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Thread: Scooty-Puff

  1. #31
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    Re: Scooty-Puff

    The rotor is a stack of twelve 3mm thick discs to hold the magnets onto the soon to be double slotted 8mm shaft and transmit power through a pair of 3.175mm round rods fitting into round cutouts in all discs. The sharp angle cuts on the outer perimeter will be coated with lots of epoxy and a layer of dyneema thread wound through the slots/grooves prior to placing the magnets in the slots/grooves of the stack. The combination of adhesive, dyneema, and magnets on the outer perimeter should provide enough mechanical reinforcement to greatly delay the likely inevitable self-destruction of the acrylic, and the use of two full-length round rod 'keys', instead of square key stock, in the inner perimeter should also reduce stress concentrations in the acrylic. Using lots of thinner pieces bonded together should also help slow the propagation of cracks since the thinner material is more flexible and a crack in one does not mean as large a loss in material still connecting the magnets to the shaft compared to using fewer pieces of thicker material to achieve the same overall thickness.

    Assembly might be a bit tricky since I did not include a jig in the order to help hold the magnets in place before the epoxy is sufficiently set to keep them from snapping onto each other and still do not have a working 3D printer yet. Basically have to get the discs reasonably well assembled onto the shaft and pins/rods then coat the exterior with epoxy and wrap with dyneema along the bottom surface of the deeper grooves and crossing around the shaft to grooves on opposite side, then insert the magnets using either a non-magnetic band or ring to help keep them from popping out of their grooves. After the magnets are placed, and if there is still room, going to wrap the exterior with another layer of dyneema thread (around the outer diameter this time to really hold the magnets well) since I have two giant spools of it and when combined with epoxy should make a nice composite structure to keep the magnets flying off into the stator (assuming the epoxy actually bonds to the very slippery UHMW-PE fiber that is dyneema thread).


    As for wheel hubs, I've been working on a very much overkill design using cheap generic 0.75" timkin (tapered roller) bearings intended as replacement kits for highway use trailers. Unfortunately, my thought to use 2.25"-OD 1.5"-ID tube and 0.375" plate steel as endcaps to attach to the wheel rims and brake rotors would be really expensive plus involve quite a bit of machining, and thinner, cheaper tube would require inserts of some sort to provide the steps needed to maintain the preload of the tapered roller bearings. Could also just use thinner walled tube and add big welds to the interior to create the bearing retaining steps instead of using smaller tube as a liner, but would probably be harder to get properly balanced.

    Thinking about how to make the hubs actually drove me to think about buying/building a furnace to get lengths of 1" diameter steel rod (preferably AISI 1144) up to ~1200[C] and forging them into the rough tube shape. After that, press/upset forge the tubes in closed dies to create the lips on the ends and reheat as necessary to 790[C] for a decent soak then furnace cool to a full anneal state. Finally, chuck them in a lathe to get them to their final dimensions and maybe another heat treatment although 1144 is already quite strong in its annealed state. Unlikely I would buy a furnace as they are quite expensive when new from McMaster and also quite small. If the interview on Tuesday goes well, thinking I might try making a cheap refractory lined box in the backyard to create a basic furnace/kiln that could have many different uses (brazing, heat treating, metal casting, ceramic firing, etc.). Of course, I would need to get the 20 ton press built well before the furnace construction should really be attempted.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  2. #32

    Re: Scooty-Puff

    I'm still not sold on the acrylic :-)

    (Btw: You know about the guerrilla guide to resin casting, right?)
    (I bet it was you who pointed it out oh so many moons ago :-)

  3. #33
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    Re: Scooty-Puff

    Quote Originally Posted by jwatte View Post
    (Btw: You know about the guerrilla guide to resin casting, right?)
    (I bet it was you who pointed it out oh so many moons ago :-)
    'twas not I.

    The acrylic is not likely to last, but does not matter in this case. It was mostly to test the layout and design and if it happens to survive a while, then all the better. At this point, it is going to end up more like a milled block of foam filler to be coated in fiber+epoxy composite.

