Suspension design concept, will this work?

[Team_Jake]

For the last year, I've been designing a cantilever suspension system for my rig. After a ton of research, conversations with pros, and a lot of tinkering in Solidworks, I had most of the details design out, but after seeing the Reulsport vehicle from the Sway Bar Tech thread a couple days ago, my brain has been really captivated by the concept. So I quickly modeled up a different design shown here.

It's like an upside down mezzanine arm, with the coilover mounted upside-down, mounted to the axle instead of the frame. Running with this idea I drew up some things in Solidworks and came up with some pretty consistent motion ratios throughout the travel (min 0.50 and max 0.52), producing ~14.5" of travel from a 2.5x8 coilover. Loading wise, I ran a static simulation on the arm at full bump, made from 1/4" plates it has a factor of safety of 3.5, and it all packages really nicely in the wheel well. My question is, is there any reason why this conecpt couldn't work? Minus the Reulsport vehicle, I've never seen a cantilever / mezzanine style suspension with the coilover mounted to the axle instead of the frame.

The Reulsport Vehicle:

My Design, Ride Height:

Full Droop:

Full Bump:

Full Articulation:

Animation:

 

[ThePanzerFuhrer]

Are the cantilevered arms allowed to spin freely on the tube that runs above the axle on the frame?

 

[Team_Jake]

Are the cantilevered arms allowed to spin freely on the tube that runs above the axle on the frame?

Yes, and each side is independent of each other, or a sway bar could be integrated to run between the two arms.

 

[HYDRODYNAMIC]

Build it already!

 

[Team_Jake]

Build it already!

That's the plan! I just want to make sure I'm not overlooking something before I commit.

 

[ThePanzerFuhrer]

I would make sure that cross tube and the connection to the cantilever arm and arm themselves are massively overbuilt. Think semi trailer axle/hub strong.

 

[bdkw1]

Why would you want constant motion ratio? Every other linkage design is for rising rate. 35 years of MX bikes has this down to a science.

 

[ThePanzerFuhrer]

Build it already!

worst thing that could happen is when he sets it down it falls down to full droop.

 

[cj3a]

Analysis paralysis. Get welding, no rules to get it right the first time.

 

[Team_Jake]

Why would you want constant motion ratio? Every other linkage design is for rising rate. 35 years of MX bikes has this down to a science.

Because a constant motion ratio behaves most like a standard coilover setup mounted close to vertically and makes tuning easy (I had some long conversations with some guys at Accutune about exactly this, they say as close to constant MR feels the most predictable when driving fast, and I trust their expertise).

 

[Team_Jake]

Analysis paralysis. Get welding, no rules to get it right the first time.

This concept is just something I modeled up today, if it's determined it won't work then just one day wasted.

 

[HYDRODYNAMIC]

Because a constant motion ratio behaves most like a standard coilover setup mounted close to vertically and makes tuning easy (I had some long conversations with some guys at Accutune about exactly this, they say as close to constant MR feels the most predictable when driving fast, and I trust their expertise).

One of the first things I looked at. Constant motion ration is easier to tune. The one that you were studying does not look constant which is hard to see from one picture but they probably have bypasses which can tune per zone.

 

[Team_Jake]

One of the first things I looked at. Constant motion ration is easier to tune. The one that you were studying does not look constant which is hard to see from one picture but they probably have bypasses which can tune per zone.

Yes, the Reulsport vehicle does have bypasses.

 

[YotaAtieToo]

Seems like a somewhat simple way to get good travel on full body rig without dumb coil over mounting. (looking at the guys in newer Jeeps with coil overs mounted 8" below the axle)

Intergrated sway bar is a great addition also.

 

[AgitatedPancake]

Yeah. I'm really liking this new way of achieving motion ratio, and I think your design is beautifully simple. I'd get to building

Ever since seeing those pics Bebop posted, I've been hooked on the idea as well. I think exciting builds will come from this concept

 

[Treefrog]

The coilovers do not need to be mounted upside down.

 

[Team_Jake]

The coilovers do not need to be mounted upside down.

The reservoirs wouldn't fit otherwise. I'm sure I could come up with something but this was easiest.

 

[Team_Jake]

Yeah. I'm really liking this new way of achieving motion ratio, and I think your design is beautifully simple. I'd get to building

Ever since seeing those pics Bebop posted, I've been hooked on the idea as well. I think exciting builds will come from this concept

Glad to know I wasn't the only one geeking out from those pics
🤓

 

[fl0w3n]

Can you boil this down in layman’s terms for my simple ass?

 

[YotaAtieToo]

The reservoirs wouldn't fit otherwise. I'm sure I could come up with something but this was easiest.

Most coil overs have a remote reservoir with a flexible hose anyway. Should be able to make something work there.

 

[IowaOffRoad]

Can you boil this down in layman’s terms for my simple ass?

Me too. I’m certain what you’re saying is true I just can’t quite wrap my head around from the pics. Load up the animation!

 

[AgitatedPancake]

The initial example from Reulsport looked far more complicated, but his example is pretty simple to explain. Basically take your normal configuration with a shock and separate sway bar. Instead of mounting the top of the shock rigidly to the frame, you mount it half way down the sway bar arm. So as the axle compresses, the shock mount raises in the chassis. As the axle droops, the shock mount lowers in the chassis. Giving ya some pretty sweet motion ratio

 

[Team_Jake]

Good explanation. Adding to that, the purpose is to get decent travel (14"+) without chopping up the bed/cab or having the coilover axle mounts hang way down low. I'll work on an animation tomorrow.

 

[fl0w3n]

Awesome I was getting the jist but that helps. So what’s the ratio of shock travel to suspension travel?

 

[Hooligan]

Yes, and each side is independent of each other, or a sway bar could be integrated to run between the two arms.

Ahh, from the pictures it looked like they were connected via that bar …effectively serving as a sway bar.

 

[YotaAtieToo]

Awesome I was getting the jist but that helps. So what’s the ratio of shock travel to suspension travel?

Maybe try reading the op

~14.5" of travel from a 2.5x8 coilover

 

[total newb]

Do you have anything showing you spring rate data?

Im having a hard time seeing how this thing doesnt just freely colaps without bananas high spring rates.

 

[YotaAtieToo]

Do you have anything showing you spring rate data?

Im having a hard time seeing how this thing doesnt just freely colaps without bananas high spring rates.

No different than a shock mounted in the middle of a trailing arm?

 

[Treefrog]

Do you have anything showing you spring rate data?

Im having a hard time seeing how this thing doesnt just freely colaps without bananas high spring rates.

Installation ratios are installation ratios. This is just another way to setting it up.

 

[mobil1syn]

lots of motion ratio, what dia shock you planning on?