Exocet Chassis: Sport or Race?

Hi everyone,

I picked up an Exocet sport chassis from a private party last fall and plan to start my build in the spring. The guy never started on it, and the chassis is unpainted, so I have a clean slate to work from. Exomotive sells a sport to race conversion kit that can be welded in, and I'm considering doing so. My chassis already has the steel floors.

I plan to use the car occasionally around town and also for track days. I don't have concrete plans to race it, but I'd like to have the option down the road. 

My primary concern is ingress / egress. I'm 32 years old, 6' 0", and 160 lbs, so I'm not worried that I couldn't physically do it. I'm just concerned it will be annoying to fit through the opening every time vs having the fully open cockpit. On the other hand, maybe the top bars would be handy to grab for lowering / raising myself in and out of the seat. 

Safety-wise, is the race chassis that much better, or is the additional cage mostly to satisfy race organization rules?

Is there anything else I'm not thinking about?

Does anyone have experience with both chassis?

Thanks!

I'm envious! Sounds like fun.

I don't have experience with cars on the street, but for race cars I've never found the bars of the cage to be that difficult to navigate, and that's with a race suit and helmet on. I'm almost the exact same size as you but nearly 10 years older and as long as you've retained some flexibility I think it's easy to pop in and out of the cage. And like you said the cage would make a convenient handle given the open top.

If I was to build an Exocet, which I would like to do some day, I would probably do the Sport. I'm not sure the additional bars would add much safety to street driving. But that's just a gut feeling.

The Race will give you considerably better protection in a crash. That's really the whole point. It's probably twice as strong in side impact and of course much better in roll.

We actually have both chassis in-house right now, although I've never driven a Race. We sold our Sport in order to build a Race.

Safety-wise, here's a couple of things I've thought about:

If you imagine a t-bone incident on the street with regular vehicle, say a truck or SUV,  I tend to think the race chassis would be more likely to stop the bumper, rather than the vehicle driving right over the side and into you.

Another thing people don't think enough about is the potential for hitting your head on metal tubing.  OEMs worry about head injury and use interior trim pieces to reduce injury.  In a significant accident, your seat will not necessarily stay stationary (if the forces can bend tubing, what do you think they do to your seat, brackets, floor) .  Hitting your head on metal tubing is bad.  A concussion, let alone splitting your head open can ruin the rest of your life or a significant portion of it.  I'd argue the exocet tube locations are a lot better than most Miata's with a roll bar.  That said, I think it makes sense to install SFI padding on the tubes where there is a reasonable chance of your head making contact.  Helmets are designed to prevent your head from cracking open, but they do very little to prevent other types of head/brain injury.

We've had an Exocet go into a tree sideways. Focused impact right on the side tubes. The driver got extremely lucky, and it was clear that a Race would have been a much better choice for that accident because it adds another DOM tube to take the impact plus it has lateral bracing where the main tubes do not.

Obviously, any tube in any vehicle that you can strike with your head should be padded.

I'm never against more safety in a toy.

I also still walk a little off from a sportbike wreck at Hallett 11 years ago.

Keith Tanner said:

We've had an Exocet go into a tree sideways. Focused impact right on the side tubes. The driver got extremely lucky, and it was clear that a Race would have been a much better choice for that accident because it adds another DOM tube to take the impact plus it has lateral bracing where the main tubes do not.

Was the intrusion much, or any, worse than it would have been in a cageless Miata?

Gieb said:

...I don't have concrete plans to race it, but I'd like to have the option down the road...
 

...Safety-wise, is the race chassis that much better, or is the additional cage mostly to satisfy race organization rules?...

Are there any sanctioned racing series that the Exocet is eligible to participate in and would require it to have a cage?

Driven5 said:

Keith Tanner said:

We've had an Exocet go into a tree sideways. Focused impact right on the side tubes. The driver got extremely lucky, and it was clear that a Race would have been a much better choice for that accident because it adds another DOM tube to take the impact plus it has lateral bracing where the main tubes do not.

Was the intrusion much, or any, worse than it would have been in a cageless Miata?

