I have afew questions about making pivot strut rods (materials)

I've been looking over the page on dazecars site about converting your stock strut rods into pivot rods and I've got afew question that maybe you guys could answer in regards to materials and parts...

1. The instructions say to grind down the strut rod so it can be threaded to 5/8"-18 threads. Does 5/8" have enough tension strength? I was thinking about just threading it 3/4"-16 which the rod is just above 3/4" as is so little or no pre-grinding. Input?

2. He uses a cast iron industrial clevis for the heim joint to attach to the strut rod mount. I was looking on summit trying to get a parts list going for this and saw this http://www.summitracing.com/parts/CEE-3422/ and http://www.summitracing.com/parts/CEE-3423/ they are 3/16" stamped steel so I was woundering if they would be strong enough? I was also thinking about using these http://www.summitracing.com/parts/CEE-3425/ to weld to a "oversized washer" of sorts and make my own clevis. Once again strength is the issue... I have seen some nice looking machined clevis for 4x4/off-roading but they are $75 to $100 a pair *ouch*. I would like to do this whole thing for less than $100.

3. In relation to the above clevis it is all held togeather and attached to the frame with all the tension strain pulling on 3/4" of 7/16"-20 threads of a Grade 5 bolt... How much strain can a 7/16"-20 take in tension? I'm sure if I look I could find a answer to that but anyway... I was thinking why not use a grade 8? and if there is not enough threads before the unthreaded section just use a die and continue the threads? or is there some reason that will make it weaker than a grade 5?

4. Swegded Tubes, do they make just a threaded tube? a 0.095" walled tube seems kinda thin. is there anyone who makes a hex tube that is threaded with LH and RH threads? I don't know the proper word to run searches with but does "joining tube" sound right? I think I did see some but they were made from Aluminum and once again I don't know if it would be strong enough...

5. This one should be number one probably, How much pressure is actually applied to a strut rod? what is the "strong enough" threashold?

I don't know if I should just order what he has listed and don't think about it and try not to worry or what. I'm probably thinking to much on it and will end up over killing it.
I was kinda planning on threading the strut rod with 3/4"-16 threads, use a accomodating swedged tube or preferably a 1" hex bar with the appropriate LH/RH threads in it, 5/8" bore heim joint with 3/4"-16 LH threads, and some kinda of clevis and use a minimum of a 1/2" bolt to fasten it to the chassis with the neccisary spacers/washers.
I've been thinking and searching over this for quight awhile but I'm not coming up with any answers. Does anyone know of any manufacturers that make some of the parts I've discribed? or has done this mod and driven on it for awhile to attest to it's durability? I would greatly appreciate it. Thank you.

 

David,

I have read your post a couple of times and gone on the dazecars site to look at what they offer, and they seem to have some nice pieces.

First, let me say that when you are building suspension pieces you need to start with good pieces/material. What I mean is that any suspension pieces that are stressed under load need to be examined very carefully especially if they are used pieces.......................they need to be aggressively cleaned and then Mag'd or X-Rayed to find any issues with
the metal that is not detected by a visual inspection.
After they have passed the test then, and only then are they safe for use. Also, when using bolts for suspension pieces only grade 8 should be used.

Rather than modify your existing ones I would visit this site and look at some of their products. As for trying to save money by fabing your own
suspension pieces is not the right attitude to have.....................as you
are making a decission to possibly put your life and others in harms way.
Unless you are an engineer and excellent fabricator I'd leave this to someone who is better qualified.

I didn't mean to be hard on you, but I have been around the block a time or two, built my own hot rods from scratch, built drag cars from scratch and raced purpose built/modified cars in SCCA racing for number of years.
It is one thing to blow up a motor/transmission/rearend at speed, but if you break a suspension piece at speed it could cost your life or even worse....................someone elses.

