Spifz

Anyone do a pushrod rear suspension with the coilovers in the rear hatch area? Maybe like this?

xpndbl3

iTrader: (5)

y? The stock style rear suspension works perfectly fine how it is. What's the benefit of this type of suspension?

Spifz

Easy spring changes, easy preload changes, easy ride height adjustability, reduced unsprung mass, relocation of the loading point from behind the axle to in front of the axle, keeping your $180 QA1's clean, ... Not that I disagree that the factory suspension works fine, but then there is the unique factor, and I think it would look cool to have coilovers in there visible through the back glass, right inbetween the factory T-top bag and plastic trim, and with carpet under there as if they were there from the factory.

Sonix

iTrader: (1)

I like your solidworks design. You do that yourself or steal the picture?

I'm afraid I haven't finished the suspension book i'm reading, *cough*, can you explain for us who aren't in the know?
The tube on the right, going straight down, that would connect to..? The top of the axle tube?
And the blue tube, where's that going? Would this change the amount of suspension travel you'd get? Would you have to add that frame rail in?
You've got my attention here...

5678TA

interesting.. so the coilover will be in the trunk area? looks like you are literally just going to move the coilover into the car..
IMO, its just adding weight to the car.. just get the Spohn rear coilover kit and be done with it..

Spifz

Yea, that's my SW work, I cosmosworks'd it too, just to see what kinds of loads this would generate. The straight down piece goes through the shock mount hole (made larger to for the pushrod) to about where the factory shock mounts to the axle housing. The Moser 9" housing I have has heavier shock mounts, so I just welded a piece onto it tapped for 1/2-20, then drilled through and tapped the shock mount as well so there is plenty of thread material for the bolt. The pushrod is solid stainless because I had it laying around and wanted to keep it small so I didn't have to open the shock mount hole up so much. The LCA in the one picture is 1.250 x .120. I decided how much suspension travel I wanted in each direction and designed the rocker ratio to make that travel use up the much shorter travel of the shock. That ratio comes into play when choosing springs then, so I have 350 lb springs but the effective rate is much less than that.

dennisbernal91z

iTrader: (2)

Thats a pretty sweet idea. I am a mech engineer and that looks like it would be a lot of fun to play around with. Right now I just have a very beefed up stock setup, with everything being adjustable. Great work so so far. It will def be a eye catcher when you go to shows. Esspecially if you get the carpet in there and all, so it looks kinda factory. I put a fuel cell in my trunk and made it look kinda factory. I love those mods.

Anyways, Let us know how it goes.

And for the people saying that the stock stuff works great... I am sure he knows that. This is not trying to fix a problem, this is trying to move in a new direction.

Apeiron

If that was a tank it would be a Christie suspension. I've seen it on the front end on a friend's Cobra replica, but not on the back end.

383backinblack

very slick.....nice work man, I love seeing people do things outside the box.

like when people ask "why" i didnt do a turbo setup......because, everyone does that now.....i want to do something different

you certainly accomplished that, id love to get a look at that in person and see how it works at the track or the drag strip.....as well as on the street.

very nice work.

Zipdrive

You really should do some quick beam/column calculations on the push rod and determine how much load it takes to fail. My engineering judgment feels that you will have deformation in the column during use.

It will be unique, just make sure that it is safe.

Sonix

iTrader: (1)

oh I get it, that blue bar going up was part of your cage...
haha, I didn't think you'd already done it! Man, that's pretty slick. Where does that square tubing connect in the back? Something stiff?

Just make sure you don't get anything caught in there while driving, that could be ugly...fingers etc.

The pushrod is solid? That would be really heavy wouldn't it? What's the diameter?

haha, looks like all the engineers are here to critique your work Where's Vader?

So then your rear end wouldn't have springs on it at all eh? Huh, that would look weird. I'm thinking if that would effect anything, since the springs are no longer behind the axle...? More downward force on the TA? Are you still using a TA and panhard?

The pivot point on your rocker, what is that? Some kind of bearing? What is the ratio?

