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Rear 4 Link

TheYeti

Active Member
Hello all,

I've got the RPM rear 4 link kit. I've been doing lots of 4 link reading.. but I can't find much of anything on 4 link in a t bucket.

Anyone got info they'd like to share or pictures of their setup?

Screenshot-20220319-070847-Chrome.jpg
 
Not a lot of room under a bucket for 4 bars. Did Ron not send instructions?

That's what I'm running into.. I need more frame kick up and lose the trunk idea.

His ebay ad said something along the lines of "instructions not included. Must be installed by a professional"

Well I'm a professional home builder lol. 3rd generation mechanic and my dad is a mechanical engineer. I'm no dummy. I just want to set it up properly to make the car hook.
 
I worked for a month trying to fit triangulated 4 bar to no avail. Now I have decided on unequal length bars with a panhard bar. When I get my steering arms done I’ll move to the rear and have some pictures then.
 
Gave up on the 4 link cause it wasnt worth losing my trunk.. morphing the kit into ladder bars
 
maybe sell them and have Ron whip you up some radius rods
 
maybe sell them and have Ron whip you up some radius rods

I'm gonna use what it is to build ladder bars. The whole point of the 4 link was making the car "hook". Ladder bars will achieve the same thing. Radius rods are for your normal cruiser.

I hate to publically say this but I'm not sure Id buy from him again...

These brackets look like a water jet gone rogue. Random nicks/cuts in the steel possibly indicating a need for calibration or worn out parts that require replacement. The holes for the 5/8 bolts are super sloppy. Could probably drop 3/4 bolts thru them... along with that it is seemed tubing.. not DOM.
 
I hate to publically say this but I'm not sure Id buy from him again....

He can defend himself, but I have a feeling that if he knew you'd be building a racer he'd have spec'd different materials. He does a lot of work for folks racing gassers.
 
If you want to hook up, a properly set up 4 link is a better choice. If you put the top link outside the frame and use a watts link or diagonal between the bottom bar you don’t lose trunk space.
 
There is a difference between a parallel 4 bar and a 4 link, and yes if you want it to hook up you should use a 4 LINK. Ron does great work and he did do some custom stuff for me, I had some other things from him and he relies on the water jet too much to make kind of sorta round over size holes, I told him just pierce a hole and I will drill it to the size I want.
 
There is a difference between a parallel 4 bar and a 4 link, and yes if you want it to hook up you should use a 4 LINK. Ron does great work and he did do some custom stuff for me, I had some other things from him and he relies on the water jet too much to make kind of sorta round over size holes, I told him just pierce a hole and I will drill it to the size I want.

Well that's an error on his part. You can see at the bottom of that photo was cropped that he infact 100% calls it a "4 link".
 
I don't usually wade in to these type of discussions but since I know Ron Pope and I have actively been designing and building drag race cars, street cars and vintage replicas of 50-60s road racing cars since around 1974 I feel I have a fairly good education in various suspension systems.

  • The term 4 link versus 4 bar is nothing more then a choice that you and sales ads make. There is no difference although I really have never heard the 4 “bar” term used.

    If you will google street rod rear suspension kits you will see a number of advertisements showing exactly what you received from Ron Pope and the attached picture from Scott's Hot Rods.

  • The 4 link you have is what I call a neutral suspension. It only is capable of pushing and pulling the vehicle forwards and backwards. It is not capable of creating any lifting forces. All four links kits are pretty much generic in design. All four tubes are of equal length and run parallel in the vertical axis. I have used these systems in recreations of 50-60s vintage road racing cars like the original Scarabs and the Aston Martin DBR1 cars. They worked very well then and still do in some modern vehicles.

