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Thread: Fabricating new front uprights for the modified Manta front suspension

  1. #1
    Champion Member Blueovalz's Avatar
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    Fabricating new front uprights for the modified Manta suspension - Part I

    Currently I'm using the early Corvette C4 front uprights (there are two versions, the latter of which is about 1" taller (too tall for 16" wheels) than the earlier version). They function very well, but I cannot leave well enough alone. One of the things I'd like to improve upon is the scrub radius and "feel" being I'm using a high ratio, manual, steering rack. So I'm trying to build an upright that reduces the kingpin angle and simultaneously reduces the scrub radius. I've got constraints such as caliper to wheel, as well as monoball to rotor clearances that makes this more difficult. I'm taking two approaches to this. First was a sheet-metal fabrication using monoballs on top and bottom. The second approach, which I started on this week, was to machine these out of solid aluminum. Surprisingly, this steel piece only weighs about 1/2 lb more than the C4 aluminum ones I'm currently using.



    Using a 1" monoball on the bottom (right in this photo below), and a 7/8" on top. The bottom one has an extraordinarily large ball diameter to ensure reliability and prevent pull-through being this is supporting the corner-weight. I could probably get away with 3/4" and 1/2" if this was strictly racing only, but I've got to keep safety in mind being this is a street car. I'm using high-misalignment bushing made just for these monoballs (FK uniball to be more accurate), which allows me to use grade 8 bolts to secure the monoballs onto the ends of the upright.





    Will continue to use the C4 early upright wheel hub due to the rotor, caliper, wheel, upright interference issues if I change any of these pieces.





    Made the upright as tall as possible for camber-gain benefits. Thus it's taller than the C4 upright, but still fits within the wheel shell. The cylinder that cups the lower monoball resides about 3/8" of the side of the rotor. I've determined that the upper monoball must be canted 8 to ensure full angular capability for the upper monoball during full suspension travel.

    Last edited by Blueovalz; 03-30-2016 at 12:38 PM.

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    Champion Member Blueovalz's Avatar
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    Okay, so my assumption that an aluminum upright would less massive than a steel one was flawed. I suspected such when, after fabricating my rear steel uprights, I had a couple of fabricators of aluminum uprights tell me that my sheet-steel rear uprights were within 1/2 lb of the weight of their aluminum uprights. Anyway, I went forward with the project just to see what I could come up with. Changes where made as compared to the uprights in the above posting. I still have plenty of material I can remove to reduce the mass. These will have an 8 kingpin angle, but this will reduce the scrub radius to about 20mm.



    Using the same Corvette C4 front bearing/hub assembly used throughout the entire set-up currently being used.



    I made the top mount removable so that I could change the kingpin angle easily without making an entire upright again.



    Last edited by Blueovalz; 04-04-2016 at 03:14 PM.

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    Champion Member Blueovalz's Avatar
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    Latest photos of the aluminum upright. Will next be making brake and steering brackets to bolt onto the upright. This brings the scrub radius down to about as short as I can get it with the current wheel offset, which is the maximum offset the wheel manufacturer could provide. Even then, the lower mono-ball cup or housing will reside within about 3/8" of the brake rotor, so I'll brad in some kind of heat shield to keep rotor heat off the bearing. Basically the improvement over the OEM C4 upright is reduced scrub radius, reduced kingpin angle, and increased effective length of the upright (meaning improved camber gain on compression).



    Last edited by Blueovalz; 11-12-2016 at 07:22 PM.

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    Administrator Sulley's Avatar
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    That looks great! I wonder if you ever sold your car what it would be worth!

  5. #5
    Champion Member Blueovalz's Avatar
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    Update.

    Taking longer than I thought to finish these. I shattered the cast-iron case on my drill press when I got a little over-aggressive with the machining of these pieces. So I looked at Grizzly, decided it was less rigid than the Harbor Freight drill press that broke (I could actually flex the table on the Grizzly drill press due to the design of the table that allows 360 degree rotation), so with a 20% coupon, I replaced the Harbor Freight with another Harbor Freight for less than $500, and then promptly toasted the motor in less than 2 hours (something was wrong with it right out of the box, so that was not a surprise). Harbor Freight replaced the motor, and now I've finished the machining on the uprights, and ready to assemble as soon as I get the proper length tubes.



    Made these pieces with as much flexibility in design as possible, which is why the caliper bracket, steering arm, and upper uni-ball mount are removable for modification or change in geometry later:



    Everything assembled without rotors or hubs (bearings):



    Need a few additional tubes, and it will be ready to bolt onto the frame:





    Yes, a drill press is not the ideal tool for milling, and as some would note, not recommended for use in any milling applications. If care is taken to ensure rigidity, stick with aluminum, avoid vibrations, and remove material slowly, it will do the job. It was something that took some learning to do, what practices to avoid, and what can go wrong...quickly wrong.
    Last edited by Blueovalz; 11-12-2016 at 07:24 PM.

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    Champion Member Blueovalz's Avatar
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    On the car. This shows one side with the new front suspension (right side of photo), and the previous C4 upright (left side of photo).



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    Gotta love a guy that builds his own stuff! Don't worry about using the drill press, I built many experimental airplane parts using my large chuck Press. Clamping and holding are big issues, mainly for safety. Having a strong table helps too. I love your work and attention to details. I'll be following all your post so I can learn me some new stuff!

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    Quote Originally Posted by MKHYTEK View Post
    Gotta love a guy that builds his own stuff! Don't worry about using the drill press, I built many experimental airplane parts using my large chuck Press. Clamping and holding are big issues, mainly for safety. Having a strong table helps too. I love your work and attention to details. I'll be following all your post so I can learn me some new stuff!
    I had a couple of fabricators of aluminum uprights tell me that my sheet-steel rear uprights were within 1/2 lb of the weight of their aluminum uprights casino bonus. Anyway, I went forward with the project just to see what I could come up with. Changes where made as compared to the uprights in the above posting.

  9. #9
    Champion Member Blueovalz's Avatar
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    I agree with the weight thing. My rear uprights are all sheet steel (.090 and .120), and they are within 1.5 lbs of some cast aluminum ones typical of that era. The entire reason for this front upright endeavor above was to have better flexibility on bearings and steering arm geometry, which will still need to be developed. My greatest angst was welding the bearing cups to the arms, and having them shrink so tight that I, 1) couldn't press the bearings into the cup without galling both, or 2) that when successfully inserted, the bearing stiction increased so much, I was't sure I was benefiting from the process.
    Last edited by Blueovalz; 04-04-2019 at 10:40 AM.

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