Protecting The Lotus Aluminium Diff Housing.

Ingenious Aussie engineering to prevent aluminium diff housing mounting lug failure.

Up to the time the writer purchased the basket case S2 elan in 1981, for more than a decade, it had a pretty hard life being flogged around many Australian race tracks, we still have the log books of competition history… and the car was even featured in the book: Racing Elan’s In Australia, and no, it was definitely not a 26R. (But I wish).

(There has also been hindsight regret from not buying the complete Brian Hart all steel twink engine for $1200.00 at the time of the S2 elan purchase – Circa 1981).

The rebuild/restoration (From 1981) was a hard slog over many years, it was a tussle to undo much of the race car prep work to return the car back to normal road use. Some would say, it can’t be done, I wont deny that it was in fact quite difficult, but we won out in the end, there was a steely grit of determination, it wasn’t about to beat me.

(And happy to report that the elan was finally Registered for the road in early 1985.)

Its amazing what you find when you dig deep, because hidden out of view were some unique mods, and little did I know that some clever but unknown Aussie race fabricator had built an ingenious four bolt diff
support cage, quite different, and far superior than anything else available. (And you have to wonder why the Euro Lotus experts/gurus have never thought of this.)

I realised much later that the cage/brace was to prevent the outer ears of the aluminium housing from breaking due to the torque forces generated from an 180-200BHP full noise competition twin cam engine. But even a standard twin cam can develop enough power and torque to eventually cause a fracture and potential breakage of the outer housing mounting ears or lugs.
That could be quite an expensive failure.

Getting back to the race mechanic of the S2 elan. With the need to change diff ratios for the various race circuits, he obviously became tired of the chore, trying to jiggle and line up bolt holes of the diff and the supplied angle brace plate at the same time. Most elan owners would be very familiar with the angle brace set up that is installed on so many lotus elan cars today, it is a fiddle to install.

But NOT the one shown below.

I always took it for granted that every elan had the unique support cage that was on the diff of my S2 elan… I wasn’t aware (Back in the early days) of the factory supplied or after market supplied and very basic looking angle brace.

So When others asked what type of brace my S2 elan had, when explained to them, it definitely piqued their interest, so it was time to hit the keyboard and write an article on my (This) lotus elan blog, which I did some time back, no doubt you may have read that piece, perhaps you even tried to make a diff brace? And as you might have found, without a well equipped workshop, they can be complex and very time consuming things to make.

The more I thought about it, the stronger the urge became to share this unique diff brace cage design with other elan owners, so the decision was made to set things in motion to manufacture a better and more refined version of the original Aussie designed S2 competition diff brace, and that brings us to where we are today.

The old original brace from the S2 has now been retired, and in its place is the new (Above) Croucher Engrg elantrikbits anti torque cage, or brace as it is often called.

The photo below illustrates the difference in diameters between the early and late type of housing mounting lug. These were the first prototype cage braces we built.

The design follows the typical Lotus ethos, adding lightness and strength for a torsionally stiff structure.

The product is light weight, well engineered, and extremely stiff when installed, any given torque loads are spread across the front plate and the four upper fastening studs, plus the two main 3/8″ HT upper diff mounting bolts, so in effect, it is actually a six bolt mounted fixture.

The beauty of the diff brace cage is that it is assembled onto the diff while on the work bench, there is absolutely NO awkward fiddling or aligning of bolts holes after fitting the diff into the chassis, as is the case with the existing and common elan angle brace. (And it should be said that the new cage brace cant be fitted with the diff still in the chassis, that is not what it was designed for, as explained, set up is done on the bench)

The old original angle brace can be hung up on the workshop wall as a souvenir of engineering from a previous era. But of course, the purist might still like to maintain the status quo, and that’s quite OK.

It has to be said, that a nice bit of modern fabrication design is a welcome and sensible addition to the Lotus elan.

This unique diff cage design has so far, provided forty one years of protection against mechanical housing breakage on the writers S2 elan.

I’ve been extremely happy with this neat bit of engineering, the new support is equal to, if not better than the existing brace made by the unknown Aussie race car fabricator so long ago, try it, we reckon you will be too. Learn more here.