I have seen similar intrusion in Miatas, but without knowing the speeds it's hard to say for sure. Since we're comparing Exocet Sport to Exocet Race, it's pretty easy to say what the difference would be so I'll just leave it at that.

If you're going to get in an accident, the Race is a better choice. If you're not going to get in an accident, it doesn't matter.

Keith Tanner said:

If you're going to get in an accident, the Race is a better choice. If you're not going to get in an accident, it doesn't matter.

You're basically saying the equivalent of a caged Miata being safer in a street accident than an uncaged Miata.  It's just not that simple, and I'm surprised you would even consider stating as such. Each layout necessarily involves safety trade-offs, the effects of which vary widely depending on the specific circumstances being considered. Assuming not using a helmet on the street, there are some types of street accidents in which the caged would be safer, some in which the uncaged would be safer, and some in which it would make no difference to the outcome. Especially based on the tube-to-head proximity in this picture, I honestly can't say that I understand your assessment (assumption) in regards to the Race chassis necessarily being the safer option for unhelmeted heads in any given street accident...Regardless of what padding is used on the tubes.   

That being said, I'd say if the car would see more track time than street time, then yeah definitely Race upgrade.  Especially if it would also be getting trailered to the track.  But if 'occasional around town use' and transit to/from the track (if not trailering it) time is greater than on-track time, then leaving it as a Sport might not actually be such a terrible idea either.

Keith Tanner said:

Obviously, any tube in any vehicle that you can strike with your head should be padded.

Emphasis added above. You say that, but how many Miatas with roll bars have any padding (10%?), let alone SFI spec installed.  :)  I think I've literally never seen a picture of an exocet which had padding installed.

Driven5 said:

Keith Tanner said:

If you're going to get in an accident, the Race is a better choice. If you're not going to get in an accident, it doesn't matter.

You're basically saying the equivalent of a caged Miata being safer in a street accident than an uncaged Miata.  It's just not that simple, and I'm surprised you would even consider stating as such. Each layout necessarily involves safety trade-offs, the effects of which vary widely depending on the specific circumstances being considered. Assuming not using a helmet on the street, there are some types of street accidents in which the caged would be safer, some in which the uncaged would be safer, and some in which it would make no difference to the outcome. Especially based on the tube-to-head proximity in this picture, I honestly can't say that I understand your assessment (assumption) in regards to the Race chassis necessarily being the safer option for unhelmeted heads in any given street accident...Regardless of what padding is used on the tubes.  

 

That being said, I'd say if the car would see more track time than street time, then yeah definitely Race upgrade.  But if occasional around town use and transit to/from the track (if not trailering it) time is greater than on-track time, then leaving it as a Sport might not be such a bad idea either.

This sounds very much like the same sort of justification used for why you shouldn't wear seatbelts, because sometimes it's better to get thrown free. I didn't insert disclaimers here about "on average" or "barring a very specific set of conditions". The Race is stronger (I don't think I need to prevaricate there). The Race offers as much or more protection against outside intrusion from any direction than the Sport. Depending on how you sit in the car, the halo of the Race may need to be padded. It's pretty unusual to have a seat/driver configuration that puts the roll bar of the Sport within head strike range.

For example, here's our own shop car. The driver here is 6' tall. Even the halo of the Race would be pretty far away, quite probably out of strike range.

Here's the result of a 4th gear side hit on a tree. Pretty much the worst possible scenario. The driver was bruised and sore, but got out by himself. You can see that if he'd hit a bit further back it would have been really bad news. I've seen this same hit on a Miata, it was also not pretty. But a Race would have added an extra 0.095" tube to the two 0.083" tubes that took the hit. The Race also adds a lateral tube connecting to another 0.095" member on the other side, right at the point of impact in this particular accident. That's a pretty significant increase in structure for this hit. I've also seen a straight on front hit on a tree, Race vs Sport would have made no difference in that case.

Keith Tanner said:

This sounds very much like the same sort of justification used for why you shouldn't wear seatbelts, because sometimes it's better to get thrown free. 