Since the coilover moves a much smaller distance than the pushrod side, wouldn't you need a very stiff spring on the coil over? You'll get say 4" suspension travel, and say 3" coil spring compression... So wouldn't you want a 800lb/in spring to get an effective 600lb/in? (I think I came to the same conclusion as you, but I feel that i'm doing it backwards for some reason...)
.
.
ok, so lets say 350lb/in, so you might be getting effectively 200lb/in lets say eh? That's just a bit more stiff than factory, but certainly in the ballpark... Very interesting. Is this a drag race car or street or...?

And one final question - decoupled torque arm to go with it?

RMerritts

deleted..

Lo-tec

Pretty neat idea!!

I give you an A+ for wow factor and execution, but an F for practicality. Kind of like GM upgrading the tried and true HEI distributor to an Optispark for the LT1.

Pocket

iTrader: (24)

Sweet ideer

Did you run your geometry thru some calculations to find out if this will help your launches/handling?

88 Z28 Guy

iTrader: (1)

I like it alot, pretty damn innovative

RMerritts

Sorry, i didnt see the pictures before. Awesome work, i thought about doing the same thing but i wasnt sure on how to brace everything so i held off on it for now, let me know how it works!

Spifz

Video link:
http://keith.gearbox.no-ip.com/Keith-PushrodSusp.mpg
The suspension is really quiet, but in the video you can hear the front end pivoting on the blocks it is on, and the trunk floor squeeking. Me jumping up and down in the trunk isn't the greatest test, but at least you can see it all moving.

As for handling, I picked the springs to get about 130 cycles per minute in the back, but the springs are pretty cheap, and there are lots of rates available, so I can go up/down if I need to. I actually happen to have 1 550 lb/in. spring sitting on the shelf, but that is like a rock. The car is street/road race, so my spring choices probably won't be the best for drag racing, but I might buy some springs to experiment with getting a better launch.

Rocker ratio 3.779 / 6.500 ~= 1.72
Pushrod: 7/8 solid 304 stainless, ~ 15" long
Pivots: 5/8 thompson shaft on a pair of needle roller bearings pressed into a solid piece of 1.500 steel welded to both the down bars and the 1x2 rectangular. The rect. ties into the frame rails behind the wheel wells with some plates.

Sonix

iTrader: (1)

Cool, thanks for the info. (i'm going to have to do some digging to find out what a thompson shaft is though...)

Just to pick you apart some more..:

- Spring changes - alright fair enough.
- Preload changes? You mean easier to adjust your adjustable shocks?
- Ride height adjustability. How do you do that with your setup?
- Reduced unsprung mass - Yep, you got me there.
- Relocation of spring point from behind to in front of the axle : This is what has me most piqued. I know that with the springs behind the axle, the natural force pushes the torque arm upwards. This would push it downwards (but only slightly I'm guessing). What is the net effect of that though?

ZONES89RS

iTrader: (2)

I only wish i could pull off some work like that, +1...

Stephen

iTrader: (12)

Absolutely sick! I love it!

I can see that being great for autocross or road course. If the rear seems too stiff or loose, a few minutes to change it.

If you hit any kind of tracks, let us know how it does for track usage.

Wish I could pull that off! Of course, I'd need a cage first. I can't image doing that without a cage for mounting/support.

DAVECS1

iTrader: (2)

That is absolutely awsome. Sounds like you did your homework.

I would get rid of the 304 stainless. That material has way too many properties that could lead to some wierd suspension behaviors

1. The modulus of elasticity for stainless is low (meaning it flexs too much and will eventually work harden and break)

2. The compressive and tensile strength will always be changing as it work hardens, thus changing your spring rates.

3. Your rod ends will eventually get siezed in there

There are a couple different materials that will give you much more strength for less weight and about the same cost. Off the top of my head
4340 Chromoly tubing (you can order lenghts with threded inserts from Chassis Works)
1020 Cold Rolled Steel: The cold rolled is importand because the hot drawn stuff will have the same issue as the stainless, and it will not even be resistant to corrosion making maters worse.

I would go ahead and cut off most of the brackets on the rear end, and take advantage of your work, in the end you may save weight. Also you could probably optimize the mounting of your pushrods so the directly counter act the torque arm, improving that setup even further.

I think your bearing and rocker arm setup are outstanding. Word of advice, make sure you selected a bearing with the correct radial loading characteristcs. If that bearing begins to freeze up you will get some weird handling characteristics that will be hard to diagnose.

