Roll Cage/Driver Fit - Interpretation of Rule 3.2.14

[AlpineMarch]

Hi all, I'm building a ChampCar legal race car with a Miata (NB chassis), and Rule 3.2.14 requires that "when the driver is securely belted in-place, the top of the driver’s helmet does not extend above the centerline of the main hoop."   Our cage was built by a very experienced cage builder who's done lots of spec miata cages, and the main hoop is very close to the inside of the hardtop, but our helmets are very close to the main hoop centerline even though we are both under 6 feet and we both have lots of room between our helmets and the hard top. 

 

In addition, the bars above both windows are bent/arched (see photos, although the driver is not belted in and therefore a little higher than when secured), and there is a center bar between the main hoop and the center of the windshield that is also bent/arched to conform to the hard top, so that our helmets don't extend past the planes formed by the bars of the cage. 

 

Even though I'm very comfortable with the safety of the cage, I don't want show up for a race and not be able to pass tech inspection.  So my questions are: 

(1) exactly how is the measurement done?  Is it a "broomstick test" measurement from the main hoop to the halo hoop above the windshield, or is it a horizontal plane extending forward from the centerline of the main hoop, even if the halo hoop, and center bar are all significantly higher? 

(2) The same rule also says "Any driver found in violation of this rule will be black-flagged and the car withdrawn from competition until repairs or modifications have been made and the car completes a re-tech inspection."  If all drivers except one would fit, can that driver just not race, and can the car race as-is with the other (shorter) drivers?

 

Thanks for any insight you can share. 

Edited August 23, 2021 by AlpineMarch

[mender]

Opinion: if you want that center bar to support the weight of the car when upside down without collapsing while forcing the front and rear hoops apart, you'll need to put bracing on the outside of the hoops opposite of the ends of that bar. Right now there is nothing bracing it. 

 

2). If your "modifiction" is to put in a shorter driver, I would argue that the car would pass another tech inspection.

[enginerd]

Lower the seat.

 

In a rollover wreck your belts will stretch and those helmets will be hitting the ground. 

Edited August 23, 2021 by enginerd

[Ian]

Lower the seat.  I wouldn't put myself in that car.

 

It's quite common in Spec Miata to run a seat drop pan, I believe there are even pre made versions available for purchase.

[hotchkis23]

2 hours ago, Ian said:

Lower the seat.  I wouldn't put myself in that car.

 

It's quite common in Spec Miata to run a seat drop pan, I believe there are even pre made versions available for purchase.

This, advance autosport out of Beloit has a kit for this that we used in our NA.  Drops it ~2-3".

[mickindy14]

mazdaracers.com  has a floor drop panel kit also. Another important thing to address in your build are the front hubs, they are a notorious weak point on the Miata. Make sure you buy good quality ones. 

Edited August 23, 2021 by mickindy14

[AlpineMarch]

Thanks, and I appreciate the suggestions about lowering the seat.  But can anybody answer my first question, which is how exactly the clearance is measured to determine if you meet the ChampCar rules (especially when the center and side bars are higher than the main hoop)?  

 

Thanks again.

 

[DEE DEE]

3 minutes ago, AlpineMarch said:

Thanks, and I appreciate the suggestions about lowering the seat.  But can anybody answer my first question, which is how exactly the clearance is measured to determine if you meet the ChampCar rules (especially when the center and side bars are higher than the main hoop)?  

 

Thanks again.

 

Might be a good idea to contact the Tech employees to get the official answer.

[TimS]

32 minutes ago, AlpineMarch said:

Thanks, and I appreciate the suggestions about lowering the seat.  But can anybody answer my first question, which is how exactly the clearance is measured to determine if you meet the ChampCar rules (especially when the center and side bars are higher than the main hoop)?  

 

Thanks again.

 

Main hoop is behind your head. Side or halo bars are different. The main hoop is your roll over protection. Don’t even have you helmet inside the space occupied by the bar. Can you get the appropriate sized “driver” to get car through tech. I’m sure you could. If it rolled over would the person in the picture be injured probably. Lower the seat gain need room above your head and be safe. Unfortunately in racing poop happens. 
experienced spec Miata cage builder should have seen this problem before and let you know what needed to be done to fix

Edited August 23, 2021 by TimS

[Ian]

48 minutes ago, AlpineMarch said:

Thanks, and I appreciate the suggestions about lowering the seat.  But can anybody answer my first question, which is how exactly the clearance is measured to determine if you meet the ChampCar rules (especially when the center and side bars are higher than the main hoop)?  

 

Thanks again.

 

 

Tech would have to answer that question specifically.  But the rule is below centerline of main hoop, and no matter how you spin it, that driver is above the main hoop full stop, not just the centerline.  Your options are, cut the cage out, lower the seat, or find shorter drivers.

 

I'm 6' 2".  I know the struggle.

