Anduril Frame

[brian]

Just began the reassembly of my car and thought it would be fun to post a picture of the newly powder coated frame. It was so seriously wounded at the Runoffs, I had to do a frame up. There is a significant brace that goes over the engine to triangulate the rear section; you can see the brackets on the roll bar. The steering column uses an additional bearing in front of the roll bar to clear my feet to allow for left foot braking. The fire bottle and master cylinders are under my knees. While not obvious from this picture, there is considerable distance between the engine and roll bar allowing for distribution of weight and easy engine removal. An engine can be on the ground in 15 minutes.

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[jstoezel]

Hi Brian:

Thank you for sharing the picture.

While not obvious from this picture, there is considerable distance between the engine and roll bar allowing for distribution of weight and easy engine removal. An engine can be on the ground in 15 minutes.

Can I ask what is the distance between the transmission mount and the main hoop plane? And from the main hoop plane to the beam mount? I found that my car has a wheel base of 83"+ (which I believe is close to the maximum allowed), the engine is right against the firewall (and the firewall gets very warm, and it needs to be removed to get the engine out), but I still have limited leg room. The master cylinders are installed inside the frame though, which brings the front of the pedals back probably 10".

Also in the picture you've posted the floor seems different than other FVs I've seen... From this angle it seems flat from the fuel cell to the front hoop, but looks like it's V shapped and raised at the front (the same way modern F1 are built). I though there is a 1" rule deviation for the bottom... But again that could be the angle of the picture.

Reading the GCR, I always thought tubing had to be used to connect the front facing brace (for the main roll hoop) back to the roll hoop/main frame. From the picture I guess gussets are allowed too.

Last thing I've noticed is that there doesn't seem to be any built-in caster on the front mount. I guess you must be using shims to set the right amount?

Either way, very interesting.

[brian]

I gave up my career in the NBA in exchange for very short legs, the roll bar is forward of the typical location by just over 4.5". Over the years, the floor rule has changed a lot. Currently it concentrates on 1' variance relative side to side and not to exceed the width of the chassis. The frame is flat from the centerline of the front axle to the rear engine mount. The traditional rear frame slopes up similar to many vees on the market.

When the rule regarding roll bar braces came out, a 1/4" gusset was an allowed variation to the tube. Many folks that had Lynx's, had serious shoulder issues with the tubing approach.

[smsazzy]

Very nice! It looks so clean.

[hardingfv32-1]

1) So per C.8.F, if I ONLY "attach" the undertray on the ends (and maybe middle?) you can have more than 1" of curvature?

2) While speed of engine removal is interesting, there are other design criteria worth optimizing at the expense of the easy of servicing the engine/transmission. In 25 years of FV racing I have never needed to replace the engine/transmission between sessions of a race day. I always thought easy of remove would come in handy someday but it never has, so it has moved to the bottom of my list of design priorities. My latest car takes 5-6 hrs.

Brian

[brian]

Brian, I think that paragraph was written to prevent diffuser trays that everyone was trying at the time. There are several vees with curved bottoms. If one looks at the Protoform P-4, the floor is very narrow, just a couple of inches, with curved body sections leading up to the sides. My engine changing philosophy comes from many years working on British sports cars which called for engine changes virtually after every session

[hardingfv32-1]

Yes, very little floor and all body.

The rear diffuser with the require downward turned end plates is the challenge, C.8.G, but.... The diffuser has the normal upward curved shape but the end plates are 1" thick (otherwise typical end plates) that have a "horizontal" flange at the bottom edge. This flange mounts to a horizontal frame member (parallel to the ground). This tray "edge" is thus horizontal.

It boils down to what is a downward turn edge. Is the end plate an "edge" in itself or is the bottom to the end plate the "edge"?

C.8.G. Transmission undertrays for cars with a rear subframe shall be no
wider than the subframe or no more than 1/4 inch wider (on each
side) than the subframe when the undertray has an upward turned
edge that facilitates mounting the undertray to the subframe or
that facilitates mounting the body to the subframe or 16 inches,
whichever is wider. For cars without a subframe, the tray shall be
no wider than 16 inches and shall not deviate more than 1 inch
from the horizontal plane. Undertray must be firmly attached and
have no downward turned edges.


Brian

[smsazzy]

What rear diffuser? Am I missing something in this picture?

