SNIPE Posted September 27, 2014 Posted September 27, 2014 Hi Quick question, If I add a return to center spring box, will this cancel out some bump steer? does the PF servo motor have return to center built in? The steering and suspension geometry is perfect besides the bump steer. Regards, Snipe Quote
Balrog Posted September 27, 2014 Posted September 27, 2014 The PF Servo Motor automatically returns to the center. Afaik it will only stay in position if you use the speed controller. With the normal PF remote a neutral position on the controller automatically centers the Servo. Quote
VKTechnic Posted September 27, 2014 Posted September 27, 2014 The steering and suspension geometry is perfect besides the bump steer. You sure it's perfect? Quote
Bricktrain Posted September 27, 2014 Posted September 27, 2014 bump steer is usually caused by the steering tie rods being the incorrect length. if your top and bottom arms are both the same length then the tie rods should also be the same length. Quote
Lipko Posted September 28, 2014 Posted September 28, 2014 bump steer is usually caused by the steering tie rods being the incorrect length. if your top and bottom arms are both the same length then the tie rods should also be the same length. Isn't bump steer caused by the fact that the turning axle is outside the wheel? Which is especially true for Lego. Quote
efferman Posted September 28, 2014 Posted September 28, 2014 (edited) lipko, bump steering in your eyes is the self steering when the wheel collides with a obstacle without compressing the suspension? Bricktrain do you call bump steer when the wheel is turning when the suspension is going up and down, because the suspension geometry is not correct? Edited September 28, 2014 by efferman Quote
Lipko Posted September 28, 2014 Posted September 28, 2014 (edited) lipko, bump steering in your eyes is the self steering when the wheel collides with a obstacle without compressing the suspension? Yes. Actually I don't know how the term is used, but I think the behaviour described by the Original Poster is the same that I'm talking about. Since a suspension-geometry-caused steer would return to center by itself as soon as the suspension compression is gone (and this kind of bump steer doesn't move the gear rack so it would be meaningless to ask about returning it to center). Edited September 28, 2014 by Lipko Quote
SNIPE Posted September 28, 2014 Author Posted September 28, 2014 (edited) Here's a pic of my setup Not sure why I'm getting bump steer I guess its just something that comes with using lego. More images I have the LXF file but some parts are connected but not lined up properly and are colliding but LDD does not remove them. Regards, S Edited September 28, 2014 by SNIPE Quote
weavil Posted September 28, 2014 Posted September 28, 2014 With the angle of the suspension arms, the steering linkage has to match perfect. The angle has to be the same - if the linkage mounts 1 stud below the height of the top arm the it must mount at the same point on the diff housing. And the same for horizontal distance from the suspension arm. Basically make a rectangle with the arm and linkage. Quote
SNIPE Posted September 28, 2014 Author Posted September 28, 2014 The steering arm is almost the same vertical angle as the suspension arms and it is almost parallel to the suspension arm. I could make it completely parallel but I cant do much about the vertical angle, the best I can get it is to put the steering arm and ball under the connecter. it wont seem to fit anyhow if I try to make the vertical angle correct. with me using a 4L thin lift arm its hard to get the steering arm in the middle of that. Quote
weavil Posted September 28, 2014 Posted September 28, 2014 Well even if everything is lined up perfect, slack/backlash will remain. Thanks to Lego fault tolerance (spacing of studs) everything on the front will seem a little loose or wiggle a bit. Quote
SNIPE Posted September 28, 2014 Author Posted September 28, 2014 Yeah I've made the parts as tight as possible The wheels have friction pins that connect to the disk brake, 6 per wheel The suspension arms are connected to the chassis using 3L friction pins as frictionless had a lot of slack Etc I might add bricks inside of the tire if it helps balance the wheels better. Quote
dhc6twinotter Posted September 28, 2014 Posted September 28, 2014 Looks like you are using 6L links for your steering, but your suspension arms are the newer 5L arms. This is probably what is causing your bump steer. The steering links should also be at the same angle as your steering arms, but I can't tell if this is the case in your pictures. If you want to eliminate bump steer, it's best to have the steering links the same length and angle as your suspension arms. Also, your inner u-joints are one stud too far out on either side. Since you are using 5L suspension arms, you will need 3L axles between the inner and outer u-joints. Quote
SNIPE Posted September 29, 2014 Author Posted September 29, 2014 (edited) The UV joints don't fit with a 3L axle. I can't think of a way to have 5L steering arms. I'm using the shortest possible suspention arms because I don't want the wheels to be sticking out too much. The steering arms are as close as I think I can get it in terms of their angle. Edited September 29, 2014 by SNIPE Quote
Hrafn Posted September 29, 2014 Posted September 29, 2014 The UV joints don't fit with a 3L axle. I can't think of a way to have 5L steering arms. I'm using the shortest possible suspention arms because I don't want the wheels to be sticking out too much. The steering arms are as close as I think I can get it in terms of their angle. The 5L suspension arms have been used by others as steering arms. It's tricky to get it to work since one end only has one degree of freedom, but might be an option. Quote
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