Not even close, LOL.  The fact that there is more to safety than point impact intrusion is far from being based on anecdotes and anomalies.  Halos on racing seats to help keep even helmeted heads away from padded cage tubing, let alone unhelmeted, and side/curtain airbags in production vehicles to help keep unhelmeted heads  from impacting the interior in an accident also all exist for very real and legitimate reasons.  

Honestly, I don't necessarily disagree with your conclusion, but I also don't automatically agree with it either.  My point of disagreement is that it's an unverifiable and subjective opinion, being paraded as an absolute and objective fact.  

Does the picture showing the relative position of a 6' driver's head and the tubes help make my opinion a little more objective and a little less subjective?

In reply to Keith Tanner :

Not necessarily. The human body and seat belts are deceptively elastic when subjected to collision forces, and there is a notable inconsistency between what yours would seem to potentially indicate and what numerous others show.

Maybe the benefits of a cage in the above impact would have been mixed as it collapsed in toward the drivers head. Maybe engineering the lower chassis to better transfer loads laterally in a side-impact without the use of overhead bars would have been even safer yet?  Maybe there is an unintended optical illusion in the pictures?  Maybe you took extra pains to get the seat lower than others?  Maybe there has been a roll bar/cage height change?  Maybe a disproportionate number of Exocet buyers are just hulking beasts of people?  Whatever it is, I personally think considerably more data would be required before any reasonable conclusions could be drawn relating to general street safety.

There are a lot of very poor seat installations out there, no question. I feel confident using our car as an example because I know it. I know what the seat is, I know how it's installed, I've driven it. I do understand the elasticity of both the human neck and belts, but it is not infinite. In order for the driver of our car to hit his head on the bar, his head would have to come off his body. I know this because I've sat in it, not just from looking at pictures online. And I assume that you would want a good seat installation with attention paid to driver positioning and head clearance as a basic requirement.

I mean, seriously, how is this not enough clearance? That driver is 5'10", which is average for North American males. There has not been a change in the height of the bar for Exomotive frames.

I will point out that Exocet drivers probably are, on average, on the larger end of the continuum simply because Exomotive is based in Atlanta. I know from having to order t-shirts for events that I use a different size range for Atlanta vs, say, California. And I also know from years of questions that Miata drivers are all 6'2" and trying to fit under a roll bar :) 

Could the lower structure of the red car have been better engineered to deal with the crash in question? Possibly, there's a distinct lack of structure between the side bars of a Sport. But that's not the question, the question is whether at least 33% more structure PLUS the lateral tubes would have been preferable. I have a really hard time saying no in that case. It's not like we're getting into crush area, that's intrusion pure and simple.

I'm going to continue to suggest that the Race is, in the majority of cases, the best choice if safety is a factor. I will suggest that anyone who builds one pays close attention to seat mounting and location, as they should in any build of any car. This is based on personal experience and from spending enough time in a Sport to decide I'd prefer a Race. A lot of people choose the Sport for various reasons of their own and I will support that, but if safety is mentioned I'm going to recommend the one that is built with surviveabilty as a higher priority, and that's the Race.

Thanks for all the commentary everyone! I think I'll be ordering the race chassis upgrade shortly based on safety alone.  

Driven5 said:

Gieb said:

...I don't have concrete plans to race it, but I'd like to have the option down the road...
 

...Safety-wise, is the race chassis that much better, or is the additional cage mostly to satisfy race organization rules?...

Are there any sanctioned racing series that the Exocet is eligible to participate in and would require it to have a cage?

Driven5 - I may be incorrect, but I believe almost all wheel to wheel racing series require a full cage. I'm also quite sure the Exocet can participate in most any series with simple class categorization by power to weight ratio. I know it can run in NASA. I think it should also be able to participate in World Racing League. Not sure about others. Given the aerodynamic issues of the Exocet, I doubt it would be very competitive except on very twisty tracks, but I'm not too concerned about that.

Its going to be classed with other cars of similar power-to-weight, BUT, those same cars have vastly better aero. At anything over 100 mph or so, it may as well be dragging a parachute.

A buddy built a 500-hp Locost and said the he absolutely creams his buddy's Evo... up to 100 mph. Above that he said, his buddy blows right past him due solely to aero differences.

