Suspension Set-Up

[GiJoe]

Is there a thread that outlines the "HOW'S and WHY"S" of suspension set-ups? Particularly for the Losi design? If not, do you all think we can start one? just like the Friction Reducing thread, I feel a suspension tuning thread specific to the Losi would really be helpful! Something explaining WHAT each adjustment means and does.

I see many different ideas and designs at play with many of these Comp Style crawlers. For example: Rear Upper Links raised and spread out, etc.


I would like to incorporate some of these suspension tuning techniques to my Comp Scalers, but to be honest, am lost as to what and how certain adjustments change performance. I simply set-up to what feels balanced, then learn to drive it!

Especially in cases where I have modified or strayed from the original Losi engineered system.


Which brings me to another question. What exactly is the original Losi link design called? I've heard its a triangulated 4-link, but never knew for sure...

 

[SuperRoo]

Have you looked at the manual for help? There is some really helpful setup information in the back as well as a gear chart. http://www.tlracing.com/ProdInfo/Files/CompCrawlerManual.pdf

If you have a look at 1/10 Comp Crawler Race Roller (LOSA0051): Team Losi Racing you will find some setup sheets from Jake Wright that might also be usefull.

Do you have any videos of your Class 2 LCC Scale rig? I'd be interested to see how it performs.

I've been watching your thread as I have finally finished converting my LCC to a Class 2 scale rig also. Fortunately my setup has allowed me to retain the suspension geometry exactly how I had it as Sportsman rig the last time I had the LCC on the rocks. The only drawback is the smaller 1.9's.

 

[GiJoe]

Do you have any videos of your Class 2 LCC Scale rig? I'd be interested to see how it performs.

I've been watching your thread as I have finally finished converting my LCC to a Class 2 scale rig also. Fortunately my setup has allowed me to retain the suspension geometry exactly how I had it as Sportsman rig the last time I had the LCC on the rocks. The only drawback is the smaller 1.9's.

I hope to get some video this weekend. Going to the Team KNK Top truck Challenge and will be competing in class 2 and 3."thumbsup"

And haha! It never dawned on me to go directly to the source "LOSI" for some of this info!:lmao: I generally buy all my LNC/LCC's used for dirt cheap and don't have any manuals. I only searched RCC, not Google! Lol.

 

[dentonmac]

I know this is probably old news to some of you, but I just read it and thought of this thread. It is worded in a way that made sense to me.

Hey JB, I don't claim to be an expert. However when we cut our link mounts I spoke with alot of people about geometry changes, and at the time I wrote it all down (my brain can't retain it) Here is what I have written down in our 4 link product page.

Link Lengths:
The upper link length controls the axle clocking, the longer the link the more the axle clock will increase with suspension travel, assuming your uppers are longer than the lowers. Since we don’t have pinions, it keeps the motor up and out of the way. The truck does feel more predictable with long upper links as it provides less movement in the axle and reduces the amount of clocking that can occur when compressed. A shorter link will do quite the opposite.

Vertical Seperation:
Shortening the vertical separation (distane between) between the uppers & lowers on the frame mount side will increase Anti Squat (rear rises) while increasing the vertical separation will do the opposite. This is assuming all else remains the same.

What is Anti Squat?:
When a crawler accelerates, the weight shifts rearward. The higher the weight is above the ground, the greater the shift off the front and onto the rear will occur. This extra weight will compress the rear suspension, making it SQUAT. But there is also a torque on the rear axle, equal and opposite of the tire torque. The axle will try to rotate upward. The links resist this torque by putting forces into the frame. These forces may try to lift upward. The upward force will cancel some of the squat from the weight shift, euqally ANTI-SQUAT.

It was in the Berg section, but the theory applies.

 

[GiJoe]

Holy Smokes!:shock:
I stumbled upon a post made by Whiplashdjs in the General Crawlers section. Several posts in succession to be exact, outlining TONS of suspension set-up and theory of all kinds! Its LONG! But a great read!

Maybe some of the more computer saavy guys here will know how to easily separate what pertains to us and add to this thread or as a sticky!:wink:

It all starts on post #76

http://www.rccrawler.com/forum/general-crawlers/4521-rccrawler-tips-cheap-tricks-parts-guide-4.html

 

[EeePee]

http://www.rccrawler.com/forum/general-crawlers/54791-anti-squat-suspension-tech.html

http://www.rccrawler.com/forum/general-crawlers/472065-another-4-link-thread.html

Quite a few out there. You might really like the first link, lotta pictures and diagnosis.

My Losi thread has a buncha crap in it, too.

 

[GiJoe]

Based on suspension set-ups I've seen on other crawlers (in pictures), I set up my rear upper links to the highest hole in the Losi adjustable mount. I also added 1/4" spacers to spread them out some....

On the bench, this really limited the amount of flex, but overall, the chassis feels VERY stable.

