Need help with suspension setup for MRC with high body COG

[Matt_]

New here, but not to forums. Been searching for a while but couldn't find someone in my situation, even in the scalar forums where I figured I would find something similar.

This is my first R/C so bare with me, especially with terminology. I'm extremely mechanically inclined so don't be shy with the responses.

In a nut shell, i'm not sure which direction to go with the suspension to get the results I want. I want to lower the body down so it looks a bit more scalar. I'm running the LOSB1439 threaded shock set which I figured would give me that adjustability I was looking for; but if I reduce the preload anymore than what's shown in the pics, the body flops all over the place and doesn't rebound to the neutral upright position.

I actually had to remove the shock oil altogether to get any rebound, likely due to the body height/weight (moment of inertia) in general.

Not sure if I should try softer springs, move the upper mounts inwards, try internal springs that actually pull inwards to suck the suspension in instead of pushing outwards (more of a droop setup), etc. As it sits, the suspension is basically fully extended, so im leaning more towards a droop setup where the springs compress the suspension, but wanted to see what you guys thought first.

Recommendations welcome

Here's how it's currently setup as a compromise to body roll and height:







Here's how it sits with the body on (note how the front suspension doesn't want to stuff, it just lifts the body with it):







And here's a video I made just showing how the body reacts to the torque (i need to adjust the reverse on the controller, it's a bit touchy )

Jeep Commander RC 3 - YouTube

[rangercat23]

I have been working on one of the mini's for a while and been looking at a lot of threads and photos. I can tell your major problem causer is because your electronics are mounted way to high.

[rangercat23]

Check out some of the pics in this build thread. It belongs to one of the guys in my local club.

RCOG's MRC Pro

[Matt_]

The electronics pale in comparison to the weight and COG of the body. Even without those components on there, with the body installed the suspension won't right itself. If I take the body off, I can cruise around without issue and it drives just fine even with the coilovers unadjusted for minimum force.

I can easily mount the battery and motor controller on the underside of the aluminum body mount I made, but I'm still going to have the body COG issue.

I'm probably going to try some pen springs inside the shocks to set it up for full droop and see what happens. If that doesn't work, then try a semi-droop setup. Was hoping to cut down the number of suspension configurations to try by having someone point me in the most-likely for success direction.

[Matt_]

Originally Posted by rangercat23

Check out some of the pics in this build thread. It belongs to one of the guys in my local club.

RCOG's MRC Pro

Wow that's a serious build. Love the knuckle weights!


I should also mention that i'm [obviously] not making a competition crawler. Just something to play around with in the yard with my kids and making it look like my Commander (also to take to the offroad parks where I wheel my Commander....makes for some fun during lunch time )

[winnerone23]

Good video, ur body roll doesn't look so bad in forward, but reverse is pretty nasty. Which may lead me to think ur link geometry is better in the rear then in the front... My comp rig is th same way, rock solid in forward but reverse is not good.. I'm sure a silly question, but can you lower the body on the chassis? Next thought, instead of droop setup, tho a pen spring won't be so bad, try a limiting strap from the center of the chassis to the center of the axle. Front an rear.. It's easier to remove if it doesn't fix the problem.. I have a scale chassis for the mrc I'm not using. Take some measurements of ur body, side to side an front to back.. it would let you stand the shocks up right an have them inside the body.. Pm me if It's a direction you want to go

[Matt_]

I believe the geometry is symmetric front to rear.... but that's a good point that it is worse in reverse. It may be my fault since I put a lot more preload on the rear springs to combat the forward TT and tried keeping the front springs with less preload in hopes they suspension would compress easier when climbing over something.

I like the limiting strap idea, that should be easy enough to try.

Lowering the body more is possible. But at its current mounting position the tires fit perfect when the suspension is fully compressed. So if I lower the body, ill have to limit the suspension travel. That's one of the reasons I'm leaning towards the droop suspension which would lower the body and chassis.

If I can't get it to work via tweaking the suspension, I'll be interested in the scale chassis. Thanks!

