MAN 6x6 Gearbox Question

[Beck]

Hello Everyone!

This is my first Technic MOC that I've posted. So here goes!

I decided to build a 6x6 MAN TGS with a simple 2 speed gearbox. I have been inspired by many other designs. You may recognize these if you are very observant. To the point of this post. On my first prototype I used Sariel's 2 speed linear gearbox which proved to be very effective, but too large. I decided to have a crack at building my own gearbox. This was the result (http://www.bricksafe.com/pages/Beck/technic_mocs/6x6-man-crane-truck-) see images "IMG_0284-IMG_0286" I tried to make it as simple and robust as possible.

My problem:

Due to the weight of the truck the gearbox makes a clicking noise whenever I add a load to the chassis. (I use my hand to apply a force to simulate a load) Also when the clicking starts the truck looses torque that I feel. What can I do to fix this problem? I have uploaded videos on my bricksafe account. For test and recording purposes I used (http://brickset.com/parts/4270473) to stay in gear.

FYI: the truck is a WIP and is nearing completion

Thank you in advance!

Any help/advice is appreciated!

[PeterF]

It seems to me that the bracing might be insufficient. The 5x7 frames can be pushed apart by the motor, which causes the gears to slip.

Looking at img_0285, you could put some 5x1 or 5x3 liftarms on there to keep them together tightly.

[TheNextLegoDesinger]

here is the version i made of Sariel's gearbox which is pretty small and it shifts very good. BTW its smaller than sariel's

2-speed-gearbox 2 by thenextlegodesinger, on Flickr

2-speed-gearbox by thenextlegodesinger, on Flickr

if you want i can make an LDD file of it

[Beck]

Thanks for all of your feedback!