I have collected a lot of photos and posted them throughout the previous front clip posts listed above.  If you are landing here via a search engine, I have made this post for you so that you can find what I looked at in one place.

Link to front clip gallery

I took the majority of these pictures from eBay and Google image search.  If any of these pictures belong to you and you do not want them displayed here, please accept my sincerest apologies and leave me a comment below describing the image you would like pulled.

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Now for the view from underneath the V8Mongrel.  Typical of a unibody design, the SA22C chassis has two sheet metal runners front to rear that look like the frame rails of a traditional body-on-frame car.  They are about equidistant from the transmission tunnel and the rocker panels, and do play an important role in stiffening the car, but are not frame rails in the traditional sense.  They also tie into the front frame horns, which means they will likely play a role in the upcoming alterations.

Those pictures are mainly of the transmission.  I never had a reason to take pictures of the underside of the floor panel.  As you can see, these rails are pretty beat up, and I don’t feel comfortable using them as-is for the basis of any kind of new front clip.  They simply aren’t true.  Fortunately, there is a way to reinforce them that I learned from MuscleCar TV.  The episode Comet Frame Rail & Roll Cage details how to add a lot of strength to a unibody car by adding real frame members to these unibody runners.

I am going to be taking a break from the front clip posts and discussing the fender flares I have been building.

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While the previous posts in this series have shown how other cars front clips are designed and built, the obvious question of how to apply that to the V8Mongrel has remained not only unanswered, but completely unaddressed.  After all, the root of the problem is my not having thought that question through far enough for another part of the project.  Plus, there are some significant differences between the full tube frame cars which I have posted pictures of and the unibody design of the RX-7.

A lot of attention has been given in the previous posts to the way in which the frame members in the passenger compartment area connect to the front frame horns.  Here is the reason why:

As you can see, the SA22C chassis has, like most unibodies, a rocker box that provide a significant portion of the strength.  That box runs from the front wheel opening to the rear wheel opening; thus the entire length of the passenger compartment.  Also, as the second photo in the pair above shows quite clearly, the base of the A-pillar links into the rocker box as well.  In the SA22C chassis, the A-pillar is set back quite far from the firewall, unlike most of the more upright sedan style bodies which I have worked on previously.

Since the rocker boxes have to stop at the wheel wells, there needs to be another structure above it for the factory MacPherson strut mount upper mount.  This member was also designed to serve as the anchorage point for the fenders.

Above, you can see the upper structure I spoke about.  note that it too ties into the A-pillar.  Also of note is the attachment to the upper cowl.  The triangular shape where the cowl joins the front structure indicates to me that the cowl and firewall is an important structural piece.  A shear panel that is supposed to tie together the two sides of the car.  This means hacking up the firewall must be done only after serious consideration and planning on how to put back that strength.

This picture hopefully better shows how the structure extends forward.  Of note is how much the upper structure widens where it meets the A-pillar.  Also, the panel between the rocker box and the upper structure is stamped in a way that makes me believe that it too is acting as a shear panel.

The detail on the A-pillar is curious.  The upper structure is not attached to the A-pillar with a continuous weld like is the case for the rocker boxes.  Not sure why this is, as I would think a full weld would be the strongest.

Up next, the view from underneath.

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I have found a few more pictures that show some different approaches to the challenging transition area from passenger compartment frame to front frame horns.  Here they are, with comments.

It looks like there are two frame members here, with the inner one angling in from the connection point with the front frame horns.

The round tube connection looks complex, and I don’t see any other connection in place.

The compromise versus the above setup appears to be moving the pedals higher.  I will have to consider this as I have floor mounted pedals in reserve and the option to use the stock units.

Interesting compromise.  I like the small tube that goes upward from the connection point and becomes part of the transmission tunnel.  Shear panels rock according to me friend Ed.

Same kind of brace from the connection point, but instead of upward, it goes backward.  Also, the round upper tube has a significant angle to it so it can be the width of the car.  My initial thought is that the companion tubing going to the center would be difficult to fit in my smaller application.