Structurely I think that is tied in about as pefect as it could be. Better than the stock sheet metal floor.

I have always thought about doing this but I am just too damn lazy. If you haven't already browsed through these books. Here is some light reading to consider

1. Engineer to Win Carroll Smith
2. Tune to win Same Guy
3. Engineering Material Kennth G Budinski
4. Introduction of Mechanics of Materials
5. There is also a book offered by SAE that ties materials and dynamics into chassis design, but I cannot think of the title right now.

P.S. If you take it to an official drag strip, they may give you a hard time if your pushrod through hole is not sealed up well. This happen when we took our formula Alantic car to the strip for some fun

ghettocruiser

iTrader: (4)

Wow man... Coming from an engineering background myself...my hat is off to ya. Good stuff. I gotta admit, I thought this was going to be a crazy idea that someone drew on the computer. Then I scroll down and see that you built it!! And you put up a vid showing it work! Thats gonna keep this thread going man. You keep stepping up and showing what your idea can do.

I really like that set up. Its not something I would do to my car probably...only because its more of a daily driver than anything else. But man...I hope you see good results fromt his out on the track. The adjustability alone would make it worth it. You can change springs and ride height and preload without even crawling under the car or jacking it up! Thats great!

Definetly keep the pictures and videos coming as you develope this idea!

Justin

novatuc

Beautiful work. Should be great for road racing or autocrossing. Easy and near infinite adjustability.

Spifz

Thanks DAVECS1 for the material suggestions, and everyone for the compliments. I had the 304 laying around, so that is what I used. I was thinking it would be nice if it was stainless so I wouldn't have to worry about rust or having to coat it, but I'll just remake it out of cold rolled or 4340 like you suggested and powder coat it. I was planning on sealing the hole where the pushrod goes through, maybe with a rubber boot or something (open to suggestions) but haven't built anything yet.
The needle bearings are rated at 2330 each, so 4600 lbs each side, but it is hard to estimate the shock loading, so hopefully that will be enough. I plan on driving it all the time, so we will see! There are also bronze washers on each side to handle the little bit of side load.

I have the SAE book "Race Car Vehicle Dynamics" (might be the one DaveCS1 was thinking about) and Competition Car Suspension by Allan Staniforth, they are both pretty good books.

357transam

iTrader: (1)

Amazing.... I have never seen something like that before and my jaw just dropped when i saw that you not only built it, but it actually worked!! bravo!! The only question that i have, how well does it keep your pinion angle from changing under cycling and acceleration?

357transam

iTrader: (1)

oops.. my bad... after looking at the pics again i realized that the struts are mounted on the front side of the axle.

ZROLimitRacing

top notch work my friend!!!!

EvilCartman

iTrader: (1)

Hummm Couple of things I'd do different would be to put the lower mount in double sheer and not do those straight vertical cuts on those brackets. Guess I've been looking at too much off-road/desert racing stuff

ABJ88

iTrader: (3)

Looks great! I'd like to see it moving and hear the results of the mod.

DAVECS1

iTrader: (2)

Race Car Vehicle Dynamics

Thats the book! Now where the heck did I put my copy? Yea stainless would be cool for corosion if it was not for all that other stuff

You did not happen to compete in formula SAE did you? That is a top notch experience. If it was not for that program I do not think I would of made it through college. I still use lessons learned from Formula SAE, doing a project like that has given me the ability to lead projects in the real business world

7 years graduated and I am a Senior engineer at a very large company!

Good luck on your project and let us know how it progresses.

HPE

I applaude your creativity and craftsmanship. Very nice work.

If I can critique the design function though as pertained to handling, it still weighs more than if you just hung the coilover upside down and just had the weight of the coilspring, cups and shock shaft rather than moving all that heavy linkage and bell lever. Even though the ratio of the shock does not have to move as much due to reduction of the bell lever ratio, you still have more polar weight to move back and forth than if you just mount the shock in the standard position upsidedown.

When you see this inboard shock setup done on F1 car, Lola prototypes, etc- they use very lightweight exotic carbon fiber link arms and lightweight exotic needlebearing bell levers with very strong, tight ratioed bell leverage under extreme forces to keep things small and reduce polar movement of parts to an absolute minimum.

