260DET Posted February 14, 2002 Share Posted February 14, 2002 When driving diagonally over a low kerb gutter, the 260 creaks so I'm guessing that torsional rigidity is not all it should be. Has anyone succeeded in improving the situation? Perhaps by using something that doesn't involve an extensive rework? I was thinking of bolting a rigid plate underneath, across the transmission tunnel just behind the gearbox. Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted February 14, 2002 Share Posted February 14, 2002 I have thought about this one a lot. I would like my 260 to be kind of like a speedster. No roof, low windscreen etc. I will probable make a back bone chassis that is welded to the trans tunnel and then will pick up the suspension. This will also require some crossmembers like you describe inclosing the tunnel. No matter what you do to improve it you are going to be in for some welding. What about seam welding and a bit of bracing like they do for the convertibles? Cheers Douglas Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted February 14, 2002 Share Posted February 14, 2002 Rory Bateman once showed me something interesting about early Zee' Look at the rear of the roofline on each side of the rear hatch. You will find a body seam that is soldered to hold the roof line in place to the rear of the body. He says the body design was engineered to incorporate a convertible style. He also showed me an across the top gap he had cut with a disc grinder in the roof line above the windshield in preparation of a converible. He slid the grinding disc along the inside of the gap all the way across to show that the gap had not closed in the few days after the cut. The body's do not rely that heavily if at all on that soldered roofline. Check the solder line seam to check on body flexing. POST SCRIPT ... I am not suggesting there is not flexing but to check for flex and not rely on body squeaks. Despite the demonstration with the disk, I re- inforced my car and still not satisfied and plan to further re-inforce the firewall and rear bulkhead as you aptly suggest. Quote Link to comment Share on other sites More sharing options...
johnc Posted February 14, 2002 Share Posted February 14, 2002 I beg to differ on how much the car flexes at the C-pillar seam. Depending on the quality of the roll bar/cage installation, you'll see many track Zs with cracks in that seam. You will also often see cracks in the floor pan at the rear of the driveshaft tunnel. Torsional rigidity is not as important in the Z as horizontal rigidity. The car flexes like a hinge in two places: at the firewall and behind the seats at the rear bulkhead. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted February 14, 2002 Share Posted February 14, 2002 John's point is the primary reason I chose a 6 point drivetrain solid mounting scheme. The front engine plate is attached to the crossmember, the rear engine plate is attached to the firewall/frame rail corner, and the tranny mount is, of course, in the tunnel. With all points solidly mounted the engine/tranny stiffens this "hinging" acting quite a bit (acts like a spine). My only concern was cracking or breaking the aluminum tranny case or bellhousing. This has not happened in over 10 years of use. Quote Link to comment Share on other sites More sharing options...
260DET Posted February 16, 2002 Author Share Posted February 16, 2002 Thanks all for your input, much food for thought there. Douglas, like your idea, providing the trans tunnel bracing is tied strongly forward towards the front suspension so as to counter the hinging tendancy mentioned by John and blueovalz. Maybe onto the tension rod's chassis brackets? Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted February 16, 2002 Share Posted February 16, 2002 I have some made some plans and it will solve that problem. It will go through the firewall and also tie into some rear strut braces. I will do the photo thing when i start. It will be around four to five months away though. My workshop is full of my house crap while my house is being built. The house was suposed to be finished in november and i still only have foudations in. and for good measure Oh well, this will be the last one i need to build. Douglas Quote Link to comment Share on other sites More sharing options...
260DET Posted February 18, 2002 Author Share Posted February 18, 2002 Through the firewall sounds good, Douglas. My guess is that the front flexing results from the firewall itself flexing where the various structural components attach. Only those mickey mouse under chassis channels are continuous. And they tend to get damaged over time. Best of luck with your house Quote Link to comment Share on other sites More sharing options...
Michael Posted February 18, 2002 Share Posted February 18, 2002 I second the observation that "front flexing" is a problem on the Z. When my roll cage was installed, before the front strut tower diagonals were in place, the car would still flex, as observed when it's abruptly lowered from a hydraulic lift. After the diagonals were installed, the flexing was significantly attenuated. The diagonals pierce the firewall and connect to a dash bar and "backbone" running down the middle of the passenger compartment. For pictures, see http://mywebpages.comcast.net/pparaska/MichaelOlsBBZ.htm Quote Link to comment Share on other sites More sharing options...
Sleek Z Posted February 18, 2002 Share Posted February 18, 2002 Many points made in this thread agree with my observations so I won't rehash them. However, I thought that some of you might find it interesting to study two introductory photos of Sam Freeman's professional convertible reinforcement bracing treatment. Sam Freeman is a well know SoCal custom car fabricator noted for his work on convertible cars, including his share of Z cars. Scroll half way down the page to the yellow convertible Cap project . Curious thing about the bracing illustrated in these photos is that it is all rectangular box channel. More photos later on will show that Mr. Freeman did quite a bit of bracing behind the seat area in front of the tool bins which would relate to one of the 2 chief flex sections noted in other posts. Eric Neyerlin Quote Link to comment Share on other sites More sharing options...
ZROSSA Posted February 18, 2002 Share Posted February 18, 2002 Wow Michael, Somehow i missed you car. I thought I had been through petes sight with a fine toothed comb. I take it the local road safty guys dont mind the bar over the trans tunnel. The guys here are trying to ban roll cages on road cars for safty reasons. There thinking is that you dont put on your helmet while on the road and can knock your head. Hence i am going the backbone chassis way. The end result will be similar. Cheers Douglas Quote Link to comment Share on other sites More sharing options...
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