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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#21
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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. |
effutuo101 |
May 11 2010, 12:21 PM
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#22
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Advanced Member Group: Members Posts: 2,735 Joined: 10-April 05 From: Lemon Grove Member No.: 3,914 Region Association: Southern California |
Love this!
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byndbad914 |
May 11 2010, 02:00 PM
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#23
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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 |
Love this! Thanks! Just got off the phone with Aaron at Penske and have the shocks on order - I have to admit I am a PITA customer getting these cuz I have tons of questions given the $$ being spent, but he is super patient and we worked out a kick-ass setup me thinks. I have to run really short springs to get the rates I will need with this car, while the installed heights are tall given the current chassis config, but he got it all worked out with extended mounting eyes, extended spring seats, etc etc to where I have sufficient travel but can run as short as a 6" spring and have adjust-ability. Pretty stoked. And he is giving me a 10% discount and including bump stops on them as well, so he is being really cool. I am going to base my initial setup on 2.2Hz frequencies front and rear (no bar) - I think a lot of road race guys shoot for higher but not me. Also he said most guys go down in spring rates once they have these shocks, so I will be starting there as that is what I basically had before and it was soft IMO so the new shocks with better compression design/tuning I will likely be fine. The motion ratios on this car with the dual As now means I have to run significantly more spring rate than say a strut with nearly 1:1 ratio - like 3-4 times as much spring rate. I am looking at 1500 lb/in rear rates and 1200 lb/in front rates to get the right wheel rates. |
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