Why not take a look at this website and some of the products they offer;

http://www.rrs-online.com/strutrodproducts.php


IMHO

 

Here's what I've been looking at:
http://www.streetortrack.com/Street-or-Track-Adjustable-Strut-Rods-pr-16135.html

A friend of mine is installing a set on his Mustang.

 

I just did this for my 66 Mustang. I cut the strut rod and used a 3/4 x 16 die instead of having the rod turned down. Same thinking as you, is it safe to turn it and put added stress on the rod.... I did use 0.095" swedged tubes but steel not aluminum. Check out Speedway Racing for them. Where I deviated from Daze's setup is in the front mount. I don't trust the bolt in tension and the cast clevis. I followed Delta Bay Mustangs setup which requires you to cut out the center of the rod mount, where the original bushing rides, and run a bolt through the the remaining mount. If your looking to return the car to stock in the future this might not be for you....I added steel washers and a 3/4" bolt to the mount (welded the washers), then boxed the front portion of the mount to add strength and keep out major road debris. The other reason I went this route is it keeps the suspension mounting points on the same location as stock which with the lower arm and strut rod is essentially a 2 piece lower A-arm. Both inner pivot points want to be as in the same line along the chassis.

 

well... my financial outlook doesn't look well enough to afford rrs componants or global west or any of those other aftermarket makers (maybe if I could find a job in my field but not where I'm currently working), so I would have to modify or make my own, safety is why I'm asking all these questions. I want these things to last, I would hate to have to go back and redo them later for some stupid/simple mistake that I could have corrected by just asking some questions to people who know more than me, or in a worst case scenario would be to have them brake and kill someone else or cause property damage (if I die than it's not that big of a loss, I'll be out of my misery). Causing someone else death because of a stupid mistake is inexcusable, property damage depending on how much would make me wish I died instead... Another words doing it right the first time is a given, if the resulting part does not seem adiquite I wount install it.

tweet66, your install may be the best way to go I just hope it can be modified and reinforced fairly quickly sents my maverick is my daily driver. also how long have you been driving on that setup, is it holding up well? thanks.

 

one thing that kinda worries me about speedway motors is that they don't give very much info on their products like strength ratings and the like... I was thinking that a heim w/zerk fitting would be nice assuming its even remotely neccisary. I've been looking on summit mostly because they give strength ratings on most of the parts, what is the minimum strength rating I should be looking at? no sents in buying a $40+ rod end that can handle 40,000lbs+ when all thats needed is one that can handle atleast 10,000lbs... I'm all for overkill but theres a point when excess becomes a waste.

 

David,
It is possible to do what you want, on a budget, safely.
I would ask why you feel you need to do it? These parts are for cars that must be extremely positive handling consistantly on the ragged edge of traction. You will notice that they transmit more road noise and shock when travelling on the road. Tracks are kept in better condition than the roads we travel and when driving a race car you are expecting to feel the road more than when you are driving grandma to church Sunday morning.
All that being said;
Your existing rods can be threaded with 3/4" NF thread, You should be able to find a local bolt place to get threaded sleaves that are steel. You should be able to get all the hardware you need locally.
A grade 5 bolt has 120,000 PSI tensile strength so 11718 lbs of pulling force is what its breaking strength is. A 3/4" grade 8 bolt has 150000 psi tensile strength and that equates to 66268 pounds of pulling force. (tensile strength) If grade 8 bolts are allowed to work they become brittle faster than the grade 5. This is something you need to be aware of because sometimes it is not the strength you need as much as the durability. Contacting a local club (racing) may give you access to some "creative" fabrication that has been proven to work and might be adaptable to your use.

The best clevis to use would be a forged clevis but a billet clevis will be almost as good. The hard part is going to be the bearing. It will need to be able to take the same loads that the rest of your hardware does and you are going to have to either buy one that is purpose built for this use or find one at a local bearing house that is rated for the same loads. Purpose built parts are more expensive but no better than one of equal strenth that is made for general use. It just takes a bit more shopping to find the part you need.

