UELVE MBC/v0.1

From Open Source Ecology
Jump to navigation Jump to search

Basics

  • A lightweight (200 kg) 3 occupant vehicle design that can be mostly DIY constructed.
  • Although intended as an EU Category L7e "Heavy Quadricycle" it can also be the basis for a USA "NEV" or a pedal-car, or E-bike "pedal assist" motors installed.
  • Dimensions 1.5 x 3.1 x 1.1 metres for a front surface area of approx 1.5 sq. metres
  • Geodesic Frame skeleton is bamboo and PVC pipes connected together with 3D-printed software-generated "Nodes", which are then entirely encased in Expoxy Resin and Fibreglass, Kevlar, Hemp, Flax or other high-strength cloth layers.
  • Double wishbone suspension is expected to be fitted at the front, whilst the rear may be swing-arm, Double-wishbone or Macpherson. This revision uses swing-arms at the rear.
  • Body panels are twin layers of Fire-resistant Non-woven Polyester with a hot-glued 4 layer latticework "Hobbycraft" 9x1mm bamboo frame inside (9x1mm is easily bendable) to create compound curves. Label-gun "barbs" every 50 mm on a grid spacing will pin the two polyester sheets at a regular 10mm spacing, and Soudal Fire-resistant Expanding foam injected into the gap. After 2 days foam curing the panels are surprisingly strong and very light.

Frame Concept

Uelves mbc.jpg

Blue pipes are 1m measure sticks. Note that the body takes whatever form we would like.

CAD Source Code


Prototype 1 Build Procedure

build log on endless sphere https://endless-sphere.com/forums/viewtopic.php?f=34&t=118802&p=1747637#p1747637

  • Use PVC and bamboo frame members
  • Wrap corners in epoxy-impregnated tape
  • Wrap the length of tube bodies in epoxy-impregnated tape as needed for additional structural integrity
  • For attachment points to metal components, embed metal mounting interface plates/mounts/components in epoxy-impregnated tape just like the corners to attach firmly to the underlying skeleton

Skeleton Frame Phase

BOM

estimated

  • 300 metres bamboo canes between 8 to 13 mm diameter, or 300 metres PVC or other pipe or straight sticks up to 13mm. (structural strength is non-critical)
  • 200 metres OD 21.5 mm ("Floplast") PVC waste pipe, ID 19.5 mm
  • 500 metres 25mm width "Painter's" Masking tape
  • 15 20g tubes of rubbery glue (Loctite Extreme, red tube - not Loctite Extreme Epoxy!). do not use hot-glue unless upgrading the 3D-printed nodes to PolyCarb or PETG: PLA deforms at only 60C. do not use strong epoxy or superglue
  • 3 tubes Araldite Epoxy
  • 5 kg PLA for 3D printing of "Nodes"

Tools

  • 3D printer with 0.8mm nozzle, set layer height of 0.6 mm and 0.2mm "support towers", full coverage. Nodes are complex.
  • Usual pliers and files for removing 3D support
  • Full wrap eye protection (from high velocity 3D print support material during removal phase: it can get behind your eyes and start scratching)
  • Hacksaw and Mitre (90 degree angle cutting)
  • Sharp pencil
  • 1 metre metal ruler and tape measure
  • A4 printer, scissors
  • 25 metres string (for tensioning). garden twine is sufficient.

Assembly advice

  • Measure twice cut once!
  • Cutting accuracy on pipes to around +/- 0.15 to 0.2 mm is pretty crucial. The geodesic frame shape amplifies errors which causes cascading problems that require partial disassembly to correct (hence the rubbery glue and masking tape instead of strong rigid epoxy or cyanoacrylate).
  • Use the 3D CAD to create 2D screen-shots then draw Node and Pipe numbers on them. As each Node is 3D printed place the same Node number on it, written on masking tape. Print out pipe connectivity listings and cut them into strips that are taped onto the pipe during the cutting phase. Be very strict and patient here because there are 135 Nodes and around 400 pipes to assemble.
  • Use the 3D CAD to zoom in onto Nodes in order to get their orientation correct. Sometimes the 2D A4-printed screenshots can be sufficient, but some Nodes are very similar. Make absolutely certain that the angle in all three axes is orientated to within under 2-3 degrees: greater than that results in pipes moving out of position and not seating correctly, and an error-cascade begins. If necessary cut all tape free from all pipes on a node, scrape off the rubbery glue then reglue and retape. Do not attempt to remove a Node from in the middle of an assembly.
  • Pipes must be cut dead flat at 90 degrees. Use a file to ensure uneven ends are level: cutting is best done using a Mitre, circular bench saw, or even better a hand-hacksaw held in a cutting jig. It is best to slightly overcut (0.25 to 0.5 mm) then file down, although this can add significantly to build time. Do not attempt to use "undercut" 13 mm OD pipes, or if risking doing so add layers of thin cardboard glued in the seat of the Node in order to get its length back up. This trick will not work with the PVC pipes: there is a 19 mm "inset" on the Node which fits inside the 21.5 mm pipe. Undercut pipes are best put aside and used elsewhere in a shorter location.
  • Start from a flat fully-triangulated base of parts then when going vertical locate 3 pipes onto one node and create tetrahedra on th3 fklat base. Use the Node seats as an accurate guide as to direction the pipe needs to go. Once one tetrahedra is created find another right next to it and asssemble that. Do not attempt to assemble from the outside inwards (and try to meet in the middle), work from one side to the other or from the middle to the outside: climbing *inside* the frame to glue-and-tape is very tricky.
  • If when it comes to putting in single pipes towards the near-completion of an assembly there is a gap that cannot be bridged by using the masking tape to "pull" the pipe at both ends, use string wrapped carefully between other pipes on the same node at both ends, tie tightly then use another piece of bamboo to prise the twine apart, or use more twine, tying that to other nodes in the same plane to get heavy tension and push the gap shut. Be extra careful as this is where mistakes cascade and get noticed.
  • The entire frame is extremely light (under 10 kg) at this stage: turn it upright or upside-down to make access easier, as needed.

