Steering for Fast Vehicles

[rkkm]

Ok, i have just ended last topic so now another question.

I need to do steering for my car ( Driving 20 kmh max ). I want to do steering with good angle, it is first question - zerobricks told that for fast car best angle is 10 degree cause of stability, but i read that best is 30 degree, but i dont know if it will be best for that fast car. 

Next question - perfect return to the center steering, i have used white shapes trick with paper stripe, but it dont work well, meh, it work hopelessly for me - it i to easy to rotate pins in tube ( dont know how to name that part ). In comments of white shapes video of this trick technic dragon said that there are other ways or perfct return to center, for example rc unit, but i got it and id dont really work, even on my friends supersonic...

So for now my most important question is how to do perfect return to the center steering for my car to drive straight, cause i was trying to make steering attachment for 2 weeks and nothing still, this weekend i spended on it all time...

[syclone]

During my own tests the 10° caster worked the best too, about the return-to-center steering I can recommend using a hockey spring or a custom assembly (I have done a tutorial on my channel) 

[Aventador2004]

Try this, it has instructions but I am not sure it is needed.

[Beck]

Simple: use gears to change the maximum deflection of the servo. 8 and 24 tooth gears will reduce the deflection angle by 1/3, so 30 degrees. Remember that two gears will offset the return position of the servo, so add 3 or more to solve this problem. Keep in mind that more gears increase backlash, which decreases the accuracy of your steering system.

Edited May 15, 2017 by Beck

[Marxpek]

Steering at high speeds can very problematic, if you check my you tube channel you will see.. you will need a good setup (my avatar is the current speed record front-end)

camber, caster, and toe-in, all help to provide stability.

check this site for basic information about that http://en.intraxracing.nl/techniek/camber,-caster,-toe-intoe-out/

I have bad experience with gearing down servo's, any play on the gears will decrease steering abilities and that play we can never prevent, over 20 km/h you will surely be uncontrollable with a geared down servo.

A self made return to center system could work, but it would need strong rubber bands as the forces on the wheels increase with speed and you don't want it to steer by itself..  (i do not own a hockey spring so i never tried those)

Going fast is easy, but have control while going fast is harder even with a good setup you can easily flip you car with a wrong movement, good luck!

[doug72]

You could try one of these:

http://www.brickowl.com/catalog/lego-technic-axle-joiner-rectangular-with-spring

Using a normal motor it has spring return to centre.

[Marxpek]

@Doug72Yes that is the hockey spring, but i have no experience with it since i don't have one, do you recon it will work with high speeds? (solid springs inside?)

[doug72]

14 minutes ago, Marxpek said:

@Doug72Yes that is the hockey spring, but i have no experience with it since i don't have one, do you recon it will work with high speeds? (solid springs inside?)

Yes if you are OK with left / centre / right. You just need a dab hand with remote to control direction.

It mounts on the front of any PF motor OK.

[rkkm]

9 hours ago, Aventador2004 said:

Try this, it has instructions but I am not sure it is needed.

I dont mean that, i got servo and rc unit but ill try using that trick on my rc unit :)

 

1 hour ago, Beck said:

Simple: use gears to change the maximum deflection of the servo. 8 and 24 tooth gears will reduce the deflection angle by 1/3, so 30 degrees. Remember that two gears will offset the return position of the servo, so add 3 or more to solve this problem. Keep in mind that more gears increase backlash, which decreases the accuracy of your steering system.

Dont mean that, i dont want to decrease rotation of servo, i want to set steering attachment angled.

 

35 minutes ago, Marxpek said:

Steering at high speeds can very problematic, if you check my you tube channel you will see.. you will need a good setup (my avatar is the current speed record front-end)

camber, caster, and toe-in, all help to provide stability.

check this site for basic information about that http://en.intraxracing.nl/techniek/camber,-caster,-toe-intoe-out/

I have bad experience with gearing down servo's, any play on the gears will decrease steering abilities and that play we can never prevent, over 20 km/h you will surely be uncontrollable with a geared down servo.

A self made return to center system could work, but it would need strong rubber bands as the forces on the wheels increase with speed and you don't want it to steer by itself..  (i do not own a hockey spring so i never tried those)

Going fast is easy, but have control while going fast is harder even with a good setup you can easily flip you car with a wrong movement, good luck!

Tryed your steering in my tricycle, it was good but still, it was driving slightly left or right, im thinking that my rc unit can have problems with servo, ill try normal pf servo today, if u want i can send u sum pictures of tricycle, it was build likely to your, but its max was 24 kmh, and rear wheel was conected to buggy motor, without gearing.

 

21 minutes ago, Doug72 said:

You could try one of these:

http://www.brickowl.com/catalog/lego-technic-axle-joiner-rectangular-with-spring

Using a normal motor it has spring return to centre.

I would see a video of how it works, before i buy it, but it could be a good idea to make rc unit's servo returning to center ideallly :)

[Marxpek]

 

Just now, Doug72 said:

It mounts on the front of any PF motor OK.

 This spring can turn a XL-motor or even a L-motor? or is it just about the mount? i'm curious about the force of the springs inside..

[doug72]

29 minutes ago, Marxpek said:

 

 This spring can turn a XL-motor or even a L-motor? or is it just about the mount? i'm curious about the force of the springs inside..

Sariels Guide book has information on how to use this and recommends its use for fast vehicles.
Also shows on page 223 - 2nd. edition how to mount on the front of an M motor using 4 x 2L x 0.5 plates with axle holes.

