Cleanest Design Produced for the Class

[rgu]

In his 1970 book on VW hotrodding, Bill Fisher looked at the then new D-13 and proclaimed it “the cleanest design yet produced for the FV class”. Fifty years later Ed Womer has produced the cleanest design for the FST class. Actually, the body and frame was done in 2010 but they have been hung on the wall of Ed’s storage building until recently. Ed bought a donor car with good parts from a fellow FST competitor in the Mid West for a pittance and merged it with his new body and frame and ended up with a stunning result. A few pics are included below.

Ed is someone not constrained by conventional wisdom and is known to think outside the box. Look at the lower cooling air scoops and of course you don’t see the upward swept exhaust. (What does hot air do?). Ed is great craftsman who would rather build a dry sump tank than buy one. The frame is got maybe the best side protection I’ve seen recently.

You can see this car make its competition debut at the FRP PIRC weekend. Weather is looking decent.

[Bardahl77]

Very smooth. By the way, Dave Starsky called, he wants his wheels back. :-)

[Jerry Kehoe]

While not my cup of tea, this looks like a very well and attractive design, certainly the nicest looking FV I have ever seen.

[FVRacer21]

You can see this car make its competition debut at the FRP PIRC weekend. Weather is looking decent.

So did it run?

Chris

[Jnovak]

In his 1970 book on VW hotrodding, Bill Fisher looked at the then new D-13 and proclaimed it “the cleanest design yet produced for the FV class”. Fifty years later Ed Womer has produced the cleanest design for the FST class. Actually, the body and frame was done in 2010 but they have been hung on the wall of Ed’s storage building until recently. Ed bought a donor car with good parts from a fellow FST competitor in the Mid West for a pittance and merged it with his new body and frame and ended up with a stunning result. A few pics are included below.

Ed is someone not constrained by conventional wisdom and is known to think outside the box. Look at the lower cooling air scoops and of course you don’t see the upward swept exhaust. (What does hot air do?). Ed is great craftsman who would rather build a dry sump tank than buy one. The frame is got maybe the best side protection I’ve seen recently.

You can see this car make its competition debut at the FRP PIRC weekend. Weather is looking decent.

Spectacular!

[Ed Womer]

Well as did run Chris, yes and no. I did get three on track sessions but not more than 3-4 laps at a time. Had issues with the oil system engine wise as well as a Chinese distributor that was replaced. The general consensus is that either the oil pick up tube has a leak where it goes into the block or the scavenge side of the dry-sump pump is not working correctly.

I have not had a chance to check it out yet and I hope it is the pump otherwise the engine will need to come apart.

Ed

[Ed Womer]

Good thing is with very little track time at least the car handled great!

Ed

[tyremueller]

Really smooth)

[Jnovak]

More pics please w/o body please

[Ed Womer]

Hi Jay, here are a few more pictures

[Jnovak]

The engine bay doesn't look as structurally sound as the front of the chassis?


Is someone building cars?

[t walgamuth]

The engine bay doesn't look as structurally sound as the front of the chassis?


Is someone building cars?

I suspect the engine is part of the frame.

[Ed Womer]

Hi Jay,

This is basically the same design as my FV car and everything triangulates to the engine tranny and I do use a front motor mount. You can jack up the car by the tranny and there is no flexing anywhere.

Although this is the only version of this car, which I originally design and built around 2007, I can make more if there is any interest by anyone. I don't have any idea as of yet how much it could cost to build a kit but I could come up with a cost if anyone is interested.

Ed

[Daryl DeArman]

The engine bay doesn't look as structurally sound as the front of the chassis?

Hi Jay,

This is basically the same design as my FV car and everything triangulates to the engine tranny and I do use a front motor mount

One thing to remain mindful of when looking at typical FV/FST chassis and the lack of structure aft of main hoop is that they are zero roll suspension design. Very little torsional rigidity needed as there are no rear suspension loads to speak of being fed into the frame. All you need is enough there to handle engine torque and braking /acceleration forces.

[Hardingfv32]

[QUOTE=Daryl DeArman;614162] Very little torsional rigidity needed as there are no rear suspension loads to speak of being fed into the frame. /QUOTE]

This is a common FALSE myth about FV rear zero roll suspension.

