Two piece driveshaft safety loop

[Slow78z]

I finally scored a set of slicks so my next step was to make a driveshaft safety loop to pass tech.  I looked at numerous pics on the web and on this forum for inspiration and finally came up with this two piece design. It wasn't to difficult to make and should be easily removable if need be. It was made from 1/4" X 2" bar and some bolts. Here are the pics.

 

I used two prexisting holes that were originally used to hold the factory heat shield in place. They both had nuts tack welded to the floor pan under the seats. The seats were removed for access to the nuts. The nuts were then removed by cutting the tack welds. My mounts consist of a 10mm X 1.5 bolt and thick washer for the topside. On the bottom a drilled and tapped 2" X 2" X 1/4" piece of bar to act as the nut and washer to the bolt going thru the floorpan. The floorpan is then sandwiched between the washer on top and the washer/nut on the bottom.

 

The next step was make a templet of the crossmember using some mechanics wire. I then used some of the 1/4 X 2" bar and made a duplicate of my template with the help of a torch to heat up the metal for bending. Next I drilled a few holes and mounted the crossmember. From this point I could make another template for the loop and then duplicate that piece with some more bar. A few more holes were drilled into the loop and crossmember to connect the two. This is the finished product.

 

Overall I spent roughly $8 in metal and the bolts I had laying in the bolt bin so it was an inexpensive fun project.

Parts list;  4' of 1/4" X 2" bar

                  4 10mm X 1.5 bolts

                  2 10mm X 1.5 nuts

[RebekahsZ]

Looks fantastic! The 240z tunnel is SO much narrower. This was a big problem. You made it look easy. Do you think we need axle loops?

[Slow78z]

Thanks! I came across a few threads talking about half shaft loops and think its a good idea. Anything could happen when your booking it at 120 mph and one breaks. I guess the worse would be the axle some how locking up the rear tire and causing an uncontrollable spin. I bet one loop right in the middle would give protection for both ends.

[Domzs]

Nice !

[RebekahsZ]

Yeah, that is what I've seen-just one loop in the middle, but I haven't seen any examples that are super clean in design.  I think it would be pretty easy with the flat plate portion of the stock control arm, but it will be tricky with my tubular control arms-it will take more mods for me.  To me it is a matter of limiting collateral damage so there is less stuff to fix.  Everybody I know who has broken an axle has also trashed brake lines and floor pans, turning a fairly easy matter in to a crisis.  This is the final thing on my winter mods list because I can't figure out if it is required prior to chassis certification, or not.  I also don't know if it has to be 2" wide 1/4" flat plate just like the driveshaft loop.  Can you show (just for review) what your 1/4-mile times were before and after slicks (include 60' times and trap speeds)?  I don't know how you were doing so well with skinny street tires-maybe it is an A/T benefit-less blood and guts getting out of the hole!

Edited October 28, 2013 by RebekahsZ

[Slow78z]

Can you show (just for review) what your 1/4-mile times were before and after slicks (include 60' times and trap speeds)?  I don't know how you were doing so well with skinny street tires-maybe it is an A/T benefit-less blood and guts getting out of the hole!

Sure. 195/70 r 14's 11.908 at 115.40 with a 60' of 1.813

M/T 26X8.5 14's 11.742 at 114.44 with a 60' of 1.665

 

With the street tires I foot stall to about 2K and roll into it otherwise it wheel hops. With the slicks I idle until the last amber shows and then floor it. The 3200 stall matches up to when the cam starts to make power so I think that probably helps with launching. I like how you put it "less blood and guts" is probably a benefit of the auto.

 

I watched a couple of your drag racing videos the other day. What RPM do you launch from with the two step?

[RebekahsZ]

With the 2-step, I can vary the rpm based on traction conditions.  Real sticky track=4500rpm.  Slick track=as little as 2000rpm.  The problem I have on slick tracks is that when the 2-step clicks off, the tires spin and the weight transfers back forward even after a good initial bite and squat.  I wish I had some sort of automated 2-step progressive controller, but I guess that would be called a real driver who can launch old-school off a clutch.  Problem with slipping clutch is heat and flywheel warp-been there and done that.  The difference between your street tires and your slicks is too little-you should be almost a second quicker just by driving the car for the next year and learning how to launch it.  I don't know anything about launching an automatic, but I was under the impression that you should be able to launch just by lifting the brake pedal off the floor (foot braking).  If I had an automatic, I'd be wiring up a delay box and doing the whole thing, because money racing depends on consistency (which I'll never have).  There's still likely a little more speed/ET in your car as it sits, although a 1.66 is nothing to cry about.  That is what I 60' when I'm spinning like crazy, so I know you can do better.

Edited October 28, 2013 by RebekahsZ

[Slow78z]

Mine probably has a little bit more in it. I was disappointed when I saw how busy it was at the track. I didn't even get to play with tire pressures. My friend that was watching said I was still spinning a little in first on launch so it might have a little more go power. I also wanted to try and foot brake it also but I don't think it would have helped much. Now if I had a transbrake, that would be the ticket. But that would probably also lead to more broken parts. I'm faily content with what it can do but I'm sure it will wear off shortyly. What kind of 2-step do you use Rebekahsz? I think I'll probably need one with the turbo setup.

[RebekahsZ]

I bought the MSD brand LS-2 step.  It is literally plug and play into the coil wiring harnesses up on top of the valve covers.  You just have to figure out how to activate it, where to mount the control box (the cables aren't very long) and how to power it.  Because of the short wiring, I mounted mine under the hood on the firewall, so I have to pop the hood to adjust it.  You need a little screw driver to adjust it, same as the little screw driver I need to adjust my shift light.

 

An alternative is the Lingenfelter 2-step which is actually a 3-step.  So you can set it to have a burn-out rpm and a launch rpm.  The third step is factory PCM controlled.  I try to limit my burn out rpm to 5000 because I've hit the factory rev limiter several times (once those tires start spinning, you can over-rev in a heart beat).  I've seen lots of cars blow up in the waterbox.   It must have longer wiring because I've seen photos of other folks' setups and they can mount it inside the car on the trans tunnel.  It adjusts with knobs that you can turn without a tool.  It also can be wired to adjust timing somehow, but the wiring looks more complicated, that is why I chickened out on it.  Supposedly you can also adjust timing retard with it, but I haven't found anybody who could tell me how that gets wired into the PCM, or if that feature even works with an LS motor.  It is more of a universal unit, whereas the MSD kit is specifically for the LS family.

 

I have a thread out there somewhere that details the install of my line lock and another that details the install of my 2-step.  When I decide that I need more driver controls, the next item is a switch operated hydraulic clutch release solenoid.  The trick to that working safely is ensuring that my line lock, 2-step and clutch all release at exactly the same time.  Right now, my line lock releases at the bottom of my clutch travel limit and the 2-step releases at the top of my clutch travel release limit.  The idea is that it reduces the chances of my clutch dropping against locked front brakes, and it reduces the chances of my 2-step releasing before the clutch is fully engaged.  The only malfunctions I have had are: 1) 2-step release switch out of adjustment, which made car launch and stay at 2800 rpm all the way down the track, and 2) my mistake of mixing up the 100rpm and 1000rpm pins which deactivated the unit and I nearly blew the engine when I went to the line and floored the car expecting a 2-step function that just wasn't there!  Scary.