Low RPM motor solution... finally!

[buffo]

I bought some borosilicate glass and a MAPP torch specifically so I could make my own torture tubes like we did at SELEM back around 2016 or so, but I haven't messed with them yet. When we did it at SELEM back in Newton though, it was super easy, and the results were fantastic.

Not sure how Greg cuts his lumia wheels, but I *think* he invested in a special saw of some kind (Lapidary saw, maybe?). Either way, I know that it works really well, as the wheels he cut were perfect.

Adam

[absolom7691]

Thanks to this thread, just received the TMC2209 V2.0 Stepper Motor Drivers from Amazon to start developing the electronics & Teensy code.
Adafruit have a pricey one as well and a good infomercial covering its features.
The 4ml vials are cheap, too.
I've had a MAAP torch in my cart for months. But, just learned that MAAP was taken off the market in 2007. Now, there's MAP+P propane, which isn't as hot, but close enough to get the torchery done, I reckon.

I have found MAPP (MAP+P) to be sufficient. With as thin as the walls are on the 4ml vial, I don't think it matters. The flame turns yellow orange pretty quickly and the glass is soft enough to manipulate. I normally press deformations into the glass, I haven't tried doing any twists or any serious deforming, so I don't know how hot the MAPP gets for that. I got a pack of 100 vials, now I can try some heavier work and if I break a few, no big deal!

When dialing in the TMC2209 drivers, be aware that the current adjustment pot is backward. CCW increases the current, CW lowers it. Steppers are generally pretty robust but if they start getting too toasty, keep in mind the direction to adjust! Also, if using the 64:1 gear reduction steppers, if you're set to 1/64 microstepping on the driver, you won't even see the shaft moving at <200hz. It will move, but it will be like, .5 RPH or less! I think I set my range from 500hz to 7.5khz for testing with those 64:1 steppers.

Interesting that you mentioned an issue with the gears sticking - I haven't experienced that myself, but I've only run mine for bench tests thus far... Hope this isn't a common problem with the planetary gearboxes.

I think I found why my gear reduction steppers were chugging, I had the current set too low. I was hovering at <100ma when I tested. Once I turned the current up to >300ma, they were smooth.

[absolom7691]

Yin vs Yang
Stepper vs brushless.
SimpleFOCmini Brushless DC Motor Driver Board
I've already designed lumia projector outputs for XY galvos + an I2C bus into the T4 LS VII PCB for RGB DACs & electromechanical whatchamajiggers.
Universal law of dualities:
For everything, there's something else.

I have messed around a little bit with the SimpleFOCmini... I got mixed results. I tried using a BLDC gimbal motor for the low speed since the winding resistance is much higher than that of drone propeller motors. I think the one I was using was about 15Ω per phase and won't draw 20A+ when the phases go high at such a slow rate. I got some weird cogging that I wasn't able to get rid of. I also tried with a HDD motor and got slightly better results, but still not great. Possibly a limitation of arduino... I'm still not sure. I may try again with a RaspberryPi.

[Displaser]

Hi folks,

I’m always glad to share my failures and success with the forum! Here’s a few lumia details to ponder:

1) It was 20+ years of doing stained glass with all the tools needed, that helped immensely when I first started making lumia wheels 20 years ago.

2) I’ve always been told that drilling glass introduces stress fractures that can eventually result in the glass wheels breaking. I see this in stained glass panels where pieces break just from cutting it, soldering it, etc. Sometimes glass has a mind of its own and will crack or run in odd ways - it’s always a pain to have pieces deep in a panel break later after completion… grrr. As a result of this drilling concern, I avoid making wheels with a drill as a means to attach a motor shaft. Maybe others that drill glass have not seen this?

3) Glass cutting boards and shower glass are tempered and cannot be cut unless you have a glass saw. Any attempt to cut tempered glass with a standard glass cutter will result in glass shards everywhere. I only use stained glass and architectural glass suppliers for my wheels.

4) My personal favorite glass pattern and the glass I typically use for wheels is “Clear Cathedral Granite” - beautiful, undulating patterns that swirl back into themselves, 0.5 to 1 rpm gearmotors, 12VDC with a non-PWM speed control (unless the gearing and drive mentioned in this thread will not be visible in the image). I would hope that anyone the forum that I’ve made wheels for in the past would agree that the patterns are nice! Here is a DZ posted video out on YouTube that shows the “Granite” lumia! (Thanks David!)

http://https://youtu.be/ppkL6-QAnLQ?is=y06OTvVzTt2HYp1C

5) I use several tools, including circle cutting jigs, a glass saw and multiple grinders to fabricate my wheels. This includes a motorized jig that grinds each wheel to a consistent diameter, removes any shards on the wheel edges and makes for safer handling of the wheel. I likely have $700-800 in tools that I use to make my wheels.

6) I’ve also used water-jet cutting with Delphi glass, but this really is best suited to doing a large number of wheels. Some of you likely have the 3” wheels with assorted glass types that I had a few years ago at
SELEM.

7) Since I don’t drill glass, I have another jig that centers a spun-aluminum hub onto the wheels, epoxied into place, cured and then it becomes integral to final completion of the wheel. These use a 6mm motor shaft. I also etch the flat side of the glass wheels where the hub is epoxied for better adhesion.

8) I settled on 3” wheels a few years back when I last made them, but I’ve made both larger and smaller, as I think 1.5” to 2” are the smallest I’ve made so far. The hubs are 1” in diameter, so that’s the limiting factor without modifying the hubs.

