Suspension Travel Rule

[engel_t]

I need some help about the rule for 1in bump and 1in rebound...
First of all what do they mean with "usable travel"?
I ask that, because I am planning to use relatively stiff springs and their static deformation because of the total car weight will be less than 1in (about .6in) and that means that during the final part of the 1in rebound the spring would get loose and it would not keep contact with the plates-preload ring.
This would not be a prob in real driving conditions beacause there would not be more rebound than .6 in.
But for the technical inspection despite that the wheels would have over 2in travel available through the shocks, the spring would not "follow" for the last part of the 1in rebound. Would this be illegal? How could I solve it by keeping the hard springs?

[engel_t]

I need some help about the rule for 1in bump and 1in rebound...
First of all what do they mean with "usable travel"?
I ask that, because I am planning to use relatively stiff springs and their static deformation because of the total car weight will be less than 1in (about .6in) and that means that during the final part of the 1in rebound the spring would get loose and it would not keep contact with the plates-preload ring.
This would not be a prob in real driving conditions beacause there would not be more rebound than .6 in.
But for the technical inspection despite that the wheels would have over 2in travel available through the shocks, the spring would not "follow" for the last part of the 1in rebound. Would this be illegal? How could I solve it by keeping the hard springs?

[PatClarke]

Engel,
This is the 'anti gokart' rule, to ensure all cars have a workable suspension, hence the 'usable travel' requirement.

It is unlikely the Tech Inspectors will check for an actual 25mm travel in bump and droop, however, they might, so you better be compliant =]

In reality, the Tech Inspectors have looked at enough of these cars to determine from shock travel and position and bellcrank travel and position whether the car will have the required wheel travel. Only if this is questionable will they do more stringent tests.

Ensure that you have sufficient ground clearance so the chassis doesn't ground over bumps or in pitch or roll as that can lead to being black flagged.

The observers may not like it if your car picks up wheels, so don't exaggerate this by overly limiting droop travel.

Pat

[df_fsmb]

Engel,

this is the question I asked judges and this forum few months ago.

The answers were the same: It is the "anti-gokart rule" (briliant, btw http://fsae.com/groupee_common/emoticons/icon_smile.gif ), BUT of course it is there in the rules so no one could guarantee me that the phenomenom you mentioned wouldn't put us in trouble at the inspection.

The thing is, if you want to have a motion ratio as linear as possible (which we do), the wheel rate has to be quite soft to get the required static deformation in springs. Maybe there is another way to go around this problem, obvious to all the other teams, that I cannot think of. If this is the case, I would be glad to learn something new, which is what this competition is about.

[Kevin Hayward]

You can use the hard springs with a helper spring. This will stop the spring rattling around and avoid any problems with it re-seating.

Kev

[engel_t]

Thank you all for your help!
I have also thought the use of helper springs as the only solution for keeping a stiff wheel rate and having the "usable" rebound travel.
But is it 100% legal and acceptable by the judges?
Have any teams competed with helper springs before?

[Bemo]

We used helper springs back in 08. Hasn't been an issue in any scrutineering (we took part in four comps that year).
I don't see any rule which sais anything against the use of helper springs - so why shouldn't you use them if you want to?

[Boffin]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by PatClarke:
It is unlikely the Tech Inspectors will check for an actual 25mm travel in bump and droop, however, they might, so you better be compliant =] </div></BLOCKQUOTE>
Pat

You must of missed seeing tech at Australia. They were checking cars to the millimeter and weren't going to pass us with 20mm-25mm travel in bump.
We had to be over 25, which we eventually were.

[Pete Marsh]

The rule says "available travel" which I have always interpreted as able to be achieved, but not necessarily set up that that at the moment. Springs are one of the things you are allowed to change, so you can/could have soft ones for tech, and change to harder ones for racing. We also have droop stops, either removable "suspension shim" types, or adjustable ones, to take up the excess travel in the shock.

Pete

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by engel_t:
during the final part of the 1in rebound the spring would get loose and it would not keep contact with the plates-preload ring.
This would not be a prob in real driving conditions beacause there would not be more rebound than .6 in. </div></BLOCKQUOTE>

Are you sure that the car will never lift a wheel in normal driving?