solution to negative caster on unimog type axle

[z3_2drive]

Hey everyone, back with a smart solution to the negative caster on axles with unimog ball joints, and a compact start to a chassis with two xl motors. I scrapped my old trial truck start but it was too complicated, and I need to stick to simplicity, with less gears and weight pics:

^while testing strength, I underestimated torque and it pulled my finger in...still hurts

I guess it will help steering and just look better, and maybe suspension will twist/compress better... hope you like it!

[Kierna]

I need to stick to simplicity, with less gears and weight

Then build a motorcycle... they win the Dakar most years you know

Just pulling your leg, cool truck, looks lightweight and strong

[Zerobricks]

I think that the caster angle as long as its low can be tolerated. The way you built it the weight rests on the rotaing axle, causing friction.

[MarkusOSX]

Hi,

Looks great.

One question ( I'm sure somebody asked already):

Where to get this awesome tires ?

Greetz

Markus

[DLuders]

Where to get this awesome tires ?

They are the RC4WD Rok Lox 1.9 Comp Tire ( http://store.rc4wd.c...ires_p_696.html ), which fit onto the standard Lego 44772 wheels.

[z3_2drive]

I think that the caster angle as long as its low can be tolerated. The way you built it the weight rests on the rotaing axle, causing friction.

What do you mean rotating axle? everything is extremely sturdy and braced, and the crawler itself will be light, so there is no extra pressure on the actual moving axles... And BTW I've figured out a simple steering unit, and I am thinking about 4-wheel-steering....Should I change the caster of the rear axle or keep it normal? Here's pics of steering system:

[Zerobricks]

The axle in the middle of the H beam carries all the weight.

[AndyCW]

Your solution has potential.

One thing about this setup though. Suspension cycle causes significant lateral movement of axle, because of the angle of the torque arms. This also means that when the suspension encounters an obstacle the lateral forces against the suspension cause it to try to cycle. This movement can cause the suspension to bind and in some extreme cases fail. Measure wheel base with suspension unloaded, then measure wheel base with suspension loaded. The difference should be negligible. There is a reason this style of suspension with these angles does not exist on full scale crawlers.

The torque arm needs to be as close to level as posible and then you can adjust the angle of the "H" frame to get the desired caster.

Does this make sense? Does anybody else see what I am saying? Am I way off base?

I see whay Zblj is saying too. The axle going between the portal hub with the 20t gear on it bears all the weight of the "body".

v/r

Andy

Edited January 15, 2013 by AndyCW

[Morj]

The axle in the middle of the H beam carries all the weight.

I almost see that grey dust...