CavGT
- Thread starter Aracer
- Start date
Hi guy's
I would challenge the handling of the replica cars when compared to the original race cars. I am not saying that the replicas handle badly but I would say that the originals handle better.
I know of plenty of replicas that suffer from bump-steer (on all four wheels) and don't have built in anti dive characteristics, and also ignore the correct camber and caster angles on all four wheels.
I expect that this could be the start of a large response but I am being realistic and know the designers of our beloved cars had many years of racing experience built into the original monocoque design. I know Frank Catt has had to make many suspension
and chassis modifications before "The Yellow Peril" handled like an original.
Regards
Chris
[ November 30, 2002: Message edited by: Chris Melia ]
I would challenge the handling of the replica cars when compared to the original race cars. I am not saying that the replicas handle badly but I would say that the originals handle better.
I know of plenty of replicas that suffer from bump-steer (on all four wheels) and don't have built in anti dive characteristics, and also ignore the correct camber and caster angles on all four wheels.
I expect that this could be the start of a large response but I am being realistic and know the designers of our beloved cars had many years of racing experience built into the original monocoque design. I know Frank Catt has had to make many suspension
and chassis modifications before "The Yellow Peril" handled like an original.
Regards
Chris
[ November 30, 2002: Message edited by: Chris Melia ]
Somewhere around here I have an article given to me by Malcolm where a few replicas were brought out to compare to the original GT-40 and Chris is correct. Although the replica did a good job on track and street, they were lacking in several handling aspects that the original posses. I'll admit though that I don't know if the handling differeneces were at the expense of creating a better handling road car. Suffice to say though, the ones I have been in certainly have handled better than anything I have ever been in.
Brian
Brian
Ron Earp
Admin
Not having driven the originals I'm sure you are correct. But, there are a lot of replicas out there and the sky is the limit on modifying them, you guys have proved that. I believe that some of the replicas have engineered some anti-dive into the chassis, it seems the RF and the New Zeland cars are done this way. Of course there is still a long ways to go from this point before the car handles like an original.
But, I wonder if you can get the replicas to handle better than an original? Maybe a little subjective, but the original is not some sort of perfect ideal by any means. Personally, I'm after a "supercar", that is a road car that simply handles very well from a road and track point of view.
This is different though from a track car that handles excellently on the track but I would suspect has fairly bad road manners as pointed out in other threads.
R
Oops, while modifying this post I deleted my first response on the topic. My first reponse indicated that I felt the CAV and ERA were not that close is terms of being EXACTLY like the original nor were they trying to be. Each chose a route with chassis, suspension, cockpit layout, gauges, etc. that fit the flavor of the replica designers. Also, both were arguably better handling road cars than the original. My comments got interpreted as the replicas were better handling period which is where the thread then next goes.
[ November 30, 2002: Message edited by: Ron Earp ]
But, I wonder if you can get the replicas to handle better than an original? Maybe a little subjective, but the original is not some sort of perfect ideal by any means. Personally, I'm after a "supercar", that is a road car that simply handles very well from a road and track point of view.
This is different though from a track car that handles excellently on the track but I would suspect has fairly bad road manners as pointed out in other threads.
R
Oops, while modifying this post I deleted my first response on the topic. My first reponse indicated that I felt the CAV and ERA were not that close is terms of being EXACTLY like the original nor were they trying to be. Each chose a route with chassis, suspension, cockpit layout, gauges, etc. that fit the flavor of the replica designers. Also, both were arguably better handling road cars than the original. My comments got interpreted as the replicas were better handling period which is where the thread then next goes.
[ November 30, 2002: Message edited by: Ron Earp ]
I can't speak for other manufacturers, but this is how I designed the ERA GT suspension:
I looked (and measured) the original GT (and other similar world-class cars), for general layout, roll center, ride height and roll stiffness.
Laid out the control arms similar to the original, but with changes that I regard as somewhat more appropriate for wider tires. And there's a bit of BobPhilosophy in there too.
Add the springs and dampers so that the car can be used for both road and track.
