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. |
byndbad914 |
May 28 2010, 08:19 PM
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#22
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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 |
doing adjustments to the five link setup before was really tough - it would often take me 2 hrs to get the rear setup at home. Now I have a much better designed setup and can change it pretty quickly. I will definitely be doing more tuning at the track now, especially with the Penskes being so adjustable just turning knobs I can easily mimic in spring rate, etc.
Agree about tire temps being key - my friend the circle track guy can damn near tune a car by only using tire temps and nothing else and I have gleaned a lot of what he does. 'course driving it will tell you a lot but you can come in, say nothing, he'll take temps and start in telling you what the car is doing without you saying anything. Brett - checked the computer and then the actual car to confirm a couple things. I know you know, but many here might like the info. The lower arms are parallel to ground - if the toe link is in plane then it needs to be parallel as well. The upper link is 17-17.5 deg, so if the toe link is mounted at the same point inside, it needs to go out at 17-17.5 degrees. In my case the link is in between them and not at 50% but closer to the upper mount than lower mount, so the angle is around 12.5 deg degrees that it needs to be. The left one bumps in with the washer stack centering the link 1/16" at 2" compression. The right bumps in just over 1/16" at 2" (not so perfect at tacking and welding in place as the computer). I can move the link up and down to vary this, and when I find what I like will custom machine spacers to get exactly what I want to remove the washer stacks... mostly cuz they are an absolute PITA to get wedge in with the rod end (IMG:style_emoticons/default/laugh.gif) Talked to John at CCW yesterday, by the time I removed my head from my arse I realized it was too late to call and order wheels today. I just needed my notes on backspacing to know what to get now. I am going to try to sell the Kodiaks tho' I like the looks better, John can get the aggressive backspace I want for the fronts and Kodiak will take too long. He can have me a set in 2 wks and has some nice light inner barrels in stock to keep weight down around 18lbs each again. I just wish his LM20 was offered in the 130mm bolt pattern and I was going to attempt to convince him to make me a set and modify the center slightly to make it work (IMG:style_emoticons/default/shades.gif) I don't want to pay for that so I need to convince him every Porsche guy would want the slightly nicer style hahaha. |
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