It will obviously take a little time to dial it in. It is pretty simple guidelines though since they still mount to the axle in the same place and movement is still verticle than you just multiply the rates previously used by the increase ratio of the bell lever- ex if it moves 2.4:1 and you had a 100 lb rate sping in there you would now need a 240lb rate spring.

Its got that show car bling though, Nice work.

DAVECS1

iTrader: (2)

Well the weight story will begin to look better if he eliminates the spring pads and associated bracketry, also some weight could be saved from using different pushrod pickup points.

All that weight is unspung, The addition of rocker arms are pretty tame comapered to that stuff and a portion of it is not unsprung. The same goes for the shock. Some percentage of its unsprung weight has been eliminated now that it is supported on the chassis.

Also I think strengthening the rear portion of the car is a plus. The stock mounting, if analysed, i bet would show plenty of distortion, due to the facts most of the loads are input to sheetmetal formation. With no real subframe present.

Just to clarify, this is not a rebuttle or attack just a logical subjective reply meant to inspire conversation on an excellent bit of work.

Patrick007

Hehe did someone mention Formula SAE? Welcome to the world of inboard mounted, pushrod actuated coil-overs. One thing you gotta keep in mind when using a bellcrank however is the motion ratio... aka... understanding whether you have a rising or falling springrate (as a function of suspension displacement).

-Patrick

HPE

Yes I agree with all your pro points (as in pros and cons)
But with as many pros he has I see as much negative effects I think personally outway any gains.
A typical inboard shock setup is 1 mainly used for reducing unsprung weight and 2 mainly used to regroup necessary weihgt of componants close to the center of the vehicle to reduce polar roll weight so I chassis can transistion faster. What he has done is added quite a bit of mass in the upper chassis as wel as it is positioned up and outside laterally of the CG.
Again, nice job, but for handling gains? No. Would be better suited just running upsidedown coilovers- Plate the tops of the stock shock mounts (Spohn sells a plate design I gave him to brace this area) and then the chassis can carry the spring load in this area- at that pont you can still cut off the axle spring plates like discribed.
I also posted on here a few years back a Mumsford link setup I designed that utilizes my original upside down coilover design and also enables the use of a chassis mounted swaybar with the bar arms and links coming back to the axle- this gets that heavy factory bar weight mostly off the axle and drasticaly reduce unsprung weight as well as further braces the chassis for the mumsford link in place of the factory panhard and brace.

ps- I am self taught, never had any formal engineering schooling. I have howeverwelded upmany chassis' and tinkered with many personal builts including some off road toys of my own built from scratch- and I win every racing challange I have ever raced in, usually by a very large margin due to my combined "driving engineer" skills. You would flip over the '67 mini cooper S project. I have extensive drawings and ideas done up already which one part includes the addition of my Jag inborad disc rearend into it- nothing more apprpriate for a little Britsh car than a British rear end. But even that Jag rearend is going to be modified with custom homemade alum arms and links- My goal is 2+ g's on street tires and 3g's on racing rubber.

Tricked-Out-Toy

iTrader: (1)

EXCELENT Work! glad to see someone actually build something rather than just talk about it. would love to know how it works out on the track. Do you have track times from the old setup? it would be nice to see the difference. Good Work man!!

MurcoRS

Wow! I'm no suspension engineer by any stretch of the imagination but wanted to congradulate you on a terrific job! I've contemplated something like this since I saw a Corvette with a similar set-up to this a few years back. My vision had the springs mounted crossways instead of laterally to the rear as you've done, mostly to minimize stress to the surrounding sheet metal, and mounting the pivots above the upper spring perches (tying them into the reinforced seat area). Your work looks totally awesome, can't wait to see it completed!
Now all I need to see is someone doing a proper watts linkage on a 3rd gen!

DAVECS1

iTrader: (2)

"A typical inboard shock setup is 1 mainly used for reducing unsprung weight and 2 mainly used to regroup necessary weihgt of componants close to the center of the vehicle to reduce polar roll weight so I chassis can transistion faster. What he has done is added quite a bit of mass in the upper chassis as wel as it is positioned up and outside laterally of the CG"

Extremely good point! To tell you the truth I entirely overlooked that fact.