The rear suspension is zero roll resistance, not zero lateral load transfer. At the rear there are lateral loads that transfer through the roll center, about 125lb@1.5g for the std FV. Also remember that roll force not controlled by the rear still have to make their way to the front suspension which is providing the resistance due to CG to roll axis roll couple.

So in fact chassis stiffness is just as important in a FV/FST as it is any any racecar.

Brian

[Jnovak]

One thing to remain mindful of when looking at typical FV/FST chassis and the lack of structure aft of main hoop is that they are zero roll suspension design. Very little torsional rigidity needed as there are no rear suspension loads to speak of being fed into the frame. All you need is enough there to handle engine torque and braking /acceleration forces.

Add lateral bending loads Daryl.

[Daryl DeArman]

The rear suspension is zero roll resistance, not zero lateral load transfer.

Agreed.

At the rear there are lateral loads that transfer through the roll center.

Through vs. "about" but I get what you are trying to say. Think about when the RR goes into bump (for example) where does that load path travel from the wheel and what is resisting that force?

Also remember that roll force not controlled by the rear still have to make their way to the front suspension which is providing the resistance due to CG to roll axis roll couple.

What roll force not controlled by the rear?

[Hardingfv32]

What roll force not controlled by the rear?

Bad statement.

Brian

[problemchild]

So in fact chassis stiffness is just as important in a FV/FST as it is any any racecar.

Brian

Bad statement!

[Hardingfv32]

So you do not think FV/FST track performance benefits from chassis stiffness?

Brian

[problemchild]

So you do not think FV/FST track performance benefits from chassis stiffness?

Brian

Your previous statement said "fact" ...... "just as important". Many zero-roll FVs with ladder frame chassis have won most of the races for the last 40+ years, the others being won by light-weight spaceframes with little or no stiffness. That would not be the case with "any any racecars" in conventional classes. Chassis integrity with FV is mostly about driver safety. I would suggest that chassis stiffness would have more effect on longitudinal weight transfer than lateral weight transfer. That builders of winning FVs do not worry about the performance benefits of chassis stiffness would suggest that your statement is not factual, and certainly not just as important. With zero-roll rear suspension, FV/FST chassis design seems mostly about safety, lightness, and ease/cost of manufacturing.

[Hardingfv32]

Or could it be that FV builders were just trying to provide a low cost and easy to maintain solution? Maybe there was never a market for a more costly and labor intensive solution. I can imagine that the benefits of a stiffer chassis might be hard to appreciate/sense for the average driver.

We know a lot of effort and expense goes into chassis stiffness in all forms of circuit race cars. From a cornering performance point of view, why should that not also apply to FV/FST?

Past winning records of current FV designs does not really provide any insight into the scientific/engineering reason for chassis stiffness. Can you expand upon the reason you think chassis stiffness does not play an equally important role in FV as compared to FF/FC?

Brian

[Daryl DeArman]

Can you expand upon the reason you think chassis stiffness does not play an equally important role in FV as compared to FF/FC?

In a zero-roll rear suspension design suspension forces at the rear are not being fed into the chassis.

Put a zero-roll FV up on chassis stands. Put the right rear wheel in bump.

What load was fed into the chassis prior to the limit of travel? Now attempt to put both rear wheels in bump simultaneously what load was fed into the chassis?

Now repeat the experiment with any conventional formula car and the answer will be obvious.

[problemchild]

In a zero-roll rear suspension design suspension forces at the rear are not being fed into the chassis.

Yes. one would assume that is why the suspension concept is referred to as zero-roll.

[Hardingfv32]

In a zero-roll rear suspension design suspension forces at the rear are not being fed into the chassis.

Going back to your earlier post, I see you re-stated my statement: 'At the rear there are lateral loads that transfer through the roll center, about 125lb@1.5g for the std FV.' The statement is correct using the word 'through'. There are two forms of lateral weight of sprung weight: Through and around the role center.

Trailing arm FV front suspension has the RC at ground level, so zero weight transfer through the CG and max transfer around the roll center.

