creating new susp for the monster, going dual A setup front and rear |
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creating new susp for the monster, going dual A setup front and rear |
byndbad914 |
Mar 31 2010, 02:19 PM
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#221
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shoehorn and some butter - it fits Group: Members Posts: 1,547 Joined: 23-January 06 From: Broomfield, CO Member No.: 5,463 Region Association: None |
Car currently has RSR front struts with custom lower arm setup (sorta like a 935 front end) and the rear is a 5-link setup that is much like any old school 60s-80s open wheel car, GT-40, etc all attached to my tube chassis setup.
Decided I wanted to lower the car more and fix a couple issues with the rear 5-link geom so I started laying out some parts, then decided F it, time for a whole new update (IMG:style_emoticons/default/laugh.gif) I can't leave anything alone. So I measured various available pickup points on the current chassis and whipped up this stuff in Pro/Engineer. The lower A is already a bit different than I have assembled in here, but close enough for convo - and JP was asking to see what I have going - I am sure so he can raz me about whether or not I actually win at DEs (IMG:style_emoticons/default/happy11.gif) I used Pro to lay out the geometry so I could measure camber gain, get zero toe positions for the toe link (which will be adjustable in case I want to put some bumpsteer into the rear), RC height and motion, etc. Is this perfectly optimal on all points? Hell no, but much better than what I have and works with existing structure - I am not about to really hack into this car. I can get tabs waterjet cut and welded into place, but not bending/notching tubes in my near future. Besides, it leaves me a little bit of excuse for why I am slow on the track cuz it certainly isn't my driving abilities hahaha (IMG:style_emoticons/default/driving.gif) So here is the rear design - it will be built using the stock trailing arm cut down to not much more than a bearing carrier. yeah, yeah, use this other thing, make that, blah blah - the stock rear bearing assy has worked for a few years now so it is fine. I intend to replace that big bearing every few years regardless of upright used anyways. I did the same layout stuff for the front and even am going to be able to use the exact same billet lower A front and rear so that is nice. I can have them waterjetted for about $170 each including the 1.5" plate material, so not bad at all. I bought a couple front strut housings from Carquip last week and had my machinist buddy endmill out that monster weld so gonna work on getting them apart down to the stock knuckle, then I have 2" diam chromoly I just got yesterday that I will have him machine down to make the front "upright". Note the two surface colors in the above image - the blue is turned down to fit in the knuckle (50mm) and the green is the stock 2" diam of the tubing - that ridge will be used to exactly place the tube relative to the knuckle so I get both spindles left to right in the exact same spot. The upper forward link will be made on the fly so I didn't bother modeling it. I need to get this stuff in the car with the right pickup points placed, then place some dual adjustable coil over assys which might be tough on the front, then build the forward link around the shock assy. At some point you stop fisting the design and just build it (IMG:style_emoticons/default/shades.gif) Being a structural analyst I also have access to finite element code so I fully analyzed the lower A designs (I have 5 of 'em now hahaha) to make sure they are structurally sufficient. If I get off track in a big way I will likely bend them, but that you can't design for without having a 10lb A arm. These are just over 5 lbs per the modeling software. |
byndbad914 |
Apr 19 2010, 11:16 AM
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#222
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shoehorn and some butter - it fits Group: Members Posts: 1,547 Joined: 23-January 06 From: Broomfield, CO Member No.: 5,463 Region Association: None |
I go back and forth on the wheels. I am going to see what the tire temps on the front are like and if they are too hot or significantly hotter than the rears then I will make that the next project (everything is easy to upgrade) on the front. However, on some tracks in circle track racing we would run as much as 3" of scrub to get heat into the tires. Scrub makes steering effort a bit tougher, sure, but it can serve a purpose.
Much moreso than roundy-round stuff, I have a super narrow selection of tires (all available slicks are GT2 category, there is maybe 6 overall slightly different sizes to choose from between GY and Hoosier), so given I am somewhat limited on width selection so I will be driven to finding the correct scrub to get the heat balanced front to rear. Believe it or not I was rather balanced on the 5" scrub, likely as the fronts are only 1" narrower than the rears with a 58% rear weight car, so that is also why I am going to try 3". On a different note, I have been thinking of getting custom setup double adjustable shocks... BIG money, holy crap, but I also know that shocks setup is a huge factor in lap times and I have put no effort there on this car. Also don't have a budget like SouthWest Tour guys did ($70K min per year) so to have $3500 more in this car in just shocks is getting stupid. Already looking at $1600 for off the shelfs... So you guys have any recommendations? I am aware of Guy Ankeny but he may be too AX oriented, dunno, but there would certainly be a dynamics difference between AX and road racing. If I lived in SoCal still I would slam dunk it since I am sure he could roll out to Willow Springs or Buttonwillow and help me get a best setup, but in CO, not gonna happen. |
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