Zero Ackerman Steering Knuckles

[K.O.M.]

Hey all, I'm in the process of exploring the 3D modeling capabilities of software we use for Architecture at work. Just recently discovered that I can export .stl files from the native program.

With that said, I'm thinking of modeling a zero-Ackerman steering knuckle for a series of Tamiya vehicles, the CC-01 included. I've found that every degree of steering added to these things really help.

Is there any other feature that other CC-01 drivers would like revised on these steering knuckles?

[K.O.M.]

I got about an hour of modeling into this one. Think I'll send it off to get printed and see how it fits. Will adjust tolerances as needed for kingpin and bearing fitment.

[IMG][/IMG]

[K.O.M.]

Parts came in. Pleasantly surprised out how well they printed. The tolerances are spot on when using bronze bushings, but a bit tight when using bearings. I'm not sure if it's worth trying to tolerance the bearing size, since even a high quality print such as this would make it too loose--would rather have people do some very light sanding by hand than have hubs that are loose. There are enough loose parts on a CC-01 to worry about.

I will need to revise the area where the pivot ball screws into, it looks a bit anemic and could use more meat. The other thing is to cut away more of the inside arm for additional clearance.

Will try to get these mounted soon on my new project and show some before and after shots/vids.

[OSRC]

For sure needs more meat at the pivot ball mount. Number 1 area where mine crack as they age. Curious to see how your steering works out after installed.

[K.O.M.]

Stock Steering Hubs and Knuckles

Look at the angle of the wheels relative to each other, and the angle of the steering tie rods relative to each other.







Started with the CC-01 against a garden border, and made a u-turn; the out-to-out steering radius is 127.5"

[K.O.M.]

Stock steering knuckles, with stock C-hub stops ground down.









Wow! Out-to-out turning radius is now down to 90"

[K.O.M.]

C-Hub Stops Ground Down w/ K.O.M. Zero-Ackerman Steering Knuckles

Compare the angle of the wheels and steering tie-rods with all the other setups above.







Mission accomplished! Steering radius is down to 80.25" out-to-out, almost 10 inches better than the stock setup with the c-hub stops ground down.

I have a few more improvements before these get released for general consumption

[K.O.M.]

Before someone asks, I am using the stock dogbones with an extra o-ring jammed inside the diff-side outdrive cup.

Currently, with the Zero Ackerman Knuckles, I have the steering servo end-points setup so that with the wheels off the ground, I can just hear the outdrives clicking.

With a CVD/universal up front, it's just a matter of grinding down the knuckle a bit more on the inside (or design it with the relief cut already there) and dialing in a bit more steering at the transmitter.

But before I do that, I would also like to point out, that to further improve the steering parallelism (is that a word?), I would like to see the the steering tie-rods at a perfect 90 degree to the axis formed by the line from the king-pin to the knuckle ball-cup. One issue I foresee with any additional extension of the steering knuckle, is that the clearance is already tight with the 1.55 setup I have, so I will have to test with 1.9 wheels to see if that would net more tire clearance.

[OSRC]

Great stuff, keep it coming!

On a side note in my beast mode thread, I just put on some Wild dagger steering knuckles on, and they are very similar to your design - just a bit longer from the ball stud to the pivot point. They worked very well so far!

[K.O.M.]

Revision 1:

-kingpin mount offset 1mm toward the middle of the vehicle
-steering pivot ball mount offset 3mm toward the middle of the vehicle
-steering pivot ball mount extended 1mm
-additional reinforcement added steering pivot ball mount
-material removed from steering arm
-material removed from exterior face of outer bearing seat
-material removed from interior face of inner bearing seat
-through-hole on kingpin mount
-revised webbing reinforcement between steering arm and hub

All the changes above should result in the ability to use 1.9" wheels with wide-ish tires within a scale look while at the same time improving the steering link geometry and adding even more steering throw--enough to bind your universals or cause the tire to rub the chassis by my estimate. Some convenience items changed so bearing fit is more finger press-fit with no sanding and tapping the mounting holes are easier.

[kongluc]

Any success?

Sent from my LGAS375 using Tapatalk

[K.O.M.]

I was out at the Sea Otter Classic for the past 4 days, and forgot to upload the file to get printed. Will update as soon as the new parts get printed. Also need to get proper universal joints to see how much the steering can really max out.

[K.O.M.]

Parts are in and did a quick test!




From left to right: Revision 1, Revision 0, and Stock


Definitely even more angle than the first version of the knuckles.


