Tube Chassis Datsun Project

Justin Olson · 06-04-09, 11:25 PM

I'm new here. I've just made the jump to doing a full tube frame Datsun 280z. The car will be powered by a Toyota 2JZ turbocharged engine. It will be backed by a Jerico or Super T10 transmission. Not sure just yet on that portion of things. The engine will be a structural member of the front suspension. I will be using C5 front uprights. I will be doing custom steel rear uprights with 300zxtt differential, axles, and hubs. I will have fairly long 4130 SLA suspension. The engine will be completely behind the front wheel centerline.

This is my first stab at designing a tortionally rigid tube frame. It currently weighs 185 lbs for the frame. The red bars are 1.625 X 0.083 4130 tubing and the green bars are 1.25 X 0.065 4130 tubing. I need to add more triangulation up front and at the rear. My next step will be taking more exact measurements of the drivetrain to place in cad.

The final 2 pictures show the wide fender kit that I've purchased for for the buildup. There won't be much datsun left in this project. I just want to have enough of it so I can register it, insure it and drive it on the street on that occasional nice summer day.

My overall goals for this project are sub 2000lbs and 600 hp.

Regards,
Justin

Dave · 06-05-09, 12:12 AM

Looks like a fun project and a whole lot of work. I've always liked those widebodies. Those 2jz's make tons of power with just bolt-ons thought I've never cared for the power curves with those engines.
I've always liked those widebodies.

Is that Darius' car at the bottom?

Justin Olson · 06-05-09, 01:45 AM

Thanks for the reply!

The widebody kit is made by Reaction Research:
http://www.reactionresearch.com/280yzgallery.html

The 2JZ definitely can be peaky. I plan on a fairly modest build for the engine. i will be using a stock lexus SC300 engine for my build. This is the non turbo version of the motor. It is just as strong as the supra turbo version. I'm just going to rebuild the engine with bearings, rings and gaskets. I plan to do a drysump setup on the car, along with standalone, and custom manifolds. I'm going to be using a fairly small Borg Warner S300 series turbo. I'm hoping for 550whp on E85 and pump gas.

The black car is Darius' supercharged LT1 powered 240z. More pictures of it can be found here:
http://s120.photobucket.com/albums/o...202/?start=all
Justin

Justin Olson · 06-05-09, 02:12 AM

Here are some dimensions on the factory 240z-280z. The car with the widebody kit is ~ 72" wide now.

Brian Hamilton · 06-05-09, 12:02 PM

Hey man. Great project. When I worked at the old hotrod shop in Austin, we had a guy there who had a 260Z with a Skyline RB26DETT in it. Friggin hauled ass. There's also a guy in Austin with a 300ZX with a 2JZ in it with a compound turbo setup. It makes about 725hp at the rear tires and the power curve is extremely linear. You may have heard about it, his name is Marc. He works at Boost Logic in Austin, TX. May be worth a call to them, they know those 2JZ's like nobodies business. LOL

Good luck on the project, I'm going to be following it.

Laters,

Brian

Justin Olson · 06-05-09, 02:27 PM

Playing in CAD more. Looks like I'm extending the wheel base to around 95" from the factory 90.7".

Doug Clark was gracious enough to share his models for the C5 uprights, hubs, and rotors. This has saved me a ton of modeling time! Thanks Again!

Next on my list is to rough out the transmission, wheels, and engine in CAD so that I can tweak the dimensions more. I am going to shorten the overall height of the rear suspension section to match more closely the control arm spacing.

Justin

SpeedQuest · 06-05-09, 07:31 PM

You would make your life so much easier if you made all horizontal bars out of square tubing. That way, you don't have the nightmare of fishmouthing all of those round tubes! (see SCCA Trans Am frames)

Darnel

SpeedQuest · 06-05-09, 07:40 PM

If designed correctly, the central backbone is not needed (redundant load path!). The outer tubes can carry the torsional loading better (think if you tried to twist a 5 inch diameter tube, it would be harder to do than if you tried to twist a 1 inch diameter tube).

Darnel

Justin Olson · 06-05-09, 08:38 PM

Quote:

Originally Posted by SpeedQuest

If designed correctly, the central backbone is not needed (redundant load path!). The outer tubes can carry the torsional loading better (think if you tried to twist a 5 inch diameter tube, it would be harder to do than if you tried to twist a 1 inch diameter tube).

Darnel

My feeling on this is that you can't triangulate the outer tubes as well to stabilize them like I can do with my central backbone. The efficiency of my backbone per unit mass I believe will be greater than if I took care of my torsional loads externally instead. I would like to play with FEA a little later on in the design process to prove this out. The priority of of the tubes outside the passenger compartment are primarily for occupant safety.

Regards,
Justin

Justin Olson · 06-05-09, 08:45 PM

Quote:

Originally Posted by SpeedQuest

You would make your life so much easier if you made all horizontal bars out of square tubing. That way, you don't have the nightmare of fishmouthing all of those round tubes! (see SCCA Trans Am frames)

Darnel

I plan to have all of the 1.25" tubing laser cut so I don't have to deal with the notching. I agree that would be painful!!!

http://www.frasersteel.com/notches.htm

http://www.youtube.com/watch?v=UeGVbtrrHjE

Regards,
Justin

Allen English · 06-05-09, 09:09 PM

Wow that Z looks cool! Do you plan to try out this place? Oregon Raceway Park | Grass valley, Oregon | The Future of Racing in the Pacific Northwest

SpeedQuest · 06-06-09, 10:33 AM

The most efficient design is when ever part has two jobs, not when ever job has two parts!

