View Full Version : New 3SD Suspension for MR03/02/015

2011.06.04, 06:23 PM
Hi everyone,

I've been trying to keep this a secret while working out the details, but yesterday night I finally took a brand-new suspension system to the track, which I am calling the 3SD system.

3SD stands for Sprung Single Side Damper -- it's quite a mouthful to say over and over again, so I needed an abbreviation lol. Essentially, I've replaced the springs on a PN Dual-Spring Shock with symmetrical springs, turned it sideways, and optimized the geometry such that one damper can replace the two side shocks of a tri-shock system. And replace it does! Relative to a tri-shock, the 3SD saves:

2 nuts
2 screws
1 shock end
1 spring collar
3 pivot balls
A lot of CF/FRP

Indeed, because I've managed to remove a bunch of complexity from the tri-shock system, I've found that the 3SD actually has a number of advantages over the tri-shock system, which I will detail below. Before that, let's have some pictures!



As you can see, the 3SD sits both farther forward and slightly higher than the tri-shock, but has a MUCH smaller footprint in the chassis. The bracket is attached to the right half of the damper arm, closer to where the damper arm attaches to the motor mount, so the damper arm will not suffer as much flex as it evidently does with PN motor mounts and a tri-shock setup. (Please don't mind that the bracket is epoxied on -- I broke a screw inside the damper arm and needed a quick fix lol.) Furthermore, because of the inboard location of the moving pivots, the 3SD system moves much less than the tri-shock under suspension loading. These factors combined allow it to fit under many more bodies than either the Reflex or PN tri-shock: in fact, it should fit under all popular non-LM bodies with no cutting, except for the F50, F355 and maybe the Enzo. I have been testing the Mosler MT900 and even when you fully slam it you only need two small cuts! Armed with this result I'm fairly confident it will fit snugly under the LM bodies too with only minimal cutting of the bodyshell. Here's how it fits under the 911 GT1 (non-slammed), you can really see how narrow it is compared to the tri-shock it replaces (two gigantic holes were cut to clear the tri-shock).


Ok, so it fits more bodies, but what about practical use? Well for starters, try this with a tri-shock:


Three screws to remove the entire assembly, that's it! Three screws and no soldering required. The damper arm simply slips out from underneath the motor wires, and the entire 3SD system can be lifted off the chassis to make motor or PCB maintenance easy as pie. Changing both springs requires just two screws and a nut. Admittedly you do have to reset and check your tweak settings every time you change springs, however a good eye and a penny test on the bench will help to get the tweak set correctly before you hit the track again.


Currently, the clearance between the mounting arm, the damper arm and the motor is perfectly sufficient in 98mm wheelbase form, but I found that 94 and 96mm lengths put the motor a bit close to the mounting arm. Not that the motor would contact the arm under normal suspension loading movement, however I do want to design some safety margin into the system so I will be raising the mounting arm using a 2-piece design rather than the 1-piece arm currently on the car.

Now the 3SD is a fairly radical and probably untested interpretation of the side damper, so I went to shake the setup down at Kenon with my 03, a Mosler body and a new 33t Mod motor. After sorting out some teething issues with Grant's help (I haven't ever run such power in my 03 before!) I'm proud to say that the 3SD performs practically identically to a tri-shock! :cool: There is less absolute travel in the right-turn direction (when the weight shifts to the left), but I found that there is still more than what's needed in real-life usage, so we're OK. I never once felt the suspension bottoming out even when violently throwing the car into the first right-hand hairpin from top speed. The effective spring rate across the car's useful suspension travel feels perfectly symmetrical -- I asked Grant and Joe Chen to verify this for me, and I did myself too with weights placed on either side of the car. Blasting through the PN Regional A Layout track, my car showed no signs of sluggishness through chicane transitions, high speed steering was the same as before and laying down the power was not an issue at all. I was able to induce oversteer with very aggressive steering input, but otherwise the car was planted, precise and very fun to drive. Tri-shock or no, that is pretty much the exact behavior I like to see in my setup, and I just can't tell you guys how much I liked it lol.

(Even slammed to the ground, the Mosler only needs a small cut to clear the 3SD's shock end! The two big holes were for the tri-shock.)

