HobbyKing BSR BZ-222 gearbox

thingiverse

Here is a gearbox for a direct belt connection without the belt tensioner. As most owners know, the original gearbox has a major problem with the belt breaking. The original design is from The Crack Fox, who designed it to be CNC cut. https://static.rcgroups.net/forums/attachments/3/9/3/8/8/6/a7856168-100-IMG_20150504_231729.jpg I really thank him for his design and STL file that I used to create this gearbox to be 3D printed. Today, I did the first test drive, and it's driving pretty well :-) Must say installing it was quite tight so I might have to move the holes that hold the motor plate just 1-2 mm. I removed the motor coverplate, and after that, installing it was easier. Still some minor things I overlooked like the two front nuts that held the two screws didn't fit on because it was too close to the wall but with a little grinding, I made it fit. I changed it in the STL file but haven't printed that one yet so I'm not sure if the room I cut away is now enough. The motor plate is held by two screws because the third hole falls in a spot where the belt is now running but it seems to hold up fine with just two screws there. I will still be making some small adjustments over time, but for now, this gearbox seems to be working great! Belt I used: 6 mm 45 teeth 135 mm length. https://nl.aliexpress.com/item/POWGE-Arc-HTD-3M-Timing-belt-C-132-135-138-141-width-6-9-15mm-Teeth/32818738308.html?spm=a2g0s.8937460.0.0.Nx8eaN Printed mine in PLA at 100% infill. Also tried a PETG version but that seemed to have more shrinkage so parts didn't fit too well. Other parts you may need: 2 * M3 20mm sunken bolts/screws 2 * M3 30mm sunken bolts/screws 1 * M3 20mm bolt (normal) 1 * M3 35mm bolt (normal, I just cut a 40mm shorter) optional >> sunken M3 bolt 10mm. This is for the hole with no nut. 6* M3 lock nuts. Also, maybe it's best to attach the shock tower with nuts also. You will need: 2 * M3 15mm sunken bolts/screws 2 * M3 20mm sunken bolts/screws 4 M3 lock nuts. Added a rev 1.1 with a straight line to hold the nut on the shock tower. Update: 3-04-2018 After like 30 lipo's, the belt is still holding in this 3D printed gearbox. I did break an arm that holds the wheelbar nut so I made a version 2.0. This one has stronger reinforced arms that should hold better in a crash. Also added a little window so you can keep and eye on the belt. Don't forget to print the cap (printed mine with flex/nylon). Update: 1-11-2018 Added a v3 version. Only some small adjustments, made holes that hold suspension balls a little smaller. Update: 29-08-2019 Added a V4 version. Thinner walls since I did notice some wear on the belt because it was hitting the inside wall. Rear hole move a little so bolt and nut fit better. Reinforced wing holder.