Custom Control Arms (How to)

Monachopsis

Member
Hello, I will be starting a thread here after my unfortunate slip and slide into the curb. As of now GT4 play wants minimum $700 for similar parts. Agile NZ wants $550. These prices are fair BUT the GT4 play ones look, well weak. The metal appears to be far thinner than needed however I could be wrong. This also isn't about money so do not let me deter you from just buying any of the units from either of these companies, they have proven to be reliable companies and as such I would trust them, however being a MECH E student that wants to get into racing as a design engineer I thought this would be great. Alongside this the FSAE car my school is building utilizes a lot of stuff I'd need here.

Currently I am running OEM front control arms but I might build some new ones akin to what Agile sells. That will also be posted here.

This first posting is to explain my plan of action and reasoning behind all design choices. I know most of you don't care as long as they work but for those who do, here it is.
Prototype 1 of the rear toe/camber arms was a failure sadly. I did not compensate for the spindle enough, however I am undeterred. I will be redesigning the bracket tonight and posting it here.

Ok so this is what I have figured out as of now.
1. Toyota hates us
2. Rust is the enemy
3. The arms are mechanically simple as such they can be broken down into parts
4. Said parts are mostly purchasable for slightly less that what NZ Agile wants for theirs. Long story short I'm in $300ish and Agile with shipping wants about $560
5. Little 'personal' work is needed but it is arguably the most important part, so if you want adjustable arms buying them isn't the worse idea

Once I have finalized my design and they function on the car I will link a BOM that you guys may use if you'd like. There is also a chance I will make these upon request to whoever would like them.

Plan of Action/Reasoning:
Ok so here's how I'm attacking this;
Swedge rod or radius rod is a threaded rod (LH one side RH other) that allows you to adjusts it's length. These will act as the main bodies as well as the adjustment vector. Change the length of the rear rod to be greater than the front rod, toe in. Inverse is true as well. It is said you can gain camber from too by extended both arms, ie forcing the bottom of the hub away from the car. Agile says 2 degrees which could be true but there could be track width/axle/strut issues if I'm not mistaken. 2 degrees seems fine, but my concern lies with the dynamics of it, ie sometimes hitting bumps, curves, etc can chamber out a tire and if that is too much chamber for the parts to stay correctly aligned, there could be wear and tear that was not accounted for by Toyota.

Heims/Rose/Tie rod ends will act as the joint to the subframe, no deflection, no loss, just feedback. There are issues here though, prime being life. I have concluded that if you 'boot' them and DO NOT CHEAP OUT they can go around 50k miles with maintenance. From what I have read as well this can be done with PTFE lube and not anything else as it will either collect debris or soak into the kevlar/teflon/nylon bushing and ruin clearances.

Bolts need to be of high grade as these are the main points of stress; for engineering types; the moment is applied at the bolts that connect it to the car however the force is applied FROM the bolts in the swedge rod, as such they have a huge shear torque acting against them

Steel is used for the 'c' bracket as I have called it. This also experiences great forces of both weight, and tire grip (as the tire is gripping it applies a force to this piece proportional to weight and acceleration, I did not do the math as it is incredibly dynamic as such I designed with a thought of 3000 lbf acting on it which is the entire weight of my car and as there are 6 of these for just the rear this should be plently overkill). 350 MPa is fine is and you can probably go lower. Agile runs a 1030 steel for theirs. As for what I got was a 'A36 A572Grade50' which isn't a real steel name. What happened is I went to a steel wholesaler for buildings asked for something that was the size I needed (this will be shown in the design pictures I'll post later) then asked for the yield. It had a yield of 50Ksi which is about 350MPa so it worked out. Finding exact metal specs is painful so just read what it says from the saler, grades are 'minimum' requirements and often do not reflect every '1030' or A36.

Proto 1 failed due to a back spacing issue in the C, however I bought too much steel so this is not an issue and I will be designing the C to be interchangeable for simplicities sake, as the two rods I'm doing are really only different in length when broken down to fundamental dimensions. Agile runs this 'idea' but gt4 play does not, nor does nyx, and I'm confused as to why, but I guess I'll find out.
 
