[Bobby Car] Cordless Drill Motor

thingiverse

This is a cordless drill retrofit kit for your classic Bobby Car. It makes your Bobby Car motor powered which doubles the fun. For now, the child has to grab back and pull the trigger of the drill to start going. My 4year old is comfortable with it. **Youtube Building Instructions and Demo:** <iframe width="560" height="315" src="https://www.youtube.com/embed/o65N0sMEa28" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe> **Features:** - Mount any standard cordless drill. - Overrunning (oneway) clutch to keep the car still pushable. It also lets the car roll to a stop instead of an abrupt halt. - Powerful and fairly durable. **Component description:** *pulley_wheel*: The large pulley to be put on the rear right wheel. It fits snugly in the "rim". Fasten with d=4mm wood screws. *cordless_drill_bracket_hinge*: Print two of those and screw them down onto the rear of the Bobby Car. It is a print_in_place part. That means, that he hinge is supposed to be printed as is and is broken loose afterwards. The slotted hole on the front might need support for printing. Fasten with d=4mm wood screws. Push cable tie through the slot hole. *cordless_drill_bracket_plain* [optional]: An alternative version for mounting the cordless drill without hinge. The hole pattern is compatible with the hinge-version. Height is lower. Try this, if your timing belt is too short for the other bracket. *pulley_clutch_casing*: Outer casing of the smaller pulley. *pulley_clutch_catch*: Inner part of the overrunning clutch that keeps the balls. *pulley_clutch_spacer*: Small spacer part, that might be needed, if the threaded portion of the M8-screw is too short. **Additional Parts Needed:** - 1x Bobby Car: https://www.big.de/en/products/big-bobby-car/ - 1x HTD470-5M timing belt. I recommend to order also a shorter and a longer version (465mm and 475mm), to mount the best fitting one. 3$ each on aliexpress.com/ebay.com. - 1x ball bearing di=8mm x da=22mm x w=7mm - Superglue or epoxy to glue the ball bearing into *pulley_clutch_casing*. - 4x balls d=6mm. - 14x wood screws 4x20mm - 1x Hex bolt M8x50 with nut - 2x bolt M6x16-18mm with nut and washer - 2x strong cable ties **Note:** Although already working quite well, this is a work in progress. Please (!) contact me, if you have ideas for improvements. Also contact me, if your cordless drill does not fit into the brackets. I will upload different sizes of the bracket if needed. **FAQs:** - Why not use a cheaper GT2 timing belt? Answ: I tried that, but the GT2 belt is jumping over the teeth of the pulleys. It is just too small. It was not working properly. - Did you try to print the 6mm balls in place? Answ: Yes, I did. It worked to some extent, but smooth, hard, spherical balls are working much better. **Credits:** The overrunning clutch (ratched) design was based on the model of Corona688: https://www.thingiverse.com/thing:207389 **Printing Tips:** - No support is needed, except for the slotted hole in the *cordless_drill_bracket_hinge*. - Print all parts with 50% to 100% infill to achieve max. strength.