Nissan radius arm FLEX design
Posted: Thu Aug 16, 2007 12:11 pm
There is a story about this and a bit of tech info along the way.
In an effort to get decent flex and performance out of my GQ I decided a few weeks back to contact one of our sponsors of the DGR lux, Mick at Superior Engineering to pick his brains on what can be done to my lwb GQ. It was worth the call as he had a heap of options for me to look at and he was currently building his comp car so I was able to try different things on it - so long as I put it back to how it was.(5" lift, drop arms, longest toughdogs . . . . .new longarm rear rearend)
Firstly I tried his rig on the travel ramp to see how it went, and he also had a customer there who wanted to try his 5" lifted gq wagon as well, so this gave me a great 'baseline' for the amount of flex available from different setups.
Here comes the tech bits! Basically what I discovered was that 3-4" lift didn't hurt the pin mount too much in terms of bind but the radius bushes maxxed out long before the shocks. (First tried the longest travel tough dogs) thinking the shocks might be the problem I removed them and brought around a set of 15" travel procomps and some 16" racerunners, just incase!!! Even with the shocks removed I could not get any more than 110mm differential measured across the shock mounting position. These measurements are also very similar to both the 5" drop arms and the STD arms with drop boxes, although the ride with the drop boxes is much better. The boys also had all the test data kept from Brian’s 5link conversion, so it gave me a great target to aim at to design a setup that had similar flex. My main design objective is always drive-ability and the way it puts power to the ground (comes from my drag racing background), which is why the DGR lux has been so successful over the years - STABILITY, GROUND PRESSURE AND POWER TRANSFER.
So a few beers later, a lot of measurements and a lot of chalk sketches on the floor, I came up with an idea!! So off to work to draw it up and test it using our FEA design package. Well the numbers looked good so it was now time to make a dummy arm, so Monday night we started cutting out the plates and making a new arm, finished it off last night and pressed in a pair of std bushes, then it was off to the ramp for the moment of truth! (The pics taken last night were crap with car headlights so Mick took some new ones early this morning on the wet grass!!)
The newly designed arms are a blend of two different styles of arms, each complimenting the angles of deflection required for controlled flex. The key is to change the planes of deflection to allow full movement and resist that terrible binding and tearing of bushes that always occurs. The other main design criteria was to transmit complimentary torque back into the chassis to reduce the 'ROLLY' feeling that 5links and Xlinks are known for. This eliminates/reduces the need for a front swaybar both on and off road. This was the hardest part to calculate as the amount of torque required is non-linear across the axle width. But after having a good play on a hill close by (insane angles!!!) it works unbelievably well. These links are purely for a test ATM, but after seeing how well they work Mick at Superior want to start selling them as a kit. They will be purely bolt on, well I did it so it can’t be too hard. They will compliment his new long-arm kit perfectly, at least now we have all the data documented – spring rates, shock lengths, shock tower heights, and travel lengths. I have certainly learnt heaps about getting flex out of nissans, a lot of setups I had always though worked well have actually proven to be very disappointing, but hopefully this might give you guys some ideas.
The parts are all designed around a complete bolt-on setup, i have all the drawings so if he does want to sell them it would be easy to get the bits all laser cut. I couldnt see the cost being mch more than a std type 'drop-arm' kit, but there are a few extra bolts, 2 mount adapter plates and spacer. Also one thing that i did find out in testing is that with that amount of flex it needed 230mm of shock travel in the front, so the longest toughdog limits travel only by about 10-15mm, so there is no need for weird shocks/&towers just std ones modified to a set height ~100-120mm depending on the spring combination, and vehicle setup.
In an effort to get decent flex and performance out of my GQ I decided a few weeks back to contact one of our sponsors of the DGR lux, Mick at Superior Engineering to pick his brains on what can be done to my lwb GQ. It was worth the call as he had a heap of options for me to look at and he was currently building his comp car so I was able to try different things on it - so long as I put it back to how it was.(5" lift, drop arms, longest toughdogs . . . . .new longarm rear rearend)
Firstly I tried his rig on the travel ramp to see how it went, and he also had a customer there who wanted to try his 5" lifted gq wagon as well, so this gave me a great 'baseline' for the amount of flex available from different setups.
Here comes the tech bits! Basically what I discovered was that 3-4" lift didn't hurt the pin mount too much in terms of bind but the radius bushes maxxed out long before the shocks. (First tried the longest travel tough dogs) thinking the shocks might be the problem I removed them and brought around a set of 15" travel procomps and some 16" racerunners, just incase!!! Even with the shocks removed I could not get any more than 110mm differential measured across the shock mounting position. These measurements are also very similar to both the 5" drop arms and the STD arms with drop boxes, although the ride with the drop boxes is much better. The boys also had all the test data kept from Brian’s 5link conversion, so it gave me a great target to aim at to design a setup that had similar flex. My main design objective is always drive-ability and the way it puts power to the ground (comes from my drag racing background), which is why the DGR lux has been so successful over the years - STABILITY, GROUND PRESSURE AND POWER TRANSFER.
So a few beers later, a lot of measurements and a lot of chalk sketches on the floor, I came up with an idea!! So off to work to draw it up and test it using our FEA design package. Well the numbers looked good so it was now time to make a dummy arm, so Monday night we started cutting out the plates and making a new arm, finished it off last night and pressed in a pair of std bushes, then it was off to the ramp for the moment of truth! (The pics taken last night were crap with car headlights so Mick took some new ones early this morning on the wet grass!!)
The newly designed arms are a blend of two different styles of arms, each complimenting the angles of deflection required for controlled flex. The key is to change the planes of deflection to allow full movement and resist that terrible binding and tearing of bushes that always occurs. The other main design criteria was to transmit complimentary torque back into the chassis to reduce the 'ROLLY' feeling that 5links and Xlinks are known for. This eliminates/reduces the need for a front swaybar both on and off road. This was the hardest part to calculate as the amount of torque required is non-linear across the axle width. But after having a good play on a hill close by (insane angles!!!) it works unbelievably well. These links are purely for a test ATM, but after seeing how well they work Mick at Superior want to start selling them as a kit. They will be purely bolt on, well I did it so it can’t be too hard. They will compliment his new long-arm kit perfectly, at least now we have all the data documented – spring rates, shock lengths, shock tower heights, and travel lengths. I have certainly learnt heaps about getting flex out of nissans, a lot of setups I had always though worked well have actually proven to be very disappointing, but hopefully this might give you guys some ideas.
The parts are all designed around a complete bolt-on setup, i have all the drawings so if he does want to sell them it would be easy to get the bits all laser cut. I couldnt see the cost being mch more than a std type 'drop-arm' kit, but there are a few extra bolts, 2 mount adapter plates and spacer. Also one thing that i did find out in testing is that with that amount of flex it needed 230mm of shock travel in the front, so the longest toughdog limits travel only by about 10-15mm, so there is no need for weird shocks/&towers just std ones modified to a set height ~100-120mm depending on the spring combination, and vehicle setup.
..... keep it up fellar... and as always mick from superior will produce a top quality work piece 
( 3 mounting points on the diff end of the passenger side radius arm ??@?@?@?@??@?@?!?!?!?! - or am I blind) there are a couple there where you would expect to see the length of the radius arm, but you can't see anything so they must be pretty well tucked up.
Can someone put some shocks on those photos for me. ASAP. 
