Khamsin Virtual Racecar Challenge 2015

[CAEdevice]

I need to read that new rules with the cad model on the screen, but, after the changes I introduced in the second race, I don't think that they will have a dramatic impact.

I have two questions:

1) Is there any change about the realism of the flow path between cooling inlet and outlet?

2) Would it be not realistic to allow the cooling outlet intersect the rear suspension in a longer volume?

[CAEdevice]

About missing Chris car: I agree with Variante! What about a presence in the not giving points race?

[julien.decharentenay]

It would be great to have as much competition as possible. The history (Nick and Luke, during the first and second year) showed that trying to organise and race a car at the same time is real time challenge...

Matteo, I am still wondering what can explain the 1000N difference. Did you try re-running the "official" results?

OCCFD: I have got around to implementing an option to run a 1/2 car, which I hope to be reasonably stable. I am still testing it and may have to withdraw it if I find it to not be stable. When using this option, please submit a full car!

Download it from http://www.khamsinvirtualracecarchallen ... edirects=0 and use the option OCCFD > More Options > KVRC Half Car. Feedback welcome.

For the challenge next race (race #3), we will be using a full car simulation. I am not game for trying something different. As a word of warning, the next race results may be running late from my side. I will be traveling back to Australia on the 29th June and will be very busy organise the move of my family to the UK...

[cdsavage]

- K4.1: Added ‘area template’ defined relative to the rear face of the inner template for the cooling inlet. The 'inlet surface' would now represent the mouth of the inlet duct, and the area template would represent the heat exchanger itself.

We discussed about this rule before the season had started, but it's been decided not to introduce it due to rule checking issues (if i remember correcly, it was me, the guy with the smallest sidepods, the one who proposed the introduction of that rule). What has changed from to those days?

As I remember it, at that time we were discussing a rule similar to one in the 2014 KVRC rulebook, governing a section of all bodywork more than a certain distance from the car centerline, at a specified plane. This rule specifies a separate template part, which must be contained inside the bodywork but which is otherwise not tied to the external shape of the bodywork. The plane containing this part is defined relative to the inlet position, not at an absolute location, so there's freedom as to where it is placed.

- K4.2: Outlet must now be at least 1000mm rearwards of the inlet (+200mm). Last 200mm of outer template may intersect rear suspension templates. Inner template may intersect rear suspension templates.

"..because..."

Intersection of template and rear suspension: something like this was requested by a couple of people and I think it's a reasonable change. In compliance checking of the 'minimal' sidepod designs, it has been very common to see the outer template for the cooling outlet intersecting the rear suspension templates slightly. The 1000mm minimum distance change could be omitted, but I think this should have been longer from the beginning. If we're making changes to the cooling system anyway, now would be the time to make this change.

Would it be not realistic to allow the cooling outlet intersect the rear suspension in a longer volume?

I think a small increase to the 200mm dimension would be reasonable if we're keeping the 1000mm minimum distance change in K4.2.

Is there any change about the realism of the flow path between cooling inlet and outlet?

It's a good question, this is definitely an area that could do with clarification. We could specify that if this path passes around the engine template (eg the Mantium entry for round 2, with the single central outlet), then the bodywork surrounding the engine template must remain at least X mm away from the template. We could regulate this with another 'guide' part, which would consist of the surfaces of the engine template offset by X mm. In the case where the path does not pass by the engine template, eg the 'minimal' sidepod design, this requirement can be ignored and the bodywork can be shrink-wrapped around the engine template as in the current rulebook. This obviously doesn't help us in cases where the flow path is close to other templates - do we supply an 'offset' version of every template?

About missing Chris car: I agree with Variante! What about a presence in the not giving points race?

Unfortunately I don't really have the time for it this year. Maybe KVRC 2016 [-o<

[CAEdevice]

@Julien: don't worry about the results of the 2nd race. The real problem I have now is that I can't run in any way the geometry for the 3rd race (the process that is running when the simulation stops is mapfields.exe).

[CAEdevice]

Wich of the next races will be the "no points" one (if confirmed)? I'm going to try something new for that race

[machin]

The 1000mm minimum distance change could be omitted, but I think this should have been longer from the beginning.

As a semi-independent person with no vested interest in this... I agree that amending the side-pod rules slightly to make the cars look a little more realistic in this area is definitely a good thing. I would probably go further and suggest 180,000mm^2 cross-section somewhere near the middle and maybe 1200mm separation between inlet and outlet.... But maybe that is too much half way through the season and the suggested figures would be a better compromise...