[Billy]

We're a team of newbies also, and are following this thread closely as we are having similar issues in our Miata, but think we are okay.  We're continuing to measure and double check everything.  IDK what seat you have but we have the TDR ultrashield 16" seat with the TDR low mounts.  This gives you about a 20 degree lean and puts you about as close to the floor as you can get and provides a bit of lean which helps with clearance.  The top of our seat back is between 3-4" below our main hoop.  We're still considering a floor pan drop, but then there's the struggle of doing that after the cage is already in.  Our main hoop scrapes the inside of our Treasure Coast fiberglass top.  Honestly it's so frustrating but hoping it's worth it...my next car will be much bigger if I build another one.  It's a struggle.  Good luck!

 

Edit:  Just wanted to add, you're probably going to have the exact same problem we're having with your harness bar, if you drop your seat the bar might be too high and you won't be able to get the correct angle on your belts.

Edited August 23, 2021 by Billy

[AlpineMarch]

30 minutes ago, Billy said:

We're a team of newbies also, and are following this thread closely as we are having similar issues in our Miata, but think we are okay.  We're continuing to measure and double check everything.  IDK what seat you have but we have the TDR ultrashield 16" seat with the TDR low mounts.  This gives you about a 20 degree lean and puts you about as close to the floor as you can get and provides a bit of lean which helps with clearance.  The top of our seat back is between 3-4" below our main hoop.  We're still considering a floor pan drop, but then there's the struggle of doing that after the cage is already in.  Our main hoop scrapes the inside of our Treasure Coast fiberglass top.  Honestly it's so frustrating but hoping it's worth it...my next car will be much bigger if I build another one.  It's a struggle.  Good luck!

 

Edit:  Just wanted to add, you're probably going to have the exact same problem we're having with your harness bar, if you drop your seat the bar might be too high and you won't be able to get the correct angle on your belts.

 

Thanks again for the replies.  At least we're not the only ones!  Also, it had occurred to me that having to lower the seat  could easily require the harness bar to be moved too.  We'll just have to see, and I am also concerned about how difficult it would be to put in a drop floor with the cage already welded in.

 

Since this issue could keep us from passing tech, I submitted a Tech Desk ticket asking how the measurement works.  So I guess we'll see what happens.  Thanks again.

[Clifford Beisler]

21 hours ago, AlpineMarch said:

Our cage was built by a very experienced cage builder

Did you recently pay for the cage to be built? 

 

[Billy]

IDK what you decided to do, but we decided to go with a drop pan.  We took a cap to a spray can and marked some lines on it with some tape.  3/4" for ChampCar (half the thickness of the 1.5" tubing), and 2" for Lemons (which requires 2" from all bars).  I'm 5'9" and would be borderline under the hoop.  Our 6' driver is nowhere close.  We will never make the clearance for Lemons, and our 6' driver will be close but think he will clear for Champ.  The drop pan will gain us 1.25" (went with https://www.advanced-autosports.com/products/spec-miata-floor-drop?_pos=1&_sid=ad72e5e7a&_ss=r ).  In addition, we can move the seat closer to the center of the car which will give us a bit more room (hoping for another 0.25-0.5").  We also have to figure out what to do with our door bars (seat will likely not drop as low as possible due to door bar being formed around seat), and our harness bar is also going to be an issue.  We figure the drop pan makes everyone safer.  I'm still not sure how people are running a top with standard height drivers (<6ft), as our main hoop is rubbing against the top.  Maybe people are putting the main hoop slightly more toward the front of the car giving additional height?  Not sure how this adventure is going to go with a cage already being in, but will let you know once we get it done which will likely be a month or so out at a minimum as none of us can weld it.

 

The first pics are the 6' driver, second pics are the 5'9" driver.

Edited August 28, 2021 by Billy

[TiredBirds]

That bar to the left of your head looks too close and too low. Is that your race seat? I'd run a full containment seat That way your helmet won't be hitting that bar on every hard turn...Once you put the padding on it you'll be 1/2" away. 

[TimS]

Seat and driver size should have been taken into account before cage was started and definitely before everything was welded together. I have heard drop pans and tiny seats are the norm for most miatas. The door bar will surely need to be fixed/moved. It is way to close. Full containment/ halo seat a must. Tough to get it all in that little car. May need to modify the tunnel also to move seat more to the center 

[TiredBirds]

5 hours ago, TimS said:

Seat and driver size should have been taken into account before cage was started and definitely before everything was welded together. I have heard drop pans and tiny seats are the norm for most miatas. The door bar will surely need to be fixed/moved. It is way to close. Full containment/ halo seat a must. Tough to get it all in that little car. May need to modify the tunnel also to move seat more to the center 

the seat must be in BEFORE you do the cage.... 

[Billy]

I PM'ed the OP of the thread with some information, but since we both were having the same issues I wanted to share what we did to fix ours.  We wound up getting the advanced motorsports drop pan https://www.advanced-autosports.com/products/spec-miata-floor-drop - it was a pain to put in after the cage was installed, but can be done.  We decided to do it ourselves after being quoted some outrageous prices on fab work for this.  It took 8+ hours for 3 of us to get it cut and tacked in (none of us are professional fabricators).  We were able to do it without removing/touching any parts of the cage. 

