how to build your own control arms

[zzzz]

Just thought I would make a post about control arm design as Pete K's thread about his buggy was getting a bit off track.

Disclaimer: I am not an engineer of any type. I am not a professional suspension designer. I have not built any control arms (yet).
I would recommend you get your control arms built by a professional welder as it is very important the links are sound.
Please seek professional advice and assistance before building and then driving a custom suspension on the street or offroad.

Having said that I have spent way way too much time researching suspension geometry, design and control arm components and hardware.
I have measured my links, control arm mounts, frame rails, axle tubes, diff centre, track bar, spring pads, etc. etc. and have used this information
to model the current short arm design and also my proposed 4 link.
I thought it might interest some of the ausjeep crew if there was some discussion around designing your own control arms and suspension

Anyways, here we go...

Here is a link to pirate4x4 where you can see how to make some simple non adjustable long arms:
http://www.pirate4x4.com/forum/showt...d+control+arms

Gives you a good idea on how to make a simple arm with a RE type joint at one end and a rubber bushing at the other end.
This end configuration is well proven and has been shown to provide more than enough flex for most of us.
RE superflex arms use a similar setup as well. Same with Shane's firetruck, which has currie Johnny joints at one end and nissan rubber bushings at the other.

The following two sections of polyperformances website give you a great idea of the hardware that is available for anyone wanting to make their own arms.
Sean at ABT4x4 has a strong working relationship with the guys at poly and can source anything you see on their pages.

http://www.polyperformance.com/shop/home.php?cat=25
http://www.polyperformance.com/shop/home.php?cat=98

As you can see you have a few options for joints on the ends.
Rod ends/heims or spherical bearing joints similar to RE or JJ.

Heims look easier as they are threaded but generally have the disadvantage of wearing out quickly and transferring more
shock load through the joint and into the frame making for a harsher ride. The tech around making them though seems to get better and better and the shortcomings are being worked on all of the time.

The currie JJ's or RE joints are rebuildable and I would have to say would be my preference for the axle end of the link.
The frame end is fine as a rubber bushing and has been proven to work again and again. RE superflex arms are built with this design and we can see how they flex, even when they are short arms.

You can also see a range of threaded rod inserts.
These can be welded into DOM tubing to provide a section that you can easily thread an end into.
Heims seems like the most obvious choice for this, but you can also purchase Currie Johnny Joints with a 3" section of threaded stud welded onto them.
Link here: http://www.currieenterprises.com/ces...nnyjoints.aspx

DOM tube can also be notched or fishmouthed to allow you to weld a RE or other joint onto that end.
The joint needs to be dissassembled first otherwise the heat of the weld will melt the race or other components.

So at one end of the link you can either notch the tube and weld the dissassembled RE or currie joint on, or you can go for a joint with a threaded section that can be used with the rod end insert.

The advantage of using the threaded insert is that you now have an easy way to adjust the length of the control arm for pinion and wheelbase adjustment.

If you use a left and right hand thread at opposite ends you then have a control arm that is adjustable for length without having to undo either end. Now that is cool

There are some decent pictures and prices on the following web site as well:
http://www.rockcontrol.com/Fabrication/fabrication.htm
They are using square tube ala claytons suspension designs and make inserts and some other hard parts to suit.
You can see they also make frame end brackets for US$40 each

So you can either buy an off the shelf short arm system or make your own arms.
Suburban are selling the RE joints, and the curries need to be purchased from overseas as we do not have a local distributor as far as I am aware.
there are also other manufacturers of similar style joints out there.

An off the shelf short arm has the advantage of being simple to acquire and you know it has already been engineered.
You just lay down the cash and then bolt them onto the jeep. Simple...
If you do decide to make your own custom arms though you get to decide on the control arm length, end hardware, tube thickness, etc. etc.
The biggest plus ( for me anyways) is that it is fun to build stuff for your own jeep.

You really need to be confident with what you are doing if you want to make a long arm system as you are changing the mounting points and geometry of the whole system.
I would suggest you spend a lot of time reading and researching before starting on the design and build process.
Start here: http://www.pirate4x4.com/forum
and search and read, and search and read

The four link calculator will let you play around with link design and is well worth looking at:
http://home.earthlink.net/~triaged/F...arLinkV3.0.zip
You can now confuse yourself with antisquat, roll axis, roll centre, instant centre, COG etc. etc.

Also there is a thread discussing this excel app that is useful.
http://www.pirate4x4.com/forum/showt...ink+calculator

I am sure that other people have plenty of input here as well, and it would be great if people just asked a bunch of questions and the more knowledgable folk could give their opinions.

Anyway, this was just to get things moving...
Please feel free to correct my mistakes and provide more insightfull information

cheers

z

[murray]

this is good for offroad use only
if u make any thing you self you will need engineers drawings and weld proceedures bill of materials and even ndt of welds
all this to ballance one word LITIGATION
just say that mod the arms and one fails and you hurt/ kill a 3rd party
its instant your balls are theres or a nice room in lime stone lodge with a roommate called bubba
i am a profesonel welder by trade
so i know whats involved to make some thing like this
2 hours to make 10 hours paer work to cover your ass(think of bubba)
not tryining to dappen any ideas just want everyone to know the ramifications

[murray]

oh and by the way i cant spell

[zzzz]

Murray - can you provide a link to a legislation to support your comments?
I am not doubting it may be the case, and there are definitely issues here for on road use, but it would be great to hear the facts in the light of the law.

Does every local fabricator have all of their welds xrayed and each component they make signed off by someone?
What about if they do cusom work and the control arms etc. can be different depending on the vehicle they are building at the time?

Is it purely a litigation issue in the sense that you have shown negligence in creating the running material which is not up to standards?
could you not then show due care and attention?

Is this listed in the ADR's at all?

I don't want to see this thread turn into a discussion about legalities, but it would be good to get some facts.

cheers

z

[murray]

it is simple under your duty of disclosure
to your insureance company
the point i was trying to make was that any mod like this needs to be done propely

[andy_n]

Since I am intending on keeping short arm for now (especially after what has happened to JimmyB), So I am going to keep my standard arms, so that I can swap back if something goes wrong with Tene's Grand and I have to use the TJ as a DD.

But I am looking at doing a short arms that use a type of Johnny Joint in one end and Patrol bushes in the other.

[zzzz]

Andy - I virtually started this topic as these were the questions you were asking in Pete's buggy thread

If I were you I would look at either the RE arms or getting something else made up with a similar design.
It is hard to go past the RE units if you can get them for a decent price

And we have seen they can flex very well indeed on JPmarks jeep on the jamboree ramp.
So they can flex heaps and then you have the luxury of tuning the setup to provide the flex you need/want.

Take a good look at the 2.5" currie JJ that has the threaded stud welded on already.
http://www.currieenterprises.com/ces...t.aspx?id=1265
Then a tube insert and jam nut.
Other end can be any rubber bushing you find for a decent price.
You can even re-use ones out of stock TJ arms.

If you do find a local source for similar joints to the large RE or 2.5" currie then let everyone else know.

It would be great If you can share more info about what you end up building.

cheers

z