    The brakes and wheel hub have undergone many revisions trying to make them easier to manufacture. Brakes currently consist of two copies of two different pieces that can hopefully be cast/forged then finish machined if needed. The pads are to be bonded to backer plates which attach with up to twelve M3 flat-head screws either directly to one of the castings that forms the outer cylinders of five 0.75" pistons, or to the caliper that attaches to the identical casting on the other side of the brake assembly. The central portion of the brake assembly is made from two castings bolted together at flanges with five 0.75" rods with ~4mm center bored holes for fluid flow to the non-flanged side and a channel milled into the flanged side for fluid flow between the five/ten rods. Sealing of each piston is accomplished with a single abrasion-resistant Buna-N 206 O-ring per cylinder held in place with a single self-locking retaining ring for 7/16" shafts. The brake pad material is cut into isosceles trapezoids by cutting 2" wide material into 1" wide strips then cutting in alternating pattern of 10 degrees at 24[mm] on the long base for minimal waste. Fluid area for each side is ~1425[mm^2] and each side gets five pieces of brake material with area ~2400[mm^2]. So very, very overkill. Partly because I remembered that the original rims from my brother's totaled '97 Honda Civic coupe are still in the basement and would potentially make a nice start for a small-ish, low-ish speed electric vehicle (got T-boned by a car turning left on yield across his lane then plowed straight into a guardrail). Would not be able to use the hubs or brakes directly with the larger wheels, but if they actually operate correctly they could potentially be scaled up. Would prefer to just buy a kei car/van or euro-city car, but nope! small vehicles like that are not at all common in the US 'cause we've just gotta have big, manly, gas-guzzling pieces of shit that just scream "we're the greatest" for us at any perceived slight against us or tiny poke at our manifold insecurities. The toupeed tangerine really is a perfect distillation of so much of US society and its willfully ignorant delusions.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  4. #34

    Re: Scooty-Puff

    What do you mean delusions? If we are the greatest, then clearly, when we say something is a way that we want it to be, then it will be that way! If you try to pretend otherwise, you're against us, and probably a terrorist.

    Separately: We have a bunch of Smart car type things here in California. But they seem slightly too big for a "ride-on toy" type design.

    Thirdly: Anyone who thinks "casting or forging blanks" is easier than just milling it all out of billet has a different workshop than I :-)

    Would aluminum work for the rotor? Or is electric conductivity a bad thing? Or do you actually want magnetic permeability, so you'd really need permalloy or something?

  5. #35
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    Re: Scooty-Puff

    For a proper vehicle (not PRS), I'm wanting something very much like a 1970s~2000s cab-over microvan. Preferably something with a cargo space capable of occasionally holding 4'x8' sheets and not really needing much in the way of passenger room/safety or any ability to break 80mph (most local roads are 45mph with the limited access loop being 65mph). Would love to get a 1980s~1990s (7th, 8th, or 9th generation) Suzuki Carry (also sold under several other names/brands) or a pre-1999 Honda Acty (1st or 2nd generation). Wanting possible future custom thingy to be modular base (chassis, suspension, drivetrain, swappable battery module, etc.) with detachable/ejectable composite body segments a bit like the GM Skateboard concept. Not planning on there being much of anything in the way of windows since most newer vehicles seem to be required to have horrible visibility anyway (and they really only turn the vehicle into a solar oven), so why bother with anything other than several cameras (and maybe an emergency periscope). Also, Toyota, how exactly is it possible in this day and age to get the clear plastic shield of the instrument cluster in the RAV4 so very wrong? My mom's first Honda many, many years ago freaked her out a bit because the lack of any glare made her briefly think there was nothing protecting the instrument cluster until she actually reached out and touched it, yet a very new RAV4 has horrible glare that even american car makers were able to figure out how to prevent quite a while ago.

    For the rotor, I had originally been planning to take a 1.25"~1.5" rod of 1144 carbon steel and turning it down to the required dimensions then locking it to a rotary table to mill the magnet slots, but lots of wasted material and potential for errors. A stack of plates is a bit less likely to have balancing problems and easier to modify as needed with hand tools, and does not really produce much more wasted material than machining a rod into shape. The clear acrylic scraps from the rotor plates will be turned into artwork/decorations of some sort; very pretty patterns. Thinking maybe a small SMD LED glued to one end to edge light them and hang from things using two very thin wires. The 25AWG magnet wire salvaged from the stepper motors would probably work well enough. The larger scrap would make a nice border for something.