Taking the car back to the bench after a long day's testing I found the shock completely caked up in RCP dust -- and surprisingly, it didn't affect the drive one bit! Normally when the tri-shock dampers got too dusty you'd be able to feel it become a little sluggish, but this PN dual-spring shock displayed none of that weakness and so I think this system might have even more longevity than the tri-shock in between rebuilds. And as noted before, taking it off to rebuild it is so much easier than the tri-shock, so you'll be able to spend much more time on the track than in the pits, and that's where the 3SD really shines over the tri-shock setup. I won't make any claims about out-performing the tri-shock setup as it's already very good, but I think I've beaten it in terms to compactness, simplicity and user-friendliness.

A final word about weight: because the current version is in fiberglass (rather than the lighter CF), I make no claims about the weight of the 3SD system yet. Theoretically, it'll be much lighter than the PN tri-shock, and should match or be lighter than even the Reflex tri-shock. It's such a simple system! If we can get a Delrin shock tube to replace the current steel one it'll be even lighter. :cool:


Questions and comments appreciated! Thanks for looking. :)

2011.06.04, 09:07 PM
Brian, i really like the idea and looks of it. Hope to see this go farthur and being sold.:)

2011.06.05, 03:41 PM
I already posted under the "Pics of your MR03" section, but I have to say it again - SICK! Love the idea, I still like the old RR Side Damper... This adds the eft/right tension via the orange springs for better reaction time though! I'd like to know more about what you and Grantfound for a setup to work with this bad boy, and obviously because most of us have a couple PN Top-Mount Dual-Spring shocks this system would be pretty inexpensive (I think) to have the Carbon/Delrin/G10/Fiberglass/whatever:D material made into the 2 plates needed, right? Keep going on this Brian, this looks like a great idea. Thanks for sharing:D

> Forgot to ask - What caster are you running with the PN REV-Kingpin setup you have? Thanks again:)

2011.06.05, 07:15 PM
That is outstanding, Brian.:eek:

I want this product for my MR03...today while running our track i felt some side shock action would help settle the corner exit of my car and came today to look for something.

Thoughts on product sales? Are you selling the plates and advising people on how to fab the side shock modifications or are you consdiering any full package?

Either way let me know because that looks hot...this design should equal performance but the comparative ease of assembly and maintenance makes it a winner to me.:D

2011.06.07, 08:53 PM
Hey guys, thanks for all the replies so far! Here's what I know:

I need to get a proper shock made, otherwise this setup won't be refined enough to be a successful product.
If there is a lot of demand I will try to get just some extra brackets, so you can replicate the mod exactly as I did.
The 3SD concept itself still needs more rigorous testing (actual longevity between rebuilds, compatible springs, optimal damping greases, etc.) before it can be confirmed "good".
Installing a 3SD to a Reflex mount is not difficult, however installing it to any PN mount is a little bit more involved. When I have a pre-production version in my hands I'll make a tutorial about how to put it together.

As for a setup, what I've found is that you can essentially treat the 3SD as a tri-shock (expected, but nonetheless I was wary). I'm using either 15k or 7k grease in the side damper, with Orange springs (will try Blue next time, see what happens!) and nothing else special except for making sure the shock is horizontal when the car's at rest with batteries and body. Everything else carries over from my tri-shock setup: PN #5 G10 T-plate, PN shock up top with Red main spring and MR02 Yellow rebound spring, 15k grease, slightly angled down for more progressive behavior on-throttle.

Also, I appear to have lied when I said there's not enough motor clearance with 94mm and 96mm. I was just soldering the motor wires on poorly. :o When you solder them pointing off to the side the motor clearance to the mounting arm is perfectly sufficient. And if you need more clearance you can break off the tab on the brushes, and solder the wire to a spot further down. This discovery means that I don't have to revise the 1-piece mounting arm anymore! However, there is still one significant hurdle (the shock) to overcome before I can actually sell anything. :)


2011.06.18, 11:00 AM
Sweet looking setup Brian.

"If we can get a Delrin shock tube to replace the current steel one it'll be even lighter"

Yeah, you touched on a pet peeve of mine. I think the PN Dual Shock is a great design but also think it is totally ridiculous to manufacture both it and the associated balls in their joints out of solid steel. Because these items revolve in delrin cups they should be made from aluminum IMO. Just as the balls in the Kyosho Yellow Shock. A 66% savings in top heavy weight with equal functionality!

2011.08.24, 12:33 PM
Color1 good job, if I believe will be produced in quantities that will be good news for many.

One question: who will end up with thick material such as carbon or FRP?