"Would be better suited just running upsidedown coilovers- Plate the tops of the stock shock mounts (Spohn sells a plate design I gave him to brace this area) and then the chassis can carry the spring load in this area- at that pont you can still cut off the axle spring plates like discribed.
I also posted on here a few years back a Mumsford link setup I designed that utilizes my original upside down coilover design and also enables the use of a chassis mounted swaybar with the bar arms and links coming back to the axle- this gets that heavy factory bar weight mostly off the axle and drasticaly reduce unsprung weight as well as further braces the chassis for the mumsford link in place of the factory panhard and brace."

This setup sounds awesome and highly optimized, I do not ever remember seeing it.

As far as the design listed here I am of the opinion that its performance could be a good improvement over stock. May take some trial an error, and the fact that everything is accessable may help with going that extra mile.

As far as education, cars, and engineering is concerned. I am more of a "proof is in the putting" kinda guy myself. Do not get me wrong I do not regret one minute of my education, but i have learned and worked with people who only have real world experience, and I have learned a great deal! There is no substitute for experience.

I personally would like to think that I have done my best to combined both worlds. I too have welded a couple chassis from scratch, as well as hot rodded a few of GM and Japans creations, and if that doesn't beat all, i put my self through college working Railroad construction (talk about motivation)

HPE

By all means yes! I wish I actually did have some formal background training at a higher level. I only stated what I did with the smile is that I got to this knowledge level on my own but I am also 40 yrs old with a lifetime of knowledge growing up around this stuff. I even currently hold a NASCAR crew license and am actively involved at a suspension man on a team. My only saving grace education wise dates way back to high school where I completed Calculus and was very good in physics as well as dabbled many years in mechanical drafting and 1 year of CAD- thrn I hit the real world and strarted my own constution business and am familiar with structure design just from general building codes and the basic priciple of radius' and trangulation.
With that I have the brain waves to comprehend complex suspension articulation- roll centers, cross, etc and have been basically self taught though being able to tinker with things and having exceptional driving skills to be able to pilot even the worst setup by tricking the car into movement with the pedals.
I appluad your comomn sence to know the importance of both hands on AND education.

DAVECS1

iTrader: (2)

So to get back on track,,,, what if spifs located the coil overs down low in the back well towards the center. The fuel tank will pose a problem, but if you could find a way around it, I am sure you could come off the axle with a direct link. Also instead of using a conventional anti sway bar, he could use a smaller device connected to the rocker arms.

In fact he may be able to do that with the current setup. Grab a couple poly bushings and some different grades of tubing and mock something up in the hatch area. If you are slick you could even partially isolate the roll spring rates from the longitudunal spring rates. I did this once on our formula SAE car. It was the front suspension only, but it pulled 1.7 G's on the skid pad

Patrick007

Nice to see another FSAE man on here . Anyway to make some comments... while yes he did mount the springs and dampers up high, i'm sure they weigh much less than a conventional full length spring/damper setup, and the net effect on CG location is probably 'outweighed' by the overall decrease in mass. Not to mention his ride height is very easy to adjust now. I personally would have mounted them in the rear well somewhere but that's another story. It looks as if the placement of your pushrods was such that you wanted to keep them perpendicular to the axle, which is fine, but since they mount with spherical joints you could have mounted the springs/dampers closers to the cars centerline and had angled pushrods. It requires a little more thought when determining the forces and motion ratios and whatnot but... it's not impossible, and brings the mass closer to the roll axis. I also agree with the about comment about the pushrod being mounted in single shear when it should really be a double shear joint. As far as anti-roll bars are concerned, you could mount that off the bellcranks (that's the typical formula car name for what we've been calling 'rocker arms') but I suspect that a cleaner, more CG friendly anti-roll bar setup could be fabricated under the car. Additionally, the selection of material and sizing of the anti-roll bar is no small task. So far so good man... I think you may have inspired me to do inboard mounted spring/dampers when I do up my independent rear end

-Patrick DeGrosse Jr.
Rensselaer Polytechnic Institute
Mechanical Engineering

DAVECS1

iTrader: (2)

All this good discussion reminds me of the good ole days with the racing discussion boards, and what not. This is what forums should be all about.

