Roll Cages

[cooper]

I heard the other day of a guy I know who put a six point cage in his car and gained a second at baskerville, that was the only change and the guy is a top driver, very consistent. This story was backed up by a cage manufacturer, apprently a second at this track is an average gain from a cage in most cars. Bloody good investment, they make you go quicker and improve safety.

[Golfwise]

Its all in the head .
As most people buy a cage and bolt it to the floor which wouldn't stiffen the car up at all.It just makes you feel safer so you drive harder.
Having a stiffer chassis will make no difference if other factors aren't changed to suit like stiffer spring rates and stickier tyres.
Actually if nothing is changed but making the chassis stiffer the vehicle will probably go slower as there will be more pressure put on the suspension and tyres as movement in a chassis acts like its part of the suspension.
Its never as easy as it seems.

[cooper]

This cage is bolted to the floor and the b pillars, as are all decent cages. If this had happened just once you could say its all in the head, but it has happened many times, so it must be the increase in torsional rigidity. I can assure you that fitting a cage and doing nothing else wont make a car go any slower, unless its an incredibly heavy cage built with no thought to strengthening. A cage bolted only to the floor in 6 places with plenty of triangulation will considerably stiffen a shell. Safety is not the only reason cages are fitted to competition vehicles, this can be seen in cage designs on all top class race cars. A cage built out of a suitable material with a main hoop, front legs and rear braces and a couple of well placed diagonals will help in most rollover situations. The additional braces seen in many cars are as much for torsional rigidity as they are for safety. Just compare a cage from a group C touring car with a modern day supercar cage, The old jiggers did the job for safety but these days people are trying for higher gains from making the chassis do work, hence the progess in cage design. Anyone thinking about fitting a cage should not be put off by thinking it will make the car slower, and other factors like sticky tyres and spring rates will most probably have been addressed prior to the first trackday for any car.

[gtimk5]

That sounds about right Cooper. My Golf was a lot nicer with the full cage. Broke into the 64s at Baskerville, which wasn't too bad for a car I could drive happly arond the streets and do road events with.
By the way, did you do the Khanacross?

[Roscoe]

[QUOTE=evorobin]Rare lockup at the Island

Mine has a little lock up in the same place evorobin. I think the only way to stop it is to go stiffer on spring rate.

Even a basic 6 point roll cage would help a Golf because they aren't a very rigid chassis to start with, especially around the back section. Any "suspension" which is caused by flexing of the chassis is not being properly controlled so a car with a stiffer chassis will always be better. Of course if you make it stiffer you will improve it further if you re-adjust the suspension settings.

[bitza]

I have to agree with the roll cage is better group.

I built an engine for a mk 1 Golf Rally Car that runs in historics down here, which had a seem welded body, and an integrated roll cage. I can only say it was the best Golf I have ever driven and it only had bilstein shocks and custom springs, no roll bars, or funny camber castor tricks etc. It drives/ drove like its on railway tracks. It communicated perfectly with the driver, and the suspension did exactly what was expected of it.

If chassis stiffness isn't so important why to F1 teams go to so much trouble to build the stiffest body structure they can. The best thing you can do to any car road or track used, is to stiffen the chassis as much as you can afford, then corner balance the suspension (equal load on each axle paired wheels) with the driver in place. Need adjustable suspension. You would be surprised how well even good stock springs and shocks work under this type of set up

[Golfwise]

I heard the other day of a guy I know who put a six point cage in his car and gained a second at baskerville, that was the only change and the guy is a top driver, very consistent. This story was backed up by a cage manufacturer, apprently a second at this track is an average gain from a cage in most cars. Bloody good investment, they make you go quicker and improve safety.

My reply was based on this above vague comment.
Point 1.
I gather person in question is at the track in his road car on road tyres with road /modified suspension.
Point 2.
The average punter puts a 6 point cage in his car and bolts it to the floor at the hoop front legs and rear parcel shelf if a sedan.All these points are panel steel.
Point 3.
There was no mention of welding it to the B pillar or any other bracing.
Point 4.
By stiffening the chassis it would allow his springs to work at their correct rate.By what percentage over what they may have been in the past.Very little certainly not a second a lap.
Point 5.
By increasing spring rate does not guarantee better handling in all cases , the factors are far too complicated.
Point 6.
The statement that a 6 point cage guarantees an improvement in lap times is far too broad.It could be shown in many cases that it doesn't.
Point 7.
Ever thought what a roll cage on a gokart would do to it.?? (apart from the weight)

Oh and I built my first race car in 1968

[cooper]

Golfwise, you say that the average punter mounts a cage to the floor and rear parcel shelf. This was the case a few years ago but common practice these days is to mount them on a box section off the inner sill and to the rear wheel arch, both very strong mountint points. I didnt mention bolting to the B pillar as this is also the norm these days.
Where did the comment of cages on karts stem from? As karts dont have moving suspension they rely on chassis flex to help generate grip, there are various bars, seat stays etc. on a kart that have adjustment to vary how much shassis flex you get at any time. Remove this flex on a kart and it would be totally useless. But the principles for karts are so far removed from the principles for a car with moving suspension that they should not be compared. I am not wanting to start an argument with you, just stating some facts.
Having been playing with race cars as long as you have you must have gained
heaps of experience.