[RicME85]

@Julien: don't worry about the results of the 2nd race. The real problem I have now is that I can't run in any way the geometry for the 3rd race (the process that is running when the simulation stops is mapfields.exe).

Have you tried using AWS?
Once I got it running all issues I had with the local solver were gone. Also all results have been pretty much exactly the same as the official result.

[RicME85]

The 1000mm minimum distance change could be omitted, but I think this should have been longer from the beginning.

As a semi-independent person with no vested interest in this... I agree that amending the side-pod rules slightly to make the cars look a little more realistic in this area is definitely a good thing. I would probably go further and suggest 180,000mm^2 cross-section somewhere near the middle and maybe 1200mm separation between inlet and outlet.... But maybe that is too much half way through the season and the suggested figures would be a better compromise...

It certainly would be better to get rid of the tiny pods, have a bit more of a realistic design.

Dont think it is too much to ask at this point, designs are changing a fair bit between rounds and thats on the high downforce tracks, I would imagine things will change again for the low downforce ones, hence Chris wanting to make the changes ahead of them.

[machin]

Is there any change about the realism of the flow path between cooling inlet and outlet?

It's a good question, this is definitely an area that could do with clarification. We could specify that if this path passes around the engine template (eg the Mantium entry for round 2, with the single central outlet), then the bodywork surrounding the engine template must remain at least X mm away from the template. We could regulate this with another 'guide' part, which would consist of the surfaces of the engine template offset by X mm. In the case where the path does not pass by the engine template, eg the 'minimal' sidepod design, this requirement can be ignored and the bodywork can be shrink-wrapped around the engine template as in the current rulebook. This obviously doesn't help us in cases where the flow path is close to other templates - do we supply an 'offset' version of every template?

If I've understood that correctly; the flow path on some of the designs go through the engine? Sounds to me like it might require the competitors to model in the duct which should have a cross-section no smaller than the outlet (with a minimum aspect ratio of 2:1 or 3:1 ?), and this duct can't clash with any of the existing templates...?

Or am I missing the point?!

[variante]

As I remember it, at that time we were discussing a rule similar to one in the 2014 KVRC rulebook, governing a section of all bodywork more than a certain distance from the car centerline, at a specified plane. This rule specifies a separate template part, which must be contained inside the bodywork but which is otherwise not tied to the external shape of the bodywork.

And where's the actual difference between 2014 rule and the proposed one, since both require the rule inspector to analyze a potentially weirdly shaped area (with all the related difficulties). The new one may be even more difficult to check because the required 150000 area may be found at an angle...

Anyway, i repeat that i'm not against the introduction of this rule...actually, i would have liked to have it since the beginning.

As a last note, notice that this rule would make all designs very similar to each other: there's no way one could keep the "open bodywork" configuration with the related advantages (this is not specifically due to the 150000 rule, but due to the combination of all the rules governing that part of the bodywork).

[machin]

I guess it is easier to measure the surface area of a complete face of a template (much like the inlet and outlet faces) than it is to try to measure the combined cross-sectional area of multiple bodies?

Either way, we are where we are and Chris now feels he has a workable solution to get the side-pods on all cars looking more realistic, and thereby make the engineering challenge more realistic, which should be applauded, regardless of how we got here.. don't you think?

[cdsavage]

As I remember it, at that time we were discussing a rule similar to one in the 2014 KVRC rulebook, governing a section of all bodywork more than a certain distance from the car centerline, at a specified plane. This rule specifies a separate template part, which must be contained inside the bodywork but which is otherwise not tied to the external shape of the bodywork.

And where's the actual difference between 2014 rule and the proposed one, since both require the rule inspector to analyze a potentially weirdly shaped area (with all the related difficulties). The new one may be even more difficult to check because the required 150000 area may be found at an angle...

In the proposed rule, the entrant creates the area template. It is included in the list of parts to submit in K1.4. You are free to position the inlet anywhere which satisfies the existing rules, and then create the area template planar to the rear face of the inner template. The 2014 rule required the compliance checker to construct a face (or multiple faces) from the intersection of all bodywork with a plane at a specified location, and then discard areas of this face(s) which were outside of the limits. The new rule would be much easier from a compliance checking standpoint, and in my opinion it's a more robust rule due to the height and width limits on the area template. It also takes into account the cockpit/engine/gearbox templates (area template may not intersect these parts), which a 2014-style section rule would not.

