bump steer

i started to get my steering set up and i have alot of bump steer. i have it set up like most of the trucks here. do u guys just run with bump steer?

[Jimbob454]

Whats Bump steer?

Tim.

[sawhit4]

i think bump steer is where objects that you are trying to go over turn the steering wheels and cause the truck to turn. i could be wrong though.

[mde]

Originally posted by sawhit4
i think bump steer is where objects that you are trying to go over turn the steering wheels and cause the truck to turn. i could be wrong though.

You are correct, that is indeed bump steer and the problem I faced with my stock Race Tin for Truck Trials.

[sawhit4]

yay go me! anyway why does this occur? i dont know if the small scale electronics are the same as 1/10 scale but on my 1/10 scale monster truck the steering servo keeps the wheels from turning when they are hit by something and then the servo saver keeps the servo gears from stripping if something hits the wheels with alot of force. are the smaller servos not strong enought to keep the wheels straight?

[Lee]

it's because when the wheel moves up and down it does so in a slight arc, ineffect making the tie rod shorter or longer, which turns the wheel

Lee

[sawhit4]

so are you saying that whenever the wheel moves up and down its gonna turn? or that when it moves up and down it allows itself to be turned?

[mde]

Bump steer is an issue all automotive engineers have to deal with. Even the mighty Dodge Viper suffers from bumb steer. I nthat case its an issue with the suspension geometry not uncommon to that class of car.

On my Race Tin Trials Truck bumpsteer is worst when one wheel hits a bump. The return spring is not strong enough to prevent the wheel from being deflected by the bump force that is pushing it both back and up at the same time.

The play in the steering system exasperates the problem. Even though you have a servo your steering linkages likely have some play in them which is required to prevent binding.

As a result the wheels turn. On this car they are moving straight up and down on a vertical shaft so the suspension does not travel in an arc.

If your truck uses a rocking solid axle your wheels will move in an arc but the steering arms move in the same arc so I don't think that is the cause in your case it is more likely the bump force moving backwards against the direction of travel that is the main issue.

You can check this by seeing if the bump steer is worse when the wheel goes over a square edge bump compared with a shallow angle bump.

On the RTs and some of the other 1/28 and 1/64 mini rc cars some people use heavy grease, oil soaked tissue or wax to take up some of the play or slop in the steering system. Some people also wrap the shafts in the system in tape to take up slop.

It will take some trial and error to determine the amount of slop you can take out without causing binding in the system.

If you can post pictures or even a video clip of the problem the members can probably help more.

right now i don't have the servo mounted so i was trying out different places to get rid of bump steer. its worst when the wheels are turned to the left and the when the axle moves the wheels go shaight. i guess the i will have to keep trying to find the best way to fix it.

[goldtj]

if you have bump steer u will probably just have to live with it im afraid. Taking as much play out of the steering linkages as possible without them binding should help.