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EOI Chassis Strengthening Kits


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Hey guys,

Just seeing if there would be any interest for a weld-in chassis strengthening kit. I couldn't find anything on the market, so decided to make one myself. 

 

To register your interest (no money or deposit required) just follow the group-buy format of e.g.

1. daretobedifferent

2. ...

 

This will be developed by myself, an ex-automotive engineer (I'm now in software of all places) and one of my ex-managers who is an ex-Prodrive rally engineer and ex-Holden engineer. 

 

The main priority for this kit is to:

(i) Prevent cracks, tears and fatigue without loading up other areas

(ii) Strengthen front and rear strut regions to retain car geometry

(iii) Strengthen the floorpan and the tunnel. Naturally the tunnel will provide most of the cars mid-section strength, but we think it can be better tied in than just spot welded around the footwell.

(iv) Maintain an OEM appearance after applying seam sealer. Anyone with a Z will know it's different, but otherwise it appears to be stock.

Without a CAD model for the car, we cannot complete proper FEA modelling so in terms of how much hp or torque the chassis can support, it'll be up in the air. However in the past we've designed and built (for internal prototyping) engine swap and reinforcing kits to test different engine combinations in different chassis' and we're also quite fond of the S2000 chassis as a benchmark design. 

 

If there is enough demand, I'll properly get it sorted with engineering drawings and work with a fab shop so each kit is toleranced, tested with a few Zs before mass production, professionally cut, bent and primed. Price-wise it will probably be in the range of $1,000-2000 for a full kit. If there is no demand, i'll probably just end up making a one-off kit for myself. 

 

It will be something along the lines of this (NOTE: these are random photos we took off the internet of a kit for a mustang I think and an S2000 diagram as a guide);

image.png.a8334cbf0913f093ac35d3c7c0e0dd10.pngimage.png.cfe35bbd3d5e03a9e23a7eb6e06143ab.png

 

Edited by daretobedifferent
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Quick update. I spent a few hours inspecting the Z shell and it's probably going to end up as a 32-pc full kit. I've mocked out which areas I'd like to strengthen and did some calcs + impact considerations. In a rear-end or front-end collision, my goal is the kit should protect the geometry of the front to rear struts and only kink the rails outside of that. This allows the car to be repairable. This is not a replacement kit for a roll-cage though, I am primarily looking to update the 240z chassis and ensure that it can adequately handle more power with spot welds popping off, chassis flexing, twisting and fatiguing. 

- 10 x square angle gussets (street: 8pc, performance: 10pc) 

- 4 x flat plates (street: 4pc, performance: 4pc) 

- 9 x rails / rail extensions (street: 6pc, performance: 9pc) 

- 2 x full sill length tubes (optional + performance only, this can only be installed if you have the outer sills removed)

- 6 x reinforcing structures (street: 2pc, performance: 6pc)

- 1x underbody butterfly brace (optional + performance only, bolt on part but requires you to drill through your floors) 

 

I'll probably make 2 kits with 2 optional extras:

(a) Street kit (20-pc kit) 

(b) Performance kit (29-pc kit) 

(c) Options

- 2x full sill length tubes

- 1x underbody butterfly brace

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There seems to so-so interest so far. 

However, I might as well make the kits, because others may need it at some point. I can just get a set made as people order them. 

I'm currently in the process of doing the engineering drawings and then I'll get a few quotes from fab shops to see where the costs land.

At this stage, the earliest I think I can get everything done is the middle of next month if there are no issues with manufacturing and fitment. 

Edited by daretobedifferent
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In case you have interest in doing this for a 280zx I'd definitely be interested... If not I'd love to see how you do it so I may be able to try something similar in any weak parts of the s130 chassis. 

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The main problem with the S30, S130 and Z31 seems to be that both the rear and front parts of the body start at the fire wall with insufficient structural connexion between the two.  Look at a modern body like the MX5 to see the difference in structure there, it's significant.

