How exactly? As the MR increases the fluid velocity/displacement decreases. Obviously the MR can't be too large because no combination of flutter disks could be tuned properly but I don't see how it could be overworked.
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Suspension design concept, will this work?
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Bebop
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Same wheel force with higher motion ratio = higher force at the shock = more heat.
Wouldn't the reduced fluid velocity/displacement compensate for that though? I'd like to know the math behind this.
CDA 455 II
ANFAQUE2
ThePanzerFuhrer
The Rock Breaker God
It will take more power to do the same amount of dampening with a setup like yours vs a long throw shock. You’re gonna have really stiff valves in there to get your dampening to an acceptable level.
Bebop
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If you compare this to a regular trailing arm, that looks much more complex.
CDA 455 II
ANFAQUE2
Yeah; definitely.
Treefrog
Book Wheeler
I'd argue that it's not that much more complex.
Up front design optimizing/tuning sure.
But, you are trading designing/building a trailing arm with designing/building a hinged arm.
Bebop
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More pivot points = more complex system, no ?
rockota
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you're correct.
But if all that mattered was complexity, we'd all still be on leaf springs on all 4 corners.
This is a very textbook approach:
Energy = 1/2 * mass * velocity^2
Force = mass * acceleration
Acceleration = velocity / time
Therefore, E = 1/2 * (F/a) * v^2
= 1/2 * F * (t/v) * v^2
= 1/2 * F * t * v
Compare say a 2:1 MR shock with a 1:1 MR shock. With a 2:1 MR, the force on the shock is doubled but the velocity is halved. Therefore the energy transferred into the shock is the same.
I think I see where the overworking issue can become a factor though -- an 8" shock doesn't have as much fluid as a 14" shock so it can't dissipate heat as well. So the overworking issue isn't because of the MR, its because of the fluid capacity. If this were a desert racer that would be something I wouldn't compromise on but this isn't a race build.
Energy = 1/2 * mass * velocity^2
Force = mass * acceleration
Acceleration = velocity / time
Therefore, E = 1/2 * (F/a) * v^2
= 1/2 * F * (t/v) * v^2
= 1/2 * F * t * v
Compare say a 2:1 MR shock with a 1:1 MR shock. With a 2:1 MR, the force on the shock is doubled but the velocity is halved. Therefore the energy transferred into the shock is the same.
I think I see where the overworking issue can become a factor though -- an 8" shock doesn't have as much fluid as a 14" shock so it can't dissipate heat as well. So the overworking issue isn't because of the MR, its because of the fluid capacity. If this were a desert racer that would be something I wouldn't compromise on but this isn't a race build.
That's what I said
CDA 455 II
ANFAQUE2
Love the different approach to the same problem "packaging vs performance". Not having tall upper shock mounts is a win.
But I agree there are more moving parts. Moving parts wear or break. AND the weight of the extra hardware, links, pivot, cross tube should all add up to more than the upper shock mount would be. They would also be more likely to break.
I can see where maybe a Jeep LJ owner that wants more wheel travel but does not want to cut the OEM chassis or tub. This could be a viable bolt on option to avoid that.
But I agree there are more moving parts. Moving parts wear or break. AND the weight of the extra hardware, links, pivot, cross tube should all add up to more than the upper shock mount would be. They would also be more likely to break.
I can see where maybe a Jeep LJ owner that wants more wheel travel but does not want to cut the OEM chassis or tub. This could be a viable bolt on option to avoid that.
Yep that's the point. My wife and I camp out of the back all the time, so cutting into the cab is not an option.
TTMotorsports
Red Skull Member
I bought a explorer that BTF Fabrication built that ran D44 spindles and wheel hubs with a mezzanine arm off it. The issue they had originally was the links connecting arm to axle weren't long and required more misalignment angle than the joint allowed so it tweaked the arm/side of frame when that happens. So if everything cycle fully with room to spare in every direction and should work find.
TTMotorsports
Red Skull Member
That Baldwin truck also gets more complicated since it runs Torsion bars front and rear. Sway a way mfg the bars and could dial it in as the vehicle and tuning needed.
That makes sense. Accutune claimed they were able to tune them to the specs I gave them, we'll see how well they perform.
Bebop
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They can tune them to perform.
They'll just perform for less time.
TTMotorsports
Red Skull Member
a sinlge 2.5 coilover will work decent for slow speed stuff. For desert high speed extended periods it won't last that long. If tight on space see if a 2.0 coilover and 2.5 bypass shock would fit. That would be much better setup for all around. I ran that setup on my 1450 desert race truck and didn't have any issues.
I already have the 2.5x8 coilovers, I was going to do a standard cantilever style but came up with this new design a couple days ago. This is basically a camping rig with tons, it won't see extended periods of high speed desert stuff. If this were a more serious desert rig I would definitely add in bypasses, but if this were a more serious desert rig I'd probably be cutting up the cab and mounting the shocks in a more traditional way.
Make the pivot a thick walled tube and add another arm on the inside of the frame for the BP.
Constant MR to make your shock tuning easier is leaving a lot of performance on the table. You would be much better off with 1.5 at bump and 2.0 at full droop.
1.8 is borderline for a 2.5 shock. Higher MR are also a bitch to tune. You need to make big changes to get the results you need. Also, the higher the MR, the more prone to cavitation it will be. You will need 300psi to keep from cooking the oil.
Mounting the bumpstop off the front of the axle is going to put a shitload of stress on the links and wear them out prematurely.
arse_sidewards
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I thought about doing that once to make a radius arm behave like a parallel link. Then I sobered up.
arse_sidewards
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No. You wind up running stiffer valving to compensate for motion ratio so that fluid winds up getting crammed though smaller spaces which more than makes up for the reduced speed.
arse_sidewards
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It has the same number of pivot points as a solid axle on leafs and less than any link suspension.The mere two pivots on the TTB is why I despise said design.
arse_sidewards
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Or literally any pickup truck owner who doesn't wanna sacrifice the ability to haul shit in the bed.
HYDRODYNAMIC
Rock Stacker
It doesn't take long for this crowd to talk you into 4" Live Valves, fully independent, portals, supercharged LS, 42" stickies, and race spec chassis just so you can go overlanding.
YotaAtieToo
Thick skull
If that's the case, I'd say just do some trailing arms to gain a little more travel from your shocks.
Unless you just want to prove your concept, then go for it.