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Monachopsis

Member
Drawings for MKII of the C clamp, will be fabricating tomorrow and installing on Tuesday when it's warmer. These are made with 'oversized' dimensions and as such reduces the length of swedge rod. In my brain that means it should clear this time and it spreads out the torque more evenly between components, ie less length of rod and more length of steel bracket means that the torques against both materials is a closer ratio preventing stress congregations on the rod. If you guys want to follow along, the note on the paper says what to cut. Please note I am using 3/16" t
thick grade 50 steel.

The shaft on the top is 5/8"-18 thread bolt which is going to be welded.
 

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Monachopsis

Member
I have been absent from here for sometime BUT for a reason. This project has gone through 3 redesigns since then but good news...They're on the car finally. Still waiting on some shorter length radius rod but once that is in it will be 100% completed. I will be posting more pictures and doing a super long write up tomorrow after 8pmish after I ride on them.
 

Monachopsis

Member
Alright Here it is: In all do honesty Agiles parts are very similar and would be easier to just buy and put on, but if you're like me and want a reason to machine then follow this below. Once I

HOW TO TLDR EDITION:
BEFORE I BEGIN ANYTHING BOLT BOUGHT MUST BE GRADE 8 IMPER. OR GRADE 10.9 METRIC.

Materials
-6061 T6 Aluminum; Blocks over 70mm x 80mm x 50mm (4)
-Radius/Swedge rod 5/8-18 LHD & RHD Threads; You'll need 2 8" and 2 7" this will be half an inch shorter than OEM, so if you can 7.5 and 8.5
-Tie Rod Ends/Hiems/Rose Joints 5/8-18; STEEL! 5/8 BORE; (4)
-5/8 ID bolt spacers; (8+) These will need to be cut and they're hardened steel; If you can custom order you'll need 46.5mm (4) then 9.4mm (4)
-Brass or Aluminum rod stock, anything above 5/8 OD works; These serve as subframe spacers so lengths of 46.5mm (2)
-Misalignment (normal you will not need high) spacers; 5/8 (8)
-Lock Nuts LHD and RHD 5/8-18; FOR THE LHD PLEASE ORDER BEFORE HAND, they are a pain in the ass to find irl. (4 each)
-New subframe control arm bolts (should be m12x1.25ish don't remember what the guy told me but I'm running the OEMS so you don't need them)
-New M14 bolts; around 85mm long whatever thread pitch just buy the correct nuts (4) I personally like nylon lockers for safety
-5/8 bolts that act as the new 'cam' bolt. Thread pitch will not matter as long as you buy the right nut. Around 80mm long
1711592876902.png

Process
1. Follow the schematics for machining the 'c' clamp that goes to the hub.
2. Machine down spacers as needed (sizes above)
3. For the subframe spacer, bore to 12.25mm (slightly over bore to make it easy to remove bolt) Then cut to 46.5mm. Make the OD 5/8" as this will need to snuggly fit into the hiem joint and spacers.
4. Keep a dremel handy with a tungsten carbide milling bit! Each side of my car was slightly different and needed some shaving on the spacers to fit nicely. The carbide will chew through anything and likes to run hot, makes the job easier.
5. Remove the correct bolts, as in the to control arms that run perpendicular to the wheel base. Once everything is removed
6. If you are having issues removing the arms, have someone pull the hub away from the car and hammer the guys out, without the bolts the rubber expands and makes it hard to remove.
7. Once everything is removed take the assembled new arms and 'hover' them in place; for the rear arms use the brass/alu. spacer sleeve and bolt it up. For the more front facing use just the spacers and use the new 5/8 bolt.
8. bolt to the hub, this may need you to extent the arm out.
9. Align the car! This is done by changing the lengths of each arm
If you have more questions please ask

