1988-1990 Nissan GTP ZX-T

Images copyright Ashley Page and Michael J. Fuller
Text copyright Michael J. Fuller

Nissan GTP ZX-T, chassis # 8805For 1988, a new Trevor Harris designed tub was introduced.  “In mid ’87 I got a call from Kas Kastner to come up to Nissan, he wanted to talk with me about GTP car ‘stuff’,” recalls Harris.  At the time Harris wasn’t working full time on the GTP project, instead he was heavily involved with Electramotive’s Stadium Trucks program, but Kastner wanted Harris’ opinion about what it would take to up their game in ’88.  Kastner elaborates, “It was apparent that the design of the car left a lot on the table even from a practical standpoint.  For example, it took eight hours to change the engine.”  The Lola’s front suspension was also very difficult to work on, Harris continues, “it was a very difficult car to do rapid chassis set ups with because the springs were very difficult to get at.  It just was plain difficult!”  Time lost setting the car up simply meant that fewer minutes were spent on track.  In addition, it had become rather clear that the tub’s safety was compromised at the design level.  After Don Devendorf’s Pocono accident it was determined that the seatbelt anchor had simply pulled out of the carbon floor due to the severity of the impact, “It was a tiny little extruded aluminum piece that had been molded in and didn’t have much of a load spread to it at all; it was just about fucking criminal.  It was just woefully inadequate.  Don’s lucky he wasn’t killed in that accident,” says Wes Moss, Vice President of Engineering for Electramotive/NPTI.  Naturally the goals for the new monocoque would be to correct the deficiencies of the Lola part it would replace.

The new tub’s design was driven by the outside dimensions of the Lola 810 monocoque it would replace as it would have to slot in and interface with the updated Suzuka bodywork which in turn was designed to fit the Lola tub.  Made out of aluminum honeycomb with machined aluminum internal bulkheads, the ZX-T’s tub ended up being on the order of 12000+ ft-lbs/degree stiff compared to around 8000 ft-lbs/degree for the Lola 810’s tub.

As Electramotive didn’t have the expertise to build the tub the task was farmed out to Jim Chapman.  The aluminum inner and outer skins and inserts were drawn up by Harris and subsequently fabricated by Chapman.  All the items were then sent to Ciba-Geigy in England where honeycomb of varying thickness (per specification called out by Harris), as well as the inserts, were then bonded together to create the component honeycomb sheets.  The entire lot was then shipped back to Chapman’s in San Clemente, California and assembled into a tub.
Nissan Lola 810The orignal Lola 810's suspsnsion operated via pushrods with the spring/dampers mounted inboard.  But in order to clear the room dedicated to the radiator inlet ducts, the spring/dampers were buried into the chassis in a very awkward assymeticaly but staggered arrangement.

Ashley Page, Electramotive’s Chief Mechanic from 1985-1990, remembers the orignal Lola's front suspension layout fondly, “It was a goofy layout to say the least and a double-barrel bitch to do a spring change in a hurry…but my opinion was at the time, and still is, that the workability of the pushrod design was a greater detriment to developing the car during a race weekend than any potential compromise the later design would have.”
Nissan GTP ZX-T, chassis # 8805The front suspension was very “old fashioned”, according to Trevor Harris, and consisted of upper and lower A-arms but with the spring/damper mounted to the outboard end of the lower A-arm and angled to a pickup point located on the monocoque.  While designed from the start, no front roll bar was ever run beyond initial testing with the observation that front roll control was of less importance than the spring platform which had to handle the high downforce loads.
Nissan GTP ZX-T, chassis #8805Here we get an idea of the packaging conundrum regarding the leading edge of the very important cooling inlets and the need to package the front suspension.  The redesign of the front suspension had to take this into account as Harris and the design team didn't have the luxury of completely redesigning the car.

ęCopyright 2012, Michael J. Fuller