Why RC rock clawers have suspension?

[gonper]

First I want to say that I am talking of competition Class 1 - Superclass and Class 2.2 rigs not other ones.

The suspension on an RC car has the the only functions of keeping the wheels on the ground in order to make it the most drivable possible and put as much traction to the ground as possible.

I am use to design suspensions and other staff for real vehicles and now I am designing an RC superclass rock crawler. And I have realized that it is a completely different scenario and most of the standards on a vehicle suspension do not apply to RC rock crawlers or apply differently.

The issue is that in order to make the suspension work as better as posible the unsprung mass should be as low as posible. But in the case of this crawlers most of the mass (provably around 90%) is unsprung mass. So now great part of the suspension function has to be taken care by the tires and foam and links.

So the question is, what is the function now of the shock absorbers, as they barely have to support any weight?
I believe they are energy reservoirs systems that are able to save some energy when dining and release afterwards when marching again. The do not act like that when scrubbing because we normally use one way only shock absorbers (may be someone have already have tried double direction shock absorbers)
So I think that we may start thinking and tunning them differently.

Please let me know your thoughts.

[EeePee]

Controlled weight transfer.

[gonper]

Originally Posted by EeePee

Controlled weight transfer.

Yes good point, that is a function that the shock absorbers have to handle.

[TheLetterJ]

Are you familiar with torsion chassis' on rc crawlers? I have a Dahu torsion chassis that I'll be building an MOA crawler around (hopefully soon) that eliminates all traditional shocks/springs/links and relies on the chassis itself to provide the controlled movement of the axles. Billet Works also sells a 1/2 torsion chassis, called the Mantis, where the front end is still sprung. These types of chassis' aren't for everybody and they are sure to drive/react differently than traditional suspension setups, but they might get you thinking further outside of the box if that's what you're after?

[gonper]

Originally Posted by TheLetterJ

Are you familiar with torsion chassis' on rc crawlers? I have a Dahu torsion chassis that I'll be building an MOA crawler around (hopefully soon) that eliminates all traditional shocks/springs/links and relies on the chassis itself to provide the controlled movement of the axles. Billet Works also sells a 1/2 torsion chassis, called the Mantis, where the front end is still sprung. These types of chassis' aren't for everybody and they are sure to drive/react differently than traditional suspension setups, but they might get you thinking further outside of the box if that's what you're after?

You are right, those are very good examples. The suspension is provided by the tires/foams and the chassis takes care of flexing and control.
The chassis flexibility is where energy is stored when dining and scrubbing.
About reactions, I think that if oil dampeners are added to the Dahu chassis in order to control its flex reactions will make it easier to drive.

And yes I am thinking out of the box for my superclass design (here: Crazy axles idea design)
Anyway I think that for a superclass a flex chasis may not bee a good idea due its size, and because it may be difficult to fine tune it.

[Sneetches]

OP have you seen the BWD Mantis chassis? BWD XR-Mantis Prototype Chassis Kit...All New!

[mewalsh100]

Articulation to keep wheels in contact with surface, therefore creating traction.

[PoorManRC]

Originally Posted by mewalsh100

Articulation to keep wheels in contact with surface, therefore creating traction.

That's actually the best argument for Shocks and Springs - particularly Springs....
To keep Pressure on the surface, with the tires.

You could almost run the Shocks empty..... as Damping at Crawler speed is nearly redundant. The Springs are doing all the work.

[EeePee]

A torsion chassis is a spring and the biggest problem with them is their lack of dampening, which is why you don't see many anymore.

[gonper]

Originally Posted by PoorManRC

That's actually the best argument for Shocks and Springs - particularly Springs....
To keep Pressure on the surface, with the tires.

You could almost run the Shocks empty..... as Damping at Crawler speed is nearly redundant. The Springs are doing all the work.

Sorry to disagree, but in this type of crawlers due its low speed the springs does not play much effect on keeping the wheels on the ground, only gravity force is the one that keeps them on the ground.
Although the springs regulate how the gravity force is distributed among the wheels, because they regulate how torsion happens and derivate some of the gravity force from one/s wheel/s to another/s.

The oil dampeners makes that the movements created by the force transitions to be slower. That avoids fast movements of the axels/wheels that may create big inertial forces that can affect the vehicle stability, so oil dampeners makes the rig more controlable.
So yes oil is necessary in order to have a more stable and easy to drive vehicle.

[gonper]

Originally Posted by EeePee

A torsion chassis is a spring and the biggest problem with them is their lack of dampening, which is why you don't see many anymore.

Yes, you are right, I think that if oil dampeners are added in order to avoid high speed chassis movements they could be great chassis due their lightness, ground clearance and toughness, at least for 2.2 class.
For superclass I thing that they may be too flexible and the axels with the double steering may be wandering around instead of following the desired paths.

[mewalsh100]

Originally Posted by EeePee

A torsion chassis is a spring and the biggest problem with them is their lack of dampening, which is why you don't see many anymore.

You don't see them much anymore, but I recently saw a guy driving one and he was doing amazingly well with it. I think some of it comes down to driving style. But, for my "style", I'll take shocks/dampeners all day long!

[JatoTheRipper]

Rock Clawler?

Am I the only one that thought of this toy truck from my childhood?

[Jboucher]

Originally Posted by JatoTheRipper

Rock Clawler?

Am I the only one that thought of this toy truck from my childhood?

This is awesome...
We need these wheels on real RC trucks.
Like paddle tires that would extend or retract based on terrain!

Sent from my Nexus 6 using Tapatalk

[EeePee]

Pimp Cane, which I never had

TCS Stick, which I had, and has one shock on each axle, on the same side

DNA SSS, here EP's 'Sportsman' SSS Axial

[gonper]

Pimp Cane, which I never had

TCS Stick, which I had, and has one shock on each axle, on the same side

I like the simplicity of Pimp Cane or TCS Stick but as they can not flex on their length, dig/scrub functions does not work as they should because they only have the flexibility of the tires to store energy.

DNA SSS, here http://www.rccrawler.com/forum/axial...sss-axial.html

That is very cool design, using links to keep the axels on position and a flex chassis parts to reduce the weight of the shock absorbers and make it more simple.
I suppose that it is difficult to tune it.

[Brainstain]

Wasn't there an emoji that was talking to a wall at one point? I feel like it is now the only appropriate response.

[STANG KILLA SS]

the other down side to the torsion rigs is they require alot of wheel weight to work well. opposite of where the sport has gone.
i had a super and later a 2.2 pimp cane.

[xCoolHandLukex]

Originally Posted by gonper

Sorry to disagree, but in this type of crawlers due its low speed the springs does not play much effect on keeping the wheels on the ground, only gravity force is the one that keeps them on the ground.

Although the springs regulate how the gravity force is distributed among the wheels, because they regulate how torsion happens and derivate some of the gravity force from one/s wheel/s to another/s.



The oil dampeners makes that the movements created by the force transitions to be slower. That avoids fast movements of the axels/wheels that may create big inertial forces that can affect the vehicle stability, so oil dampeners makes the rig more controlable.

So yes oil is necessary in order to have a more stable and easy to drive vehicle.

Some crawlers can spit out some pretty good speed. My brushless AX10 can hop a pretty good gap. Without shocks it would bounce like crazy.


I typed this almost auto correctly free