Now for what happened with me and how I feel about them. I only have 2 on as of now, due to ordering issues with the parts but GOT DAMN the car hops into action EVEN WITH a garage alignment. The car wants to move now and it's great. I'm still on the OEM rubber hub bushings which I will be making Delrin or brass ones. Aligning the car is so easy too! EXTRA CHAMBER IS HUGE! I was at -.7 but I roughly measured -1.5.
The car likes moving around now which is good, tomorrow i get the correct parts to get the other 2 on then I'm roadtripping up to gunnison for the weekend so I'll get to play around. Some Cons though; speed bumps, pot holes, curbing, is truely back breaking. It hurts but thats the only stuff that feels stiff in a painful way. Here's some pics from my parts
20240324_040313.jpg20240326_150748.jpg20240326_150752.jpg20240326_150756.jpg
I wished I grabbed a pic of my tire on the toed out side....poor guy is bald in just line

Mechanical Side and Analysis for NERDS!!! like me...
So for those who would like to know why this was designed and how it was designed this section is for you.

Material Choices;
First off bolts; Imper. Grade 8 is has a good yield strength but isn't super duper brittle. It's also accessible, and mostly importantly is the grade already utilized in automotive applications. 10.9 Metric is the metric equivalent, but they have also been nicknamed 'car bolts' due to their frequency in cars. Fun fact, toyota uses 10.9 but just won't tell you! (Because they want to sell a bolt for $11 a piece rather than an equal bolt from a wholesaler for $1.50). Now why does this matter? Well the bolts are under the most stress (Force/area) by far. The c clamp has a lot more area, the rod as well. They also experience the brunt of every load in every direction, whereas certain parts will experience low load in some motions and high in others. If you can I would recommend getting them yellow zinc coated as this helps prevent rust really well but is pretty pricy upcharge for these applications. For the bolts MCMASTERCARR is the godsend! My Local boltwholesaler was more headache than it was worth.

Next the clamp: Aluminum 6061 T6. I tried steel and welds for the first 3 attempts and it never held the geometric dimensions I wanted it too. Anything that would work was also so unworkable that bending it would be next to impossible without hydraulic benders which I did not have access to. As such aluminum was the only other metal befitting of control arms. There are 2 grades that are even worth it 6061 T6 and 7075. 7075 is stupid hard to find and as such is an arm and leg. Both are aerospace metals and well are built for that case (250MPa yield). Strong yet machinable. There were a couple of issues though, the strength being about 100 MPa under what I wanted, so I had to fatten the part up in order to reduce stress. Alongside that I increased the rear tearout (Line that the bolt would take to 'tear' through the metal and free itself) for both spindle clearing issues with MK1 and also to help in compression which is seen in hard impacts with the road. (Think the control arm would like to go into the car but the bolts prevent it so the metal clamp must take the hit.) I did increase front tearout (the smaller one) by 3mm from oem but I couldn't reasonable do anymore without bumping into the shield which although mine are mangled, I would still like to keep them. This is the area I'm most worried about but it can take 3000 lbF with a FOS of 1.135 so basically the weight of the entire car pushing it through. There are going to be 3 of these (control arm, leading and trailing arms) per side which means they really shouldn't even think about getting to 3000lbf, even in track cases AND the spindle mount also was not considered so as such it is WAY over built, just the way Toyota intended!
Well see how he holds throughout time.

Now the store bought stuff
Hiems I used are booted and chromoly without grease. Why? Simple, longevity and durability. The chromoly is strong and pretty corrision resistant but the boots just help keep grime out helping with the lifetime more, as wells as keeping teflon lube in. Why teflon lube; because anything else will ruin the bushing internally and grease will collect debris. The rods are just steel rods that are IMCA approved so good enough for me!, LHD/RHD helps adjust alignment easily.

But yea that concludes this until I make the bushings also after testing I am willing to build and help build these, you can PM me and we can talk once i feel these are safe enough for me to make them for others.

As for the bushings I will be selling those once I make them because those are easy and could just be a nice mod since the rubber once are discontinued. Stay tuned!
 

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