[Tamar]

Posted 17 March 2019 - 02:12 AM

Spotting the tales of Tail-end Charly
So with me taking a bit of time off watching motorsport, not much work has been done on the car this week, but..there's plenty of stuff I have not posted yet.
One of the things I'd thought at least someone to notice, was the work done at back of the car. I mean there were more than enough hints in some of the pictures I posted.
But apparently nobody dared to ask what I had really done to my Tail end Charly...the huge diffuser sticking out the back of the Ford. 
Ever since the ACO/FIA/IMSA aero rules changed a couple of years ago diffusers, almost bigger than those seen on LMP's have become a trade mark on the GTE/GT-LM class cars.
And as such they've started to appear on slot-car models. Not that much of a problem on a stock chassis, but as we learned with the BMW M6 ....
they can get you into trouble on a podded chassis with lots of suspension travel.


 
The wishbone's connected to the collar bone, the collarbone is connected to?
On a podded chassis with suspension, you max amount of suspension travel should ideally be smaller than the ground clearance your running. Other wise you chassis will rubb the track.
No matter how long your screws are or how tall you springs are...your looking at 1-1,5 mm of travel max. But as the back of the chassis sticks out behind your suspension mounts...
...a small the amount of travel at the suspension mounts will be translated in to a bigger movement at the back.
Meaning that if a lot of chassis is sticking out at the tail end...  like on the Ford....it will be rubbing the track way before you get near 1,0mm of travel.
So somewhere in early februari, I'm working on the chassis side suspension, fiddling with the motor-pod, mounting it to the chassis for the umpteenth time. 
To keep the pod in the correct position for me to drill the holes for the suspension screws, I fully tightened the rear pod screws.....and then it hit me!
With the pod now firmly connected to the chassis and the rear diffuser behind it... no movement between the two parts, the diffuser was just as much connected to the pod.
What if.....




So at the end of first shakedown on Sunday feb 10th there was one more test we needed to do. The "What if" I wanted to test was how the handling of the chassis would be influenced...
...if the diffuser was not connected to the chassis but mounted directly to the motorpod.
As this would be a "no way back" kind of test, we first tested if the handling of the car became worse with the rear pod screws not connected to the chassis at all.
The handling of the car remained the same..all we needed to do was ad some extra spacers inside the springs to limit the suspension travel. Ok ..so far so good, next step.
Now it was time to cut the back of the chassis off and mount it fixed to the motorpod. Immediately we noticed that even with the full amount of suspension travel the diffuser was no longer rubbing the track.
Yeeeeeeeeeeeah  

With a big smile I added the pod mounted diffuser to the number of modifications to be discussed the next day with Stefan Nalbach to be incorporated in the MK2 chassis design.


On the left the diffuser cut of the prototype MK1 chassis here the diffuser was still mounted with screws from the bottom, on the right the MK2 version with the top mounted screws. 
Rubber washers were added for e bit off extra flexibility in case of a hard hit to the rear of the car.
 
to be continued

with kind regards
Tamar