Chopped off another 8" from the previous turning circle. I've got it down to 72"

[K.O.M.]

Just to make sure I don't celebrate too early--I have been using 1.55" RC4WD wheels with the Mickey Thompson Baja MTZ tires, which is on the small side, if not the smallest scale type wheel/tire I've seen on a 1/10th crawler.



Here is a comparison between the stock "Black Edition" wheels and tires to what I have been using. For reference, the stock Tamiya tires are 3.70" tall by 1.40" wide. The RC4wd Mickey Thompson MTZ tires are 3.25" tall by 1.00" wide.

I didn't get an actual wheel offset from either wheel, but I'll have to measure to see what the variance would be to other 1.9" wheels.



The fitment is tight. I can probably sneak two sheets of printer paper between the tire sidewall and the rod end.




The 1.9" wheels and tires did add some additional scrub radius, but based on repeated left/right circles, it's only about 1/2" wider diameter circle when compared to the 1.55" wheels and tires.

So, before finalizing the model, should I leave it as is or should I move the axle out even more, thus increasing the scrub radius, but preserving the steering angle?

Bear in mind, this is still with stock dogbones and not universals. With universals (which I have ordered) I can easily bump out the track width an extra 1mm on each side to get the tire clearance AND add even more steering angle with no noticeable effects on diff outdrive end of the axle.

I'm thinking one more round of changes, then test with universals.

[OSRC]

I'm no expert on the akerman/scrub radius, etc but how's the bump steer? may as well address that too. I usually mount a small spacer under the steering link to keep the steering link roughly parallel to the suspension arm and it all but eliminates BS. Maybe add 5mm of meat to the arm where the steering link mounts on 1 side so you could flip from side to side for stock or less bump steer?

I wish I had a better pic cause this is kind of a dumper fire of an example, but you can see the knuckle and the silver spacer in this pic (upside-down of course) - a 1 piece mold would be killer.


Not sure if that makes sense or not.

[K.O.M.]

Originally Posted by OSRC

I'm no expert on the akerman/scrub radius, etc but how's the bump steer? may as well address that too. I usually mount a small spacer under the steering link to keep the steering link roughly parallel to the suspension arm and it all but eliminates BS. Maybe add 5mm of meat to the arm where the steering link mounts on 1 side so you could flip from side to side for stock or less bump steer?

Not sure if that makes sense or not.

I've had that on the back of my mind, it can be optimized, but due to the placement of the steering rack on the chassis and how it doesn't travel in a perfect parallel, the effort would be wasted for a marginal gain. The problem is that in the CC-01, the large bearings toward the back, are narrower than the pivots holding the links that the tie rods connect with. You have a really funky path that the tie rods follow from center to full lock on one side: it either goes in and back or out and forward.

I've started to address the parallelism of the steering tie rods by lengthening the steering knuckle arm as you can see in the full lock photos above.

Solving bump steer would also be fairly straightforward by making the radius that the steering tie rods travel in be concentric with the average circle that the upper and lower suspension arms travel in. And yes, adding a spacer on the knuckle end or molding it thicker would solve it, but by my eyeball, I'm looking at least at 4mm of additional thickness to get the steering tie rod parallel with the lower control arm. That introduces more of the problem I'm trying to fix--to be able to comfortably fit a roughly 1.5" wide tire without rubbing.

The second solution, which I've hinted at in your thread, is to lengthen the upper and lower control arms along with the steering tie rod. The horizontal displacement for any given wheel travel is less with the longer arms.

But I think getting at least an average size 1.9" scale tire with some clearance for beefier links would be a nice goal before seeing where to go from there.

[cartronicshn]

I am needing two sets at least.

[cartronicshn]

Hey did it go with the Project? any updates?

[K.O.M.]

Originally Posted by cartronicshn

Hey did it go with the Project? any updates?

Waiting on the latest version to print. I guess at this point it is no longer zero Ackerman, but rather much reduced Ackerman steering

As soon as I'm confident with the design, people can PM me on how to get them.

Possible that I can be a vendor also offering custom turned links, but I don't have a strong business case to spend $100.

[cartronicshn]

Originally Posted by K.O.M.

Waiting on the latest version to print. I guess at this point it is no longer zero Ackerman, but rather much reduced Ackerman steering

As soon as I'm confident with the design, people can PM me on how to get them.

Possible that I can be a vendor also offering custom turned links, but I don't have a strong business case to spend $100.

Hey good to know, whatever you decide to do (i'd rather you become a vendor and buy the knuckles from you) or if you decide to share the design and be sent to print elsewhere.