    Reason I like casting and forging is their limiting of wasted material that requires reprocessing. The two pieces of the brakes are essentially: 1) a 108 degree arc with OD 172mm and ID 120mm by 23mm deep with five 19mm (+0.1/-0.0mm) diameter holes cut 20mm deep into one face and twelve M3x6mm tapped holes in the opposite face, and 2) a 108 degree arc with OD 172mm and ID 120mm by 4mm deep with five 19mm (+0.0/-0.1mm) diameter rods protruding an additional 21mm from one face. Lots of waste if have to mill from billet, and casting aluminum is surprisingly easy: create slightly over-sized 3D print of part and use that to make greensand mold (fine play sand + some fine ground clay kitty-litter + just enough water to get it to hold its shape when compacted), then remove printed part from mold (if possible without damaging mold), melt aluminum scraps, scrape slag off top of melt, and pour into mold. Forging steel is not so easy, but very much prefer it for its strength and hardness. Or even just build the rough shape up out of MIG wire on a bit of scrap steel sheet then machine down to final shape (essentially free-form 3D printing using metal wire). The upfront cost for forging steel is quite high with producing durable molds and acquiring presses and possibly ovens/furnaces, but casting aluminum is not very difficult or expensive or require much specialized equipment. When making many copies of a part, mill and lathe work can require a lot of time, tool wear, and wasted material, and I want two copies of each part for each of the four wheels with spares being very nice to have.


    Aside: I've been looking at RFM69HCW modules for bot control and telemetry via custom psuedo-random frequency hopping protocol in the 915MHz ISM band. 'Commercial' DSS radio controllers required for a certain competition with lots of interference on the 2.4GHz ISM band, so a sort of 'roll your own with proper serial comms and make it look professional' workaround since I never use hobby R/C (multi-channel PWM-output) receivers for anything. And speaking of RF, another thing I need to take care of is getting a cheap, temporary 3G/4G phone since the 4G LTE RePhone will not actually be available until around April 2016 (due largely to issues finding a suitable Cat 1 module that supports enough bands/provider and can fall back to 3G and/or 2G) and AT&T is nixing their 2G network at year's end. Will rather miss my old 2G Nokia clamshell as it has been a very reliable companion since late 2007.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  6. #36

    Re: Scooty-Puff

    'Commercial' DSS radio controllers required for a certain competition
    You can still get one, and turn it on, as part of your system. You could even use the "gas" trigger as your remote safety dead-man's-switch. And then use an "auxiliary telemetry" add-on which just happens to be an nRF24L01+ with an after-market 10W end stage :-) It's not like someone will audit your power output the day of ...
    (Actually, the PA+LNA version is probably good enough for a few hundred meters)

  7. #37
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    Re: Scooty-Puff

    So... made no progress on any projects recently. Depression has been biting quite fiercely the last while. I can deal with the suicidal ideation as always, but not so much the powerful sense of boredom that makes being awake very unpleasant and largely unproductive. It's almost like panic attack need to do something new/different to get my mind off things, but extreme guilt at the thought of actually doing anything. DnB therapy over the last day seems to have helped a bit although I still have not done anything productive besides settle on what chainsaw (Ego CS1401) I should buy to help complete my privet extermination campaign in a timely manner (chop down to stump and spritz wound with roundup). Harbor Freight cordless 18V reciprocating saw powered by 4S 20Ah LiFePO4 pack takes way too long cutting green limbs more than ~5" diameter. Also need to start the 500+ native milkweed seeds and native joe pye weed seeds so they will be ready for planting by the time the temperature finally stops breaking 85F and I can safely work outside again.