Construction order

  • Bonnet
  • front (turn bonnet over, add front upside-down)
  • dashboard (turn front nose-down, add dashboard)
  • floor and floor support (keep front nose-down, add floor vertically)
  • Driver seat box (on f!oot, after floor detachment from front)
  • "Back" box (behind occupants)
  • Door sides
  • Roof (separate assembly resting on driver box and backbox)
  • Rear frame
  • Bumper
  • Doors

Construct in 4 subassemblies:

  • Bonnet, front, dashboard and 1/4 of the floor (assemble whole floor, along with floor support; brace - double-up the bamboo with epoxy - then separate at the footwell line)
  • Driver seat-box, "Back" box on floor, door sides, then brace around the Driver seat-box and separate another 1/4 of the floor
  • Roof and top section of the "Back box"
  • Rear frame continuation of the remaining "Back box" and add bumper

The subassemblies may be tightly taped to each other for checking rigidity and overall assembly correctness. After the Cloth-Resin Phase, bolt-holes will be drilled through, metal spacers inserted and epoxied in, so that the four sub-assemblies can be bolted together with Castle or Nylon lock-nuts.

Rear Section Assembly

The rear is very hard to identify "tetrahedra" and there are curved-arch roofline sections extending behind the two passengers. Follow this procedure for left side then right:

  • CAREFULLY using a hot-glue covering just the inner 13mm circle place a bamboo stick dead-upright in the cone. Bear in mind that the Joints are a cone, sphere, cylinder joined together and it is the CONE that points in the direction the stick has to go. You can if you like pre-prepare an 80 mm strip of Masking Tape around the cone which is squashed around the hotglue. Do however keep the cone upright whilst the glue cools and hardens. OVERUSE OF HOTGLUE may melt the PLA so be extra careful: use less then add a second batch if necessary.
  • When connecting Joints via Rods make absolutely certain the Nodes are not rotated incorrectly. Use the 3D CAD to get a proper visual feel for orientation if needed, but be accurate to within a few degrees. The hotglue will bend by about 5 degrees but fights it: two or more rods once incorrectly assembled at off-angles require disassembly and starting again. This is harder with hotglue than it is with Loctite Extreme rubbery-glue, so be extra careful and meticulous.
  • Add Joint R3 to R4 (see Rear Section build diagram), then R13, then R14, followed by R11 onto R12-R3, and R14 onto R13-R11-R4 in that order
  • Assemble NOT USING HOTGLUE but masking-tape and Loctite Extreme Glue (non-resin, rubbery) Rear Bumper B3-B2-B10-B11 at the bare minimum but if preferred include B6-B7 for a full rigid sub-assembly. 21.5 mm Floplast PVC Pipes tend to stick well and stay pointing in the right direction (as long as the PLA has been cleaned up and the PVC cut perfectly perpendicular).
  • With some care, B3 can be tetrahedra-triangulated to R3-R4 whilst R4 can be linked to B10 and B11. Use hotglue for 13mm bamboo and ensure the subassembly is not stressed (use spare 21.5 mm PVC and masking tape as temporary bracing, bearing in mind it tends to roll)
  • R3 can be braced to B2-B10, again remembering that this subassembly is not yet rigid (can rotate about the R3-R4 line)
  • TODO - Using hotglue some bamboo leading across to back box can be added and left to point in free space, temporarily, using Masking tape to loosely bind poles to the same Node.
  • BackBox14 onto R11-R3-B10 is one candidate
  • BackBox15 onto R14-R4-B3-B10 is another
  • BackBox0/1 only have a single strut to R11 and R14 respectively. DO NOT join any other poles onto R11-13 to BackBox because these are actually part of the (detachable, bolted) Roof Assembly.
  • TBC

Videos

https://www.youtube.com/playlist?list=PLBtNqZjUZB81KyRPnMHSmX-vF8i7h5kcA

Screenshots / Images

MBC doorframe geometry.jpg

Useful Links

Retrieved from "https://wiki.opensourceecology.org/index.php?title=UELVE_MBC/v0.1&oldid=279647"