[JJ2]

I would recommend using a very robust custom made steering hub and using wishbones instead of the 6L links if you car making it suspended, if not I would recommend about a 30* caster angle and a kingpin incline, they will make the steering have very little bump steer with will improve performance.

I might make a moc'up of one and post a picture

[rkkm]

2 hours ago, JJ2 said:

I would recommend using a very robust custom made steering hub and using wishbones instead of the 6L links if you car making it suspended, if not I would recommend about a 30* caster angle and a kingpin incline, they will make the steering have very little bump steer with will improve performance.

I might make a moc'up of one and post a picture

It would be great, im kinda mad now and from yesterday i didint even take any brick in my hand, 2 weeks spended on steering, no results...

Problem is that i dont got wishbones, got only 6l link no 9l (  i got 12 6l links )

i got two of this: 6571

Rc steering unit complete

4 of 92908

2 of 6572

4 of 57515

2 of 11950

2 of 11949

nothing more for steering unluckly ( not inclui]ding normal parts ) i cant buy nothing now, even if its cheap - im poor :D i have bought slash's wallpaper and metallicas, 3 lifepo bateries, new charger for them, ner rc unit, new supersonic and 2 brand new buggy motors, rest of month ill eat just bread :D

[rkkm]

and whats the kingpin>?

[Zerobricks]

One suggestion. Keep gearing to minimum and instead use as long as possible steering arms. This way you have much less play in the system and accurate steering control.

[rkkm]

21 hours ago, Zero (Zblj) said:

One suggestion. Keep gearing to minimum and instead use as long as possible steering arms. This way you have much less play in the system and accurate steering control.

Which steering arms u mean?

On 15.05.2017 at 3:56 PM, JJ2 said:

I would recommend using a very robust custom made steering hub and using wishbones instead of the 6L links if you car making it suspended, if not I would recommend about a 30* caster angle and a kingpin incline, they will make the steering have very little bump steer with will improve performance.

I might make a moc'up of one and post a picture

So whats up with moc? it would help me so much :)

[JJ2]

Just now, rkkm said:

So whats up with moc? it would help me so much :)

Do you want suspension?

[rkkm]

no, i dont want to complicate it, i want to build and non suspended fast vehicle, im lucky cause i got closed intermarche near me, and parking area is soo big cause it was intermarche super :D

[Marxpek]

@rkkm here are some pictures of my steering unit built on the RC front end.

This simple but effective setup did nearly 29 km/h as you saw in my video however don't expect to be able to make a fast turn when going over 20 km/h you WILL flip your car, this was made for minor steering corrections at high speeds, but it can still be somewhat nimble at lower speeds.

It has positive camber, negative caster and toe-in set wheels, all to those make your car want to go straight when used correctly.

But i understand you do not have the 9L links, but there is always a way!

But what exactly is your goal here? make a car fun and fast to drive? or will you try to break my record? Your goals should determine your setup i think.

If you want a a car for pure speed, go with a setup similar to mine, i'm sure it can be improved! But if you want a fun car to drive, pick another setup, maybe one with suspension.

And by building/trying yourself, you will learn the most! of course we are happy to help out here for tips and info!

 

[rkkm]

if i want to break record, i would work at my tricycle, i want to make fast fun car, with perfect return to center steering, i hate when i dont steer and my car drives slighltly left or right

btw my tricicle has same steering as yours, i tried to rebuild yours with 6 l links and it worked, but still, it was driving slightly left or right, i dont know whats the fault, i have seen that my steering unit and those pins used for steering got wrong position but it cant be repaired, when turning left or right, those pins are not returning in the center perfectly, one is placed a bit too far to right.

[Marxpek]

Just now, rkkm said:

i hate when i dont steer and my car drives slighltly left or right

At high speeds this is nearly impossible to avoid, Lego always has some play in the system and Lego was not built to go over 20 km/h (maybe the old dirt crusher rc car, but besides that nothing that i know of) even on my first record car without steering i always had a minor deviation of the route i set out, sometimes left, sometimes right, (this had no caster camber or toe in, just a axle with wheels), with speed all forces increase exponentially and connections can get loose easily.

Be sure to check every connection in the car before each run to be sure, but over a 100m run i always had at least 3m of deviation ( best run was about 140m with a deviation of about 4m, which i considered a "near perfect run" they always end with a crash though :D)

 

[rkkm]

• i saw white shapes video, his car was driving max 20 kmh, and perfectly straight driving, but his trick dont really work for me, i need wishbones, i probably buy some today

[Marxpek]

The wishbones are great i guess, but i guess they are not cheap or easy to come by (i'm guessing)

And considering the amount of parts i have destroyed with crashes at 20km/h+ i personally would not use them, i broke several 7L lift arms in the steering unit (and wheels.. and axles.. and a hand full of pins...) with crashes and to me they seem a lot more rigid than the wishbones, it's a great solution but not if you have the slightest chance of crashing, and at 20 km/h outside a small rock could cause that...

I do not own these wishbones so i cannot tell you for sure, maybe anyone else has them and want to test their breaking strength compared to a 7L lift arm? I guess not ;)

[rkkm]

no, 18 wishbones will cost me 2,50 euro and 2,50 euro for shipment, meh shipment is too expensive, i want to buy 9 l links but paying 1,50 euro for links and 2,50 euro for shipment...

[Marxpek]

That is less then i would have guessed, but maybe wait and design first (maybe you can work in LDD?) you might need more parts, place a bigger order and save on shipping, don't rush into it.

 Btw: i never order parts separately, if i need parts i try to find sets that contain them and try to buy that, gives a lot more bang for your buck with all the extra parts, just takes a bit longer most of the time (i try to buy used item first)