[hardingfv32-1]

Yes, as always...

Brian M stated: " I think that paragraph was written to prevent diffuser trays"

Brian

[smsazzy]

And as always you have turned a post into a debate.

What does this have to do with Brian posting a picture of his car? He doesn't have a rear diffuser, nor do any other mainstream vees.

[qposner]

And as always you have turned a post into a debate.

What does this have to do with Brian posting a picture of his car? He doesn't have a rear diffuser, nor do any other mainstream vees.

This should be fun.

[Rolling Stone]

And as always you have turned a post into a debate.

What does this have to do with Brian posting a picture of his car? He doesn't have a rear diffuser, nor do any other mainstream vees.

This should be fun.

WE need to Diffuse this situation

[jstoezel]

Hi Brian:

Thanks for the reply. This is a general question, not related to your chassis though. In other FV series, like in the UK or in Australia, it seems like rear roll hoop bracing is preferred, as opposed to the front roll hoop bracing imposed by the GCR.

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9.4.5.C.1 The main hoop must have 2 forward braces extending from the hoop and attached to the frame, monocoque, or front hoop.

As a driver I think it is safer to have a rear bracing structure, as it opens the cockpit, and it would be easier to come out of the car in most situations. At the same time theres a few cars running in SCCA with what could be seen as rear bracing. Why is front bracing promoted by the GCR?

Like a FC Van Diemen which falls under similar roll bar requirements as FV

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Also, could somebody provide some history with regards to appendix I (2007 roll cage rules)? The main difference I see is the fact that the number of bends on the roll bar is now 4 (or you need to use a bigger tube diameter). The rest seems similar to the rules enunciated in 9.4.5.C.1...

I gave up my career in the NBA in exchange for very short legs, the roll bar is forward of the typical location by just over 4.5". Over the years, the floor rule has changed a lot. Currently it concentrates on 1' variance relative side to side and not to exceed the width of the chassis. The frame is flat from the centerline of the front axle to the rear engine mount. The traditional rear frame slopes up similar to many vees on the market.

When the rule regarding roll bar braces came out, a 1/4" gusset was an allowed variation to the tube. Many folks that had Lynx's, had serious shoulder issues with the tubing approach.

[brian]

Can't really speak to the "down under" philosophy other than to say that with a true 4 corner car the extra stiffness for the rear is an advantage not needed with zero roll. The forward mounted braces accomplish several things. Engine swaps are easier; some forward braces provide additional head protection from side impact; and provide additional strength and a deterrent to digging in, if you are upside down and going backwards. The original incident that generated the brace rule involved a Lynx that had a collapsed roll bar when impacting something going backwards forcing the side bars down.

The HANS devices are of little help in the case of side impact. The Anduril has bodywork over these braces to provide side head restraint.

[jstoezel]

While I agree with most of the points you listed, I would think that going backwards on the rollbar, a rearwards structure would work better, since the members would work in extension, not compression, and there would be no possibility of buckling. Hitting forward with the rollbar would get the rearwards members to work in compression - which again is bad. Maybe that's why SCCA has elected to use front bracings, to better protect forward crashes.

Can't really speak to the "down under" philosophy other than to say that with a true 4 corner car the extra stiffness for the rear is an advantage not needed with zero roll. The forward mounted braces accomplish several things. Engine swaps are easier; some forward braces provide additional head protection from side impact; and provide additional strength and a deterrent to digging in, if you are upside down and going backwards. The original incident that generated the brace rule involved a Lynx that had a collapsed roll bar when impacting something going backwards forcing the side bars down.

The HANS devices are of little help in the case of side impact. The Anduril has bodywork over these braces to provide side head restraint.

[hardingfv32-1]

1) First you are talking about an accident, you have no idea what direction you will be traveling when upside down. There is always going to be a chance that the roll bar snags on something and breaks/bends above the bracing. If you are worried, then choose a thicker gage or diameter to calm your fears. You are engineering for a random event of unknown magnitude, so good luck. The fact is that our current specs have served us well to this point.

2) The Van Diemen and other similar designs are kind of trick. They form a pyramid with an included angle of 30 degrees, thus satisfying the rules. Neither bar is vertical, but the front bar is called the brace. There is no requirement for the main roll-bar to be vertical.