By the way I will show my age a little here.

Founding member of the Formula SIU Racing team
Southern Illinois University
Go Salukis!

HPE

Here's that Mumsford link I earlier spoke of. With this design I could incorporate a 3pc swaybar with aluminum arms coming back to the axle that the torsion bar itself could hang from the cross brace that replaces the panhard brace.
Shocks would be coilovers mounted upsidedown. The Mumford axle mounts would need further design work for strength and fitment but would be alot like the single shear track bar mounts we use on our supertruck 9" housing.

That little added brace bracket on the right may not be necessary but I just added it for additional twist force of the beam just to keep the factory 3 drivers side chassis bolts from loosening over tme due to any leverage vibration against the beam from the mumsford link .

This link basicaly is lighter weight and as vertically functional as a watts linkage with far better roll center adjustmnet ranges and a much better ground clearance than the bottom link of a watts faces.
https://www.thirdgen.org/forums/susp...ighlight=watts

DAVECS1

iTrader: (2)

That is a cool link. I like the pictures! I have never seen a Mumsford link in person, just read about them.

I guess one comment I would like to make, is about the Watts link and how it is difficult to mount and locate the IC. It is possible to mount the WL horizontally. In fact I have done it on a couple of 2000 mustangs. The pivot is mounted to the top side or bottom side of the third member. It is usually fine in signle shear with the proper hardware. The outer rod ends are then attached to the chassis. Just need to make sure that the links remain the same length or you will get side ways movement during articulation.

HPE

The problem with a Watts is in FACT that the center pivot must be on the axle housing and the links attached to the chassis- if you mount the center pivot to the chassis and the links to the axle(reversed) it will not motion directly vertically and will have lateral movement still.

This is the beauty of the Mumsford, the pivot CAN be mounted on the chassis and still have absolute 100% vertical location through suspenion travel.

Now, to setup a Watts properly AND have good ajustment range for roll center dial-in, you need alot of bulk bracketry on one side (usually the drivers side of the chassis) that hangs down very low to accept the bottom side link of the watts.

Now part 2- as you mentioned, the problem of mounting the center pivot on a Chev 10-bolt with the typical removalble rear diff cover and make it A) strong enough, B) with good adjustable mount height range), C) removalble or spacious enough to be able to service the 10bolt diff. I have seen many very, very bulky and very, very ugly attempts. Plus rom is not a premium undr there- things are very tight with the typical F-body exhaust and fueltank.
ps- I will definately be in position to make this prototype within 5 more years. I have been trying to position myself in life with tools and the means to manufacture small quanities of very custom race products in the future- as well as time I am positioing myself to somewhat retire and change careers by the time I am 48 years old- I am now 40. It is my goal and also future hobby intention also for my '67 Mini build.

83 Crossfire TA

iTrader: (2)

I’m with Tim and Dean here. Yea, it’s cool looking, interesting, but I don’t’ see a handling advantage. Tim, you compared it to the optispark… at least the opty got rid of any some of the inaccuracies due to the multiple chain and gear linkages to the distributor and later gave a good source for a high resolution signal that is used to detect misfires…

The problem here is that not only did you use the same hardware somewhere else, but had to add linkage, bellcrank, the added frame rails… and adds all of it both outside and behind where it would usually be, adding to the polar inertia of the chassis, raising the CG and increasing total weight.

Like I said, I would be shocked if there was an overall decrease in mass with this setup, and as dean mentioned just running upside down mounted shocks/coil overs should result in a greater decrease in unsprung mass as well as total mass.

Within the chassis limitations of an f-body, at the very least the coil overs could have been mounted inboard, towards each other which would have at least kept the weight down by only needing to add crossmember rather then the 2 frames, and would have kept the weight added to the center of the body. Possibly an even better approach would be to mount the shocks along the part of the floor that makes the seat back, moving them even closer to the center of the body, using up space that most f-body owners find useless and keeping the weight at about the same height as it is in the stock location plus making most of it sprung weight.

