rails.

I think I am having an issue with either some crossed wires or how Bus Request works with the Z80 versus how the Bus Enable of the 65x chips work. I think one or all may have some type of routine that does not high-z the buses immediately... a problem for tomorrow.

I watched Anton Petrov's last upload on the impossible merger of intermediate mass black holes,(https://www.youtube.com/watch?v=8p6PgXqL6OQ).

Do two orbiting black holes have a gravitational resonant effect that is different than a single object of an equivalent mass?

I woke up to this idea for some reason. I come from having owned an auto body shop twice and doing custom graphics and airbrush work for a decade. One of the biggest expenses in auto body work is abrasive sandpaper. Few people ever take prints to anywhere near the finish quality of automotive paint, but that is another thing entirely.

In optics, metrology, and machine tools, often reference flats are made by rubbing two objects together by various means of lubrication.

Likewise with auto body refinishing, I am always thinking in terms of sanding blocks. Sanding blocks are either bought or custom made. Commercial blocks are usually foam or rubber of various hardnesses. Sandpaper is attached or just wrapped around the sanding block by hand. The purpose of the block is to only sand the high spots without touching the low spots, kinda like a bridge. The flexibility of the block allows it to conform to the broader curves of panels, but its overall length determines the size of depression it will bridge.

This is super important for auto body work where the clear coat reflections will be plainly visible in the end, and depending on the color, will show several types of errors that other categories of finished objects are never subjected to by critique.

So, if you follow thus far, let's go one level further. The next level of block sanding involves reproducing positive contours that a block cannot bridge. Most jobs can be sculpted freehand, but sometimes this just doesn't suffice and it still looks wonky. The way to fix this is by making a custom shaped sanding block. Often balsa wood is a good choice for making a custom block by cutting thin boards in a stack of contoured profiles. At least this is how I did it back before 3d printing was a hobby accessible thing, and if I couldn't use another method. The most common method I used was simply a collection of oddly shaped and contoured objects I kept around for the purpose of sanding.

The purpose of my bla bla bla is to contextualize this overall post idea and abstraction. This is a very advanced and niche concept involving high quality finishes. So let's combine the ideas.

1. Like polishes like, or precision abrasion is possible with similar objects and abrasives like with optics.
2. Sanding is about bridging to abrade the highs without touching the lows, and following contours.
3. If fiber infused filament is much more abrasive than regular filament, it has potential to abrade a part as a tool.

So my idea here is that there are many potential small run applications where a sanding form could be printed that will shape or finish the final print. There are many possible techniques I can think of for this type of application.

If you have messed with sanding ABS, you may realize it has a somewhat unique texture and feel. It is the primary plastic used in automotive bumper covers and trim parts. The reason why it is used is because ABS has very similar thermal expansion and adhesion properties that make it compatible with automotive paint refinishing systems. It would be my choice for the best plastic to use for this idea of a fiber infused print as a sanding abrasive.

With any type of sanding, special care is required to ensure finer sharp details are retained. Like on an automotive panel, I often turned any sharp transition like a crease or corner into a sharp edge throughout the filler and primer phases. I only shaped these contours at the end, just before the final primer sealer.

With a print, let's say something like a chess piece, I should be able to print a 2 part shell out of a fiber infused ABS. This should have a small gap that surrounds the final print. Then print an abrasive version of the final product. If these are fastened to something like the sanding surface of a dual action power sander, the two like forms should smooth any layer lines without requiring effort from me. Then once the final part is printed without any fibers infused, is placed inside the shell and the DA sander is run, the extra abrasiveness of the shell should last for a small production run. Adding water into the process like wet sanding would likely speed up the process and make the abrasive shell last longer.

Overall, the complex formed abrasive might enable an unique form of manufacturing process. The potential for automation greatly reduces labor costs in time. Even just as a basic abrasive material, it may be cheaper to print something than it is to use sandpaper in some applications. I have no idea how effective it will be overall. If mostly automated, the time does not matter.