Problem with rule T6.6.2 Jacking point

[Phil1988]

Hey everybody,

Got a little Question due to rule T6.6.2

-With the bottom of the tube 200 mm (7.9 in) above ground, the wheels do not touch the ground when they are in full rebound.

I measured at our car. And we have 215mm when the wheels do not touch the ground. It is a huge amount of effort to change the jacking point ant the lifting jack.

Can some scrutineer od judge tell me if this is still okay?

Best regards Phil

[Bemo]

Once more I can just give the advice that the rules comittee of the competition you are taking part at is the only authority to give a definitive answer. On this forum you can get personal opinions which don't count if a scrutineer at the event gets picky on that rule.

I'd say in general this is one of the rules scrutineers aren't too picky, as it is quite hard to measure the 200mm anyway and in doubt the tolerance is usually pro team (at least to my experience).

If you send an official question to the rules committee, I'm pretty sure you will get told that it has to be rules compliant as there is no objective reason why it shouldn't.

As I see it you have basically two options:

- Leave it as it is and hope that the issue doesn't come up at competition (if your coming to FSG and/or FSA, I will be there as a scrutineer and now you already confessed it isn't rules compliant http://fsae.com/groupee_common/emoticons/icon_biggrin.gif)
- Take the effort and change it. Then you can come to the competition and have at least not to worry about this one.

[MarkSchaumburg]

You could also just lower your ride height 15mm, assuming you made your push/pull rods adjustable in the rear. However, if you designed your suspension with EXACTLY 1" of bump and rebound travel at the normal ride height, when you change it you will no longer have a legal amount of rebound travel. This is another thing they don't actually measure, so either way your probably fine.

[Bemo]

I would be careful with that. If I have the feeling that the suspension travel of a car is a bit low, I measure it. Especially rebound in the rear is quite simple to measure. You just lift the car with the quick jack until the tires don't touch the ground anymore.

[Racer-X]

This is just my opinion. 15mm over 200mm is 7.5% error, most things checked in tech have tighter tolerances than that.

Of course its your call but its an easy thing to check at tech and its a lot easier to fix in the shop than in your trailer at comp.

[Michael Royce]

Phil,
The easy way is to weld a length of 25 mm OD tubing onto the underside of your current rear jacking point. Fix it to keep Bemo happy.

[MarkSchaumburg]

Originally posted by Bemo:
I would be careful with that. If I have the feeling that the suspension travel of a car is a bit low, I measure it. Especially rebound in the rear is quite simple to measure. You just lift the car with the quick jack until the tires don't touch the ground anymore.

I wasn't suggesting he actually do this. I was more just making a comment tech inspection in general. I've been to 6 competitions (including FSAE-A) and I don't think I've every seen a tech inspector measure the suspension travel, they usually just push down on the chassis and if it moves some arbitrary amount they can apparently eyeball, they pass you. However, given that there is only a limited amount of time to get teams through tech inspection, I'd much rather they focus on safety critical stuff anyway.

[Michael Royce]

My understanding of the original intent the + or - 1 inch suspension travel was to prevent teams using go kart suspensions, i.e. an FSAE car has to have to have a "working" suspension. So the norm at US events has been, as Mark says, to see if there is some real travel. However, some competitions may take the dimensions literally.

Now, if the competition does have quick jacks to move the cars off the track quickly, (and I have sent pictures and dimensions of the US ones to several other competitions), and your car does not meet the jacking bar height rule (too high off the ground) and the organizers cannot get your car off the track in a hurry when they want to ..., goodness only knows what they will do!

[AxelRipper]

Another way to look at this: When was the last time the officials used a quick jack on one of the cars? I don't recall them ever putting a quick jack under the rear and checking that the tires come up. From what I ever saw it was a walk around to the back and go "yep, I see an orange bar" and call it good.

[Michael Royce]

We used to have 2 or 3 at Tech Inspection at the MIS event in case a car needed to be checked. hen they went back out for the Dynamic Events. Cannot say what has happened in the last couple of years.