Spifz

Not that this matters much, but just for the sake of information, I used the shortest QA1s, and consequently, a 7" spring, not the long ones that are used when mounting them in place of the original shocks. Clearly the smaller shocks and springs don't make up for the added weight of the rockers, pushrod and support frame. I think it would be pretty hard to mount the rocker so that the coilovers would point at each other in the middle. It sounds simple to say it, and everybody sees that design on F1, SAE, ... but think of the pivot location necessary to do that. The coilover will either be in the middle of nowhere, in front of the back 'shelf', or if you angle them back, in the way of the T-top location. (That is if you keep the pushrod coming up through the shock hole. If you move the pushrod or angle it, then you have a hack job somewhere else.) Since I was putting rear bars in for the roll bar, I just made sure to line them up so they would be right where I needed them for the pivot. There is also the nice piece of frame rail to attach to in the back.
For some this may be unheard of, but I am not really being weight conscious with this car. I also agree with (and understand from a handling and mathematical sense) the fact that I increased polar inertia, raised CG and added weight. Yea, I want it to handle well, and am planning on road racing it (for fun), but at the end of the day, I'll have my coilovers doin' their job right alongside the T-tops in the factory bag, or more likely, a stack of rack mount servers on their way to a site.

DAVECS1

iTrader: (2)

The problem with a Watts is in FACT that the center pivot must be on the axle housing and the links attached to the chassis- if you mount the center pivot to the chassis and the links to the axle(reversed) it will not motion directly vertically and will have lateral movement still.

actually as long as the arms on the WATTS link are of equal length, what ever the pivot is mounted to will move linearly.

After Drawing the motion circle for the Mumsford, I can see the advantages especially for long travel. In essence it is a WATTS link folded over. Instead of having an extremely large pivot with long arms, you split the distance over two pivots that allow you configure an overall virtual pivot point.

Like HPE point out before it all is a matter of space and travel.

Spifs, I would not worry too much. about your set up and weight. In my opinion these cars are nose heavy to begin with. If you have added rear weight I imagine even though the overall weight is higher it is better distributed. And while one guy is making due with his spring setup up because it is 90 F out and he doesn't want to crawl under a hot oily car. You will simply pop your hatch and make a simple adjustment.

Wanna do my car??

HPE

Dave, You'll have to do a working model to see the problem that arises when you mount the pivot on the chassis side- It will NOT work. Because of the axle articulation (meaning one side up, the other side down) the pviot being on the center of the hosing has no affect on axle articulation as the center of the housing travels up and down itself- the two atriculations stay separated and function properly.Now, when the pivot is on the chassis side and the arms(links) attached to the end points of an axle, AND you get both lateral articulation as well as up and down supension travel the axle center will yaw left going up and right going down (Based on which sides the up and down mounts are on, this can be reversed).The pivot has to be on the axle center on a watts link.

305TA85

Excellent thought, innovation, and accomplishments. You have not said how the actual ride is. I am curious to know. A friend and myself have been looking into other issues with the rear in these f-bodies. The panhard bar. Have you any thought to that problem? The problem? you may ask. The arc. I understand this needs another post probably, but it seems there are the appropriate peoples already here. I have put no calculations into this idea yet only thought. Yeah the dreams are coming out. Has anyone thought of using a spring design to elminate the arc, and still be strong enough to hold the rearend corectly inside the fenders. I work as a designer at a testing equipment company. I will be starting a new thread soon and was just curious if any thought to the issue has already been taken.

ghettocruiser

iTrader: (4)

Is the arc created by the panhard bar even that significant?? My panhard bar sits pretty level...which means it doesnt move left/right much at all during normal suspension travel. I mean...that type of suspension configuration is proven and works really great. And Spifz looks like he used rod ends on the axle end, so those would help keep the motion smooth even if it does arc.

I think I know where you are going with the spring idea, and I just think that if the spring is strong enough to hold the rear in place, yet soft enough to allow for arc correction, that those two properties will cancel each other out. Like you cant have both... and you NEED it to keep the car in line.

Just my thought, but Im no suspension genious

I really like his inboard coil overs the more and more I think about them. Im really anxious for Spifz to get it back together and on the road to try them out. Still too much fab for me to want to try it...but if nothing else, his vid of him adjusting them is making me want to go to coil overs..haha.

Justin