Technical Analysis: WRC Cars 2017

[NickRally]

Or rather "would you please state without any shadow of a doubt, when your hydraulics or control mechanism fail, is your diff locked or open?"

[Mrpengski]

What, you weren't satisfied with "we lost hydraulic so we were RWD"?

I can't say anything chiefly because I myself don't fully understand everything, so I can't distinguish what's common knowledge and what's trade secret. How much detail is available in the public domain, from the last generation of active central diff cars? What would surprise me is if 1) this technology from a decade ago is still considered secret, and 2) if there were in fact any groundbreaking development this time around. I have only recently joined rally from circuit side, and one thing I definitely learned is that everything is much more conservative and tend to gravitate towards proven solutions, rightfully so.

[NickRally]

By the way, one other question on diffs - Mrpengski are you happy to tell us what the full version of the tech regs says about the front and rear diffs – presumably it requires purely mechanical units with no active functions? Or does it allow for more freedom there?

[Mrpengski]

We will have to wait until they publish the new regs in the fully condensed format, like article 255a for 2016 which you can find on the FIA website. From 2016:

2016.jpg

[br21]

255a for 2017, so new spec WRC cars is available on FIA www already for many months, currently freshly updated.

[NickRally]

br21 - the updated rules still have the relevant fields blanked off under the 400/01 banner

[br21]

yes, homologation regulations will never be officialy published.

[NickRally]

Why? Why are the restrictuon on the size of the diffuser or the type of differential for example such big secret in rallying, but not in just about any other form of motorsport?

[Mrpengski]

That's another funny point. The 2016 255a is cleaned up and presented in portrait A4 format, which is what is typically available to the public. They haven't done that yet with the 2017 255a, rather just the "manufacturer only" info is replaced by a reference to 400/01, but the landscape A3 page format of the full working copy remains. What really gets me is, that when they decide to convert the redacted version to cleaned up version, in some cases more information becomes available. If you open 2016 vs. 2017 side by side and find the same section I posted above, you will see what I mean.

[Lundefaret]

Re: doors. Don't forget that these doors are first gutted out (OEM side impact beam and all) then filled back with energy-absorbing foam. Of course, the OEM beam is replaced by the roll cage, but this is not realistic for a road car, and neither is filling the entire door + outer extension with foam. Among other things, the window won't go down! Incidentally, in my previous job I was involved in a lightweight electric car project with composite monocoque and bodywork. Inside the door was a CFRP side impact beam which housed an outside-firing airbag. I believe it was for pedestrian protection more than occupant protection, but interesting nonetheless. So maybe something like this could be applied to road cars, before we see extra thick rally-style doors.
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As you say, maybe not that relevant for a present VW Golf, but more for a future 2-seater individual electric transportation pod, where seating is for-aft, and the "car" is made narrow to go two side by side in a normal lane.