Swing axle rear suspension is the opposite, max transfer through the CG and zero around the roll center. This is using the std FV CG.

A zero roll design really does nothing to change these fundamental/basic forms of weight transfer.

What zero roll goes is prevent any of the weight transfer at the front, do to weight transfer around the roll center, from being fed into the rear suspension. Roughly speaking it is like removing a rear sway bar. It is a tool to improve/change chassis balance.

Thus, use of zero roll does not answer the question of the relevance of chassis stiffness in FV.

Brian

[Daryl DeArman]

Thus, use of zero roll does not answer the question of the relevance of chassis stiffness in FV

Okay, if you say so.

Ask yourself why it's desirable to have a torsionally rigid chassis in a typical formula car. What is the goal?

If that doesn't make the reasons clear as day, look at an old Z-bar design FV, why are those chassis designs at the rear substantially different than a zero roll design? (hint: it's not laziness or frugalness of chassis builder)

[Hardingfv32]

Do you understand my statement about two type of lateral (sprung) weight transfer? This is fundamental to understanding this subject.

Do you accept what I mean when I say a zero roll system is similar to removing a rear sway bar? Weight transfer at the front is not being allowed to transfer to the rear suspension with a zero roll system. It has nothing to do with preventing the rear suspension from creating weight transfer at the rear. Transfer at the rear still happens through force applied to the RC, not around it in the from of roll couple.

Chassis stiffness relates to a driver getting accurate and timely feedback from his inputs into the chassis. A chassis lacking stiffness is just another spring in the system which provides variability and slows feedback.

Brian

[Daryl DeArman]

Chassis stiffness relates to a driver getting accurate and timely feedback from his inputs into the chassis. A chassis lacking stiffness is just another spring in the system which provides variability and slows feedback.

Agreed.

So, look at this pic and tell me how torsionally rigid the rear of the chassis has to be when a load is fed into the right rear contact patch?


And what about when an equal load is fed into both the right and left rear tires?

[Hardingfv32]

1) Rear lateral loads at the rear are fed through the axle housing into the transaxle then chassis. No lateral loads fed through the zero roll rocker system. Google the 'swing axle' design to understand and verify this critical point. Understanding this is fundamental to this subject.

2) Your pictures are just illustrating that the vertical loads iinto the rocker system are affected by the jacking force generated by the swing axle design. No bearing on the lateral load transfer.

Agree or disagree:

A zero roll system is similar to removing a rear sway bar? Weight transfer generated at the front is not being allowed to transfer to the rear suspension with a zero roll system. It has nothing to do with preventing the rear suspension from creating weight transfer at the rear. Load transfer at the rear still happens through force applied to the RC, not around it in the from of roll couple.

Brian

[problemchild]

A zero roll system is similar to removing a rear sway bar? n

Another bad statement. It is not similar at all. A conventional 4 shock car puts load into the chassis, on each corner, with or without anti-roll bars.

[Purple Frog]

I wholeheartedly applaud Ed for the obvious driver safety enjoyed by his design. (from one that got T-boned)
I like real steel tubes vs, kevlar panels,,,

[Jnovak]

There may be zero roll stiffness on a zero roll FVee. However there sre still lateral forces involved going through the axle tubes and the engine transmission frame structure!, thus there can and will be be compliance steer/camber effects happening all the time!

[Hardingfv32]

It is not similar at all. A conventional 4 shock car puts load into the chassis, on each corner, with or without anti-roll bars.

Not worth discussing as it is a distraction from the point about the importance of chassis stiffness in FV/FST

So is it your contention that zero roll rear suspension negates the requirement for FV chassis stiffness when discussing cornering performance? What about the lateral loads going into the axle tubes that Jay mentioned?

Brian

[Daryl DeArman]

1) Rear lateral loads at the rear are fed through the axle housing into the transaxle then chassis. No lateral loads fed through the zero roll rocker system. Google the 'swing axle' design to understand and verify this critical point. Understanding this is fundamental to this subject.

I understand that. I didn't say lateral loads. I said loads, and am speaking as to why the chassis (in the rear) does not need to be as torsionally rigid in a zero-roll FV than other conventional Formula cars.

