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Re: drop spindles
[Re: Viol8r]
#1177898
02/22/12 04:47 PM
02/22/12 04:47 PM
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Joined: Jan 2003
Posts: 5,405
Pikes Peak Country
TC@HP2
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Posts: 5,405
Pikes Peak Country
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How does the inner tie rod pivot position change with drop knuckles?
As far as I know, the location of the upper and lower ball joints as well as the tie rod stay in the same place. The only thing moved upward is the spindle and caliper mounts.
I can see how lowering a vehicle by relaxing the torsion bars would cause that problem, however.
Legit question. All things being equal drop spindles would raise the inner mounting point of the tie-rods vs. lowering stock suspenion. Whether that is a noticable effect of bump, not sure. I would think if you are real serious about all this, these things will need to be checked before you hit the track.
Any time the vertical location of a tie rod end changes, it alters bump steer characteristics. Cranking the t-bars down or cranking them back up, the vertical position of the inner tie rod end will change. Yes, the drop spindles allow you to put the inner tie rod back closer to its original position, but in this case original does not mean optimal. In original form, mopars suffer greatly from bump steer. Restoring to original only duplicates the same problem. If anyone was contemplating a competition application with a stock suspension mopar, I'd wholeheartly recommend checking all this. For the average driver doing a fun track day, it may not be as important up front, but their desire may eventually lead here.
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I attached a few different scenarios of the effect that drop spindles can have on roll center. Bottom line is if you just bolt on drop spindles you effectively raise your roll center, unless mods are made. Your car will appear lower but the performance could be compromised. These are hypothetical drawings, just for reference.
Roll center issues are also relevant to the spindle situation as well. Whether or not raising roll center height is detrimental is a situation of “it depends.” Raising roll center does create a greater jacking effect on the front end, but also has the side effect of shortening the moment lever arm of the roll axis over the length of the car. While a larger t-bar rate would be needed to counter act the roll center height change, shortening the moment lever arm means the car will transfer less weigh laterally. So which is the bigger benefit or greater evil? It depends on the application. Minimizing weight transfer means you will have less dynamic change to adjust for or work around. However, using bigger torsion bars has limitation because there are only a few decent sized ones out there anymore. I admit I have not done any detailed analysis of roll center locations with drop spindles to get much more detailed than that. I do know with the stock ABE spindles, you can crank the car down low enough to put the roll center location underground. In this situation, switching to taller FJM spindles will raise the roll center back up within a reasonable range, plus provide an improved camber gain curve. So in this case raising the roll center is a benefit. However, a drop spindle would not duplicate this same situation because all of the upper and lower control arm pivot points also change with it. What a lot of readers on here probably don't realize is that using drop spindles, installing Hotchkis upper control arms, using an alternate upper ball joint such as a Howe or any other raised pivot unit, or simply swapping the wheel centerline position via a rim swap can have an impact on these relationships for a positive or negative result.
If I was seriously considering using a drop spindle, I'd hassle with all the analysis realted to my car, but that isn't on my agenda for any time in the foreseeable future and I'm happy with my cranked down t-bars.
Patrick, thank you for that excellent explaination of cast/forging differences. I believe a good portion of that helps explains why cast steel crankshafts are more readily accepted by performance engine builders today than they were 40 or even 20 years ago.
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Re: drop spindles
[Re: patrick]
#1177901
02/28/12 12:18 PM
02/28/12 12:18 PM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
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<snip...>and I do agree, pounding on the tip of the spindle with a sledge is not scientific, repeatable, or any way representative of the way the part is loaded. With no strain gages measuring strain and a controlled and measured application of force, you have no way of saying which are "stronger". Personally, as an engineer, I'd be embarrassed to have my name associated with this "test", but that's just me. yeah, a low carbon factory forging might bend over before it breaks, but how much force caused it to bend?
Magnumforce claims their parts are 130ksi ultimate tensile strength austempered ductile iron...a typical 1018 forging has a UTS of about 64ksi with a yield of about 54ksi. 1010 forgings are about 44ksi yield, 53ksi UTS. in the ferrous world, UTS and yield are related to the hardness of the material-- the harder the material, the more stress before yield. Again in the ferrous world, the harder the steel, the less % elongation before failure (the part snaps instead of folding over).
Austempering is a special heat treat process used mainly with ductile iron that allows the continuous steel phase to remain in it's austinetic crystal structure at room temperature instead of forming martensite in a traditional Q&T process. you end up with a more homogeneous grain structure, and a stronger, less brittle part..you typically see higher yeild and UTS levels with higher % elongation than you see in typical Q&T steel. austempered ductile iron can give an ultimate tensile strength as high as some of the strongest quench and tempered alloy steels....played a bit with it in my days at college.
granted, I can't say if the cast spindles are truly austempered, but in theory, a cast part, if properly processed, can be as strong as a forged part. the forging process works by refining the grain structure of the material. if you do heat treating to it, you eliminate any advantage of the forging process over casting, because part of the heat treating process is heating it into it's austinetic phase to basically "re-do" it's grain structure. <snip>
All true, and guilty as charged (but not in the least embarrassed). Yet, you also can't argue with a bazillion miles of drop-forged with zero (known) failures, vs. several known crashes of expensive "classic" Mopar iron with castings (admitted to me by a vendor).
And you also can't argue with taking a small-bearing A-body 9" spindle and bending it over until the knuckle part hits the vise (done at least 4 or 5 times by me over the years), with no failure, vs. 2 MF ones that snapped (the first one, not in the video, snapped instantly, but MF claimed that one was "known defective".)
