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Unread 06-25-2014, 04:23 PM
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Fair! Fair! is offline
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Join Date: Jul 2004
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Default Re: Vorshlag Miata LS1 Alpha Project

continued from above

The goal was to be able to use stronger OEM based and commonly available hubs, brake parts & other consumables (not one-off fabricated or race-only parts), and have the same wheel bolt circle front and back. This way if you blow through your brakes or wear out hubs at a track event, you can run to a local parts store to get replacements fast.

Ryan jumped into the new rear suspension and subframe design with both feet and spent a full day making measurements (see above) and checking suspension geometry using 3D node software, to check camber change through suspension movement. Using the short upper and long lower arms and moving the pick-up points in computer space, then checking the camber change under movement. The final pick-up points and geometry chosen looked great and the dynamic camber change was well within normal parameters.

This is major fabrication work coupled with suspension design, and not something usually done by just "anyone that can weld". Luckily it wasn't too challenging for our crew - we are primarily a suspension shop and all of us are racers - and the new subframe and suspension design was knocked in a little over 70 logged hours.

The start of the upper structure of the rear subframe is shown above and left. The beefy new subframe unit will bolt to the 6 factory mounting studs in the rear of the chassis, without any cutting or welding. Once it is finish welded I will share the final weights vs the OEM bits, but it should add little to no weight over the stock rear assembly. The picture above right shows some of the tubular steel custom rear lower control arms going together. These are adjustable and feature polyurethane mounting bushings for some cushion but nowhere near the slop of a rubber mount. This should be suitable for a dual-purpose street/track car, but we could also make these arms with spherical ends for track-only set-ups.

These hub-mounted stands worked well during geometry checks and suspension mock-up and fabrication. Lots of fixtures and welding jigs were built to be able to make the parts uniformly and mirror imaged from side to side.

Here you can see the aluminum 8.8" diff housing starting to be fitted to the tubular steel rear subframe structure. Polyurethane (red) bushings were used in the front and rear mounting locations for this housing.

The front diff mounting brackets are shown below at right. There is a gusset to add on each side but otherwise that section of the subframe is finished.

You can see the rear chassis studs and bolt holes that the new subframe mounts to, below. There are some scalloped areas that will be added for more bolt/nut clearance, and small tubular gussets here and there, but this is the final layout we're going with.

There are a few gussets to be added, then final welding can be done and the subframe removed for powder coating.

What's Next?

We've already had started on the front subframe and it was mostly done. Now we are tweaking the front geometry to allow for more camber and caster adjustment, using the RX8 eccentric bolts/washers and OEM style "cages" around these bits. Once the front subframe is completed we will design and build the LSx V8 motor mounts (takes about a day and a half). After that the prototype header fabrication and a driveshaft can be built. We have an aggressive schedule to finish this car this year, so stay tuned for more updates. We will be making production runs of both subframes, for use with LSx V8 swaps as well as racers with boosted Mazda engines that want the reliability and durability of the higher strength hubs, halfshafts and diff housing we're using.


Last edited by Fair!; 06-25-2014 at 04:39 PM.
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