[Matt_]

Are these the TCS droop springs everyone mentions? (ie AX10 shocks have similar dimensions to the Losi threaded shocks im using):
TCS Internal Shock Springs for Axial AX10 Scorpion - Medium Strength - 4 each*-*Suspension Parts: Shocks, springs, links, rod ends*-*-By Truck: Axial AX10 Scorpion, SCX10, Honcho*-*The Crawlers Store LLC

For $4 a set im thinking of just getting the medium and hard springs. Try the medium first with some light wt oil, then step up to hard if needed (possibly with a soft outter coil spring for a semi-droop).

EDIT: Nevermind about the springs... found the right ones

[winnerone23]

It would be nice if they gave is the od of the springs to be able to check. If they are the right ones an someone knows, ill head that direction as well.. good question!

The limiting strap will do the same as droop. Lowers everything an a good way to test how droop will work.
Have you thought bout using a slightly smaller tire to get overall setup an ability dialed in? Tho big tires are nice, I'm realizing on my comp rig that ability is out wayibg the extra tire height an allowing me to crawl more things. Less clearance but more performance..

[Matt_]

I may be the test dummy and let ya know if those springs work. Worst case I've added $8 of spare parts to my "junk bin" hahaha.

As far as tires are concerned I'm actually going the opposite direction and knowingly sacrificing crawling ability to get the aesthetics.

I bought this MRC used from someone who actually competed with it... so it came pretty well built for crawling. I'm sure some guys here will cringe at the fact that I've basically disabled an already well built crawler. ...

[Matt_]

Found the right springs:
TCS Crawlers Internal Shock Springs for Losi Mini Rock Crawler (Medium - 4 each)*-*-By Truck: Team Losi Mini Rock Crawler*-*The Crawlers Store LLC

They only have medium and light. So i'm going to get a set of the medium and see what happens.

[winnerone23]

Good work on the springs! I would of never known the existed..

Taking apart a comp rig! I have seen worse done to great looking rigs.. like boxing them up or leaving them outside an never moving them.. its getting a new chance at life since ur using it an building it! Good work!

[Matt_]

I figured for $5 after shipping I might as well order the set of new springs rather than try a few different pen springs from varying manufacturers and age... lol trying to keep variables to a minimum as I change things to see what works!

I never thought of it as bringing new life to this comp rig..... that's a good point, thanks!

[Matt_]

So far so good. Put the medium weight internal springs in with 35WT shock oil.

I didn't get a chance to test drive it though.... both my LiPo batteries were getting "low voltage" warnings when I tried charging them (i bought this stuff used, so im not sure how old they are or how they were handled... For $25 i just ordered 2 new batteries to play it safe).

In the mean time, I've pleased with the results so far

[winnerone23]

Sits much nicer! looking good.. Got a trick for those batteries.. or just send them my way, ill take care of them.. lol..

Ok, so ur getting a lv warning from ur charger an it won't charge ur batteries? Bump them on nimh for 30 seconds... Or is it nicd.. hmm, look it up... After that, put them back on lipo an charge away.. I have bumped mine on nimh without a problem, but can't ever remember which is right or if there is a wrong.. tho its all wrong to do it from get go..lol, it does the trick tho..

[Matt_]

Thanks. I actually looked up that trick earlier today and thought about cancelling my battery order... but figured they're probably near the end of their life regardless so $12/ea shipped for peace of mind (especially with all the LiPo horror stories)

[winnerone23]

It's always good to have batteries.. I think I'm close to a dozen an a half.. trial an error an all..(with size an use)... I only ever lost a couple batteries, two do to a bad capacitor an one an a half to a bad esc..

It works tho...

[Matt_]

I did the "trick" and have one charging now. Going to crawl over some of my kids' toys once its ready to go

[Matt_]

Thanks for everyones help. Got the RC Commander exactly how i want it!

Does this forum accept embedded youtube code?

Here's two videos. Don't give me too much crap about my crawling abilities... this was my first time and neither the stick pile or the rock pile were "setup"; just wanted to see what i could run over

Jeep Commander RC Crawler - YouTube

Jeep Commander RC Rock Crawl - YouTube

[Matt_]

Oh... and the battery I used started puffing up. Guess I did kill it!