Problem with 8069 Backhoe Loader

[wgemini]

I just built this set and it's fantastic. However, I have one issue. The back section (with the digger) wobbles around for some reason. It has a worm gear for the rotation. However, since the space is slightly bigger than the worm gear, the gear can move without being turned, which means the back section has a lot of play. Am I doing something wrong or is there a way to fix this? 

Thanks.

 

[HallBricks]

I don't have that set, but I can see that the rotation of the back section is driven by a worm gear that meshes with a 8 tooth gear. That configuration usually has quite some play, and since the worm gear is slightly shorter than 2L it can slide sideways with increases the play even more. I would say the play you are experiencing is normal, unfortunately. 

[kolbjha]

I can confirm what HallBricks writes. It sounds like normal. I did a mod, using a 24 teeth gear instead, and the play was reduced a lot. I remember it was not straight forward, required some rearrangement. Unfortunately, I disassembled it long time ago (despite it is one of my favorite Technic models...), so I can't post any pictures.

[wgemini]

Thanks. Yeah, that's the exact problem. The worm gear is ever so slightly shorter than 2L so it slides around. I think I will try to change the pins above and below to make it tighter. 

[doug72]

A simple solution is to use thin nylon washer to take up the slack of the worm gear and use the latest version of 8T gear.

Edited May 29, 2017 by Doug72

[mocbuild101]

That's normal for that combination of gears, it's because of the large backlash combined with the sliding of the slightly shorter than 2 stud worm gear.