Fatman Fabrication Wonderbar Rear Suspension

[68Formula]

Anyone using this? http://www.fatmanfab.com/06page23.htm

Looking at it, it seems simple and inexpensive. But I wonder whether there is a noticable improvement in handling, ride, and/or traction.

[baz67]

The silence is telling you something.

[68Formula]

So it isn't just me that thinks its... shall we say... not really a good design? I noticed there is a Superchevy article giving it praise, but that's all I can find.

The silence is deafening.

[Mean 69]

I would guess you can find all that you need with a search, if not, that will further tell you something!
M

[68Formula]

Yes, all searching came up with zilch (here and google). Guess I'm stuck with the leaf springs. Oh well, that was out of my price range anyway. Thanks for the input.

[RobM]

At first i thought it was a quarter eliptical setup but on second glance It almost looks like a make shift trailing arm (truck arm) suspension. that would be a VERY easy set up to make your self. i dont want to step on any ones toes but i would make that my self for wayyyyyy cheeper. the only peices in there that you cant get at any junk yard are the coil overs and the rod ends. looks prone to wheel hop

[astroracer]

I've been looking at this setup for a while. I think it would be worth a try. Like RobM said it is a trailing arm suspension but it is also a true 3 link. The built in compliancy of the springs is what intriques me. The half leafs and front bushings will allow for any roll and deflection and wheel hop could be controlled with CalTrac bars or something similar as they would mount as designed in a normal leaf spring situation. A long panhard bar would be the berries to keep side/side deflection at a minimum.
A good set of double adjustable coilovers would be a necessity and it would be easy to play with spring rates (or shockwaves) for ride and handling.
The proof would be in the pudding though as I have no idea how to model this in a suspension program.
I have decided to give this a shot on Bad Ast's rear suspension. Nothing to lose if it doesn't work as I will retain all of the original leaf spring mounting points in the current design...
Mark

[wendell]

astro,
how is it a 3 link? From reading the link I got that it was the front half of a leaf spring to locate the axel for/aft, a pbar for side to side and coil overs for up and down. Am I missing some thing? If my description is right then I declare it the dodgiest contraption known to man. Certainly not fit for cars.

[sinned]

astro,
how is it a 3 link? From reading the link I got that it was the front half of a leaf spring to locate the axel for/aft, a pbar for side to side and coil overs for up and down. Am I missing some thing? If my description is right then I declare it the dodgiest contraption known to man. Certainly not fit for cars.
I concur...with everything. Looks like a half-ass throw together that’s sole purpose is to allow for easy use of coil-overs for height adjustment. Greta for trailer queens I guess.

[astroracer]

astro,
how is it a 3 link? From reading the link I got that it was the front half of a leaf spring to locate the axel for/aft, a pbar for side to side and coil overs for up and down. Am I missing some thing? If my description is right then I declare it the dodgiest contraption known to man. Certainly not fit for cars.

Count the axle attachment points. There are two fore/aft locators (the springs) and one crosscar locator (the panhard bar). That's three locators. So I call that a three link.
If you count all of the axle locators in a "4 link" you actually have a "5 link" when you add in the panhard bar...
I can see this being a decent suspension. There will definitly be more compliance and articulation in the suspension as a whole because the "leaf link" is not constrained at the rear like a full length leaf spring. The inherent bind that is present in a "5 link" is practically non-existant with this design as there are no upper bars to hinder deflection as the car body goes through roll plus, the "leaf links" themselves will offer some radial "give" as they twist with the rear axle. I can see this design out performing a "5 link" any day, especially on a wash board surface or off camber corners. I wouldn't hesitate to give it a try....
Mark

[wendell]

Thanks Astro,
I get where you're coming from with the three links now. I was afraid I missed a link in the description. I'm going to stick with my original verdict. I've spent a lot of time developing a leaf spring suspension package for a road race first gen. My goal has been to make the system act like a 3 link (4link in your world). The biggest impediment has always been the roll stiffness and compression/ wrap under accelaration of the leaf. To a lesser degree the co-definition of the RRC by the leaf and the pbar/watts has been a problem. For the life of my I can't understand why any one would embrace those attibutes and design a suspension around them.

I guess we're lucky it's a free country. You've got a heck of a project going with that van and I hope it works out for you.

[astroracer]

Thanks Astro,
I get where you're coming from with the three links now. I was afraid I missed a link in the description. I'm going to stick with my original verdict. I've spent a lot of time developing a leaf spring suspension package for a road race first gen. My goal has been to make the system act like a 3 link (4link in your world). The biggest impediment has always been the roll stiffness and compression/ wrap under accelaration of the leaf. To a lesser degree the co-definition of the RRC by the leaf and the pbar/watts has been a problem. For the life of my I can't understand why any one would embrace those attibutes and design a suspension around them.

I guess we're lucky it's a free country. You've got a heck of a project going with that van and I hope it works out for you.