    It's going to be so much fun digging up the yard to turn two sections of creek bed back-filled in the 1970s into retention ponds instead of dumping 10+ lots and three roads worth of runoff into a tiny 18" drain currently buried in the creek bed and eroding a very deep ravine down the middle of the second lot. Currently been dumping brush into (and parallel to) deeper sections of the ravine in the second lot to act as small temporary dams/baffles to try to absorb some of the energy and slow the flow velocity to limit further erosion. Overall, things should be quite nice once all the earth moving operations are finished, but will take a while with just a shovel and wheelbarrow that needs a new tire. First task is clearing the old vegetable cages and buried plastic tarps (for weed control) from the former garden in the back yard, then digging out at least three segments of the 18" concrete pipe to pull it open. After the drain line is opened up, have to expand the ditch into a pond-like excavation to handle more of the incoming water and restrict the flow to the outlet at the second lot to prevent further erosion. Second larger pond is going to be in front yard by the road drains, but requires building a properly reinforced dam to keep it well isolated from the house. That section of lawn is bound by three hills and currently barely below the slab level, so a dam is needed to prevent any above ground flow between the two ponds since it would be right by the house. So the overall goal is: runoff flows from road for a few feet of existing 18" pipe to drain into front pond with overflow draining into middle segment of existing 18" pipe to drain into back pond with that overflow initially draining into a restricted input to the last segment of existing 18" pipe and eventually just flowing over a 4~8' wide weir to drain into the ravine that will be slowly partially back-filled to restore it to a proper wide and shallow creek bed. No more uncontrolled flooding of the yard around the basement, no more severe erosion in the second lot, and all the ponds and hills get replanted with lots of milkweed and other butterfly/hummingbird plants that never need to be cut anywhere near as often as grass. Yay!

    Another eventual project is ripping up a small sidewalk and trenching along the house to install the reclaimed 18" pipes to provide adequate drainage for the driveway so the garage will stop flooding. Want to rip up the dipped section of driveway immediately in front of the garage slab that is currently drained by a frequently clogged little 4" pipe to the poorly draining back yard and replace it with some pervious concrete that feeds into the 18" pipe that then routes the slightly filtered water to rainwater cisterns under the current porch with overflow going down the hill into the back retention pond.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  8. #38

    Re: Scooty-Puff

    I was hoping for progress on the self-would motors! Oh well. Physical labor is actually good therapy, too.

    not so much the powerful sense of boredom that makes being awake very unpleasant and largely unproductive
    I have a period of very similar feelings. I have an almost-finished RPi Hat that I just need to measure the UART output on to determine whether it's complete; that's stalled for 4 months.
    I have the current Money Pit (with independent AX-12A for four-wheel steering) and I haven't even pulled the data from the Robogames competition.
    I still have to make a call on four-leg or two-leg for Mech Warfare, but that, too, just sits there, taunting me on the coffee table, while the best I can accomplish is playing some computer games and laying on the sofa for a bit... (work drains all determination I might have.)

    And sadly, my kids inherited this in duplicate :-(

    With luck, next year will be an up-swing again and I'll get some stuff done!

  9. #39
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    Re: Scooty-Puff

    Quote Originally Posted by jwatte View Post
    I was hoping for progress on the self-would motors! Oh well. Physical labor is actually good therapy, too.
    So I've heard... "Just exercise and you'll feel sooo much better". I can barely motivate myself to function like a human, yet I'm supposed to somehow magically get motivated to do mind numbingly boring exercises. In the lower points, I've had trouble just getting out of bed*. I still can't motivate myself to regularly go a few feet down the hall and into the basement to ride the bike set up on a training stand. I couldn't even get myself to use the old treadmill I had in my bedroom beside my desk more than a dozen times in the year that it was there (partly because the room is so small it left me drenched in sweat after only a minute or so). Moving several dozen cubic yards of earth (old leaves/compost, some sediment, lots of red clay) anywhere from 5 to 100+ yards with only a shovel and wheelbarrow is not my idea of a good time, but it needs to be done and that is the only reason it might actually get completed in the near future.

    *technically, "off the floor" as I've been sleeping almost exclusively on the floor of my bedroom since ~Dec 2012 when mirtazapine royally borked my ability to sleep soundly. Actually removed the bed and rearranged the room when I brought up the treadmill hoping that having a monitor sitting at eye-level at the front of the treadmill might make me use it, but I kept sticking with my netbook at my desk instead of watching movies or playing games while walking.



