Flemke - Is this your McLaren? (Vol 5)

Flemke - Is this your McLaren? (Vol 5)

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Discussion

Nockenpaul

70 posts

24 months

Sunday 18th October
quotequote all
marine boy said:
That's correct, I flew out the repair kit of machined aluminium bars/glue with me on a last minute flight

Don't think the story of getting these parts out to Le mans has ever been told as it could have gone wrong in so many ways before the race had even started
Fascinating! Seriously, glue? Well, it makes sense when you think about it, but I bet nobody told Gordon Murray about the reinforcement as he would probably get a heat attack ;-).

Nockenpaul

70 posts

24 months

Sunday 18th October
quotequote all
shirt said:
remember the engine/trans mounts only need to support the weight of the assembly, no road loads are transferred through them. hence 3 point suspension the same as any other car.

this link may help. the bulkhead mounts are taken from single seater design in which the engine/trans is a stressed member so whilst the car is lighter, the loads are higher.

https://www.f1technical.net/forum/viewtopic.php?t=...
Cheers, thanks for the link. About no loads being transferred thru McLaren F1's engine/gearbox - well, I guess you are right about suspension loads, as the dampers mount to the chassis. Still, wishbones mount to the greabox. Don't the wishbones react braking torque, for instance?

flemke

22,615 posts

195 months

Monday 19th October
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Nockenpaul said:
Ok, let's geek out and dig in the movie I linked above. One thing that caught my eye were engine mounts, seen in the lower left of the pic below:



Pretty similar placement to what is on the F1, but much wider spacing, or possibly the same spacing with a smaller engine. For comparison:



(next to the blue coolant hose one can see a beefier engine mount that also holds some ancillary - oil pump?)

One thing I didn't realise is that F1's (and presumably t50's, as it seems to reheat a lot of the same approach) engine is attached from the front only with two of those famous asymmetrical compliance bushes, see the pic below:



I guess that there is also third mount on a gearbox and the whole assembly hangs off a bronzish bridge across the engine bay as shown below, but I am unable to verify this:



It's amazing to me that this rather flexible, by the looks of it, arrangement is supposed to contribute to the stiffness of the chassis and transfer suspension loads (although not quite - the rear dampers are mounted to the protrusions of the tub, not to the gearbox in F1). Of course, if GM's calculations showed that it is enough for a road car, then it is, period. However, do I recall correctly that later race cars had additional subframe to stiffen up the rear portion of the chassis?
On the GTR, the torsional stiffness of the tub was augmented by the roll cage. IIRC, the mounts of the block to the firewall were solid as well.
The GTR's different suspension control arms were devised not for additional stiffness but to allow for camber adjustment.


Nockenpaul

70 posts

24 months

Monday 19th October
quotequote all
flemke said:
On the GTR, the torsional stiffness of the tub was augmented by the roll cage. IIRC, the mounts of the block to the firewall were solid as well.
Thanks. I managed to find Peter Stevens interview (https://www.motorsportmagazine.com/archive/article/december-2015/96/lunch-peter-stevens), and he says it the way I remembered it:
Peter Stevens said:
The chassis stiffness behind the cockpit wasn’t as good as in front: the engine and gearbox were soft-mounted, so we made up a sub-frame at the back to stiffen it up.
By sub-frame, does he mean the solid mounts you mentioned?
flemke said:
The GTR's different suspension control arms were devised not for additional stiffness but to allow for camber adjustment.
Yep, but as S1KRR and marine boy allude to, people running the car adjusted camber a lot more than they wanted when they managed to bend the arm during testing ;-)

flemke

22,615 posts

195 months

Nockenpaul said:
flemke said:
On the GTR, the torsional stiffness of the tub was augmented by the roll cage. IIRC, the mounts of the block to the firewall were solid as well.
Thanks. I managed to find Peter Stevens interview (https://www.motorsportmagazine.com/archive/article/december-2015/96/lunch-peter-stevens), and he says it the way I remembered it:
Peter Stevens said:
The chassis stiffness behind the cockpit wasn’t as good as in front: the engine and gearbox were soft-mounted, so we made up a sub-frame at the back to stiffen it up.
By sub-frame, does he mean the solid mounts you mentioned?
flemke said:
The GTR's different suspension control arms were devised not for additional stiffness but to allow for camber adjustment.
Yep, but as S1KRR and marine boy allude to, people running the car adjusted camber a lot more than they wanted when they managed to bend the arm during testing ;-)
I think the change in the rear wishbones was not to beef up the cross-section but rather to increase the distance between the bores, making the angle at the outboard end of the triangle less acute:


Nockenpaul

70 posts

24 months

flemke said:
I think the change in the rear wishbones was not to beef up the cross-section but rather to increase the distance between the bores, making the angle at the outboard end of the triangle less acute:

Ah, so that's how they ultimately solved the wishbone problems. Besides the longer base, the mounting eyes in the racing wishbones have different orientation. Both necessitate a new mounting arrangement to the gearbox, seen above. Maybe this is what Stevens was talking about although I can't see how this 'subframe' (mounts, really) is supposed to stiffen up the chassis.

(edited for clearer wording)



Edited by Nockenpaul on Saturday 24th October 09:50