Spur gear transmission

Here is the spur gear transmission that I have designed . The overall ratio is 4:1 ( 2x 2:1) . It can be mounted to either reduce or increase rotating speed . My intention was to have a cool mechanical toy on my desk . I used 6x 608 RS ABEC-5 bearings (8x22x7mm) . In simulation I have used simplified models of the bearing ( solid rings actually ) so if you dont have them , it might work to print those and put some grease between them and shafts . The external dimensions of the body are 200x64mm so it should fit most of the printers . Bearing covers are not a must , yet I designed them to have a good looking enclosure for them . Mounting holes will also be able to house the top cover if It will be designed but I think there is no point in covering the insides .Handle is not a must , I have made it just to make it easier to move the gears . You can attach whatever you like to the transmission . One shaft ends with a 4x4mm square socket at a depth of 10mm . The other one , where the hand