I don't have the $$$ for a repeatable lab test. If you do, and are willing, I'll gladly send you an untouched pair of MF dropped-spindle knuckles, and some 200,000 mile stockers. But I want a video and report!
I'd like to see someone design and produce a Mopar knuckle to take a late-style bolt-in hub/bearing. Then it could safely be a casting, or even aluminum.
Rick
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Re: drop spindles
[Re: Rick_Ehrenberg]
#1177903
02/28/12 02:48 PM
02/28/12 02:48 PM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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Posts: 16,123
Grand Haven, MI
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Quote:
All true, and guilty as charged (but not in the least embarrassed). Yet, you also can't argue with a bazillion miles of drop-forged with zero (known) failures, vs. several known crashes of expensive "classic" Mopar iron with castings (admitted to me by a vendor).
And you also can't argue with taking a small-bearing A-body 9" spindle and bending it over until the knuckle part hits the vise (done at least 4 or 5 times by me over the years), with no failure, vs. 2 MF ones that snapped (the first one, not in the video, snapped instantly, but MF claimed that one was "known defective".)
I don't have the $$$ for a repeatable lab test. If you do, and are willing, I'll gladly send you an untouched pair of MF dropped-spindle knuckles, and some 200,000 mile stockers. But I want a video and report!
I'd like to see someone design and produce a Mopar knuckle to take a late-style bolt-in hub/bearing. Then it could safely be a casting, or even aluminum.
Rick
I'm sure there's been failures of stockers, but it's probably a very, very small percentage...this is the first reference I've heard of "several known crashes" with MF parts, granted I am not as near to the front lines of the hobby as you are.
what you're showing is elongation, and yes, a weaker, softer material bends and plasticly deforms, where a harder material breaks.
an unfilled polypropylene knuckle will do the same as the stock low carbon forged spindle--it'll bend over before it snaps, but I would take my chances with a MF one over a plastic one.
if I had to guess as to the failures, it probably is a failure in QC during the austempering process, which if not done properly, could leave the steel continuous phase of the nodular iron in a more brittle state....or there was a problem with the makeup of the iron, such as not enough magnesium to create the spherical graphite nodules, so you get some hybrid of ductile iron and grey cast iron (where the continuous phase is graphite, and therefore the material is very hard and brittle)
if I was still at my old job, I probably could have gotten some rudimentary load/deflection curves and some hardness data, since we had a fully functioning test lab and a lot of gearheads in it.
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: drop spindles
[Re: patrick]
#1177906
02/28/12 09:25 PM
02/28/12 09:25 PM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
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Marlboro, NY, USA
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...this is the first reference I've heard of "several known crashes" with MF parts, granted I am not as near to the front lines of the hobby as you are. <snip>
I didn't say it was MF - it is NOT. Another well-known outfit, who swears that their (Chinese) supplier has "gone back" to drop forgings.
Interesting that all the newest Chrysler engines, even the new NA I-4s, have "gone back" to hammer-forged cranks and rods.
Rick
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Re: drop spindles
[Re: AndyF]
#1177907
02/28/12 09:26 PM
02/28/12 09:26 PM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
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How about a Mopar knuckle that accepts a slip on hub assembly? This design gets rid of the precision grinding required for the tapered roller bearings. The slip on hub assemblies are really inexpensive due to the OEM volume behind them.
Looks like a forging, no?
Rick
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Re: drop spindles
[Re: AndyF]
#1177909
02/28/12 10:08 PM
02/28/12 10:08 PM
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Joined: Feb 2011
Posts: 4,302
Nebraska
72Swinger
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Nebraska
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Andy would that use like a Jeep TJ or Cherokee hub? Or Mustang?
Mopar to the bone!!!
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Re: drop spindles
[Re: Rick_Ehrenberg]
#1177910
02/29/12 09:43 AM
02/29/12 09:43 AM
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Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
patrick
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,123
Grand Haven, MI
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Quote:
Quote:
...this is the first reference I've heard of "several known crashes" with MF parts, granted I am not as near to the front lines of the hobby as you are. <snip>
I didn't say it was MF - it is NOT. Another well-known outfit, who swears that their (Chinese) supplier has "gone back" to drop forgings.
Interesting that all the newest Chrysler engines, even the new NA I-4s, have "gone back" to hammer-forged cranks and rods.
Rick
My bad, I didn't realize there were other options for dropped spindles besides the cast MF and the fabricated fatmans.
really? I thought the 5.7 used a cast crank and cracked cap powdered metal rods?
1976 Spinnaker White Plymouth Duster, /6 A833OD
1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!***
2011 Toxic Orange Dodge Charger R/T
2017 Grand Cherokee Overland
2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)
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Re: drop spindles
[Re: patrick]
#1177911
02/29/12 08:31 PM
02/29/12 08:31 PM
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
Rick_Ehrenberg
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Joined: Sep 2003
Posts: 1,688
Marlboro, NY, USA
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Quote:
Quote:
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...this is the first reference I've heard of "several known crashes" with MF parts, granted I am not as near to the front lines of the hobby as you are. <snip>
I didn't say it was MF - it is NOT. Another well-known outfit, who swears that their (Chinese) supplier has "gone back" to drop forgings.
Interesting that all the newest Chrysler engines, even the new NA I-4s, have "gone back" to hammer-forged cranks and rods.
Rick
My bad, I didn't realize there were other options for dropped spindles besides the cast MF and the fabricated fatmans.
really? I thought the 5.7 used a cast crank and cracked cap powdered metal rods?
The knuckles I'm referring to are the common "repro" 73 A-body "disc swap" ones.
I said latest Chrysler engines, 6.4L Apache and 2.0 / 2.4L Tigerhsark. (Can't emember the 3.6L offhand).
Rick
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