Just to be sure everyone is on the same page, this is the wording of the relevant part of K4.1:

• The K4.1 inner template is an extrusion of the inlet surface rearwards along its normal for a distance of between 500mm and 1000mm. This template must be entirely enclosed within the bodywork and must not intersect any other parts or templates.
• The K4.1 area template is a single continuous shape which is coplanar with the rear face of the inner template. In addition to covering the entirety of the rear face of the inner template, this shape must be at least 150,000mm2 in area, and must be no more than 600mm wide and no more than 450mm high. This template must be entirely enclosed within the bodywork and must not intersect any other parts or templates.

As a last note, notice that this rule would make all designs very similar to each other: there's no way one could keep the "open bodywork" configuration with the related advantages (this is not specifically due to the 150000 rule, but due to the combination of all the rules governing that part of the bodywork).

It will definitely make the 'minimal' design much less viable. Looking at round 2, you, Brook, CAEdevice, DHRacing, and TalnoRacing followed this design. Of those, arguably only you and CAEdevice made any use of the free space. So while you could argue that there may have been future developments on these designs which are no longer possible, I don't see there being any great reduction in variety compared to the design's which we've already seen. On the contrary, I think packaging a larger cooling system could lead to some new design challenges and force everybody to think outside of the 'single-seater with wheel covers' box.

Is there any change about the realism of the flow path between cooling inlet and outlet?

It's a good question, this is definitely an area that could do with clarification. We could specify that if this path passes around the engine template (eg the Mantium entry for round 2, with the single central outlet), then the bodywork surrounding the engine template must remain at least X mm away from the template. We could regulate this with another 'guide' part, which would consist of the surfaces of the engine template offset by X mm. In the case where the path does not pass by the engine template, eg the 'minimal' sidepod design, this requirement can be ignored and the bodywork can be shrink-wrapped around the engine template as in the current rulebook. This obviously doesn't help us in cases where the flow path is close to other templates - do we supply an 'offset' version of every template?

If I've understood that correctly; the flow path on some of the designs go through the engine? Sounds to me like it might require the competitors to model in the duct which should have a cross-section no smaller than the outlet (with a minimum aspect ratio of 2:1 or 3:1 ?), and this duct can't clash with any of the existing templates...?

At the moment there's a rule stating that there must be space around the templates for the flow path, but this isn't regulated with any dimensions, so it's difficult to draw a line where a design no longer complies with this rule. In many cases the 'duct' follows a complex 3d path - in parametric modelling packages it might be simple to create a sweep along this path with constant or linear/cubic varying cross-section area, but it might be quite difficult in a basic polygon modeller. The larger issue with this though would be checking the duct geometry for the cross-section at every point along a 3d path.

[variante]

Either way, we are where we are and Chris now feels he has a workable solution to get the side-pods on all cars looking more realistic, and thereby make the engineering challenge more realistic, which should be applauded, regardless of how we got here.. don't you think?

You wouldn't be so enthusiastic about the news if you had to redesign 3/4 of your bodywork. You would be even less once you'd remember that other last minute changes were made. You wouldn't be enthusiastic at all if you had asked for the definitive version of the rulebook to be completed for christmas.

So yes, it does matter the path that got us here.

In case someone gets it wrong, i repeat again that i am in favour of a more realistic version of this challenge, and i do applaude the work that Julien and Chris are doing.
At the same time, however, i recommend a more democratic management of the challenge.

[cdsavage]

Either way, we are where we are and Chris now feels he has a workable solution to get the side-pods on all cars looking more realistic, and thereby make the engineering challenge more realistic, which should be applauded, regardless of how we got here.. don't you think?

You wouldn't be so enthusiastic about the news if you had to redesign 3/4 of your bodywork. You would be even less once you'd remember that other last minute changes were made. You wouldn't be enthusiastic at all if you had asked for the definitive version of the rulebook to be completed for christmas.

So yes, it does matter the path that got us here.

In case someone gets it wrong, i repeat again that i am in favour of a more realistic version of this challenge, and i do applaude the work that Julien and Chris are doing.
At the same time, however, i recommend a more democratic management of the challenge.

This is why we're posting it here. No decision has been made. If the consensus is that this is an unwanted change, then no change will be made.

There are 2 months until the round where these changes will/would come into effect, and this round has always been marked as a non-championship round. I don't see any way this could be construed as 'last minute'.