Torsional Rigidity
Discussion
Am i missing something here? But none of the tests specs that i can find detail the "centre" around which the chassis is to be rotated?? This must affect the "stiffness" result as it will change the balance of "pure torsion" to "shear" ratio for any given chassis???
Some of the pics show a "knife edge" pivot immediately below one of the chassis lower bars, the professional rig shows a pivot point that looks to be about 12" below the chassis lower point???
I wonder if thats where all the "different" nm/deg values are stemming from???
Some of the pics show a "knife edge" pivot immediately below one of the chassis lower bars, the professional rig shows a pivot point that looks to be about 12" below the chassis lower point???
I wonder if thats where all the "different" nm/deg values are stemming from???
The way I've seen it done was three corners of the chassis was attached to structured floor posts then the 4 corner was loaded up. The chassis load as far as I can see have to go thought the normal load points i.e. the shock upper mounts, as this is where the load would normally be applied. This at least keep the normal Load-Paths the same as when the car is driven.
It's not where you apply the moment thats important (well it is, but not the point i am wondering about) it's the position of the centroid of that moment! Imagine you had say a 100mm diameter steel tube, welded to a immovable steel block, pure torsion would be trying to twist that tube around a point that co-incides with the tubes diametrical centre. However, if you say welded a lever to the outside diameter and pushed on that, you would be applying both a torque and a bending moment to the same tube, and it's stiffness will be very different in each case??
Max_Torque said:
Am i missing something here? But none of the tests specs that i can find detail the "centre" around which the chassis is to be rotated?? This must affect the "stiffness" result as it will change the balance of "pure torsion" to "shear" ratio for any given chassis???
Some of the pics show a "knife edge" pivot immediately below one of the chassis lower bars, the professional rig shows a pivot point that looks to be about 12" below the chassis lower point???
I wonder if thats where all the "different" nm/deg values are stemming from???
This is the way i understand it, If the Chassis is attached rigidly by the hubs at the rear, and the torque load is applied to the Hubs at the front, then the centroid will be through the centre of the chassis about which it twists itself. The front support is only there to provide vertical support to overcome the downwards effect of gravity. And load applied at this point would be cancelled out in the torque calculations as its radius arm equals zero. The correct way to do this test would be to allow this pivot to be able to slide from side to side under the chassis so that it is always under the centreline of the centroid about which the chassis twists. Its probably not going to make a huge difference to the result but would be producing a small inaccuracy.Some of the pics show a "knife edge" pivot immediately below one of the chassis lower bars, the professional rig shows a pivot point that looks to be about 12" below the chassis lower point???
I wonder if thats where all the "different" nm/deg values are stemming from???
As the chassis is attached by the hubs all loads should flow back to the chassis via the suspension members, and the solid bars that have been used to replace the springs and shocks. Any deflection in the hubs/bearings/suspension pivots/wishbones/mounting brackets will be removed from the test results by taking the measurements of dial indicators that are attached to the chassis and set to Zero before the loads are applied.
if the tests are done differntly then they would produce different results.
I have been speaking to a local engineering business (who are building a single seater for me) and they have been doing some fabrication using some steel out of China recently, general comments have been that its harder to welded and not as stiff even though it supposedly meets the same engineering standard. Not having a go at china, but merely pointing out that there could be different performances out of different batches of steel or production runs which would also account for differences in what is a bespoke low volume product. For Me – Ii will have to go through the test if I commit to getting an Ultima on the Road, so the question doesn’t necessarily become “how stiff” – but “how do i get the box ticked off and pass before they change the rules again” as id rather be driving than fighting bureaucracy.
I honestly do not care if the chassis is measured stiff or not, but I have not yet noticed any problems with the car feeling soft, but I noticed a soft feeling very quickly with the boxter compared to the cayman. however I still wonder how you can drive so quick around the top gear track with a chassis that is not even meeting saloons figures. So in the end stiffness might be not so important or the flex is just more important than assumed ?
I know this is a silly question but unless we are racing the cars, what does it matter if there is a little flex.. the roads in the UK are so bumpy , traction is more important to me than if the chassis flexes a bit and maybe on these roads it might be a good thing?? On the track a completely different story..
Dom
Dom
Bombardier said:
THE chassis test results I posted have come from a just registered GTR in NSW Australia.
The answer to the question about being leagal/suitable for Australian registration is a definate - YES.
Thanks, Good to know. Any photos, Maybe start another thread so as not to get lost in this one. Would be realy interested in seeing what was involved.The answer to the question about being leagal/suitable for Australian registration is a definate - YES.
Adam GTR said:
Hi all,
Can anyone tell me the results of torsional rigidity test conducted on the Ultima chassis.
West Australian regulations require a minimum of 6000Nm for anything over 2.0lt engine capacity.
Has anyone had a test conducted in Australia ?
Thanks in advance
Adam
huh..wha..eh...There is an Ultima in Perth?!?! Would love to have a nose around that one day!Can anyone tell me the results of torsional rigidity test conducted on the Ultima chassis.