Check, modify, re-check both ends of the car for appropriate bumpsteer. (In spite of building-in generous wheel travel for road use, our bumpsteer is neglible over the full range of travel - at both ends.)
Test on road and track.
Go home.
It might be that the original GT is a better track car - after all, it was a single-purpose design. But the difference is small on the track, and the ERA GT can be made into a fine road car too.
I looked (and measured) the original GT (and other similar world-class cars), for general layout, roll center, ride height and roll stiffness.
Laid out the control arms similar to the original, but with changes that I regard as somewhat more appropriate for wider tires. And there's a bit of BobPhilosophy in there too.
Add the springs and dampers so that the car can be used for both road and track.
Check, modify, re-check both ends of the car for appropriate bumpsteer. (In spite of building-in generous wheel travel for road use, our bumpsteer is neglible over the full range of travel - at both ends.)
Test on road and track.
Go home.
It might be that the original GT is a better track car - after all, it was a single-purpose design. But the difference is small on the track, and the ERA GT can be made into a fine road car too.
Hi Bob
What's up with J10? On another note why don't you have an open house on a sunny weekend next spring? I'll bring up J6.
Best
Jim
What's up with J10? On another note why don't you have an open house on a sunny weekend next spring? I'll bring up J6.
Best
Jim
Having raced in vintage both an original Mark1 and Mark2 here is my opinion.
The original Mark1 is a very fine car. It is a race car and doesn't have any creature comforts at all. The Mark2 with a 427 tunnel prot is a beast to drive. It tried to blow the tires off it at anything under 140mph.
I am the US dealer for Roaring Forties so I am a little biased. The RF car is far more comfortable on the street and at high speeds. In my opinion is does handle better than the originals. At the track the closest car I can compare it to is a Ferrarri 360 challange car but quicker.
Also having sat in or driven most of the replicas out there. I do fit more comfortable in the RF. I am 6'3" and built like a line backer. All replica's do have ther strengths and weeknesses. IT is up to you to decide what is the best car for how you want to use it.
The original Mark1 is a very fine car. It is a race car and doesn't have any creature comforts at all. The Mark2 with a 427 tunnel prot is a beast to drive. It tried to blow the tires off it at anything under 140mph.
I am the US dealer for Roaring Forties so I am a little biased. The RF car is far more comfortable on the street and at high speeds. In my opinion is does handle better than the originals. At the track the closest car I can compare it to is a Ferrarri 360 challange car but quicker.
Also having sat in or driven most of the replicas out there. I do fit more comfortable in the RF. I am 6'3" and built like a line backer. All replica's do have ther strengths and weeknesses. IT is up to you to decide what is the best car for how you want to use it.
Hi all
People that have racing experience in the UK have also found that the addition of full six point roll cage, has helped to stiffen the chassis on the replica GT40s to an expectable level. That is with the rear two legs of the roll cage attaching to the rear suspension turrets. I also except that for road use rubber bushes are needed and these can be improved by the use of polyurethane suspension bushes. There are three levels of compliance available in the polyurethane bush range, however I think that the top and bottom lateral links on the rear suspension of the replica GT40 can only operate properly if a spherical set of joints are used as on the original cars.
Regards
Chris
People that have racing experience in the UK have also found that the addition of full six point roll cage, has helped to stiffen the chassis on the replica GT40s to an expectable level. That is with the rear two legs of the roll cage attaching to the rear suspension turrets. I also except that for road use rubber bushes are needed and these can be improved by the use of polyurethane suspension bushes. There are three levels of compliance available in the polyurethane bush range, however I think that the top and bottom lateral links on the rear suspension of the replica GT40 can only operate properly if a spherical set of joints are used as on the original cars.
Regards
Chris
G
Guest
Guest
Well said Gordon Levy, well said.No two 40s or their derivatives were the same , especially in the body department and a good friend of mine,who incedentally still has his original tools and FILES for body fitting when he worked for Wyer at Slough,recalls being asked by him to get the alignments as best possible given turn round time and the aliveness of fresh moulded fibreglass bodies!!