  • The drag race 4 link normally has a long lower tube that is somewhere close to horizontal. The upper tube is around ¾ the length of the lower and runs at a negative angle. There really is no “correct”angle. The way it is designed is the the two links on each side project a imaginary line forward and theoretically intersect at some point forward. That point is calculated from a number of things including axle torque, vehicle weight and a number of other things. The upper bar will attach above the axle housing. It use to be that a team just experimented by making a number of 60 ft launches and trying a lot of combinations. The engineering types started calculating all the forces and came up what worked for that car. Now there are computer programs that work for you.

    So as they used to say,

    You pays your money and takes your choice

As most of you probably know the early days of racing began on the salt flats and in southern California. A number of those early racers worked in various aircraft factories and took their craft and knowledge to the various garages where great cars were built. There is one other thing I want to discuss. Having ties to aircraft work many years ago I to learned a number of those standards and have lived by them since then. Fasteners or bolts are a number one issue with me. When I order any flat metal brackets requiring holes for fasteners I always specify a pilot hole from the waterjet, laser or plasma cutting shop. I order a fractional size hole diameter under the bolt size I will be using. I then use a metric size under the drill size. Last pass will be a finished hole size using a ream. All work will be done on my vertical mill and clamped down to insure no accidents. If the cutting source can hold very close tolerances I will call out a .010 undersized hole and ream it in one pass. Now you are probably wondering why the close fit I want. All commercial bolts both Grade 5 and Grade 8 have a wide diameter tolerance. You can google that for information and be able to see the allowed diameters.

Aircraft fasteners are much closer fits and often require reaming to fit. Drill bits have a history of drilling overs zed without using a ream to get a close hole diameter. In a racing application commercial bolts can hammer out the hole causing it to egg shape. It can also cause deformation on the bolt shank. Either is bad and should be avoided if possible. There is one other big difference in commercial and aircraft fasteners. Commercial bolts have a fixed length un-threaded shank with varying threaded lengths.

I like to have all bracket holes to ride on that solid surfaced shank. With brackets and poly bushed 4 link eyes that's not possible. Threads on smooth hole Ids puts the treads in shear and possible damage or even failure. Aircraft fasteners have the same length of threads no matter how long the bolt is and never put threads in shear. Now I realize this might seem over thinking but in the racing world in can cause failures that can be very costly. This is just my thinking and how I do things and I'm not telling anyone how to build their car. Take it for what it is. Last but not least.. Chrome plating bolts. Really a bad move. Not allowed in aircraft and possibly in the Fuel Dragsters as they have gotten a lot more rigid in their specs. Hydrogen Belittlement is the problem. Hydrogen molecules can and will find tiny flaws or cracks in steel bolts and weldments which can lead to a failure under stress. Aircraft fasteners had to undergo a special oven baking process but the EPA made plating so expensive that they now color etc those parts. Take it for what it's worth.


I was not going to mention this but decided to bring up op one more thing. I have seen people on this forum try to ask advise or order parts from the advertisers many times over the past years. I don't understand why anyone would want to conduct their business on a public forum. But the real issue I disagree with is complaining about work or services from the sponsors. If I were to receive parts I didn't like I would contact them directly. I have known Ron Pope for a number of years. I also know that he would take parts back or recut them but one thing for sure. He will make it right. He uses a plasma arc cutting table and has cut non automotive parts for me and they worked perfectly. Common sense would tell me to keep my displeasure to myself until I spoke with him.

Now that I have said my peace I will say no more.


George
 
Well said George. Secondly, if I remember correctly, the term "4-bar" is simply a copyrighted term coined by Pete and Jakes, and can mean anything they want it to mean.
 
Well said George. Secondly, if I remember correctly, the term "4-bar" is simply a copyrighted term coined by Pete and Jakes, and can mean anything they want it to mean.
I appreciate that. As for the "bar" term. I think you are correct. After writing this I opened a new Speedway catalog and that's the only term they use. Not sure about P&J but will look later on today.
Take Care!
George
 
Gave up on the 4 link cause it wasnt worth losing my trunk.. morphing the kit into ladder bars
I did the same thing. Started with 4 link and discovered there's not a lot of room for it. Ended up going with radius rods.
 

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