Same picture as before but this time  highlighted to show, the round upper tube which seems to make a longer, more gradual run to the outer width of the car than the previous car.  Also, the second, lower round tube would be very hard to package, I think.

That is a complex solution.  Not sure exactly what all those bars do, but I want to find an easier way than this.

These rails seem to have a lot less spread to them.  It is a dirt car, so perhaps that is not required.

Up next, the RX-7 side of things.

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I have posted previously about how you always have to be on the lookout for opportunities and ideas.  This weekend, I took the kids to see the America 200 at Rockingham Speedway and found another such opportunity.  The America 200 is part of the ARCA RE/MAX series, and is the final race of the season.  I have already created and posted a gallery if you are interested.  I really like all kinds of racing, and the ARCA races are great value and are setup in a way that works well for my kids.  The top level NASCAR races are expensive, require a lot of travel and the races are often four hours long or longer.  Yes, they are a lot of fun, but ARCA at the Rock is just as enjoyable and a whole lot easier.

Before the race, as the kids and I were walking to our seats, we passed a car corral with half a dozen race cars in it.  Stock cars from different eras.

Most are pretty rough as it appears they sit outside all the time, but they are still interesting.  The one pictured above appears to be about a decade old and from the NASCAR Busch Grand National series.  Notice how the front end seems high?  That is because there is no engine in the car.  That large fender gap allowed me to poke the camera in and snap a few pictures.

Nothing earth shattering, but just another data point for my own efforts.  I have collected some more eBay images as well.  At this point, I need to post them all up, organize them and continue my analysis of the different options.

Planning – Front Clip – Getting Acquainted (Part 1)

First, here are some more pictures I have found on eBay of tube frame front clips.

Second, here are some observations on the pictures posted previously.

How the front frame horns tie into the rest of the frames appears to be the most complex design element.  If you consider the car a three box layout – box one the engine bay, box two the driver compartment, box three the trunk area – the difficulty appears to stem from the fact that boxes one and three have narrower frame widths than box two.  So how bridge that gap without sacrificing strength or adding a lot of weight is a design challenge.

I will be looking for more pictures of that area and posting them up.  If you see any, leave a link in the comment box below please.

Having come to terms with the fact that I have some major work to undo and then an even greater amount of work to do, I have started looking at how others do what I need to do.  Specifically, I have been looking at the front clips of various stock cars.  Step one was to get on eBay and see what was for sale.  In the next few posts, I will breakdown the differences and how I think they apply to me, but for now, here is what I have found:

I am also going to look at professional road racing chassis to see what they are like.  The difficulty is that road racing cars are mostly either production based, therefore having things required by the rulebook instead of good design criteria, or mid-engined, therefore not applicable to the V8Mongrel.

Three things of note to break what has been a lean time for posts to V8Mongrel.com.

1. The site has had visitors from 100 different nations.  The world wide web truly is, and it never ceases to amaze me that there are so many people who take interest in what I have to say.  To all of you who read this, thanks.  It makes me feel good that what I put here is of interest, and maybe even of use to automotive enthusiasts like myself.
2. After talking to my wonderful, smart, sexy, understanding and extremely tolerant wife last night, I have reached a major decision regarding the project.  I am going to have to undo many hours of work and will be looking anew at the front suspension and steering.  Together this time.  This was a tough decision to make as the car is very close to being on the ground, and this course of action will move it a long way from that status, but there really is no choice.  These are critical systems that cannot fail without major consequences, so a ‘good enough’ or ‘whatever will fit’ solution is not applicable here.
3. I really don’t know what is going to happen once things are torn down.  I have so many idea in my head at this point that I cannot say.  I do know that I will be logging whatever choices I make here, and will try my best to take pictures of it too.  After a period of pretty negative sentiments towards things, I am feeling some relief that I can finally just get back at it, even if that isn’t the path I originally wanted to be on.

So, that is it.  Lots of time wasted for sure, but not point in wasting more time not fixing it.  Not the first time the project has suffered a major setback, and I doubt it will be the last.  But onward I go.

Planning – Steering – Stock Data
Planning – Steering – Calculating Final Steering Ratio

After having done the math, I wanted to confirm that I was correct in thinking that steering arm length does truly matter when looking at total steering ratio.  Furthermore, I wanted to make sure that the computed results were confirmed by actual movement.  I am not much of a math person, so I don’t trust those results completely.  Mounting parts on the car to test things was out of the question because of the previously revealed problem:

So, I had to do some modeling to get what I needed.  Perhaps I could have found a computer program.  Perhaps I could have drawn it out.  Perhaps I could have been really clever and done it all in Excel.  Any of these would work, but none would allow me to easily see what is going on.  For that, I turned to tongue depressors, foam insulation board and brads.  The height of sophistication and truly cutting edge technology, I know.

Here is what I did.  Hopefully (mostly) self explanatory, as it was intentionally simple.

I made three sticks, one for the Pitman arm, one for the steering arm and one as the center link.  I anchored the arms on the line I drew on the board, then attached the center link through a hole five inches up on the Pitman arm and 6½” up on the steering arm.  Pushing the brad through the holes makes a mark in the foam board that I could measure from.

I then moved the top of the Pitman arm a set number of degrees (leaving the bottom anchored) and attached the center link to it.  Again keeping the bottom anchored, I moved the steering arm so that the center link could be attached.  Finally, I took out all the sticks, connected the holes with lines and measured them with a protractor.  The results were exactly the same as those given by my mathematical method.  EXCELLENT!

My modeling days aren’t over yet, however.  I will be trying to make a model that has a tie rod involved, instead of the current situation where the center link acts directly on the steering arm.

Previous post:
Planning – Steering – Stock Data

As I have posted before, the rated ratio of the steering box or rack will not always translate to the final steering ratio.  In my Internet searches, I found many posts on multiple forums claiming that steering arm length doesn’t matter.  I am here to not only say that it does, but to show you how I came to that conclusion.  This will probably take more than one post, so please be patient.  I will list all the posts as I go so that anyone interested can more easily find the whole story.

The difficulty that I had on my first go around was understanding the difference between rotating motion and linear motion.  Since the steering box output shaft rotates the Pitman arm, it is rotating motion.  Through the center link it is transferred into linear motion, then the outer tied rod end pivots, or rotates, with the ball joint as the center point.

The first process I used to investigate how this all works was via simple math.  If unrestricted, the Pitman or idler arm would turn a full circle.  The arm length is the radius of that circle and with simple 2 pi R, I computed the circumference.  What the circumference gave me was the ability to measure travel of the Pitman arm end for any angle.  For example, 90° is ¼ of the whole circle, so the the Pitman arm moves ¼ of the circumference.  It is impossible for the steering arm to move a greater distance as they two are rigidly connected.

For the next step, I computed the circumference of the circle that the steering arm would create.  I then took the distance that the Pitman arm traveled in 90°, divided it by on fourth the  steering arm circumference (same ¼ travel for 90°) giving me what I labeled the reduction factor.  This is the percentage change in travel that the steering arm goes through compared to the Pitman arm.  Dividing the steering box ratio by this number gives the final steering ratio at the wheels.

All calculations here are based on the steering box system, but by removing the Pitman arm variable, you can likely transfer it to rack and pinion calculations as well.  Furthermore, the calculations ignore Ackermann and angled tie rods.  Because of this, I did not stop at this point, and will show the other methods by which I verified my findings in later posts.

As you can see in the table above, the longer the steering arm, the slower the steering.  This method indicates that turning the Pitman arm X° does not always result in the steering arm, and hence wheel, turning X°.  From the factory, the Mazda system resulted in X° at the Pitman arm becoming .909X° of steering.  The longer steering arms of the V8Mongrel spindles makes the system even worse.

I found these results interesting, but did not want to jump to conclusions.  So I decided it was time to build a model.  That will be the next post.