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Yeah a chassis in its rudimentary form should at least take on the structure of a ladder to ensure the four corners retain geometry (think of a truck chassis). Then design upward from that for performance and handling, and then reinforce specific areas and spread the load but ensure that it doesn't end up creating a small stress concentration area elsewhere which results in tears/splits.

A big downside to the Z is also the front strut tower regions. While its shape provides some strength, it's only supported by the upper fender rail (which is weak - spot welds seem to give way here quite often) and not to the firewall or chassis. A decent design is the mx5 front strut tower regions - if you compare it to the Z it is sunken a lot lower but still raised, strengthened inward to prevent caving into the chassis rail, and a thickening plate is welded around it to provide 1-1.5x additional sheet metal thickness on-top of a compounded curve to spread the load in the fender direction. 

@marc280 When I finish the S30 kit, happy to take a look at an S130 and make a kit for that chassis as well. 

Edited by daretobedifferent
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20 minutes ago, daretobedifferent said:

A big downside to the Z is also the front strut tower regions. While its shape provides some strength, it's only supported by the upper fender rail (which is weak - spot welds seem to give way here quite often)

Strange that these issues were not corrected in the latter S30 models as I imagine they showed up in the 240Z cars that were rallied by Nissan.

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43 minutes ago, AndBir said:

Strange that these issues were not corrected in the latter S30 models as I imagine they showed up in the 240Z cars that were rallied by Nissan.

Might be because of the rally rules with respect to body modifications outside of a cage. There are also clearance issues with bits in the engine bay as well hence maybe why they didn't update it perhaps. If you look at the 300zx front tower regions its already a much better design. 

Would be interesting to see how many Zs have retained their front strut geometry. Quick and dirty method is to use a tape measure and measure the different between the centres of both front struts it should be 913mm for the 240z (might be diff for 260s)

Edited by daretobedifferent
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Quote

Strange that these issues were not corrected in the latter S30 models as I imagine they showed up in the 240Z cars that were rallied by Nissan.

I think they were addressed to some extent weren't they? From my observations the 260Z shell is an improved construction over the 240Z, albeit heavier. But then people also complain about the added weight. So I guess much depends on how the car is to be used.

But certainly if a car is being stripped down to bare metal for a complete rebuild then that's the time to seam weld it in various areas rather than rely on spot welds. And putting a strengthening kit to tie the front end to the rear end better, such as is being discussed and designed here, is a great idea and a great initiative.

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Would there be any advantage to having an 'Export Brace' (google it) such as used on early Mustangs? A heavy gauge one-piece ribbed steel brace in a V shape that connects the top of the front strut towers to the central part of the firewall, replacing the standard rather weak bolt-on angle braces. Along with a strut brace it triangulates the front clip.

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1 hour ago, gilltech said:

Would there be any advantage to having an 'Export Brace' (google it) such as used on early Mustangs? A heavy gauge one-piece ribbed steel brace in a V shape that connects the top of the front strut towers to the central part of the firewall, replacing the standard rather weak bolt-on angle braces. Along with a strut brace it triangulates the front clip.

I personally think the export brace is a nice touch without running into clearance issues.

At the moment the Z is only supported by the fender rail. Usually you'd at least have the fender rail and chassis rail, and if clearance permits the firewall as well. If you look at the r35 its got all three :)

image.thumb.png.f0211c49628acb4a78b7dd2e775d3aab.png

Edited by daretobedifferent
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The S130 and Z31 are very similar structurally, for some reason Nissan just seemed to carry the basic design over. Back in those days structural strength did not seem to be a priority like it is now, for safety and noise minimisation reasons too. 

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  • 1 month later...

Just a quick update. The design of the kit is roughly 50% complete. 

However, I sent my car off to the chassis straighteners about a month ago, and they still haven't been able to get around to measuring and straightening my car yet. I'm not exactly sure when I'll be getting it back as they still have a few other customer cars ahead of mine. 

The joys of delays ...

 

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