My question is...what did this adjustment actually do? This rig hasn't seen power yet so I don't have any real world seat of the pants feel. Just a little sumthin sumthin I been tinkering with:twisted:

 

[ghtpdm5]

it affects the rear anti-squat.

with the stock chassis (and i've really got to get you off those), the squat/anti-squat is more on the squat side, even using the lowest hole. the raising the rear upper link mount allows you to get to a neutral anti-squat, maybe a touch on the anti-squat side.

there are some really involved equations and calculations that more or less simulate what the link setup will do, but my preferred way of checking is to rotate the rear tire rearward (the axle rotates rearward under power) and see what the shocks do. if they just sorta sit as you rotate the tire, neutral. if they go up or shoot up, anti-squat, but you're not looking for a real shooting motion. if the shocks retract, then you're in squat and i'm not a fan of having the suspension in squat. the rear axle rolls up under the rig and can cause some unloading problems as you drive. i had the stock chassis get bound up and just start rabbit kicking the rear axle. was kinda funny, but it did nothing to help the situation and in the end, spaghetti'd an lnc lower.

 

[Olle P]

I'd guess it will also add some bump (or should it be "tilt") steering, which typically isn't good.
Separating the upper links on the axle will make the axle turn (more) when it's tilted sideways.

I'm still looking for some suspension setup advice that are arranged more like Problem <-> Solution rather than just explaining the general effect of something.

For example:
While moving up steepish slopes where the wheels need to flex a bit there's a tendency that one or the other front wheel is lifted from the surface.
Should I soften the front, the rear, or both to get the wheel back down with maximum grip?
(Seems like it's common to have a relatively stiff front and soft rear.)

 

[ghtpdm5]

for my setup, running a softer front has proven more beneficial than stiffer. the shocks may appear to be identical front and rear, but i've been using rpm 2 stage pistons for a while now. the softer compression on the front and harder on the rear reduced axle hop with sedonas (they are a very hard tire to tune the hop out of unless you shave them to nothing) and now with the leopards, the thing just holds its ground. running 25wt oil on all 4 corners, about an inch of rise in both link mounts.

the axle swing is something that took a small bit of getting used to, but it was the simplest way to get the breakover i was looking for. running on broken concrete, the stock chassis was just too big and too low. would get hung up on everything.

as far as the tire lifting, that seems to be related to motor torque as well in my experience. if i'm laying on the throttle going up a loose slope, i will see some tire lift. on a really steep slope, it can pop up, but coming to a gentle stop, digging if its an option, and going at it with a very light throttle finger is the way to go. you could tune this out in suspension with a little stiffer spring on the rear opposite corner, you could stack on weight, or you could adjust for it.

rig time is irreplaceable. make one change at a time until you've tuned the rig to how you drive, and also learn how it wants to be driven. what we give each other are benchmarks that are generally a good starting point, the hard part is putting in time, taking videos if that's how you roll, and getting the truck as close to perfect as possible.

 

[Tgreer]

OllieP- soften up your front suspension, and possibly raise your rear links at the axle.

GiJoe- take those spacers of the sides and move those upper rear links back in against the mount. Get four 1/4" spacers and lift your mount off the axel giving your rear uppers another 1/4" lift at the axle. See what this does for you!"thumbsup"

 

[GiJoe]

GiJoe- take those spacers of the sides and move those upper rear links back in against the mount. Get four 1/4" spacers and lift your mount off the axel giving your rear uppers another 1/4" lift at the axle. See what this does for you!"thumbsup"

Thanks for the advise everyone! Tgreer, I set-up as per your quote. Put some temporary power to this rig for shake down, and my results are bittersweet. Maybe you guys can help me dial this in.

First off. The climbing and sidehilling is amazing! "thumbsup" By far, the best set-up I've had on a scaler to date! Problem is, i'm getting a lot of the "Tire Lift" that Ollie P was describing. When going for a really gnarly vertical climb or obstacle, with one or both front tires, I start "wheelying" very easy. If I stop and wiggle the front tires, I can usually get it to settle back down. But not always......

When it does settle down, I get traction back almost immediately and will pull up and over the obstacle. If it doesn't settle down, well then i'm doomed to a reverse or backflip!:shock:


Im gonna let the cat out of the bag for a little here and share what I've been working on...:twisted: A build thread will follow later, just trying to keep this rig on the down low for a bit.

Essentially, Im going for a new (EASY TO MAINTAIN!) Class 3 rig that will come close to maxing out SORRCA Scale points.

Its my typical chassis layout: L-Trail Chassis mated to an LNC skid. The reason i'm showing you this is to understand the mechanics and weight distribution...

I've cut down and modified an LCC trans to act as a working Transfer Case with DIG. A LNC Trans is mounted up front in the frame rails (more weight on the nose) with a divorced driveshaft between the LNC and LCC trannys. Steering servo in stock location.

Front shocks are stock LNC with Light (gold) springs and 50wt oil
Rear shocks are bone stock LNC.
All shocks are mounted "outboard" to clear the full frame rails. Shock angle is for the most part "non adjustable", but is pretty close to the stock geometry.

Front upper links are in middle hole @ chassis
Rear upper links are stock length, but mounted about 3mm lower and 3mm back from the stock lower holes @ the chassis (see pics) This allowed me to rotate the pinion up for a strait driveshaft angle.

Rear upper links @ axle are as suggested by Tgreer

Sorry for the long winded post, but wanted to throw out as much info as I could! :mrgreen:

 

[Tgreer]

I think your rear uppers are to low at the chassis, try going up a touch.
Are you running any knuckle weight or weight in the tires up front?
Also that last pic is way too much articulation, you want to fit a 2.2 tire under it not a tall paint can. I would start by trying a 1/4" internal spacer in your shocks, this will lower your rig giving you better COG and it will limit those shocks, my losi sits at about 2.5" belly clearence.