Agree or disagree:

A zero roll system is similar to removing a rear sway bar? Weight transfer generated at the front is not being allowed to transfer to the rear suspension with a zero roll system. It has nothing to do with preventing the rear suspension from creating weight transfer at the rear. Load transfer at the rear still happens through force applied to the RC, not around it in the from of roll couple.

You're half right. Similar yes.

Load transfer at the rear occurs based on the difference in height between the RC and the CoG and is of a much lower magnitude than that being fed into more typical formula car suspension during high speed compression.

[Daryl DeArman]

There may be zero roll stiffness on a zero roll FVee. However there sre still lateral forces involved going through the axle tubes and the engine transmission frame structure!, thus there can and will be be compliance steer/camber effects happening all the time!

Yes, what's the approximate magnitude of those lateral forces? Now take a FC/FX/FA chassis with 700#/in wheel rate hitting a curb, what are those forces? What happens when a zero-roll FV hits a curb with the rear tire?

If you build a zero roll FV chassis feel free to triangulate the bejesus out of the rear if you wish I'd rather have the weight and rigidity between the beam and the main hoop.

[problemchild]

Not worth discussing as it is a distraction from the point about the importance of chassis stiffness in FV/FST

So is it your contention that zero roll rear suspension negates the requirement for FV chassis stiffness when discussing cornering performance? What about the lateral loads going into the axle tubes that Jay mentioned?

Brian

If not worth discussing, why did you bring it up?

I never said there was no load being applied from a rear wheel on a zero-roll FV. I said that it was minimal, and that "So in fact chassis stiffness is just as important in a FV/FST as it is any any racecar." was a bad statement.

I believe the load input to the transmission by the axle tubes is insignificant. I believe primary the load input is on the pivot points represented by the little arrows on Daryl's drawing, and that is minimal. That is also why some cars mount those pivot points lower, and/or on the axle tube centerline. As Daryl's drawing points out, that force may not even be applying to chassis roll. It may even be used as a tool to reduce chassis roll. These are my opinions. I will not be issuing any engineering papers to support my opinions. I consider most FVs to have completely inadequate side protection if built to allow #200 lb drivers to meet minimum weight. I put any available weight structure into driver safety rather than performance driven chassis stiffness. YRMV

[Hardingfv32]

I'll take another approach to this topic of the importance of stiffness in relation to cornering performance.

First it is important to understand that the load transfer numbers are generated at a constant lateral G load number. In the spreadsheet I am using it is 1.5G. Tire grip level, suspension type.... even car type are not required to be known. !.5G is the constant that makes for a simplified calculation. The CG height and how the chassis reacts to this height are what is important.

So that said, it is probable that a FV, with its lower CG, has a lateral load transfer numbers at least equal to a FF.... at 1.5G. So from that one could logically imply that if chassis stiffness is important to FF, then it must be important to FV.

From the spreadsheet for a FV with a 10" CG total (sprung and unsprung) lateral load transfer at 1.5G are:

Front 133 lb
Rear 175 lb

The rear load transfer is greater at the rear and a decent number considering that total rear weight is about 560 lb.

Remember as stated before, type of suspension is NOT part of the calculation. I do not need to consider anything about the quality of the suspension being used. No lateral load equation requires that type of input.

PM me with an Email and I will provide the spreadsheet.

Brian

[Daryl DeArman]

Brian,

You are hung up on lateral load transfer and therefore ignoring much larger forces at play.

[Hardingfv32]

What forces are more important while cornering? Roughly how are they calculated?

How do they relate to the importance of chassis stiffness while cornering?

Brian

[Daryl DeArman]

If we were racing on glass smooth tracks then you would have a valid point, we aren't.

You have calculated lateral load transfers of 150# range.

Take a FF car with a wheel rate of 250# and a displacement of 2.5" during an event. That's 625#. With peak damper speeds of 20+inches/second it should be much more apparent how much stronger that chassis has to be to retain the opposing end of that damper.

In a zero-roll FV that force is not being resisted by the chassis, but rather the opposite rear tire and the pivot points on the bell cranks trying to elongate their mount. Steel tubing is a whole lot stronger in tension than compression.