 

The pan drop does a few things - adds 1.25" additional clearance baseline, provides a completely flat seat mounting surface, and allows you to shift the seat much closer to the center of the car where the highest part of your cage is.  You can see from just the back of the seat where the belt goes through how much space we gained.  Also note the tallest driver (6 ft) is now ~1" inside the main hoop.  We don't have the seat permanently mounted yet, but we can get even more clearance by adding more lean.

 

For any other newbies that find this thread in the future - do the pan drop before the cage.  If you don't do a pan drop, do not run a hard top and run a much larger main hoop.  Use an aluminum seat, mount it on the floor.  If I bought another seat, I'd buy a kirkey containment seat.  Mount seat closest to center of car, and mount it and the drop pan before doing cage.  If you screwed up like we did and put your cage in first, you can fix it, just it's a huge pain to do so.  After dropping the pan, adding a new harness bar is going to be required as it is no longer in the correct position.  After our adventure, I think every Miata needs the pan drop - it's going to give everyone more space from the bars and gives you way more freedom for positioning the seat.  I wouldn't build a Miata without one.  Feel free to PM me if you get in this situation and I can provide more details, pics etc.

[smitham32803]

Now you need to re-adjust your harness attachments...

[AlpineMarch]

Just to close the loop on this thread, here's an update after some additional changes to get more clearance:

• We weren't confident about either passing tech or safety with the seat in the position in the original post above (fiberglass Sparco WRC-R FIA-rated seat, and was mounted on Planted miata-specific brackets, without sliders, bolted to the stock mounting holes on the floor).
• We didn't have time to  put in a drop floor pan before our first race (Dec 4-5 at VIR North), so we ended up removing the two seat mounting "humps" in the floor that contain the stock mounting holes for the stock sliders.  We just drilled out the spot welds for the mounting humps and pried them out, which left us with a flat-ish floor to bolt the seat to.  
• However, the Planted brackets wouldn't work for that because the rear mounting holes were directly beneath the back edge of the seat, and would prevent us from getting a bolt through the mounting holes, so we had a local fabrication shop make some custom brackets with longer extensions at the rear so the mounting holes could be drilled further aft of the seat. 
• We then just drilled holes through the floor and bolted the seat directly to the floor, which gained us almost an inch more clearance. 

That ended up working out well, and we passed tech at VIR no problem.  We ran our first race (8+7 hour enduro) and the car ran well.

 

However, that's not the end of the story because we still can't get bigger drivers into the car, so over the winter we're looking at a drop floor kit.  Although the Advanced Autosports and 5x Racing kits both look fine, we'd like to put the seat on sliders if possible, so the tall and short drivers can change out at will.  Guarino-Watson Racing (another ChampCar team) has an impressive looking kit (https://docs.google.com/presentation/d/1eYNphsjCqokin5Y5AlKrlJUBJDrrN7lXwPp5qrnZIeY/edit?fbclid=IwAR2BylHhg5Dv_e08mqu4bersgyd-j8ikt_7OC0UuFoXmc8SjFhnZcPMor3U#slide=id.g6e1710594c_0_36) - I'd be interested to hear from anybody who's used one. 

[QuaTTro]

@AlpineMarch I'm also looking into new seat sliders.  Have you picked which ones you plan to use?

[CoachMK21]

@AlpineMarch I found this thread that C Watson posted in about his initial product and someone else posted their progress with it too.  Maybe you've seen this already.  I've been toying with putting a drop seat in my spec miata, but would like a slider if I decided to do some ChampCar races with it too.

 

https://www.miataturbo.net/race-prep-75/floor-drop-kits-101825/

[Fitsbain]

one thing I know some teams do, is recline the seat slightly (helps tall drivers) and then put the sliders on an incline. This allows the short drivers to move forward and up a bit.

[TimS]

I’m adding a set of Sparco sliders to my seat this season. 

[enginerd]

19 hours ago, AlpineMarch said:

However, that's not the end of the story because we still can't get bigger drivers into the car, so over the winter we're looking at a drop floor kit.  Although the Advanced Autosports and 5x Racing kits both look fine, we'd like to put the seat on sliders if possible, so the tall and short drivers can change out at will.  Guarino-Watson Racing (another ChampCar team) has an impressive looking kit (https://docs.google.com/presentation/d/1eYNphsjCqokin5Y5AlKrlJUBJDrrN7lXwPp5qrnZIeY/edit?fbclid=IwAR2BylHhg5Dv_e08mqu4bersgyd-j8ikt_7OC0UuFoXmc8SjFhnZcPMor3U#slide=id.g6e1710594c_0_36) - I'd be interested to hear from anybody who's used one. 

That kit looks great. I didn't know they dabbled in miatas. Knowing Will, I would buy it in a heartbeat if I ran a miata.

Edited December 22, 2021 by enginerd