EB48:Part 2 – Bulkheads and Diffs

EB48:Part 2 – Bulkheads and Diffs

Designing a whole car is a daunting task.  But taken one part at a time, it’s not much different than our other aftermarket products.  The big difference is the fact that it’s a clean slate, a blank page.  You aren’t locked in to anything yet so you can do whatever you want.  But you still have to start somewhere.  For 4WD 1/8th scale buggies, the bulkheads and diffs (and chassis) are usually the first parts to consider.

The bulkheads are simple enough, but the rest of the car is built around them.  If you make an early decision on the bulkheads that doesn’t pan out and something needs to change, there could be a lot of rework to do throughout the rest of the car.  Diffs, shock towers, steering assemblies, suspension geometry, the chassis and more could all be affected.  With all of this to consider, the progress on the EB48 was slow at first because the bulkheads and diffs needed to be solid before we could really move forward.  There were literally dozens of different bulkhead designs, many of them making their way out of the 3D printer for analysis.

 

TKR5012 – Gearbox (front)

We were trying to figure out a way to significantly minimize the chassis overhang while still achieving strength and a narrow inside pivot suspension geometry.  A millimeter here and a millimeter there – it began to add up.  The front bulkhead also needed to compensate for the chassis kickup so that the driveline could remain straight and efficient as possible.  Finally, we settled on a design that was lightweight, durable, and provided the best clearance we’ve seen in any 1/8th scale chassis.  The rest of the car could now be designed with the security that only small changes to the bulkheads might be needed.

The bulkheads house the front and rear diffs.  We didn’t do anything revolutionary with our diff design except to make them as smooth, light, and durable as the competition.  We also focused on leak issues we’ve seen in some other cars.  We came up with a new diff case insert design (the metal part that the outdrive goes through on the diff case) that helped prevent leaks better than what we’ve tested.  We have a couple more ideas for the diffs that may make their way into production later on.

Now that the bulkhead was 90% designed, it was time to consider the front and rear end of the chassis design to go with it.  Most cars have bulkheads that are open on the bottom and they rely on seals or a tight fit to ensure that dirt doesn’t get in.  This is so the diffs and outdrives can sit as low as possible on the chassis.  Inevitably though, dirt gets in and causes wear.  Wear requires more frequent rebuilding and parts replacement.  Our bulkheads are completely sealed and sunken into the chassis without requiring seals or large holes in the chassis.  This makes our diffs more consistent and cuts down a little bit on replacement/rebuild costs.  And when you do open the bulkhead for a diff rebuild, it’s nice and clean inside :).

Stay tuned for the next article on the making of the EB48.

A platform to build from…

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