West Australian regulations require a minimum of 6000Nm for anything over 2.0lt engine capacity.
Has anyone had a test conducted in Australia ?
Thanks in advance
Adam
What are your plans for it...Road use only or are you going to track it?
Now that your chassis has been tested and passed does this pave the way for other potential builders to be able to build a car and NOT have it tested?
Adam GTR said:
This is a photo of the test bed that will be used to test the Ultima prior to registration.
As you can see it is a fairly substantial piece of equipment.
Adam
Is that a Sylva Riot? In Perth?!As you can see it is a fairly substantial piece of equipment.
Adam
It never stops amazing me just how many rare sports, race and rally cars there are knocking around in Perth with its small population! Some are kept very well hidden to.
Ultima factory said:
GTRCLIVE,
Undeveloped? You should really address this criticism to Ferrari/Mr Schumacher and their £2million Ferrari FXX track car. We've laid down our benchmark of 1min9.9secs on the top gear track, best of luck to anybody with a road car who can get anywhere near that time......
Any body can stiffen the suspension some much your teeth fall out... How about spending some money instead of resting on your laurels... Please if you've altered the chassis in the last 20 years I'm all ears ....Undeveloped? You should really address this criticism to Ferrari/Mr Schumacher and their £2million Ferrari FXX track car. We've laid down our benchmark of 1min9.9secs on the top gear track, best of luck to anybody with a road car who can get anywhere near that time......
GTRCLIVE said:
Ultima factory said:
GTRCLIVE,
Undeveloped? You should really address this criticism to Ferrari/Mr Schumacher and their £2million Ferrari FXX track car. We've laid down our benchmark of 1min9.9secs on the top gear track, best of luck to anybody with a road car who can get anywhere near that time......
Any body can stiffen the suspension some much your teeth fall out... How about spending some money instead of resting on your laurels... Please if you've altered the chassis in the last 20 years I'm all ears ....Undeveloped? You should really address this criticism to Ferrari/Mr Schumacher and their £2million Ferrari FXX track car. We've laid down our benchmark of 1min9.9secs on the top gear track, best of luck to anybody with a road car who can get anywhere near that time......
Oh goodness! What have you started Clive?
Overall the Factory get my vote, and that is measured not only by their products (nothing out there is ever 100% IMO), but by their aftersales service which frankly in this imperfect world we live in is one of the best around.
The Car market (never mind kit cars) is rife with poor service and not-so-good products..and Ted/Richard and co are a shining example of how it should be - ie at the top of the pile, for me anyway!
Being complimentary is not usually my forte, and anyone who knows me will vouch for the fact I give suppliers a very, very hard time when things are not satisfactory...
errr...so Richard, calm down man...don't rise to it!
It is only but one opinion - you have a lot of fans out there.
....and everyone is entitled to express an opinion provided it is not libelous or offensive
Lets get REAL!
Luv
Keith
It think what maybe getting people's backs up is the fact that seemingly there are proven ways to significantly strengthen the rigidity of the chassis with very little changes and seemingly the factory has been notified of these changes for free and they aren't interested.
As to what gains could be had by making these changes still remains to be seen but they 'should' improve the handling, I don't think that anyone at any point doubted it's current capabilities but bluntly ignoring free advice just sounds a little naive.
Maybe I'm way off base here?
I know nothing of chassis design though the murmurings I hear are generally:
- For cars, as stiff as possible and let the suspension do the job it's supposed to.
- For bikes, as stiff as possible with some designed in flex in certain areas.
Quite why the factory has taken specific umbrage to this thread and actually made comments as opposed to other ranting threads I don't know....
As to what gains could be had by making these changes still remains to be seen but they 'should' improve the handling, I don't think that anyone at any point doubted it's current capabilities but bluntly ignoring free advice just sounds a little naive.
Maybe I'm way off base here?
I know nothing of chassis design though the murmurings I hear are generally:
- For cars, as stiff as possible and let the suspension do the job it's supposed to.
- For bikes, as stiff as possible with some designed in flex in certain areas.
Quite why the factory has taken specific umbrage to this thread and actually made comments as opposed to other ranting threads I don't know....
Moogle
I think that the factory and others have become outspoken on this because Clive built and owned a GTR for about 8 years ago. Many of his posts are constructive and helpful to owners but many come across as a personal crusade against everything Ultima and American Speed have done. Many visitors on Pistonheads are potential owners of an Ultima and if they read some of the posts would walk away from such a good product. It is a shame that a former owner wants to try and put such a good product out of business!
I think that the factory and others have become outspoken on this because Clive built and owned a GTR for about 8 years ago. Many of his posts are constructive and helpful to owners but many come across as a personal crusade against everything Ultima and American Speed have done. Many visitors on Pistonheads are potential owners of an Ultima and if they read some of the posts would walk away from such a good product. It is a shame that a former owner wants to try and put such a good product out of business!
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