Puting a 4 link on a unibody???

[aseaman92]

ok this might be crazy but, i'm in the process of putting a ford 302 in a 1992 nissan 240sx. It's a unibody car with independent rear suspension but that is not good enough so I'm wondering the process in changing that into a 4link. i would be using a ford driveline(engine, transmission, drive shaft, and rearend). so if you know of anyone that put some type of solid axle in the rear of a unibody let me know i'm sure a couple of mustang guys did it.

 

[aseaman92]

see there is a ton of geometry in make a 4link not so much in a 3link and very little in a 2link. SO what do you guys think of a 2link that would go up to under the drivers seat would that be a good setup for a strip/street car? but if you guys think that a 4link or 3link would be better i would need a fare bit of help with the geometry so the angles it should be at and so on.
another question is there any good books or forums on how to build any of these setups?

 

[patprimmer]

I am already on record as saying a 2 link is not suitable for street use.

Regards
Pat
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[NormPeterson]

There is at least one company that fabricates truck-arm kits for somewhat larger road cars than the 240SX. Kinematically it isn't as good as a 3-link or a torque arm, but its shortcomings can be mitigated somewhat by careful design. In larger, heavier cars it is quite predictable at speed - that the various NASCAR driving experiences turn complete newbies more or less loose on real oval race tracks with real hard walls in real race cars cars so suspended ought to be sufficient demonstration.

The lighter your car gets, the stronger I think the argument gets for using one of the other solutions. Other arrangements may be able to give you a better combination of anti-squat/SVIC location and roll steer with less structural reworking.


Norm

 

[evelrod]

Pat, I was only 21 in 1961 so I did not know that a two link would not work on the street...So, I put an Olds V8 with a four speed Hydromatic in my '46 Ford Coupe along with a '49 Olds rear end (4.10 R&P) with a two link factory GM setup with custom mounting for coil springs. Worked just fine for the two years I drove it. Turned mid 12's on Atlas Bucron Cushionairs. Only problem I had was balancing the Olds rear drum brakes and the Ford front drum brakes...caused a big spin and crash on a wet road. We learn, often the hard way!

Rod

 

[aseaman92]

so would this work?

http://i283.photobucket.com/albums/kk317/aseaman92/4barparallel.jpg

if it would work, could you explain it like what angles and stuff that is very important. pretty much how do i start?
what parts should i buy to make this go smoothly and successfully with very little knowledge going into this project.

 

[patprimmer]

From what I can see that looks like a 4 link. The upper links are mounted very low so minor compliance will create a significant change in pinion angle. Also the torque reaction from the reaction of the power applied to the axle will have more leverage over the top link.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[GregLocock]

Yes, that is a good approach, for a 4 bar.

The angles are important. I suggest you copy one that works, exactly, or else hire someone who knows how to do it, or accept that you may have to modify your design after building it.

Your big problem with attempting to design something is that you probably don't know what you really want, so even if you knew how, you wouldn't know what to aim at. That is not an insult, defining the requirements from a blank sheet of paper is very hard.

The excellent program susprog3d has a template for this suspension.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[aseaman92]

ok I found a guy that could help me. But what would be better a 4bar or 4link?

 

[GregLocock]

4 bar+panhard is what I would prefer, but drag racers seem happy enough with 3 bar + panhard. It probably depends on packaging as much as anything, you may not have the height to accomodate a 4 link, you may not have room for a 3rd link.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[evelrod]

Greg, I know you are familiar with the MkI Lotus Cortina's coil over rear suspension

In 1980, I reworked a 3 link plus Panhard that had been fabricated by Strange Engineering of Chicago to a setup very similar to the OEM, ie, using the lower V link (A link to some) and two upper links attached directly above the forward mounting points of the lower V link---Not at the OEM mounting points. This simplified the mounting system and eliminated the Panhard bar. It also lowered the roll center a bit. The OEM problems of broken axle center section was easily corrected with proper reinforcement at the bottom attachment point in combination with the longer upper links...something the Lotus works seemed to miss? Also, to continue along the lines of cleaning up the underside of the chassis, I mounted a 7/8" tubular ARB in the boot with the links going forward through slots cut in the wheel wells to links above the ends of the rear axle. The bar mounting trunnions were bolted to brackets welded to the rear supports of the roll cage. I still use this method of mounting the rear bar on our current Lotus Cortina.

Giving credit where credit is due, even after all these years...Help with this setup from Steel Therkelson (one of the Cortina works techs and later for Chapman) His experience was invaluable.

Rod

 

[izzmus]

4 link in IRS car.

Look up how Ford did the 4 link setup on the Mk1 Escorts to convert from leaf springs. Essentially they cut slots in the floor and welded in boxes. Simple, quick, and effective.

 

[aseaman92]

so i just found these clips on bearsperformanceproducts.com and it looks like that i might just get one of them to make my life a little bit easier.
but if i did that how would i make my front end to last? i heard something about capping the frame rails from the front to the back would this work?

 

[patprimmer]

Greg

I know plenty of drag racers who are very satisfied with their 4 link designs, in fact, I would think it is the most popular design for cars with rear suspensions.

This link has examples of both types.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[hemipanter]

The four link could be thinked of as a doubble A-arm system, that is working in the driving direction.
However, it is not used in top fuel or funnycars, but these are entierly different cars.
Goran

 

[patprimmer]

No suspension at all is still popular in the top levels of drag racing, but it is hardly suitable for the car in the OP.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers