Daytona '15 - BOSS not quite ready for retirement...

[Z20WHAT]

While everyone is anxiously awaiting that new car, the 'old car' is picking right up where they left off last season...

http://m.imsa.com/articles/johnson-sets-unofficial-track-record-daytona-ford-mustang

Apparently Jim Click fared pretty well in the opening session, too.

http://m.imsa.com/articles/jim-click-mustang-paces-opening-session-daytona

Just awesome!!! I hope Multimatic runs both cars at some races this season...

 

[Noellenchris]

I love this type of news. Makes my day. Also wish I could try that some day.


Chris

 

[cloud9]

Great showing for the "old boy"!!!

 

[VoodooBoss]

Not bad for a stick axle car. I'm sure Billy is salivating waiting to get his hands on the wheel of this car.

https://trackmustangsonline.com/index.php?topic=9016.msg131072#new

 

[steveespo]

Great to see Billy Johnson putting it down out there. Should be a good season.
Off topic question, wonder why Watson doesn't curve the front halo bar on the cage to follow thr roof line better? I don't believe it would be a technical violation as an arched shape there would be stronger than a straight bar. For me it would look cleaner and be less visually distracting when driving. I plan on having mine fabricated tp follow the header more closely.
Steve

 

[ArizonaBOSS]

The seat is lower than stock, you won't notice the bar. Plus most teams run 6-9" tall windshield banners that cut off that part of the windshield. I don't mind it one bit

 

[Grant 302]

Great to see Billy Johnson putting it down out there. Should be a good season.
Off topic question, wonder why Watson doesn't curve the front halo bar on the cage to follow thr roof line better? I don't believe it would be a technical violation as an arched shape there would be stronger than a straight bar. For me it would look cleaner and be less visually distracting when driving. I plan on having mine fabricated tp follow the header more closely.
Steve

A curved bar would not likely be stronger than a straight bar...unless it was also a heavier/wider/deeper section.

 

[steveespo]

Grant
I disagree, an arched or cambered shape spanning vertical supports at both ends resists compressive forces better than a straight member of equal size and material. I build buildings for a living and large span beams are always set with a positive camber prior to receiving their permanent loads. A second benefit to arching that bar is to get it farther away from the drivers head. Look at this picture of what NASCAR has done with the 2013+ roll cage, they have 2 front halo bars, and both are curved to follow the roof and windshield arcs.


Steve

 

[DGRacing]

I'm no engineer and there are some good points for and against. But here's my thoughts (with limited knowledge).

And arched roofline would require the metal be "bent". Bending it makes it weaker at the bend angles doesn't it? Some areas of the cage probably allow bending more than other more critical junctions perhaps?

Now, the arch shape is certainly stronger than a straight shape when the arch is symmetrical, and when force is applied perpendicular to the arch (at apex) assuming the supports of the arch transfer the load exactly vertically downward and nowhere else, but the arch will be weaker on forces coming laterally which is perhaps a more common occurrence in racecars?

That said, there probably is still a way to have both: a cleaner more concealed roofline and strength by using welded sections angled up and gussets or additional bracing angling back onto the side bars which will add more weight and maybe why its not done. aesthetics < weight in terms of importance.

 

[Grant 302]

Darren- That's very well explained. And most of what I was just about to reply!

Steve- Camber in beams is usually set so that the beams are flat or near flat when static/dead loads are applied. Essentially, the structural engineers know that the beam will deflect/sag under its intended load and camber the beam by that predicted amount so the final structure is level and flat. It's done a lot with concrete fill on metal deck structures since the majority of the dead load is added during the concrete pour.

Reasons to bend a member in a cage are mostly for visibility and clearance. The bent bar in the picture you posted is not stronger than a straight bar in the same location, but it's certainly more practical to look under and will be further from the driver in a crash or roll and provides large debris protection. Frame structures are strongest with straight members arranged in triangular shapes like a crane boom/tower or as used in floor joists. Unfortunately, in a race car, using only triangular shapes wouldn't be practical and everything else is a compromise.

 

[steveespo]

Is that why the Hoover Dam is curved?