As for chassis flex once i bonded panels to the frame all flex disappeared and in theory i could of saved considerable weight by not rivetting as well! Adding roll cage rear stays for racing has made no difference to rigidity, only weight.As i have said in a previous post all drivers and constructors are so very different. I doubt for one moment that had the 40 continued to this day in production that it would be made in such a heavy and awkward way.This originality thing is getting me down as some of us have more "original" parts than several so-called right cars!!Finally, think about this.If you own a GTD chassis car you actually have more of a true production run car than any other and Ray Christopher should really register his old company for FIA listing for future historic rating.The factory actually made 12 cars for one customer several years ago!!
VIVE LA DIFFERANCE!?!?!
GTA.
As for chassis flex once i bonded panels to the frame all flex disappeared and in theory i could of saved considerable weight by not rivetting as well! Adding roll cage rear stays for racing has made no difference to rigidity, only weight.As i have said in a previous post all drivers and constructors are so very different. I doubt for one moment that had the 40 continued to this day in production that it would be made in such a heavy and awkward way.This originality thing is getting me down as some of us have more "original" parts than several so-called right cars!!Finally, think about this.If you own a GTD chassis car you actually have more of a true production run car than any other and Ray Christopher should really register his old company for FIA listing for future historic rating.The factory actually made 12 cars for one customer several years ago!!
VIVE LA DIFFERANCE!?!?!
GTA.
I second that emotion!!!
Lets build them and drive them
Lets build them and drive them
Hi all
I remember someone saying that their GT# chassis had to be cut and re welded so that their GT# radiator would fit! (this is not an isolated incident)
If they can't get the radiator brackets right after producing so many cars then what chance is there for suspension geometry?.
I would also suggest that the rear struts in the roll cage benefit cars that have over 300bhp. Its all to do with torque you see.
I would also say that before removing the rear cage struts to lose weight, I would try fitting an alloy manifold and heads as a better option. (You could appreciate this if you ever put it on its roof).
Yes, replica GT40s are fantastic and handle well but I still say that the originals were better. I am not saying either that you are not able to improve the handling of the replicas you are, so please don't kid yourselves that your replica will handle like the real thing without a lot of work straight out of the box.
Regards
Chris
I remember someone saying that their GT# chassis had to be cut and re welded so that their GT# radiator would fit! (this is not an isolated incident)
If they can't get the radiator brackets right after producing so many cars then what chance is there for suspension geometry?.
I would also suggest that the rear struts in the roll cage benefit cars that have over 300bhp. Its all to do with torque you see.
I would also say that before removing the rear cage struts to lose weight, I would try fitting an alloy manifold and heads as a better option. (You could appreciate this if you ever put it on its roof).
Yes, replica GT40s are fantastic and handle well but I still say that the originals were better. I am not saying either that you are not able to improve the handling of the replicas you are, so please don't kid yourselves that your replica will handle like the real thing without a lot of work straight out of the box.
Regards
Chris
Jim Rosenthal
Supporter
This is one of the more interesting threads recently, lots of fun to read and I am glad all had something to say.
I agree that if the GT40 were being built today that they would not build the chassis the original way, as it was difficult and maybe needlessly complex. As proof of that, I think the Mark V chassis was redesigned both to be simpler and to allow it to be built up without having to have a metal-stamping company involved such as Abbey or Tennant.
I do not know of any MkV cars that were raced; does anyone else? Does the handling of the MkV compare favorably with the original? I would be curious to know. I have had a ride in an original (brief) and longer in a MkV- definitely the MkV was tighter and more solid, but that does not necessarily equate to better handling.
I agree that if the GT40 were being built today that they would not build the chassis the original way, as it was difficult and maybe needlessly complex. As proof of that, I think the Mark V chassis was redesigned both to be simpler and to allow it to be built up without having to have a metal-stamping company involved such as Abbey or Tennant.
I do not know of any MkV cars that were raced; does anyone else? Does the handling of the MkV compare favorably with the original? I would be curious to know. I have had a ride in an original (brief) and longer in a MkV- definitely the MkV was tighter and more solid, but that does not necessarily equate to better handling.
