[WIP] crawler/monster truck

[Leif]

My first attempt at a crawler.

I posted some of the setup in the Axle thread earlier as well.

the geometry is excellent. steering is weak but correct(!) which means Yes Ackermann, No Bump steering

Which I as a returning AFOL after some 30 years feel as a step forward for myself

Steering has to be stronger, got some ideas there. Chassi is good and BB is already easy to remove for battery replacement so that feels good. build is modular although repitive of course.

However, with this strong, braced design, I actuall get gear grinds between bewel and differential. That is the only weak point. More in one direction than the other, but I guess you all know about this...

Any ideas of how to improve on this? I am thinking about a setup feeding the diff from both sides but direction change of gear will be difficult to achive without a lot of gears.

[That_LEGO_Guy]

a good idea would be to put gear reduction after the diff

[Leif]

a good idea would be to put gear reduction after the diff

of course but that would mean wider chassi and/or the dreaded portal hubs...

[Rockbrick]

how about the F1 car hubs and CV joints and making it more centre point steering - I know you said no bump steer but with those bendy 6L arms and such a distance away from the centre point of steering

crawling could be an issue in some situations

Edited November 26, 2014 by Rockbrick

[Leif]

how about the F1 car hubs and CV joints and making it more centre point steering - I know you said no bump steer but with those bendy 6L arms and such a distance away from the centre point of steering

crawling could be an issue in some situations

thanks, I got the 42000 hubs, 8466 hubs and some more, but CV = breakage! there is no way you could build a strong crawler with huge tyres and CV joints...

My build has to be with UV joints and centre point steering must be "as good as possible" due to the build around thoise joints. The race hubs with CV are always the best solution for steering geometry but they wont last when it comes to forces being applied...

[LeocornoProductions]

I would love to see the finished product

[Leif]

Today I caved in and choosed the portal hubs....

At least I know the reason why I have to do this.

Making the steering and the hub powerful enough, I could at the most save ½ stud compared to just mount it all on a portal hub....too much bracing and brick next to brick to get the results (ackermann, no bump, sturdy!)

Yeah, pivots for steering are not optimal but I have to avoid those dreaded CV joints...at least for this crawler/monster!

So now I got strong setup, good gear down after differential which should mean no/less grinding.

But first, London and Bricks 2014 for some days now

[Leif]

Some progress and actually a chassi built.

This is a crawler with the PP tyres and it is really a challenge to build something that can keep them in order!

Features independent suspension on all 4 tyres and finally I think I have everything stable enough!

Testdrive showed that the steering links could pop out so I made "reinforcments with a vengeance " see LDD pics below which are now in place as well, the images below are before it got mounted though.

Anyone else experienced steerings links popping out int this kind of build? And with "this kind of build" I mean crawler with PP tyres and similar!

For me I think it's as much as I can do with 4x4 and independent suspension. This really shows that you got to have live axles and nothing else when it comes to deliver real power...!?

https://www.dropbox....ering4.lxf?dl=0

[Rishab N]

I like the suspension, but the chassis seems a bit short for the PP wheels

[Leif]

I like the suspension, but the chassis seems a bit short for the PP wheels

Yes you are probably right but so far I have only focused on proof of concept of drivetrain and steering. Extending the chassi is just a matter of longer beams and will be done!

[Nalyd997]

If it is to be a monster truck it has to go fast!!!

[Leif]

If it is to be a monster truck it has to go fast!!!

Oh yes, but PP tires and current Lego motors (and gears..), that will never happen..maybe some RC motors but those tires really are like a giant flywheel - and with friction as well...

I have now decommissioned this build, having finished all my POC, Proof of Concepts I was aiming for.

For example, the "Technic, Steering Arm 5.5 x 2 with Towball Socket Rounded, Chamfered" (why 5.5, it really is 6 in length?!)

works really good with the regular 6 length technic steering links for independent suspension and no bump steer, but really cannot hold everything in place when you start to climb rocks!

Live axle is the only solution for climbers, I now have concluded..if you want true strength..