And the bridge that spans the Colorado in downstream of it?
If you are considering the lateral forces of a side impact wouldn't the horizontal dash level bar transmit the forces of a door impact though to the opposite vertical structure (A pillar bar/pillar) and not the halo bar, or not enough that it is significant in an impact. Also the corner A pillar to Halo bar gussets create the triangulation desired at that intersection to resist a blowout of that joint and keep transmitting roll over forces vertically into the tie in points when a roof impact occurs. I like these discussions, I think the reason is simplicity in fabrication more than structural, aesthetic or visibility concerns. I can't muster the energy to do the calcs but if you guys can please do, .120" mild steel, 1.75" diameter main bars, 1.25" triangulation tube gussets. Assume the width of the connection points are 60" and the radius of the arch formed is 114.5" with a 4" peak from horizontal datum. I know it's complicated, that is why I need you guys for the rest. I'll have my structural engineer work on it tomorrow, he'll think I'm crazy.
Steve

 

[Grant 302]

I'm glad you like the discussion! I have some time today, because I passed up a track day due to rain But I'm also going to pass on doing any calcs, as I'm pretty sure I've forgotten more than I've retained over the years!

Both arches in your examples really get their 'strength' from the adjacent abutments. The arch is an efficient way to transmit those loads mostly outward and in compression (and compression is 'better' for concrete structures like the dam and bridge. Concrete is weak under tensile forces). And it's also why you can build an arch with loose stones or bricks. They all handle compression well. That's unlike a straight bar or structural beam when loaded perpendicular to its axis where part will be in tension and part in compression which is 'bending' and that's (arguably) more appropriate for steel.

Each bar in a cage has two main crash/impact purposes IMO. Resist impact forces to itself and to support other members under impact. In those two functions, the curved bar is not stronger, but as you suggest will transfer more compressive loads through its ends/joints. However, when supporting other bars, the arched bar in tension or compression will have more eccentric loads and will bend and deflect more than a straight bar in that function. Perhaps compression with regard to joints and welds is just safer or more reliable.

I know all of this discussion over 'strength' is just academic. In a crash, I would rather have a bar with a 4" arch 24" away from my head vs a straight bar 20" away from my head that blocks more of my view.

 

[Z20WHAT]

Official entry list for Daytona 200 went up Thursday. No sign of that other car with the weird paint job that was briefly seen at the Roar...

http://www.imsa.com/sites/default/files/uploads/2015CTSC%20Rolex%20Entry%20List.pdf

 

[VoodooBoss]

Not bad that a stick axle car with a 10 year old platform still dominates the class with 7 entries. I'm not familiar with Zero Zero Racing, are they a new team?

The rumors are the GT350(?) will debut at Sebring.

 

[Berol]

Official entry list for Daytona 200 went up Thursday. No sign of that other car with the weird paint job that was briefly seen at the Roar...

http://www.imsa.com/sites/default/files/uploads/2015CTSC%20Rolex%20Entry%20List.pdf

Anybody from BMO going? We should meet up for the race. I'll be there.

 

[El_Tortuga]

I'm glad you like the discussion! I have some time today, because I passed up a track day due to rain But I'm also going to pass on doing any calcs, as I'm pretty sure I've forgotten more than I've retained over the years!

Both arches in your examples really get their 'strength' from the adjacent abutments. The arch is an efficient way to transmit those loads mostly outward and in compression (and compression is 'better' for concrete structures like the dam and bridge. Concrete is weak under tensile forces). And it's also why you can build an arch with loose stones or bricks. They all handle compression well. That's unlike a straight bar or structural beam when loaded perpendicular to its axis where part will be in tension and part in compression which is 'bending' and that's (arguably) more appropriate for steel.

Each bar in a cage has two main crash/impact purposes IMO. Resist impact forces to itself and to support other members under impact. In those two functions, the curved bar is not stronger, but as you suggest will transfer more compressive loads through its ends/joints. However, when supporting other bars, the arched bar in tension or compression will have more eccentric loads and will bend and deflect more than a straight bar in that function. Perhaps compression with regard to joints and welds is just safer or more reliable.

I know all of this discussion over 'strength' is just academic. In a crash, I would rather have a bar with a 4" arch 24" away from my head vs a straight bar 20" away from my head that blocks more of my view.

So much this. If the primary load (compression or tension) is along the length of the tube, straight is better. If the primary load is perpendicular to the tube, curved has more capacity.

 

[blacksheep-1]

Back on topic, looked like the Mustangs faded badly....That's the problem with the ROAR, too many sandbaggers, you have to add up segmented times for misc cars to get a true picture of what is going on...