Zero ackerman steering for you AX-10

[am4x4]

I keep hearing all this talk about how great the new losi 1/10 steers. A big part of why it steers so well is because it has zero ackerman angle built into the steering. For those that don't know what ackerman angle is I will try to explain. Draw a line from the screw that attaches your steering tie rod to the steering arm, through the screw that hold the knuckle to the axle "C", and end that line at the rear axle. If you do that to both sides and the lines are parallel you have zero ackerman. The ideal ackerman angle for a STREET driven vehicle has those lines meet in the middle of the rear axle. With that design the inside tire turns sharper than the outside tire. For some reason the AX-10 was designed with the opposite ackerman angle whish causes the outside tire to turn sharper than the inside tire, this causes to tires to fight each other when turning. The ideal ackerman angle for us is zero. With zero ackerman angle both tires turn at the same angle.

Because of this design "flaw" I was not happy my steering and set out to fix it. First I took some measurements and figured out that I needed to move the tire rod screw out .380" on each side to achieve zero ackerman, then I measured the distance between the two holes on the steering arm (.220"). I also had the issue of my servo not having enough throw to steer all the way so I moved the tie rod and drag link toward the knukle pivot apx 1/8" to give me a little more angle.

Once I had these measurements I laid them out on some .060 AL sheet, drilled the holes and cut out around them. I needed to use countersunk screws to mount the tabs to the steering arm so I countersunk the top holes before cutting them out. To extend the tie rod and drag link I used a long 3mm screw with the head cut off in place of the stock long set screw with one 1/4 AL spacer and two .065 plastic spacers on each side. I also used one .065 plastic spacer on each post under the servo mount plate to keep the tie rod from hitting the rod end on the servo horn

On dry concrete my turning radius only droped from 82" to 73" but on the rocks there is a noticable differance in how sharp the rig turns.

I also found one additional benefit to this mod. I run 8 cell saddle packs on TCS axle plates and with the stock setup the rod ends on the left side would hit the battery and prevent full steering to the right. With the new set up the rod ends are further away at full turn and no longer hit the battery. For now my steering angle is only limited by my axles but with CVDs you could replace the front "C" mounting screws with countersunk ones and steer even tighter.

FYI all of the spacers I used were from the local hardware store. look for a store with a good selection of Hillman brand hardware.

What would be really cool is for one of the aftermarket guys to make AL knuckles with zero ackerman already built in. It would only require a slight design change to the arm off the knuckle. HINT HINT.

[TSK]

That's a pretty cool setup you got going on there I just picked up a set of Egressor's knuckles with arms for both zero ackerman and correct ackerman and I'm loving them.

[gunnar]

It's great that you fabbed up something to get stock parts to zero ackermann. There are a few companies that produce zero ackermann knuckles, as the King stated. Many crawlers want to increase thier steering angle. You'll find your turning circle reduced alot more than 9 inches on flat ground. It takes alittle moving around of things, and some aftermarket parts, but the result is worth it in the end, just as your efforts have proven.

[Mini]

Yea thats why I love my Vanquish High steering knuckels. Plus with gunnars help of remove the angel link ends and putting straight one's I love the fact that I can go head-on to a rock and the tires hit first.

Great mod, way to think outside the box, a huge part of this hobbie is thinking outside the box.

[engineerjoe]

Nice setup but this zero ackerman thing is overrated, I'm not dissing your idea - it WILL help with your performance

the common misconception of crawlers is that you want zero ackerman. this is not absolutely true. with zero ackerman your tire will still be fighting themselves while turning (because the inside tire has a shorter radius than the outer) Ideally you want both tires to be turning around the same point.

IMO, the ideal ackerman angle is -15 deg (meaning the inside tire will turn more than the outside)

if you do BTA steering you'll see the banefits of this with stock axial knuckles

[yotachump]

Originally Posted by Mini

Yea thats why I love my Vanquish High steering knuckels.

The VP knuckles dont change the Ackerman.

[arcticjeff]

Not sure what BTA is? If you could give an explanation and or pictures of your setup I and probably others would apprectiate it.

[engineerjoe]

Originally Posted by arcticjeff

Not sure what BTA is? If you could give an explanation and or pictures of your setup I and probably others would apprectiate it.

BTA means "behind the axle" steering. basically puts the steering linkages behind the axle for more clearance up front. This also effectively "flips" your ackerman angle from positive to negative.

On all of my rigs i have stock knuckles (wrong ackerman) and I actually run with quite a bit of toe out to help my turning radius.

[am4x4]

Originally Posted by engineerjoe

Nice setup but this zero ackerman thing is overrated, I'm not dissing your idea - it WILL help with your performance

the common misconception of crawlers is that you want zero ackerman. this is not absolutely true. with zero ackerman your tire will still be fighting themselves while turning (because the inside tire has a shorter radius than the outer) Ideally you want both tires to be turning around the same point.

IMO, the ideal ackerman angle is -15 deg (meaning the inside tire will turn more than the outside)

if you do BTA steering you'll see the banefits of this with stock axial knuckles

It would seem to me that any time you have one tire turning less than the max possible angle you would be giving up some steering at full lock. The reason for neg ackerman on a street driven vehicle is to prevent tire scrub. To a small degree zero ackerman will try to rotate the front end around the inside rear tire instead of making a big arch. For our application there is an added benefit. There are alot of times when we only have traction from one tire when turning. With pos or neg ackerman you have one tire at less angle at full turn, what happens when that is the tire with traction?