3) I can see where the quality of the chassis attachment point of a rear facing brace could be questioned, especially with some DIY chassis. Looking at the Aussy FV, what is going to prevent the mount point (at the chassis) of the top rear facing roll-bar brace from buckling? Can you depend on the transmission being there? Does the car have a frame under the engine? How strong is that going to be with a offset joint at the main hoop? Will the top frame member that the rear brace is attached to (above the transmission) buckle just beyond the lower rear facing brace? This is not a simple force path to evaluate.

Brian

[jstoezel]

1) First you are talking about an accident, you have no idea what direction you will be traveling when upside down. There is always going to be a chance that the roll bar snags on something and breaks/bends above the bracing. If you are worried, then choose a thicker gage or diameter to calm your fears. You are engineering for a random event of unknown magnitude, so good luck. The fact is that our current specs have served us well to this point.

Absolutely. It's interesting how the problem is approached from different parties though, history of accidents maybe? Both forwards and rearwards braces used at the same time may work as well, I wonder how that would compare weight-wise with a bigger diameter/thicker wall thickness on the main hoop.

2) The Van Diemen and other similar designs are kind of trick. They form a pyramid with an included angle of 30 degrees, thus satisfying the rules. Neither bar is vertical, but the front bar is called the brace. There is no requirement for the main roll-bar to be vertical.

Alright I see, I guess the BRD FV falls into this category too.

3) I can see where the quality of the chassis attachment point of a rear facing brace could be questioned, especially with some DIY chassis. Looking at the Aussy FV, what is going to prevent the mount point (at the chassis) of the top rear facing roll-bar brace from buckling? Can you depend on the transmission being there? Does the car have a frame under the engine? How strong is that going to be with a offset joint at the main hoop? Will the top frame member that the rear brace is attached to (above the transmission) buckle just beyond the lower rear facing brace? This is not a simple force path to evaluate.

Brian

The triangulation on this Rapier FV frame looks intricate enough that it may well have been computer designed. Who knows, they may have run an FEA study (that also integrated the transmission and engine) that addresses your concerns. I didn't find the information on their site though: http://www.volksengineering.com

[brian]

Several years ago, the CRB was confronted with an issue of production car, single hoop roll bars digging into the soft ground and crushing the driver. This was not an esoteric conversation but a reaction after an fatal incident. At that time, a very unpopular decision was made to require full width rear hoops or full cages. It took us years to finally agree on the language. Every few years, Formula car roll bars become an issue and one school of thought proposes full cages for open wheel and sports racing cars. Needless to say, this goes over like a roast pig at a Jewish wedding. Fortunately, we have not had any fatalities recently. The engineering of crash containment is very complicated and not very well understood. I think that explains all the opinions and theories one sees in the cars out there. Many times, asthetics or weight issues get in the way of safe design. That said, I think this is a good time for everyone to make sure they have used the correct SFI approved padding and have at LEAST the 2 " clearance required by the GCR. We saw driver's heads strike roll cages 8" away in Sprint cars, so remember our bodies stretch a lot. Be careful out there.

[hardingfv32-1]

"Triangulation on this Rapier FV frame looks"... Looks, from an engineering perspective, terrible!

Many of the braces end at poorly formed joints (nodes) and and others end in the center of straight runs. A lot of the bracing probably is just for side protection, so maybe it doesn't matter.

Hanging the engine from a top frame section can be useful, but note how poorly it is implemented in this case. The brace coming from the mid point of the boll bar does not make it to tube that is used to mount the front of the transmission. The top cockpit frame members going to where this brace is located have a bend in them where they attach to the roll bar. I am assuming there is no frame under the engine. Looks like the engine must be remove downward.

Brian

[lbaconll]

Very interesting article! Been following the thread. Not being an engineer, but having some common sense, I have always added roll bar height to My cars. Case in point, Vector GB4 I endoe'd and flopped down roll bar down at Thunderhill a cuople of years ago. I did not like the Roll bar height of the standard car so being a bit tall for a Vee driver (6'4") I had Huffaker Eng add 8" to the main roll hoop. Lots of comments about the car looking like an airport luggage cart etc, BUT, when I had the "big one" I firmly believe that at the least the tall bar saved Me from a possible spinal injury, and probably saved My life. I remember sitting in the chassis upsidedown and thinking how close Mother Earth was while I was suspended from the belts, I doubt more than 2" was the gap....... At rest there was at least 8 or9" above My helmet belted in! The Vector has both front and rear main hoop bracing and in fact the crash investigators from SF Region were very impressed as to how well the structure held up.
It is Your butt on the line. I will sacrifice a little astehtics and "aero" for the exponential increase in survivability and damage control a taller hoop affords. So much so that My current Mysterian M2B also benefits from a 6" extension done by Ron Chuck that looks very Swift DB1 like.
My 10 cents. Race well, be safe, go fast!