G
Guest
Guest
Chris, you are not reading the posting right. AT no time did i say that iwas taking the roll cage stays out.Rules do not allow that and radiator spacing has nothing to do with the basic thread of this topic.This forum must stop being the basis for these jibes.
GTA.
GTA.
An interesting thread indeed! for my 2c worth, I've only driven one GT40 rep (my own) & found it soft & vague. Straight line stability is very poor, altho it'll hold it's line in a corner, ie it's better when you lean on it.
Altho I haven't taken it on a track, at my local roundabout (in the wet!) I've found the car neutral to oversteer (which I like) & put this down to the weight distribution. (including driver, fluids, air-con, etc f-r dist is 44.5%/55.4%)
After a basic geo check, camber & track are ok, so I can only assume the vagueness & wandering is caused by bump steer, & poor aerodynamics. The suspension pickup points are quite different from side to side & this suggests to me there was a lack of accuracy when the chassis was originally jigged.
This the main reason I've chosen to go for rose-jointed suspension & I'm prepared to suffer a loss in ride quality to get accurate geo. I feel this is especially relevant for 17" wheels.
I believe I can improve the aerodynamics with a new nostril & some ally panelling but only time will tell if I'm right.
I agree with Chris's comments re fitting a roll cage. I've almost finished fitting the front cage & am very happy with the amount of strength & stiffness it'll add to the chassis. Again,it's a compromise against weight, but I've made my own decisions!
I believe the other main area for improvement on my chassis is the height of the engine/gearbox & this is another issue I hope to address.
Having ridden in other reps I think my car is a bad example & I'm confident that after my re-build & re-spec it'll handle *much* better.
So to summarise, the basic 'standard' package from *my* replica manufacturer is *OK*, but can be improved, if you have the time/ability/money etc!!!
Altho I haven't taken it on a track, at my local roundabout (in the wet!) I've found the car neutral to oversteer (which I like) & put this down to the weight distribution. (including driver, fluids, air-con, etc f-r dist is 44.5%/55.4%)
After a basic geo check, camber & track are ok, so I can only assume the vagueness & wandering is caused by bump steer, & poor aerodynamics. The suspension pickup points are quite different from side to side & this suggests to me there was a lack of accuracy when the chassis was originally jigged.
This the main reason I've chosen to go for rose-jointed suspension & I'm prepared to suffer a loss in ride quality to get accurate geo. I feel this is especially relevant for 17" wheels.
I believe I can improve the aerodynamics with a new nostril & some ally panelling but only time will tell if I'm right.
I agree with Chris's comments re fitting a roll cage. I've almost finished fitting the front cage & am very happy with the amount of strength & stiffness it'll add to the chassis. Again,it's a compromise against weight, but I've made my own decisions!
I believe the other main area for improvement on my chassis is the height of the engine/gearbox & this is another issue I hope to address.
Having ridden in other reps I think my car is a bad example & I'm confident that after my re-build & re-spec it'll handle *much* better.
So to summarise, the basic 'standard' package from *my* replica manufacturer is *OK*, but can be improved, if you have the time/ability/money etc!!!
G
Guest
Guest
I would suggest that a decent replica could be made to handle better than an original. In straight line blasts the times done by originals at places like Brighton and other hill climb events in the late 60's and early 70's are beatable by todays GTDs. Over the half mile at Brighton a typical GTD was about 1 sec quicker. Roy and Tony Marsh's cars most liklely would have pulverised them there today. I once had Justin Bell lined up to drive my GTD at Brighton but he faxed to pull out at the last minute as he had to be in USA testing on the day. Shame.
