before I get too far into iterations and troubleshooting…
Because I am doing a Family Night at a racetrack for a local non-profit, I thought to make a couple of toy dragsters with interchangeable wheels for kids to experiment with {change wheel size, change weight…}
I am thinking acrylic or wood for some parts and PLA for others.
Chassis :
laser cut wood or acrylic, it is about “adult “hand size
the gray areas I am thinking to etch a recessed spot to help hold motors, holes are for tie wraps to really hold motors (so this depends on size of your motor)
https://cuttle.xyz/@makervan/chassis1-Ab651LBLWVwu
I am thinking a hole towards the back for a switch to turn motors on/off.
Also some holes for tie wraps to keep a battery pack in place (3 – 1.5 V).
What batteries depend on your motor. I could use 2 – 1.5 v up to a 9 V with mine.
Watch batteries do not work – I assume not enough current.
Not sure how I am attaching front wheels… maybe eye screws big enough to hold a skewer/dowel rod. So I would want some holes towards the front smaller than the screw.
Wheel hub :
Partially designed in cuttle because they have that “rotational repeat” and I want 4 screw holes to attach wheels. It is 25 mm in diameter and I am thinking 3 mm holes for M3 screws (i found some #4-40 screws in our space that fit) (https://cuttle.xyz/@makervan/wheel-hub-5xzTCyCGPZTi )
Then I take that svg into tinkercad to add the nub that will attach to the motor. Nub is 5.5 mm in diameter, 10 mm tall, with a hole that is 2 mm in diameter and 8 mm deep.
(https://www.tinkercad.com/things/iVyNuqqOpj4-fantastic-hango/edit?sharecode=c-RS1YTB7irArdffkh2cD6OsmLTZN2UcbEMm39TKaUM )
I made one hub that is 2 mm thick and one that is 3 mm thick. Combined they took 18 minutes to print.
This import into Tinkercad is where I ran into trouble…it doesnt come in at 25 mm, it comes in around 70 mm. So for one of them i just shrank it down to 25 mm on the work plane, for the other I imported at 35.7%. The screw holes were slightly smaller in the one I shrank on the work plane.
The problem I do have is the 2 mm hole is too small for the motor spindle. “Easy” fix, T&E til I get the right size that fits.
Wheels :
I copied the hub design in cuttle and made the outer circle larger, this time 40 mm.
I laser cut them out of acrylic and wood.
2 wheels takes 35 seconds
I need to be careful about screw length so that they dont hit the motor.
But I might want a few different lengths in case someone wants “fat tires” (multiple layers).
NEXT STEPS
– get the nub to fit on the motor spindle
– front wheels (thinking similar but skewer will need diff size hole)
i could glue a coffee stirrer or straw on and run the axle through that instead of eye screws
– battery pack & switch (in the mail)
-make 3 cars
-multiple wheel size options
This could be a good purchase for components to get started
https://www.amazon.com/dp/B08GPPJR1T
UPDATE
motor hub… hole needed to be 2.4 mm. decided on 2 mm thick. looked at 1 mm and thought too flimsy. Though it takes 5 mins to print 1 mm version and 8 min to print 2 mm version
{ https://www.tinkercad.com/things/fSIMy9KTR5p }
For the front wheels if I use a skewer, the hole needs to be 4.2 mm diameter (& still 8 mm tall ; the nub is 8 mm diameter x 10 mm tall – on a circular base 25 mm x 2 mm with 3 mm holes)
https://www.tinkercad.com/things/4q3u6Kg8L2Y-wheelhub4point2mmhole
Anyone have a “better” way to attach instead of tiny screws…those are tough for my fingers??
A thought came to me about using Lego Technic connectors…I tested on laser and a 4.7 mm hole fits nicely…but 3D printed it was too small. So 4.8 mm (and 2 diff printers printed same file slightly differently – hole not exactly the same)
there is a little gap between hub & wheel because of the design of the connector.
Each side of the connector is ~ 5mm and we are not filling it up here…issue?
Be sure both sides are seated against the middle or will have wobbly wheels.
It takes some force to put the wheel on & take it off – not sure that will be possible with hub on the motor…or will kids just take hub off the motor to switch wheels??
Leave a Reply