[sabre1]

Jstoezel,

Just curious, but do you have any other pics of the Rapier(?) car, especially the rear suspension? From the pic you posted, it looks like they have an interesting set-up - something I don't recall seeing before...

I agree with Brian H. about the rear of the car. It looks like the engine and trans are basically hung from the bracing off of the back of the main roll hoop, and with what looks like 1" square tubing extending backwards.

-Jim

[jstoezel]

Hi Jim:

I don't have more pictures, just a video of it. The system they use at the back is from airbag man: http://www.airbagman.com.au/lightvehicle.html# ("on-air" I believe). Here's the video of it in action on the Rapier: http://www.youtube.com/watch?v=c5Xd0G6i ... re=related

Doesn't this seem a bit on the soft end? The guy seems to be getting 1/2" of travel with one push of a leg-the guy could be strong too I guess.

On a side note has anybody watched this 12 video series? http://www.youtube.com/watch?v=6iK_b7lU ... re=related. This is still from Australia.

The guy is documenting the building of the Supavee Evo - I guess this is what is called a First or a F1600 here. I find him difficult to watch as he gets lost in details only purists may care about. Never the less it's interesting. The way he mounts the engine is interesting. I can see how his transmission mounts come handy if you ever decided to change the rear ride height of the car, or needed a different engine angle for some reason. The frame is way different than anything you may see on the tracks here. Whatever his results are, it is cool to see that there is still some interest in building FV cars differently, even after 40+ years of design/racing.

Something that may be of interest to Brian H: he is designing the car with a raised floor, for cooling purposes.

Jean

Jstoezel,

Just curious, but do you have any other pics of the Rapier(?) car, especially the rear suspension? From the pic you posted, it looks like they have an interesting set-up - something I don't recall seeing before...

I agree with Brian H. about the rear of the car. It looks like the engine and trans are basically hung from the bracing off of the back of the main roll hoop, and with what looks like 1" square tubing extending backwards.

-Jim

[FVartist]

Can I assume to think your car is near completion, since you are entered to race at the end of the month?

[brian]

I'll post a picture later, but the Anduril has a pivoting rear engine mount to allow for ride height changes without changing camber. Difference is that I do not tie down the front of the engine via an engine mount. It has been debated on the forum before, but I have seen HP loss, on the dyno, when an engine is not allowed to flex when higher temps are achieved. Many years ago, I assisted with the development of a VW aircraft engine and the fronts mounts were discarded after tests showed the "binding" problem. Many vees and late model VW buses use an front engine mount but either the bolt is left loose to provide for movement, ala D13, or in the case of the bus, the mount is located in rubber.

[jstoezel]

I have a lynx, that was modified to zero roll. The transmission is bolted to the beams using the lower mounts only. The car came with a front engine mount, that uses the lower front case bolt. The mount broke last year while on the track, it made for a very difficult car to control, as the engine/trans were pivoting around the trans mount (there's a video on youtube that actually shows the car getting looser and looser).

I guess there is no way to go without the front mount on a lynx, unless I installed bracings from the hoop to the upper transmission mounts? I was (am) getting a new front engine mount built, that uses the 2 front mounts.

Is this the thread you are referring to? http://www.formulavee.org/interchange/v ... gine+mount

I'll post a picture later, but the Anduril has a pivoting rear engine mount to allow for ride height changes without changing camber. Difference is that I do not tie down the front of the engine via an engine mount. It has been debated on the forum before, but I have seen HP loss, on the dyno, when an engine is not allowed to flex when higher temps are achieved. Many years ago, I assisted with the development of a VW aircraft engine and the fronts mounts were discarded after tests showed the "binding" problem. Many vees and late model VW buses use an front engine mount but either the bolt is left loose to provide for movement, ala D13, or in the case of the bus, the mount is located in rubber.