The description may sound worrying, but i `ve chosen it because the result of my work had remember me on those famous radiator mascots like the "Emlily" from RollsRoyce or the wildcat from Jaguar.
The Idea behind had started with a simple task and ended up in a long time project that i d like to share here.
It may not fit perfectly to your kids or other bike, but maybe my instructions will inspire you to create a own version.
As you will see in the later steps, the carrier unit can used also standalone and the ornament could be replaced with your own creation maybe made of plywood. It only has to fit in the allocated space of the top plate.
Also the ornament can be swapped with others without tools.
You can skip the cad descriptions and go straight to the last step if you like. Or you can get inspired and read the whole stuff.
All described programs i used are openSource :)
Anyway, all has begun with a Puky children's bike that was own by our daughter when she was a little one.
Now she has already a 26 " sized bike and the puky bike is supposed to give away to my nephew, who has reached the age to ride this bike.
The mudguard of the front wheel originally had an edge-protection with a little flag on the top. Both was lost due the years and within, the mudguard was left with a sharp edge.
Ok, i got an 3d printer, some ideas. why not making a own cover?
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Step 1: BOM: All You Need Is ..
The printed parts:
- shoe.stl (blue)
- plate.stl (brown)
- top_plate.stl (green)
2 Neodymium Magnets 15mm diameter x 2mm thick
1 Screw with Hex head 5mm x 20 (or allen key - see last step)
1 Nut M5
Also glue to fix the magnets safe.
Metal saw and files, sand paper.
Step 2: Task One: Reverse Engineering of the Tin
The main question was how to get the mudguard into the cad?
Unfortunealey i ow no 3d scanner, at least not a big one to lay in the unmounted mudguard.
So i fixed some how the mudguard with the front profile site on the glass of my ordinary Epson 2d scanner. The focus range of this scanner is wide enough to scan the far more bevel parts almost sharp. The profile describes a bow from the top view and lays due this reason not flat on the scanner.
After some try `s of scanning i edited the image in gimp to make it more visible. First i turned it to b/w and then i reversed the colors. Finally i played with the contrast curves to get a sharp monochrome picture. The picture looks a bit x-rayed like.
Now i imported the pic into inkscape and drew with bezier curves the profile almost like the picture. The picture appeared not symmetric behind and so i drew only one half, mirrored a copy of the paths and connected the path points. For the following step the path has to be not solid and closed. See also attached svg. file.
Step 3: Task Two: Make the Profile 3d and Create the Cover
After firing up FreeCad i imported the svg path.Now i had to sweep in part-mode the profile along a path that describes first the mudguards radius and second a segment of it. So i made a sketch with a circle segment to sweep along.
Almost done, the tin is inside the cad! Now i created a profile for the cover and let the tin cut i inside with a boolean operation. Now i added a screw an let it make a cut on the place where the original tin has already a hole. For this i modeled a hexagon head screw.
The cover was finished after rounding the corners on some edges in the final edition.
My Hint: it`s easier to make a sketch with straight lines than putting the round corners into it. So the sketch is easier to parameterize.
The project would end here as single boring cover if i hadn't have the idea to put a mascot on it ;)
Step 4: Task Three: Fix Dat Bird
Still in FreeCad i had to create a carrier for the bird.
The bottom part has to carry the nut and fix the cover. The replaceable top plate has to carry the ornament. Also both parts are supplied with a neodymium magnet to fit together without using tools.
Both parts where made with a profile sketch which was turned then in part design mode. Now the plate was cut with the nut, screw and the magnet, the top plate with the magnet too and the slot on top.
Finlay the outer hex-shape was made with a surrounding hexagon cutting both plates on the outline. The slot is designed in a straight mm unit of 4x14 mm to make it easy to fit in other self made ornaments.
If you study the cad file you will see the slot and the screw-head/nut are a bit over-sized. This is for better fit and because of my (and sure many other) printers makes inner-holes smaller than in the file. Nevertheless less of good calibration.
Step 5: Task Four: Create an Ornament
At this step you can make your own ornament if you want to give it a individual note. Due the primitive slot measures it has only to be 4mm thick and 14mm wide at the fixing point.
I am not a big artist in creating 3d animals so i decided to make a simple penguin in Inkscape.
After finish the simple paths i imported it into freeCad and extruded the single paths solid in part mode. You can also do this step in blender etc. As you can see in the penguin cad file, i `ve meshed the extrusions too to make the edges rounder as they came out after importing.
You can see in the svg and cad file too,that i `ve made extra wings, belly and eyes. At least i decided to print only the body in black ABS. The black penguin body rather looks like a crow then ;)
After finishing the print i filed and sanded the bird. How i get him smooth you can look in www. I don't want describe it here in case of security reasons and a comment-storm about the dangerous handling of acetone.
Anyway, i painted the beak, belly, feet and the eyes simply with acrylic colors and sprayed it with transparent varnish to save the paintings.
Step 6: Put All Together:
The mounting is quick done if you have the parts and materials already laying beside you.
For better mounting i recommend to unmount the front wheel.
First slip the shoe called part (the blue one here) over the mudguard until you see the hole. If you can fit the shoe on an other mudguard, but you may drill a hole on this place with 5mm.
Then put the screw with the head down from the wheel side through the shoe and the plate (yellow) . Now drop the nut in and fasten it by turning the plate part tight. The stopping point may not fix with the top plate. If you like you can replace the hexagon screw wit a allen key type and fix the plate by turning the screw. So you can set the position.
At least take care that the screws thread doesn't reach the hole where the magnet comes in. You can mark the over-standing thread with a felt marker and unmount all to saw the screw there.
If all fits you have to glue one magnet in the bottom and one in the top plate. I used 2 component resin glue. Clean the magnets before with alcohol and make sure that the polarity fits before glue the magnets in.
Finally you have to glue the ornament into the slot. Maybe yo have to file a bit to make it fit tight.
Now the bike ride can start into a new adventure with a leading storm-bird on the shield ;)