At Goodwood Revival, Andrew timed the originals running in 1966 or earlier spec. Bearing in mind that GTD owners are amateur drivers and have limited talent compared to modern F1 test drivers and the like, a GTD could mix it with the cars that took part. But then you are using 1980's (and later)design against 1966 machinery. As yet no professional driver like Willie Green or Darren Manning has done timed laps in a GTD at a venue like Goodwood where direct comparisons could be made. Brian Redman and Willie have done laps at Spa in Robin's Yellow Peril and definately gave it the big thumbs up. They had to shoe horn Brian out of the car he liked it so much. I seriously beleive that a typical track prepped GTD would compare well with a typical track prepped original Mk1 with equal driver skills. After all, a full race prepped GTD with Mk 2 body won the Swedish GT championship a couple of years ago against all comers of modern machinery (GT2 Porsches and the like). Indeed I also once heard that a team did try and get a GTD entered into Le Mans but failed to get past pre qualifying as the lap time was not deemed quick enough compared to the modern cars it would be up against. Unfortunately that is all I know of that attempt but if someone knows more please speak up.
I would also suggest that setting your camber, castor and other suspension angles to that of an original car is a waste of time. Which replica has the exact suspension mounting positions (and other detail) of an original? Therefore the settings would not necessarily be the best. I have played around a lot with settings and have driven quite a few GTD's. They all handle differently as each owner specs his car to how he wants it. F1 drivers in the same team do not use the same settings. This applies to 40's too. A lot of people think my car is very stiffly set. I think that other cars are very soft. Personal preferences dictate the final setup.
I would also suggest that a lot of replica owners do themselves a dis-service by not getting their cars set up properly. This is either because they don't know how or don't realise that their pride and joy could be even better than it already is! A standard GTD out of the box set to factory settings and done properly is a damn good supercar. But a road car, as that is how it was initially designed. Therefore any decent race car will be quicker on the track, like for like. Make some component changes,as most road cars being converted for the track get, and you will have a brilliant track car too.
Budget can have an influence here as some parts cost one heck of a lot more than others so options become limited. The best anti roll bar setups I have seen and liked cost I believe about £1000 each end of the car! I would love to have these but no chance at that price.
At the end of the day handling is always a compromise. You set a car up for the purpose it is to be used for and nothing else. If you want to mix it between road and track then you compromise the track settings so expect a pure track car to be quicker. Or for your fillings to drop out when on the road! After all is it not common knowledge that Golf GTi can beat a Lambo on twisty stuff?
Malcolm
At Goodwood Revival, Andrew timed the originals running in 1966 or earlier spec. Bearing in mind that GTD owners are amateur drivers and have limited talent compared to modern F1 test drivers and the like, a GTD could mix it with the cars that took part. But then you are using 1980's (and later)design against 1966 machinery. As yet no professional driver like Willie Green or Darren Manning has done timed laps in a GTD at a venue like Goodwood where direct comparisons could be made. Brian Redman and Willie have done laps at Spa in Robin's Yellow Peril and definately gave it the big thumbs up. They had to shoe horn Brian out of the car he liked it so much. I seriously beleive that a typical track prepped GTD would compare well with a typical track prepped original Mk1 with equal driver skills. After all, a full race prepped GTD with Mk 2 body won the Swedish GT championship a couple of years ago against all comers of modern machinery (GT2 Porsches and the like). Indeed I also once heard that a team did try and get a GTD entered into Le Mans but failed to get past pre qualifying as the lap time was not deemed quick enough compared to the modern cars it would be up against. Unfortunately that is all I know of that attempt but if someone knows more please speak up.
I would also suggest that setting your camber, castor and other suspension angles to that of an original car is a waste of time. Which replica has the exact suspension mounting positions (and other detail) of an original? Therefore the settings would not necessarily be the best. I have played around a lot with settings and have driven quite a few GTD's. They all handle differently as each owner specs his car to how he wants it. F1 drivers in the same team do not use the same settings. This applies to 40's too. A lot of people think my car is very stiffly set. I think that other cars are very soft. Personal preferences dictate the final setup.
I would also suggest that a lot of replica owners do themselves a dis-service by not getting their cars set up properly. This is either because they don't know how or don't realise that their pride and joy could be even better than it already is! A standard GTD out of the box set to factory settings and done properly is a damn good supercar. But a road car, as that is how it was initially designed. Therefore any decent race car will be quicker on the track, like for like. Make some component changes,as most road cars being converted for the track get, and you will have a brilliant track car too.
