[WIP] Portal axle concept

[JGW3000]

What do you think of this home-made portal axle? Will the axle-8 with stop, not being as well supported as by Unimog portal axle assembly, for example, be able to handle stresses and weight of an attached model? I am anticipating a medium sized chassis but maybe four motors plus servo on the finished machine. Of course cross-bracing and other attachments can be added, not shown to keep this simple.

Thanks for commenting - here is the lxf - http://www.bricksafe...portal axle.lxf

Edited February 26, 2014 by JGW3000

[jantjeuh]

I think it will come apart at the bottom if high torque is applied.

[Lakop]

I think it will come apart at the bottom if high torque is applied.

Yes. I think it needs some strengthening near the larger gear and then it could be a solution.

H

[Marcel1980]

Even after that i still think its kinda weak. But how do you want to add steering or attach it to the chassis?

[JGW3000]

Thanks, I am also concerned about the bottom, but adding sufficient bracing somewhat negates the whole concept of having a portal axle, as too many parts at the bottom limits the extent of ground clearance. I guess this is why LEGO made specialty parts for this function. Something to sleep on...

For steering, I will work out some form of strengthening of the universal joint, there are ideas in Sariel's book for doing this. I haven't worked out the connection between a steering rack and the axle yet, though..

[Junpei]

Hmm... I'm not sure about this at all. Firstly, it will not be able to handle high torque, and may not even be able to steer; at least change that 8L input axle to a 4L one, but the turning radius even shortened 5 studs is absolutely ridiculous... :/

TLH

[nicjasno]

That is very very weak. That red 2 stud connector... you want the liftarms to be at the wheel. Otherwise it'll all bend like chewing gum. In all directions.

[unimog123]

With a setup like that it is practically impossible to brace it enough to prevent the 13L beam from bending under the weight of the vehicle. Also why do you want such large gears? They only cause more friction, and if you want a better gear reduction you could do it with much smaller 8t and 24t gears.

[nicjasno]

And then the whole setup would fit inside the rim. At that point you can just take the unimog portal hubs.

Edited February 26, 2014 by nicjasno

[JGW3000]

Wow, some great experienced comments, appreciate it.

Using smaller gears would be better, but gives less clearance.

@20LH - axle lengths were selected in this example for clarity, I guess I would have figured out issues with turning radius eventually.

Well, its back to the drawing board, I was hoping to use parts on hand rather than BL'ing proper portal axles, but may need to reconsider.

[Hrafn]

Wow, some great experienced comments, appreciate it.

Using smaller gears would be better, but gives less clearance.

@20LH - axle lengths were selected in this example for clarity, I guess I would have figured out issues with turning radius eventually.

Well, its back to the drawing board, I was hoping to use parts on hand rather than BL'ing proper portal axles, but may need to reconsider.

If you want to avoid having to buy the Unimog portal axles, it's very possible to build robust portal axles that use smaller gears using basic parts. Sariel for example did so in his Hummer:

Or see the instruction photos for his Jeep Wrangler.

I realize that might not have the clearance you're looking for, but it does show that you don't need the Unimog parts.

Edited February 26, 2014 by Hrafn