    Would have go into the basement to forge the wire(s) into long, flat, rectangular strips since it involves lots of banging with a hammer as I've still not bought that 20 ton bottle jack to fix the basement door and build a multipurpose press/shear. Also have had all the parts to make the jig to make my acrylic hanging garden pots for several weeks, including ceramic insulation tape lined up on a piece of MDF with the bend/heat locations traced out all sitting on the workbench, but just have not made myself go back down there and finish assembling the jig and making some pots with the four sheets of 18"x24" acrylic.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

  10. #40
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    Re: Scooty-Puff

    Still not managed to do much other than a bit more thinking about, and modifying the layout for, the motor controller. Chopping it down to a stack of discrete boards that can fit inside a Hammond 1590BFL enclosure with the power and motor connections embedded into the flanged lid and the bulk of the enclosure having little-to-no-contact with the PCB stack (other than heat transfer media at the MOSFETs). Already cut the power PCB down to 100mm x 50mm with just the MOSFETs and MOSFET driver ICs, and the size reduction also means that I get two of those power boards per 100mm x 100mm 'panel' PCB from seeed when properly v-scored. Using the 1590BFL with additional gaskets means I get to just attach the module to the exterior of the vehicle with some screws and have all the internals and flange-mounted connectors well-sealed from water and possibly add water cooling just by drizzling water over it.

    I am also going to try making DIY non-contact current sensors with a DRV5053 hall-effect sensor inserted into a gap cut out of a ferrite toroid core. Nice thing about the DRV5053 is the output is always 1V+/-0.8V regardless of the 2.5V~38V input supply. Expect that multiple ferrite toroid cores will be sacrificed to get any useful assemblies since ceramics can be painful to successfully modify without the proper tools. Think the round/wire-core carbide hacksaw blade that I have might be too large, since I need a radially cut slot 1.5~1.6mm wide and thinking it is closer to 3mm diameter. After getting the toroids modified, it is simple: solder the TO-92 package hall-effect sensor centered on a large diameter non-plated hole in the PCB and just sticky/foam tape the modified toroid in place (with a dab of glue holding one face of the sensor to one face of the gap), then pass the power wire / buss bar through the hole/cutout. Was first thinking about a four-channel 25mm x 100mm PCB with 4 boards per 100x100 panel, but probably going to break it down into two-channel 25mm x 50mm for v-scored 50x50 panels since I don't expect to need 40 of these things unless I am very certain it actually works and someone else is actually interested in them.


    Also working on some mods for that LCD monitor from ~2008 (Asus VW246H) with its junk right-angle buttons. The little board they are attached to is connected to the rest of the monitor with a 7-pin JST-PH header (GND, BTN_COM_3, BTN_COM_2, BTN_COM_1, LED1_BASE, LED2_BASE, 5V) with each of the six buttons connecting one of the three common pins to ground via 10k or 20k resistor and the LED pins controlling BJTs at the cathodes of the common anode, bicolor LED. Pondering that I might ditch the entire plastic enclosure and mount it into a tabletop/desktop and try building several types of multitouch surfaces on top of it using one of the Teensy-3.6 for all the touchscreen processing, controlling the monitor buttons, and controlling a possible future motorized monitor mount.


    Also, also interested again in solar CHP for the house partly because I'm applying to an energy engineer position that opened up nearby and went on another long wikiwalk. As much as I hate vapor-compression cycle devices, I think I might wind up attempting to repurpose the compressor and heat exchangers from the 20+ year old dehumidifier in the basement instead of just recycling it - after getting the refrigerant purged and collected at an HVACR repair shop (given its age, it probably uses R-12 or R-22 which can be salvaged/recycled for use in other devices still requiring those refrigerants). A CO2-based heat pump sounds like a rather interesting experiment since both the water heater and furnace are currently natural gas and likely approaching end-of-life. Heat pump water heaters also operate as coolers+dehumidifiers in the space they are located which helps remove the need for the standalone dehumidifiers that keep dying, but quite expensive and would require expanding the service panel capacity. The AC uses R-22, so that will be getting even more expensive if it requires recharging and that is in addition to the rather high energy costs.
    Please pardon the pedantry... and the profanity... and the convoluted speech pattern...
    "You have failed me, Brain!"
    bleh

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