Nissan GT-R LM NISMO (REIB and Welded Steel A-arm)

[Will M]

Was watching this video about Nissan's new FWD car for Le Mans tomorrow and I noticed something odd.

Unless I mistaken it looks like this rather advanced race car has weld steel a-arms with a square cross section and rod ends in bending.
I was very surprised by this as that setup sounds like something we might do for a quick test.
This video may have been recorded a while ago and these components may have since been replaced.

Any way here is the video, you can see the components in the attached photo around the 19 minute mark.
https://youtu.be/fw_2N3tGMEg?t=19m

Thoughts?

-William


(the attached photos are of the same area but at different angles to see around a something partially blocking the view)

[Jonny Rochester]

This "rod ends in bending" seams to be standard practice to build A-arms in supercars and prototypes from before the 60s right to present day it would seam. (And of course hot-rods copy or do whatever they like).

The first pic is a pushrod, the rod end itself is not in bending, but there would be some bending stress in the bracket below it.

The second pic seams to show rod ends to the upright, these would be "REIB" as you point out. But worth noting they don't have heaps of thread showing, and they are not a 5/16" rod end, but much bigger. Also possibly "single shear" bolt attaching rod-end to upright.

This style of connection would work fine in FSAE with ~7/16" rod-ends, and that's what UTAS had in 2001. It didn't fail, but our design was slammed and we redesigned wishbones for 2002 with 7/16" and 5/16" sphericals which where lighter and more elegant, but less adjustable.

[CWA]

The new Nissan car was also 20 seconds a lap off the pace during the last practice run I paid attention to. Causation / coincidence? I know I couldn't possibly say.

[njgedr]

He also said that it was a "show" car.

[JT A.]

The new Nissan car was also 20 seconds a lap off the pace during the last practice run I paid attention to. Causation / coincidence? I know I couldn't possibly say.

Something tells me REIB isn't going to cause a 20 second per lap difference in speed.

[Will M]

The first photo was just to show that they had push rods rather than pull rods meaning that the other rod end was pretty heavily loaded.

My surprise comes not from the added weight which would be fairly small but from the lower strength/reliability.
FSAE courses are nice and flat and there is basically never contact between cars.
While Le Mans is bumpy and contact is fairly common.

So while a rod end could be sized for your expected dynamic loads wouldn't a encapsulated bearing be more robust?
Especially if you go off track or someone bumps you?

Nor would the threads offer easy adjustment during the race.
Maybe on the top a-arm, but why the bottom?
Unless like njgedr said it is only a show car.

-William

[CWA]

Something tells me REIB isn't going to cause a 20 second per lap difference in speed.

Haha, yeah I know bud.

I was trying to imply that the same attitude that lead these designers to fit rod ends in bending may have lead them to make the other poor design decisions which in turn lead to a car completely off the pace. A loose insult perhaps, but it was supposed to be half-funny too. It is Friday after all, and I have beer

[Jonny Rochester]

I think it's worth noting that wishbone/pullrod failure is common in FSAE. And it's not REIB that is causing the failure, but adhesives failing when a carbon part is bonded to a metal part. If the judges can ban REIB (can't remember if its an actual rule or not), then they could just as legitimately ban adhesives in suspension and steering. I think it's better to relax the rules and student designers can make the call.

Auburn failed with this at Michigan.

[Ahmad Rezq]

Jonny
REIB isn't banned in FSAE. Although Judges consider it bad engineering. I agree with those who don't use (Bad Engineering) to describe REIB as long as you know what you are doing.

[Tim.Wright]

I think we need to better clarify what's actually in those pictures. The GT-R LM has pull rod front and rear from what I remember.

Rod ends in bending are like single shear interfaces. They offer advantages in asssembly, manufacturing, tolerance conttol and adjustability in exchange for a small weight penalty.

There's nothing iherently wrong wm, them.