I hope this helps.

 

David, the conversion took me about 4 hours for the strut rods. I also made my lower arms into a roller bearing pivot at the same time. All together, arms, rods, mount modifications took me a weekend. I can't say how they work just yet. I'm in the middle of making brackets to put Cobra 13" brakes on the front. Wish I could afford to just buy the stuff, but I'm poor...besides I find it more fun to build this kind of stuff myself.

Call Speedway directly. They have all the information and if you get one of their catalogs there's additional specs in them as well.

 

As a note the swedged tubes do have a purpouse. Swedging puts specific strains on the material, thus in turn making it a much stronger unit with a much lower weight ratio, and smaller profile. (Much the same as shot peening does to components)
A good example we make the nose landing gear actuators for the 747 which is a big plane. If you look at the landing gear actuator you will see it is roughly comprised of several pistons ranging in the 4-6" diamater 4 feet long. Now if those pistons were solid then they would weigh in at several hundred pounds,(infact the forged blanks weigh about 350 Lbs). But we drill a big hole in them and have them swedged this both reduces weight but it pre-loads the piston rod with internal stresses so it will handle the shock load of the aircraft landing. So in the end we are left with a giant hydraulic piston that weighs 50-60Lbs instead of 350-400Lbs but is just as strong, if not stronger...(Ps we mag inspect and Eddie current inspect those pistons, we dont have an x-ray machine)

 

I don't know much about suspensions but I remember from some schools at the power company that bolt threads are not actually cut from the factory. They are more or less cold rolled in some form or another. What I am getting at is if you take a grade 8 bolt and use a die to cut more threads onto it then it is probably not a grade 8 anymore. The die cutting new threads onto it has weakened the bolt.
clint

 

Yes, grade 8 bolts have rolled threads. Grade 5 do not have to be rolled.

 

not necessarily it all deals with the strength of the material used to make the bolt, the heat treat and the tempering.

 

Mark,
You need to do a bit of research. Grade 8 bolts are made of a stronger alloy than the grade 5. All grade 8 bolts have rolled threads. Some grade 5 bolts have rolled threads but they do not have to be. The alloy used is what determins the strength and the heat treatment is done to assure that strngth has not been compromised in the manufacturing process.

From the "Pocket Ref":
grade 5 (SAE J429) Medium carbon steel quenched and tempered
Maximum tensile strength = 120000 psi
Proof stress (yield) = 85000 psi
(1/4" - 1")

Grade 8 (SAE J429) Medium carbon alloy steel quenched and tempered
Maximum tensile strength = 150000 psi
Proof stress (yield) = 120000 psi
(1/4" - 1")

Grade 8 bolts are made from a stronger alloy than the carbon steel of the grade 5.

 

I want to do this to make them a more long lasting part, I have polygraphite in there right now which I know now to of been a mistake, I have some rubber ones I picked up just never installed because I'm worried that they wount last very long... rubber just doesn't last long in arizona, expecially when exposed to the ellements. Also freedom of movement is also a agreable result.

So far finding a appropriate clevis has been the main problem... I'm temped to pick up a couple of those I mensioned above the one with the 3/4" mounting whole than perhaps make another bracket that would be fit on the outside on that one reinforcing it with 1/8 or 3/16 steel...

I've found alot of heim joints out there with ratings from 8k lbs up to 40k lbs... as far as noise I've heard that the teflon lined ones are quighter and if I go with QA1 most of their heim joints have a optional zerk so they could be greesed.

Tweet66; I was looking at the rod mounts on my mav and it turns out that what you did wount work because it doesn't have the parrallel supports that you drilled and ran a bolt through so I'm going to have to find another type of heim joint receaver.

So would a 3/4" grade 5 be a better choice as a main mounting bolt through the bushing hole than a grade 8? I plan on having it torqued down so it doesn't "work" around.

