Updated RC car differential gearbox

prusaprinters

<p>I'm posting the latest version of my design, as file update on an existing model seems broken…</p><p>So disregard the other design as it is now missing some files…</p><p>This new version has a simpler sun gear output axle (no screws, &nbsp;one single part !)</p><p>-----------------------</p><p>In my RC 4WD design I'm only using ball bearings and M3 hex screws and nuts and PLA/PETG. So, no metal diff box or shock absorber from online vendors! Here’s the diff box.</p><p>(There is quite a lot of ball bearings in the overall design, check the 5 to 1 GB, my other design). https://www.printables.com/model/225851-5-to-1-gearbox-for-2216-motor</p><p>I'm using the MR115-2RS B115 (5x11x4 mm) and 608 ZZ (8x22x7 mm) ball bearings.</p><p>If you are familiar with diff box design, the tricky part is that there are two concentric axles, the one of the crown gear and the one of the sun gears… That’s why you need 2 different sizes of ball bearings. Plus, the fact that I wanted everything to be printable!</p><p>I’m also quite happy with my bevel gears designed without script (meaning starting from one tooth and doing all the math!). That’s 3 gears total because the sun gears and the spider gears are identical gear side. I was also pleased with the tolerancing that worked quite well.</p><p>The Diff box further reduces the motor speed by a factor of 2. Now at max speed (with my 2216 motor) the wheels will go at 700 rpm.</p><p>For the Diff box you will need 6 x MR 115 and 3 x&nbsp;608 ZZ ball bearings and a number of screws and nuts of different lengths. 40mm to secure the diff cup onto the crown gear.</p><p>The pictures should help with the assembly.</p><p>The gears and axles should be PETG the rest can use PLA.&nbsp;</p><p>I will use 6 couplings in the design: 2 will power the 2 diff boxes and 4 will drive the wheels.</p><p>I'm attaching the latest progress of my overall design (F360 view) … I've yet to try to print everything. I've made the design dual steerable. There are optional “blockers” which prevent the wheel to steer (this should be for the rear wheels). This part is replaced by the steering levers for the front wheels. The picture shows the front of the car (but you cannot tell because the steering part is hidden behind the differential and the tires). This will be a big thing as tires have a 16 cm diameter.</p><p>PS: The Diff box works! When you hold one output axle and rotate the pinion the other output axle rotates. If you need to change the output rotation direction just flip over the crown gear assembly in the casing from right to left.&nbsp;</p><p>You will need to remove some in-design supports with a small screwdriver (screw holes in the gears)</p><p>The bearing holders hold 2 BB: 1 MR115 and one 608 ZZ.</p><p>I've since released the car ! You can get it at:</p><p><a href="https://www.printables.com/model/281110-4wd-rc-car-185-parts">https://www.printables.com/model/281110-4wd-rc-car-185-parts</a></p><p>&nbsp;</p><p>&nbsp;</p>