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Trailing arm with spool setup

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    Posted: Apr/25/2014 at 4:29pm
we are planning on using a trailing arm with a spool setup at the rear 

but after going through this forum i have not found any examples of the setup being used by anyone else. are there any inherent problems with these two elements being used together that we are missing ?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2014 at 9:25pm
USF, TTU, and Oklahoma had great success in the past with this setup... I am not sure if any team is running this anymore.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Richie_Dagger Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2014 at 9:15am
Trailing arm IRS or swingarm?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akss_bellatore Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2014 at 1:49pm
Trailing arm IRS
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akss_bellatore Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2014 at 1:51pm
What are the reasons behind this setup nt being seen anymore


Ive seen most teams going with either a 3 link or a semi trailing arm with a spool setup at the rear... any specific reasons
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2014 at 2:13pm
Several teams still run independent trailing arms with a spool... It is a nice setup because it directs all of the shock and link loads into the RRH, so the rear frame can be much smaller / lighter. The only obvious issues I see with it are no camber gain in roll (your tires will not remain perpendicular to the ground in a corner and thus reduce your lateral force) and it puts your rear RC on the ground, meaning you likely need an anti-roll / sway bar to tune roll stiffness separately and get the over / understeer gradient sorted out.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akss_bellatore Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2014 at 2:39pm
Isn't the aim of using a trailing arm to increase the over steer gradient and achieve the rear sliding out in sharp turns?

Is it that the trailing arm coupled with a  solid axle or spool increases the over steer gradient to an undesirable level ?

and how can i incorporate an anti roll or sway bar , the damper mountings being on the RRH as u said
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/26/2014 at 2:50pm
You need to be careful to distinguish the difference between a single rear swing arm / trailing arm where the wheels are locked together on a solid axle without CV joints and independent trailing arms where the rear suspension is totally independent and the axles requires articulation joints.

A dependent swing arm style has roll stiffness governed by the torsional stiffness of the swing arm and is typically very high to slide around corners. Independent trailing arms are completely decoupled and the shocks are pointed nearly entirely in the vehicle forward direction, yielding very low roll stiffness. You can either increase your spring rates and ruin jump and bump behavior or incorporate a sway bar to try to separate bump and roll characteristics. Single wheel bumps will still remain a problem as it will engage the sway bar when you would ideally prefer it didn't.

The shock position is irrelevant for a sway bar in terms of packaging though. you can mount the torsion bar in tight by the RRH like RIT and FEI have done or you can run it across the back of the frame above the transmission like Cornell and Queens used to. The location does not matter as long as you design the link lengths and torsion tube geometry appropriately.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2014 at 3:55pm
Semi-Trailing arm IRS can be designed to have a roll center higher than the front suspension, thus oversteer (however roll center changes with suspension travel such that you might transition to understeer in a hard turn or vise versa)(anti-roll bars exist for a reason).  You'll also get a camber gain (not that off-road tires care) and take some slop out of the CV joints.
 
This should be helpful.
 
Its better to refer to swing arms as twist-beams ("roll-oversteer" camber & toe gains depending on how hard you turn assuming chassis mount is higher than axle/axle-stubs).  The roll-oversteer effect increases as the H-beam is moved farther from the chassis.  The stiffness of the H-beam makes it semi-independent to fully dependent (live-axle).
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2014 at 3:58pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Semi-Trailing arm IRS can be designed to have a roll center higher than the front suspension, thus oversteer (however roll center changes with suspension travel such that you might transition to understeer in a hard turn or vise versa)(anti-roll bars exist for a reason).  You'll also get a camber gain (not that off-road tires care) and take some slop out of the CV joints.
 
This should be helpful.
 
Its better to refer to swing arms as twist-beams ("roll-oversteer" camber & toe gains depending on how hard you turn assuming chassis mount is higher than axle/axle-stubs).  The roll-oversteer effect increases as the H-beam is moved farther from the chassis.  The stiffness of the H-beam makes it semi-independent to fully dependent (live-axle).
 

Welcome back Akron!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akss_bellatore Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2014 at 4:29pm
Ok  so a trailing arm IRS does not give me any camber gain with suspension travel, correct me if im wrong,
In Indian Baja events teams with trailing arm IRS have had great success . the winners from last 2 years (COEP and SGSITS ) have both run Trailing arm IRS but with differentials

my basic concern was with using a spool setup with trailing IRS as for us its an unchartered territory

Soccerdan and Akron thanks for the help 
we may look into using a sway bar
AKSS
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Apr/27/2014 at 4:52pm
Originally posted by akss_bellatore akss_bellatore wrote:

Ok  so a trailing arm IRS does not give me any camber gain with suspension travel, correct me if im wrong,
In Indian Baja events teams with trailing arm IRS have had great success . the winners from last 2 years (COEP and SGSITS ) have both run Trailing arm IRS but with differentials

my basic concern was with using a spool setup with trailing IRS as for us its an unchartered territory

Soccerdan and Akron thanks for the help 
we may look into using a sway bar

You are asking VERY basic questions. Please visualize a trailing arm suspension in your head or use a small model, or CAD and you will be able to answer these questions yourself...

Camber is overrated.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2014 at 11:52am
Thanks JeiB, I've been lurking in shadows.
 
Akss,
 
Reliability can be more important than anything and people try to apply too many road racing principals to off-road out of ignorance.
Road tires are sensitive to camber and scrub thus formula cars have IRS with camber control and limited slip differentials.
Off-road tires are deliberately insensitive to camber due to dirt paths not being level and a differential is more likely to get you stuck in a rut than help you around a corner (which is slick with mud such that scrub isn't a problem in the first place).
Even if a trailing arm doesn't look like it has a camber/toe gain; it probably flexes under load such that it does. 
Semi-trailing arms have "Jacking Force" while pure trailing arms don't, a car that rolls over is really slow.
 
A lot of stuff to consider.  You need to quantify what you think is important or not and design a suspension/drive train that makes it happen.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akss_bellatore Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2014 at 12:18pm
thxx guys
AKSS
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paasch Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2014 at 3:55pm
Originally posted by Akron 1998 to 2004 Akron 1998 to 2004 wrote:

Reliability can be more important than anything and people try to apply too many road racing principals to off-road out of ignorance.

Amen. At yesterday's UTEP endurance race there were maybe half a dozen cars (out of ~80) that didn't come off the track for anything but fuel. You can't score points when your car is back in the pit being repaired.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote gearhed31 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/28/2014 at 11:34pm
my team, sunyit baja, has used independent trailing arm setups for many years with success. in our opinion, it offers decent handling, while taking bumps better than any other suspension type. the first year we ran it was 2009, and have not run anything else since. i will say though, that it is very hard to manufacture, as there is only one link to the suspension system, it takes all loads and supplies the camber and toe angles, and also is not normally adjustable 
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