[am4x4]

Originally Posted by gunnar

It's great that you fabbed up something to get stock parts to zero ackermann. There are a few companies that produce zero ackermann knuckles, as the King stated. Many crawlers want to increase thier steering angle. You'll find your turning circle reduced alot more than 9 inches on flat ground. It takes alittle moving around of things, and some aftermarket parts, but the result is worth it in the end, just as your efforts have proven.

Who makes those? I dont remember seeing any that claimed zero ackerman but obviously they exist.

[EGRESSor]

Originally Posted by engineerjoe

BTA means "behind the axle" steering. basically puts the steering linkages behind the axle for more clearance up front. This also effectively "flips" your ackerman angle from positive to negative.

On all of my rigs i have stock knuckles (wrong ackerman) and I actually run with quite a bit of toe out to help my turning radius.

http://www.rccrawler.com/forum/showthread.php?t=163665
pos. or neg. or zero ackermann

[gunnar]

Originally Posted by am4x4

Who makes those? I dont remember seeing any that claimed zero ackerman but obviously they exist.

Those knuckles are CKRC hi-steer units. I don't know if they are zero ackermann or not. I used them to get the tie rod above the pumkin. That is an older photo, things have changed around, and will change again, but the knuckles are still on it.

[Kraqa]

i just drilled a new hole closer to the knuckle pivot point. works awesome.

and no special parts required!

[MKDU2]

A diagram of Ackerman with explanation.

Also my 0 degree Ackerman setup with BTA and 45 degrees of steering.

[TSK]

Originally Posted by engineerjoe

Nice setup but this zero ackerman thing is overrated, I'm not dissing your idea - it WILL help with your performance

the common misconception of crawlers is that you want zero ackerman. this is not absolutely true. with zero ackerman your tire will still be fighting themselves while turning (because the inside tire has a shorter radius than the outer) Ideally you want both tires to be turning around the same point.

IMO, the ideal ackerman angle is -15 deg (meaning the inside tire will turn more than the outside)

if you do BTA steering you'll see the banefits of this with stock axial knuckles

I think BTA is over-rated also, as there is the obvious packaging issue, and drag links that are prone to failure due to the fact that most of them have to be bent in all sorts of weird ways for clearance, Egressor's knuckles are dope, arnd are available for zero ackerman, and the correct or true ackerman for standard sttering setups, as well as versions for all of you BTA lovers. Regardless of how your steering is setup, zero ackerman with high steering angles will greatly improve your turning radius, and even mor so with correct ackerman. Although a little pricey, Egressor's knuckle are awesome, and provide further tuning optons as they are both high angle, and available for what ever setup you choose to run.

[gunnar]

I admit too, I've seen a few funny looking BTA setup's. I think if your going to run a BTA, the simplest servo to tie rod connection is just run a link from the horn to the closest knuckle, as long as there is no interference. The only thing I don't like about BTA is usually the servo has to to be mounted up higher off the axle, where my preference is to run the servo as low as possible. So many things to place there, not enough room, front axles can be tough sometimes. There are clearances in my build that are measured at a hundredth of an inch.

[engineerjoe]

Originally Posted by TheSCorpionKing

I think BTA is over-rated also, drag links that are prone to failure due to the fact that most of them have to be bent in all sorts of weird ways for clearance, Egressor's knuckles are dope, arnd are available for zero ackerman, and the correct or true ackerman for standard sttering setups, as well as versions for all of you BTA lovers. Regardless of how your steering is setup, zero ackerman with high steering angles will greatly improve your turning radius, and even mor so with correct ackerman. .

I dislike BTA steering for the same reasons you do, I was just pointing out that when the stock knuckles are flipped and used in BTA setups that the ackerman is correct.

Good post

[MKDU2]

Originally Posted by gunnar

I admit too, I've seen a few funny looking BTA setup's. I think if your going to run a BTA, the simplest servo to tie rod connection is just run a link from the horn to the closest knuckle, as long as there is no interference. The only thing I don't like about BTA is usually the servo has to to be mounted up higher off the axle, where my preference is to run the servo as low as possible. So many things to place there, not enough room, front axles can be tough sometimes. There are clearances in my build that are measured at a hundredth of an inch.

Gunnar,
I agree with you on the down side of most BTA setups, It is very hard to get a very low mounted servo with out some really funkey linkage.

The setup I am going to try uses straight links with out any clearance issues so far and the servo is not any higher than the stock location, just not lower.

As far as Ackerman goes I plan on using a dig when turning tight corners,
and want 45/45 not 45/40 degrees of steering, so let the tires scrub!

[TSK]

Originally Posted by MKDU2

Gunnar,
I agree with you on the down side of most BTA setups, It is very hard to get a very low mounted servo with out some really funkey linkage.

The setup I am going to try uses straight links with out any clearance issues so far and the servo is not any higher than the stock location, just not lower.

As far as Ackerman goes I plan on using a dig when turning tight corners,
and want 45/45 not 45/40 degrees of steering, so let the tires scrub!

That is a nice setup so far, but from the looks of it, you'll have some problems getting the shocks mounted at a decent angle in relation to the chassis. The straight drag link will definitely need to have some bents to provide for clearanc. The only way I realistically see that design working is on some sort of torsion chassis, or have shocks that are mounted extremely horizontal.

[gunnar]

He could make up some kind of offset shock mounting, I was toying with that idea, when I just decided to inboard mine instead. He has done some pretty good work so far, if he machined his ring and pinion himself, he's certainly got my attention. Sorry for the slight hijack, am4x4