Anti Squat and Suspension Tech

[Desolas]

Seeing your after photo brings up another question for me ... at what point does going after the right pinion angle harm your caster? Looks like you've got a insane caster angle now...is that going to harm the truck in any way?

I've been playing with my links more and more, yesterday I squared up my caster regardless of my pinion angle and the truck seems to be working better because of it. I have -6 degrees in the front, 0 in the rear. It screws with my pinion angle though, but the truck appears to work better in general.

[JohnRobHolmes]

Caster in the rear doesn't do anything with a 2ws vehicle. Caster in the front affects your steering on different angles. Having the front knuckles kicked back makes it walk up inclines with more initial steering, but it is pretty minute compared to a good pinion angle IMO. Once the rear axle gets to the base of the incline the caster advantage goes away. It is all relative to the plane of the axle centerline vs the contact patch, which is never constant with a crawler.

[EeePee]

Well that was fun. It's good to know that the asymmetrical link set up works on a full drooper too.

My Scorpion has never been better.

It started with the Boomerang mount from TCS, and the asymmetrical upper links, and standard blue springs with no preload, and the limiter inside the shock, then later another limiter outside the shock too. Worked good.

Then the skidplate mod to put the links inside the chassis, and went to Axial green color coded springs. Didn't really change too much, which is a good thing. Little bit less axle steer, but I don't find that to matter too much. So at this point I'm running softer springs, but didn't notice an increase in torque twist. Good.



Way far inboarded lower links like the CKRC Stage 2 kit mounts them. Just not good, not good at all. The links swing the chassis when they articulate, which is due to the new arc they travel. There was this one truck at a GTG we recently had that had the full Stage 2 kit, and there was this section that would grab the rear tires and it was almost comical to see the effects of the lower links swing the chassis over. I noticed more torque twist with this set up keeping everything else the same.

(Not my picture)



Like the TCS skid plate kit mounts them. Which was okay, but still exhibited a little bit of that pushing of the axle I saw with the CKRC Stage 2 set up. But not nearly as much.

There's spacers near the shocks and links. I was able to flip the shocks over though. I figured with a limiter on the inside, and a limiter on the outside, the piston is always in oil. And either way, I always pumped the suspension up before I use the truck.



Swapping the shocks and links around so the links are inboard, which is fine. Then finally back to the way Axial has them, still using the TCS skidplate and Boomerang, and now the axle is mostly twisting and not pushing also. Look at the lower link angles. At this point I have one Axial limiter on the outside, and two on the inside. I've lowered the truck a little. I have Axial green springs on the back, and whites on the front.



And check out my side view. Pinion angle.

[Mr_Freeze]

Originally Posted by EeePee

And check out my side view. Pinion angle.

Damn... that looks familiar

Did you make these changes after my post???

I'm predicting that particular setup in our photos will become the standard. Asymmetrical upper rear link. Laid down shocks. And pinion angled up.

.

[EeePee]

I've had it like that for a while.

For some reason I don't have a build thread for my Scorpion. I should have done that.

Tilting the rear pinion up should be standard practice. I know I've done it for years on my TLTs.

[Mr_Freeze]

I "normally" angle it up too.... but it's nice to know that it has another advantage other than clearance. I like to know how and why rather than "just copy mine... it works for me"

Nice to get some progress on this torque-twist

.

[bmuzz1]

Thanks for the idea! When I get my new VF dig set-up I will give this a shot, but right now I've got that servo sitten back there for my current dig and can't move my upper links from below the boomerang.

[CrawlinROCKS]

Wow, I just got finished reading this whole thread and I must say that it is quite possibly one of the most informative and best threads I've ever read. I have learned a lot from this thread and hope to be able to provide more useful data in the future now that I've been bitten by the "tweak the suspension" bug. Although my dream rig is a NewAge that shouldn't see any of these problems, my current rig is a WK, so I know I'll have some tweaking to do.

Thanks for providing the information to get me off to a great start.

-Ari

[Destroyer]

Bringing it around another time....

Having trouble getting my setup to climb verts. I have a test board of thick plywood with two 40 grit belt sander strips taped to it. All tests are done at a crawl to avoid "burning up" the belts.

The best I have got so far is 63* before it will just tip backwards, which seems weak compared to some of my previous trucks, but I have no actual numbers for them.

Current setup, balancing at it's "tip point".


Without wheel showing links:


Using the tip point, I estimated CoG and got the following:


Not sure if that is right, feel free to correct me.

Using that, I then found this:


Seems like it would be fairly neutral then...

As a note- I do have double triangulated links, and have only the smallest bit of torque twist, just enough to get the front right a little "light", but not enough to actually cause it to lift and break traction with the ramp when climbing.



What do I need to do here to get this thing climbing better?

[JohnRobHolmes]

Does your rear end compress or extend when you climb? The simple answer is to lower your CG, but how does your rear act on the incline board?

[Destroyer]

Well I don't know exactly where the CoG is, but I don't think I can get it much lower...I already have lees ground clearance than many, no dig up high, battery under links, etc. Electronics normally go on the rear links, but I found the made no difference in testing today anyway.

When it climbs, the rear does not do much of anything. I run a little bit of droop all around (the springs do not quite push the shock to full extension), but it does not try to walk under the truck like some setups I have seen. At 62* it walks right up w/o slowing, at 64* is just falls back.

I will add that the weight is just under 6 pounds, and with the tip point nearly centered, maybe this is more of a weight issue than link geometry?

Edit: 2 quick videos comparing a slope of 63* to 64*

http://s251.photobucket.com/albums/g...rent=63deg.flv

http://s251.photobucket.com/albums/g...rent=64deg.flv

[Hildy]

Sounds like your getting too much traction to the rear tires making you flip. I'd either add weight to the front, or take some out of the back.

Its about finding that happy medium.

[Destroyer]

I added some more weight to the front wheels, moved the rear shock mount to the same hole as the fronts, and limited the rear to compression only. I can now crawl up the ramp at a 65* slope. With the rear tied all the way down with zipties, I can get to 68*, but tying down the front does not provide any improvement.

This leads me to believe there is still some issue with the rear links that could use some adjustment.

[JohnRobHolmes]

I did see a slight bit of unloading on the rear, which it sounds like you fixed. It looks like your rig is pretty dialed in though. Adding weight to the front wheels certainly helps too, as it puts the CG lower and more to the front. On a climb the farther forward your CG is the less likely you are to tip back.

[Destroyer]

I did not have the threaded adjuster on the right rear, which did allow a little more droop on that side. I guess I don't know what kind of angles I should be shooting for though...what I am getting does not seem impressive to me, but may actually be decent. My front tire/ wheel setup currently weigh a combined 1lb 12.7oz.

[extreme]

ahh its good to see someone set up a testing board like this! i mentioned the idea for dirks proline tire test using a slicker sandpaper.

id like to see other people try this setup and see what they get as well, if i had some 40 grit and an angle finder id do it up!

[Shoei1]

I thought i read this thread pretty well but i guess i didnt. I have tried a lot of setups and i cant seem to get my rig to climb verticaly vary well. i dont even think it can do 60* which to me is sad. So if you all could help me out that would be great.

[Hildy]

Shoei01,
Try moving your rear shocks higher on the chassis to lower that rear end.This will also give you more squat.

What does your rig do on a vertical? I am guessing a little twisting action in the rear? Perhaps not, but just from looking at your rear drive angle Get that chassis more level and it will flatten your drive angles

[Tanis]

Shoei, also try dropping the rear upperlinks down a hole at the chassis.

[Shoei1]

ya i will move the shocks and the links and give it a try. ya my rig has zero twist which is great.