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 2 2010, 01:31 PM
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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 |
so the whole coil over thing with the RSRs started because they couldn't get a stiff enough torsion rate so they added helper springs in parallel with the torsion bars to get a higher spring rate (the spring rates add when in parallel).
So the original RSRs had lower rate springs than you would run in a strictly coil-over setup, which is what everyone does now. Because of this, the rebound rating on the stock RSR is too low and also the compression was somewhat high (the 161/160 values) which is more of a question of dynamic roll, etc. Anyway, Bilstein came up with the set that I have, and pretty much everyone uses now, which has the spindle lowered (for lower ride height without having to F up the lower A arm geom on the front) and has the better valving for working with higher rate springs. The better rebound value helps to control the higher rate spring while the lower compression lets the higher rate spring do its job. That is as I understand it (IMG:style_emoticons/default/smile.gif) I was plenty happy with the RSR struts but I really want to get my car low to the ground, so I either put them thru the hood or go dual A. Also, I am going to go to double adj shock valving and in case you aren't aware, those puppies are MONEY so I would rather just build a dual A and use "universal" shocks I can buy for much much less off the shelf. If you are looking to have a good setup with fully adjustable ride height front and rear (you can buy rear adj height coilovers easily thru Bilstein, etc) and can corner balance the car, the RSRs are a great way to go for the money. Art... I will PM you about my parting price and so forth. |
ArtechnikA |
Apr 2 2010, 01:48 PM
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#223
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
So the original RSRs had lower rate springs than you would run in a strictly coil-over setup, which is what everyone does now. QUOTE If you are looking to have a good setup with fully adjustable ride height front and rear (you can buy rear adj height coilovers easily thru Bilstein, etc) and can corner balance the car, the RSRs are a great way to go for the money. no rear adjustable coilovers for 911 AFAIK ;-) but it's OK - I am not building a true competition car - I am building a 'period-correct' 2,8 RSR without going crazy overboard trying to convince myself or anyone else that it is authentic. I don't mind a slight uprate here or there (i.e. front coilover rate) but I'm not building a car like we'd build it now, I'm building a car like I remember them. And I'll be glad to enjoy it like that, period-correct warts and all. |
byndbad914 |
Apr 2 2010, 03:41 PM
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#224
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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 |
no rear adjustable coilovers for 911 AFAIK ;-) I know you can get slip on threaded sleeves that fit over stock 91 rear shocks so you can easily upgrade to that in the rear... in fact, if you are doing simple upgrades here and there that is something you should definitely do IMO, and then in conjunction with the front RSRs you have a fully tuneable suspension for ride height and corner balancing, etc for the track. |
ArtechnikA |
Apr 2 2010, 04:15 PM
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#225
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
no rear adjustable coilovers for 911 AFAIK ;-) I know you can get slip on threaded sleeves that fit over stock 91 rear shocks so you can easily upgrade to that in the rear... in fact, if you are doing simple upgrades here and there that is something you should definitely do IMO, and then in conjunction with the front RSRs you have a fully tuneable suspension for ride height and corner balancing, etc for the track. If it doesn't look like something they had in 1973 it's probably not going on. But 911's have had adjustable spring plates for a long time (not quite 1973...) but it is a very subtle modification to the spring plate. Coilovers in back would be a big (visual) change but I'm OK with the spring plate mod. So I'm covered for height and corner balance. |
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