In reply to Keith Tanner :

Is seat mounting and positioning really up to each individual builder on the Exocet?  Is there no standard seating arrangement that the car was designed to 'properly' accommodate? 

I'll agree that specifically as yours appears built, it should be about as 'safe' as I'd expect possible with the overhead bars added, regardless of the mixed bag of pros/cons I feel the overhead bars generally provide on the street.

In reply to Gieb :

Yeah, if w2w is the type of racing you plan to do with it, then incorporating the cage now is probably the way to go regardless. 

The race chassis is REALLY hard to get into - I have a halo seat so it's not helping matters. 

If you're driving it on the street you're going to need to wear a helmet - no matter how you pad the roll bar. Brain boxes lose when you hit them onto even high density rollbar padding.  

Driving a "race car" on the street is never safe - it's never going to be safe. I've done it a lot, but be realistic: exocet's lose the mass war, they lose the height war, they have virtually no crumple zone, and your upper torso has nothing between it and what T-bones you. Full-bodied cars have a ton of advantages. It's not going to stop me from driving mine, but know the facts. I mean - a motorcycle is worse in all regards, but tons of people still ride them. 

Some interesting stuff in this thread.  :)  That's a nasty crash side crash into a tree for the exocet!  That type of hit is often fatal in any type of vehicle and I agree the driver should be very thankful he wasn't more severely injured.  Considering the hit, the floor structure actually held up reasonably well and the bars connecting to those which deformed at the side seem to have remained reasonably true.  I think it's difficult to argue against the idea of increased safety from the race chassis, but I agree that people need to be much more aware of the need for bar padding to protect one's head and not all cars are put together with the same consideration as the FM exocet.  I think Accordianfolder makes some good points.  I tend to think Warren from Exomotive should feel good about his work.

Compare that to a ND Miata hit at a mere 35MPH, which had let's say 6" of penetration compared to say 12" with the exocet at a higher speed.  That said I wouldn't have wanted to be in the ND without the side air bag.  Watch at 1:52 here:  https://www.youtube.com/watch?v=gE6cz4cR5zw

Then look at these and try to imagine what a crash with an NA Miata, perhaps with a roll bar might look like.  :)  

1998 Corolla front offset crash into a 2015 Corolla at 40MPH: https://www.youtube.com/watch?v=zxDHuthGIS4

Caged 626 spun back first into inside wall, maybe 60MPH:  https://forum.champcar.org/topic/17135-learning-moment-crash-damage/

Having owned an Exocet Sport, if I were to order another it would be a race chassis. Yes, I would wear a helmet whenever I drove it, and I would be happy doing so. 

IMO the sport is a great "motorcycle" experience without being on a bike. The race is much, much safer overall and is what I would prefer if I were to do it again.

EDIT: I'm 6'5" and would still go with the race despite the ingress/egress difficulties. You're not driving this thing every day.

Driven5 said:

In reply to Keith Tanner :

Is seat mounting and positioning really up to each individual builder on the Exocet?  Is there no standard seating arrangement that the car was designed to 'properly' accommodate?

It is. Trace the history of the Exocet back to its roots and you have a cheap and cheery thing to do with a free MOT failure in the UK. The builder was expected to use the entire car, including seats. When Warren re-engineered it for the US, it was massively improved but some of the concepts remained. One of those is that you use the factory seats - although almost no US builders do. There are two cross bars that you're intended to bolt the seats to, that's it. Those two 1" square tube bars are also the only lateral structure between the front and rear bulkheads in a Sport, by the way.

The good news about Exocet safety is that it's far better than an Atom!

I've seen an NB Miata crash that was similar to the Exocet one. The car came through our salvage operation. The hit was on the passenger's side, which would have been a bad place to be that day. Without knowing more it's impossible to say if it would have better or worse, but it's a worst-case hit in any vehicle.

accordionfolder said:

The race chassis is REALLY hard to get into - I have a halo seat so it's not helping matters. 

To add a bit more information - I'm 5'11" 175lbs - so not a big guy

I'm 6' 200lbs. I was able to get in and out of a race chassis pretty well with freshly broken and dislocated shoulder. So I ended up ordering a race and don't regret it at all as I build it.