For some reason I can't find anything in the phoenix area from a "bolt" store or a decent general "machine" shop... I appreciate all the responses from everyone, my quest continues.

 

Is that not what I said? Or are you saying that all Grade 8 bolts have to be rolled? If that is the case then how come grade 8 bolts are rolled but grade 8 nuts all have cut threads? If you are using a grade 8 bolt and grade 8 nut together then does that not nullify the extra strength properties of the formed threads on the bolts.:16suspect

But the answer is..No grade 8 bolts do not have to be rolled, neither do the grade 12 bolts that we use for flight hardware that they grind the threads on. The material just has to meet the minimum tensile strength put forth by ASME for the grade of bolt.

The reason why the majority of the grade 8 and grade 5 bolts that you buy from the store have rolled threads is because they make them with a bolt making machine that rolls the threads from a sized stock. They do that because it is cheaper to produce them that way in mass quantities then it is to cut or grind the thread.

Here is some of the ASME Data that set the standard on the strengths of different grade bolts.

Bolt Strength

The Society of Automotive Engineering has issued standard J429, which sets forth standards for both strength.
The SAE grade of a bolt is marked on it's head in the form of short radial lines, the number of lines being two less than the SAE grade (i.e.. 3 lines for grade 5).
SAE Grade____ Size____ Range Strength (psi)
_____1_____ 1/4" to 1-1/2"______ 60,000
_____2_____ 1/4" to 3/4"_______ 74,000
_____2_____ 7/8" to 1-1/2"______ 60,000
_____5_____ 1/4" to 1"________ 120,000
_____5_____ 1/8" to 1-1/2" _____105,000
_____7_____ 1/4" to 1-1/2" _____133,000
_____8_____ 1/4" to 1-1/2 "_____150,000
ASTM standards are sometimes used as well; A325 bolts are the equivalent of SAE 5, and A490 bolts are the equivalent of SAE 8.


Here is a good page for showing bolt strengths for a wide range of sizes
http://www.derose.net/steve/resources/engtables/bolts.html
if you note they dont talk about rolled or cut threads nor any of the other thread forms, like the buttress threads, the acme threads, the J threads, they just talk about the standard UNC(united national course) and UNF(united national fine) threads.

We have to cut or grind almost all of our threads because we utilize J threads in most situations so instead of 1/2-20 UNF it would read 1/2-20 UNJF. The J thread utilizes a modified root radius then the standard thread form.

Heat treating is done for several different reasons, first you have a quench this can create a tough outer coating while leaving the inner material to be more of a fluid structure. The process for quenching is to heat the material past the austenic temperature and then dunk it into a cooling liquid, usually water, oil, heated brine(salt) or air.
Then there is this is annealling this is used to soften the material to relieve internal stress making it a similar density throughout and re-aligns the crystaline structure of the material giving it a stronger binder. The process for this is to heat the material past austenic temperature but before it becomes a liquid state then allow it to air cool. This is also called Normalization.
Then there is tempering, most material is tempered basically you heat the material to a sub austenic temperature and exert forces or pressure onto it making...(this is also the same processes for forging, go figure..you know like forged cranks) We are generally held to AMS 2759http://www.nitrexmetaltech.com/docs/ams2759_10a.pdf as it is an industry standard in heat treat and per military standard MILSTD-6875,MIL-STD-1684A, plus all the BPS and BMF standards that required of us just for heat treat alone.

as for the alloys there are many different alloys, heck steel in itself is an iron alloy but the alloys added to steel dont necessarily determine the strength. Take 12LR14 it is an alloy steel but the alloy in the steel denoted by the L is Lead this alloy is put in for ease of machining, as is sulpher. But also you start to add nickel and you start to reclassify it as stainless steel. Some of the alloys do make it stronger, and some make it weaker and more pliable, but as long as the carbon(or other modifier) to iron content maintains a high enough tensile strength it can be utilized as a higher grade material.