Darnel

Justin Olson · 06-06-09, 08:04 PM

I'm all ears on ways to make the chassis more rigid. What I don't want to do with the the chassis is have a petty bar, or any other bars that run through the passenger compartment in that manner. I don't have room to triangulate the door bars in the lateral direction. Also, I'm not planning on adding any roof bars or A pillar bars. I will triangulate the roll hoop back to the rear suspension pickup points so that it won't fold over.

Justin

Russ Noble · 06-07-09, 12:17 AM

Your passenger compartment will be comparatively stiff compared to the front and rear sections which have no longitudinal triangulation shown. Bracing the roll hoop back will not significantly improve the rear stiffness, although it may help support the roll hoop.

Justin Olson · 06-07-09, 12:52 AM

The front and rear sections are very pliminary at this point. I will be adding more triangulation there once I get the differential, engine and trans modeled.

I do plan on trying ORP at some point.

Justin

Justin Olson · 06-07-09, 03:55 PM

I've been thinking more regarding my backbone design. It seems by having a direct connection between my front and rear suspension, I am creating a very direct load path through the chassis. I don't find many chassis designed like I'm proposing. This isn't very confidence inspiring

It would seem to me that my truss design wouldn't be very stiff in bending front to rear due to the relatively long chassis length to height ratio. I'm looking at a chassis without rollbar that is ~22" tall with a length of ~115". I may need to add more bars in this plane to stiffen the chassis in this direction.

I've been toying with the idea of using a torque tube transaxle from a corvette in this project. This would shift more weight rewards and give me added rigidity. I don't need more rearward weight bias by my calculations at this point. I'm looking at a 45/55 F/R ratio thus far.

Justin

Terry Oxandale · 06-08-09, 09:25 AM

Nice project Justin (nice to see another HybridZ member here). These guys on this site are tops in fabrication and chassis advice. The've been very helpful in my new endeavor since departing with the BlueOvalZ.

Justin Olson · 06-12-09, 01:00 PM

I've been trying to determine what I want to do about wheels/tires and brakes for this project. From my research, I can run as small as 16" diameter wheels with C5 uprights. Smaller than 16", and I'd need to run a drop spindle for a C5, which cost over $1000/corner. I would like to run used race slicks that can commonly be found very affordably. These generally aren't found cheaply above a 16" diameter, and are more readily available in 13" and 15" diameters. There really are no affordable R compound tires in the 17" & 18" range. So I'm planning on running 16" take offs to keep expense down. This impacts my brake selection greatly, as most of the corvette brake solutions focus on 13"-14" rotors that won't clear a 16" wheel. I will likely start off with using stock C5 rotors front and rear, with wilwood or outlaw calipers on custom brackets. For the street I'm going to run a set of 18x10.5 C5-Z06 rear rims front and rear with some 285/30-18's. These wheels can be found relatively cheaply, and are light for their size.

Beyond all of this I'm trying to learn more about suspension motion. I'm currently researching the following topics:

-Camber Gain & Loss in Bump and Droop

-Caster Change and its relation to anti dive

-Anti Dive (How much do I really need? Must be based on COG & front/rear RC's I think)

-Roll Centers Calculations

-Roll Axis' (Roll, Pitch & Yaw)

Initially my biggest concern is accurately estimating my COG so that I can correctly build the proper suspension geometry. Any tips on estimating this?

Justin

Ron Earp · 06-12-09, 01:12 PM

Quote:

Originally Posted by JustinOlson

I would like to run used race slicks that can commonly be found very affordably. These generally aren't found cheaply above a 16" diameter,

I don't know if it'd be a good idea to base this decision on "used slicks cheap". Used slicks are just that, slick. I know I don't toss my race tires until they are done and let me assure you, you'd get no more life out of my cast offs!

More to the matter is the idea of cheap used race slicks. The tire bringers in the Southeast (Appalachian is always on site at all the SCCA road race points races) keep the cast offs and recycle them or the re-seller out of TN picks them up. The re-seller typically gets around $50-$75 a tire, but the tire is done - I know, I've used them a few times. Much better to simply get a new tire around $175 that will actually WORK.

Unless you're already paired up with a racer that is willing to pass tires on to you with 30% or more life left in them I don't think you're going to come out ahead. Not too many racers are going to be passing on sets of tires with >30% life left in them and getting tires that are only good for three or four heat cycles is hardly worth the effort of mounting and balancing them. YMMV.

Ron

Justin Olson · 06-12-09, 02:24 PM

Thanks for the heads up. I've just been reading of datsun guys of getting good takeoffs FA slicks. I've never actually ordered a used set.

Anyway, The slicks I'm looking at are as follows (Hoosiers):
Front: 43660 23.5 X 12.0R-16
Rear: 43676 25.5 X 14.0R-16

It is very important to me to run a relatively short front tire, as this directly effects the overall height that I can run the car at due to front fender to tire top clearance. I want to get the car down to 42"-43" static ride height.

Justin