Budget can have an influence here as some parts cost one heck of a lot more than others so options become limited. The best anti roll bar setups I have seen and liked cost I believe about £1000 each end of the car! I would love to have these but no chance at that price.
At the end of the day handling is always a compromise. You set a car up for the purpose it is to be used for and nothing else. If you want to mix it between road and track then you compromise the track settings so expect a pure track car to be quicker. Or for your fillings to drop out when on the road! After all is it not common knowledge that Golf GTi can beat a Lambo on twisty stuff?
Malcolm
Hi all
Julian has hit the nail on the head, and I would say his approach is spot on.
I am particularly pleased he raised the point about the height of the engine in the replica cars, as he said they can be lowered substantially to assist in the handling characteristics of the replicas. Engine height in the replicas was high in an effort to reduce drive shaft angularity and I would suggest therefore that to invert your trans so that the output shafts are above your input shaft is the way to go. The big problem is that not all transmissions like to be turned over, and this could be a deciding factor when choosing a trans.
I Know Frank Catt has had good results reducing engine height, but on the GTD chassis this also involved modifying the chassis at the rear to allow the trans to sit lower.
Regards
Chris
Julian has hit the nail on the head, and I would say his approach is spot on.
I am particularly pleased he raised the point about the height of the engine in the replica cars, as he said they can be lowered substantially to assist in the handling characteristics of the replicas. Engine height in the replicas was high in an effort to reduce drive shaft angularity and I would suggest therefore that to invert your trans so that the output shafts are above your input shaft is the way to go. The big problem is that not all transmissions like to be turned over, and this could be a deciding factor when choosing a trans.
I Know Frank Catt has had good results reducing engine height, but on the GTD chassis this also involved modifying the chassis at the rear to allow the trans to sit lower.
Regards
Chris
We solved the engine height problem by simply requiring that you use a ZF transaxle in its original configuration.
It's more expensive, but worth it...
Jim,
I have driven a MK V at speed twice at Watkins Glen (and did a good job of holding up 1075, not via superior driving skills but because I was all over the track and scared him enough to make him think twice about passing me)and not having driven a Mk I at any speed I can't make a true comparison...but the MK V did handle very well. In fact the car was so far above my skill set that I remain in awe of the abilities. This was on BF Goodrich Comp TA tires, good but not state of the art. This particular car was not well sorted and I am sure with a competent driver and some sorting it would be most competitive with any 40 variant. The car suffered cooling problems due to a junk reman water pump installed by the engine builder that seriously limited track time, tough to put together a coulple of good laps when you gotta pit every two laps to add coolant. A new high flow pump solved the problem to the point where the car could idle on a 85 degree day with the fans running and never overheat.
Point is I think any well designed suspension setup can be made to handle well with a sufficently stiff chassis and good tuning. Bobphilosphy...I like that one, goes a LONG way towards explaining a lot of the ERA ideas.
Rick
[ December 02, 2002: Message edited by: Mark IV ]
I have driven a MK V at speed twice at Watkins Glen (and did a good job of holding up 1075, not via superior driving skills but because I was all over the track and scared him enough to make him think twice about passing me)and not having driven a Mk I at any speed I can't make a true comparison...but the MK V did handle very well. In fact the car was so far above my skill set that I remain in awe of the abilities. This was on BF Goodrich Comp TA tires, good but not state of the art. This particular car was not well sorted and I am sure with a competent driver and some sorting it would be most competitive with any 40 variant. The car suffered cooling problems due to a junk reman water pump installed by the engine builder that seriously limited track time, tough to put together a coulple of good laps when you gotta pit every two laps to add coolant. A new high flow pump solved the problem to the point where the car could idle on a 85 degree day with the fans running and never overheat.
Point is I think any well designed suspension setup can be made to handle well with a sufficently stiff chassis and good tuning. Bobphilosphy...I like that one, goes a LONG way towards explaining a lot of the ERA ideas.
Rick
[ December 02, 2002: Message edited by: Mark IV ]