Thanks for the compliment on Bad Ast Wendall, I appreciate it.
I highlighted your statement above concerning roll rate & spring wrap. That is why you will never get a leaf spring style suspension to act like a 3 link. To much constraint and the leaf spring is a varaible rate spring so how do you tune it? Granted sliders at the rear shackles can help but these are very wear prone and inconsistant due to car attitude and side loading during cornering.
This "leaf link" design takes the leaf out of the picture. All it does is locate the car fore/aft and, to a lesser degree, crosscar. The coil over now becomes the spring and is fully tunable to the point of changing spring rates if necessary. The panhard bar can be positioned for optimum Roll Center. With no need for upper bars that get in the way the options for the Pbar are endless.
I think this design merits some deep thinking as I can see a lot of benefits with a few minor side effects that are controllable...
Mark

[sinned]

Just for clarification for the sake of any lurkers or newbies; having 3 locating links including the PHB does NOT make a particular arrangement a "3-link" under the generally accepted terminology. The lateral locator is never taken into consideration when counting the number of attachments points to the axle.

Basically this “kit” has the same characteristics of a truck-arm without the benefit of the 60+ inch long links; one of the only attributes which makes it worthwhile. Total junk and waste of time.

[RobM]

i would think those quarter eliptical leafs would have to be pretty stiff to stop wheel hop

[wendell]

I've never seen the benifit to sliders on leafs. My goal has been to minimize the roll stiffness of the leaf by using either a soft bushing or monoball in the front eye. I've always used shackles with soft bushings in the back. Adjustable shackles alow you to distribute weight when scaling the car. The roll complience that these two things allow helps to mitigate the spring's contribution to the roll center. This way you can run a low pbar (if you're into that sort of thing) with out bind from the RC being co-defined.

If your spring rate is much higher forward of the axel that it is behind, and you've got the torsional loads minimized(from above), your leaf starts to look a lot like a link w/ a coil spring. Add a little something for antisquat and you're in business. At least that's how I see it. I'm not a suspension engineer, I'm just a student of the art. That said, I'm hoping to see a 1:01-1:00 at Lime Rock this year.

[RobM]

a stiffer rate in front of the axle also will help greatly with wheel hop almost acts like a built in traction bar, wendell what do you use for springs? do you know a good sorce for custom springs? lime rock is my home track, a 1:00 there aint bad. when im back in CT we should meet up. I also have alot of friends in boston

[wendell]

This springs on the race car are about 200# five leafs that are a custom pack that the car owner built. They were assembled from a bunch of old leafs that he dynoed and mixed and matched. I think a 1:00 is flying for a 3000# 302cid car on 8.5/9.5 hoosier TDs.

I'm all for hanging out with people. We'll be at LRP in August (september?) for the Rolex event.

[Rick Dorion]

I'll be there. Used to time trial my 240Z in the 70's. Enjoyed seeing the GTO's do well last monday.

[wblanton]

I have no personal experience with the Fatman setup but I am not too far away from them and the company that is restoring my car has a good ralationship with Fatman. The suspension setup "front and rear" are on his personal car and the guy who is doing my car has driven it and says it handles awesome. He is putting this suspension set up on my 69 Conv. so I guess I will see first hand how it will work. I will let you know when I get it going.

Top LS 69

[Bk455]

I have no personal experience with the Fatman setup but I am not too far away from them and the company that is restoring my car has a good ralationship with Fatman. The suspension setup "front and rear" are on his personal car and the guy who is doing my car has driven it and says it handles awesome. He is putting this suspension set up on my 69 Conv. so I guess I will see first hand how it will work. I will let you know when I get it going
Top LS 69

How did this build work out? Did you finish it and take it out for a ride?

[2gofaster]

I've yet to see something from Fatman that didn't need modifications to work correctly, IMO. Their strut setup for the classic mustang is a perfect example. The amount of time modifying it was more than it would have taken to build it from scratch.

[blakes72x]

wow talk about back from the dead

[Tom Welch]

Seems to me that a lot of time is spent figuring out how to not use leaf springs. What is so bad/inferior about a multi leaf rear spring with the second leaf half wrapping the front spring eye and a watts link? This setup is simple to install, it works. I don't have data for comparison but why do so many re-invent the rear suspension of cars with rear leaf springs?

[mikedc]

IMHO leaf spring rears are decent for doing almost everything but they aren't the best setup for anything. Most guys souping-up cars are trying to build their ride to be more specialized for some specific type of driving.

[Norm Peterson]

I imagine that somebody who's really sharp and fully understands leaf springs could do a really good job with them. The problem is that you're faced with somewhat contradictory requirements that you're trying to resolve in just the same two suspension components that also provide both ride and roll stiffness.

It's generally easier (for most of us anyways) to be able to split the rear axle control duties up a bit more so that whatever you change to improve one thing doesn't affect all the other things that you improved during previous design steps nearly as much.

Most of the devices that improve leaf spring behavior (acceleration grip and hop elimination in particular) end up solving that problem at the expense of good drivability during hard driving such as you'd experience at an autocross or out on the big track or they introduce some sort of nonlinear behavior as they switch between one contact state and another.


Edit - that the Fatman link is 404-dead probably suggests something . . .


Norm