9) Lastly, I’ve used the low rpm Hankscraft gearmotors, but these are hard to find, used by the model train community and are “used” when they available, plastic gearing, etc. I have since switched to Servo City as a supplier, as they sell a large variety of 6mm shaft gearmotors at prices only slightly more than some of the used Hankscraft motors. I could likely grind wheels on a different shaft diameter, but it will require modifying my current jig to do so.

I’ve got some other wheels that I must finish first, but if there is interest in another group buy for whatever wheel types are desired (and there are MANY choices, Catherdral Granite just being a favorite), that will be the easiest means to do this unless you want to invest in the time and tools to make them yourself.

I’m open to whatever helps - advice or making wheels, just let me know. That’s the “full disclosure”, no hidden secrets…

And a final reminder… carry a laser pointer with you, go to stained glass shops (Hobby Lobby sells clear stained glass including Granite) thrift shops and other places that sell clear glass, crystal and plastic housewares (Home goods, Goodwill, TJ Maxx, IKEA, Ross, etc.). There’s some great glass that’s out there waiting to be discovered… we can talk about acrylic and lenticular plastic wheels as yet more possibilities later.

Thanks,
Greg

[Displaser]

Laser Cronies…

I’d also mention torture tubes and dimple tubes, both as done in the past as yet another option. I also have the glass saw, so any cutting of glass to include a consistent size, mounting to actuators, etc., can also be done.

Greg

[absolom7691]

Hi folks,

I’m always glad to share my failures and success with the forum! Here’s a few lumia details to ponder

Greg

Thank you for sharing info, Greg!

I noticed I was have no success cutting glass with the central bit in the hole saw. I finally cut out a centering guide at the same diameter of my hole saw so I could keep the saw centered without using a bit. It worked much better. I was able to get a disc cut out with no issues. I'll say it again, soda lime glass it the worst! lol. I plan to mask and sandblast the center of the glass enough to roughen the surface and then use a motor shaft flange, also roughed, with epoxy to bond the hub to the disc.

[absolom7691]

I love the Whittemore & Durgin glass. This last sampler pack I ordered had a lot of really good pieces, about 12 in total. I decided to try cutting some tonight. I wanted to get four pieces cut but, because I lost the light, I only got two done. I have been going low and slow with the cutting and it has worked out for me, but man... it takes some time. Not amazingly great results but pretty decent for my rig. It's better than the squares of glass I was dealing with before.

Mounted to these tiny nema 8 motors, each lumia element is only 2.5 inch (63mm) volume. It's pretty damn compact. I can get an overlapped eggbeater element crammed into a 4" wide space. I'm really looking forward to minimizing my projector.

1.jpg2.jpg3.jpg4.jpg5.jpg

[laserist]

Someone here turned me on to Whittemore & Durgin's sampler years ago.IMG_20260723_073430.jpg
In the photo the right side is a Whittemore & Durgin disk cut in two passes. First pass was cutting the 3/8 hole into the center. Then I cut the outside edge while holding the glass down using the 3/8 hole. Both were done with diamond hole saws with about a 60 RPM spindle speed and just enough pressure on the quill to maintain contact. On the left side is a plastic disk from my Laserium days. It has the pebbled texture on one side and the other side is flat.
IMG_20260723_074712~2.jpg
In this picture you can see the difference between the "flat" surfaces via the reflection of the flash. All in all I prefer the old Laserium plastic disk. Its pebbled side is lower frequency and the Whittemore & Durgin seems to have a second higher frequency component to the pebbling that requires careful control of the beam size to make it look the way I want. I've tried to find the Laserium plastic over the years with no success. The plastics I've found don't have a flat side nor the same frequency. Disappointing. I've thought about polishing the Whittemore & Durgin obverse flat or sticking it in a kiln to try to slump the higher frequency features, but so far life has been too short.

[absolom7691]

All in all I prefer the old Laserium plastic disk. Its pebbled side is lower frequency and the Whittemore & Durgin seems to have a second higher frequency component to the pebbling that requires careful control of the beam size to make it look the way I want.

I have noticed that when testing with different lasers. The lasers that have a small diameter at aperture and wide divergence need to be "tuned" to get a useable pattern that's not too chaotic, but also not too minimal. Since I'm using diodes in my rig, using the collimator to tune this aspect has been relatively easy. I imagine, if still using ion from the old Laserium days, it adds a little bit more complexity to the optical train. The refractive indices of the different materials probably affects it quite a bit.

Very clean work on your glass, though. I clearly need a lot more practice cutting glass.

[absolom7691]

Yes, beam "diameters" can also be effectively optimized/blurred by scanning. Personally, would rarely scan imagery through any lumia other than diff gratings.
On the other hand, multiple points of different colors and areas can add layers and directional cloud control. Slowly scanned points around sweet spots can also mimic sfx rotation.
For y'alls' static beam use cases, I've also considered using a dichroic pickoff mirror, redirecting low band colors onto one side of the rotating lumia glass, with the high band remains shooting through the opposite side, moving in the opposite direction for bi-directional, bi-chromal layering, and cross fade mixing between.

I'm mainly a static beam guy for rotational effects but I am working on a selectable, rotating scan-thru turret. I have found that specific, narrow-throw lenticulars are amazing. I don't know where Greg found the the stuff that I bought from him, but it's awesome.

Ions inherently have smaller diameter, low divergence beams from the get-go, which sharpens the interference patterns.

Also the perfect multi-line beam profile/alignment , especially if at TEM00. It just can't be done with dichro combined beams. Maybe some day... Super continuum lasers are still evolving!