V1 Desert Sasqwatch #155 Track (mods) - 08 SS/TC crate LNF F40

[Desert Sasqwatch]

Guess I'd better update my build log, its been a while, and I have accomplished a few things. I completed the anti-dive geometry changes to the front suspension by moving the forwardmost UCA and LCA mounts - upper raised 3/4 inch and lower dropped 1/2 inch. This changes the instant center of the front control arms to increase anti-dive from a nil geometry (arms are parallel) to about 18% - UCA angle is 4.5 degrees and LCA angle is 2.5 degrees. Changing the mount locations to get to the ideal 20% was limited by the physical characteristics of the DF frame. For reference - road race chassis are typically between 25-35% and performance street cars between 15-25%.

I made a new exhaust, since my frame modifications at the rear of the frame will not allow the stock DF exhaust to be mounted. It's basically a stinger with a 'muffler' (uh-huh, right) and polished tip. Cost a whole $90 for all parts and material, plus It's made from all stainless steel with dual vortex cones inside the muffler to help reduce the dB level to (hopefully) within legal noise limits. It's just going to be loud.

I fabbed up a 'trunk' lid out of CADboard and fiberglass, it covers the rear 1/2 of the engine bay. Still indecisive for the air venting - debating if louvers or cut slots/mesh. It is a very convenient license plate location and 3rd brake light.

I finally received the correct Vue EPS, after receiving the incorrect EPS when ordered the first time - my bad, and too much time has passed so I cannot send it back. Know anyone with a '07-'10 Vue, Equinox, or Torrent in need of a EPS? At some point in the very near future I will have a Cobalt EPS up for sale - known working condition when removed from donor.

The new rear suspension is progressing slowly after completing the new tube subframe. Drive axles sizing (length) to match up with the proposed wider rear suspension control arms is complicating the final dimensions and geometry. The F40 transmission causes the axle shafts to be different lengths - 2 inches shorter on the driver's side. I could purchase the special shortened F40 mod axle from the aftermarket, but have been searching for a standard available axle that is around 1 inch shorter than the Cobalt axle. Finding an axle that is 1 inch longer than the Cobalt axle is easy, there are several different available. Once the axles have been purchased, I can finalize the control arm design.

I've also been designing new rear hub uprights to replace the Cobalt uprights. They will be machined from aluminum, much like the DF front uprights, but will accept the drive axle hubs - larger diameter - and will be taller to accommodate the difference in the rear geometry. Still trolling around for a shop who would be willing to machine them - unless Lonny wants to offer up his services (I'm open to discuss).

Anyway, my retirement project is still moving along, when the home financial advisor allows me to make parts and materials purchases.

 

[Desert Sasqwatch]

Auxiliary heat exchanger brackets welded - yes they have speedholes. Tacked in the threaded bungs into the bottom frame rails for the wet-pipe - 3/4 NPT thread. Will be finish welded when I can turn the frame over again (drivetrain is still in mockup and installed).

 

[Jareth]

Are those Hose Tubes capped off so that Arizona Lizards don't enter them?

.

 

[Desert Sasqwatch]

LOL! Never know what critters crawl into places like that! Actually, it's to keep my poor welding technique - read weld spatter - from getting onto the threads.

BTW, since I lost a bunch of speedholes by ditching that clunky Cobalt subframe, I'm down on total speedhole count - Racer X is not happy. Anyone need a subfame?

 

[SmsDetroit]

Just curious if you think you will get your goblin driving this year. I know it’s been a huge project for you so please don’t think I’m judging. I really want to see racer x done

 

[Desert Sasqwatch]

The biggest delay since the middle of summer has been funds. Left my previous job due some issues I didn't want any part of, so I've been looking (casually) for another job - problem is I so specialized that these jobs don't come around very often. There's hope on the horizon since the space satellite job market has posted a couple jobs in January, I'm hoping to be reemployed in the not too distant future.

But with that said, I'm working on things I have parts and materials for currently. Making some headway, but I'm also still digging into the rear suspension engineering - the more I dig, the more I need to consider in the design. Hopefully I can get into the meat of this sooner than later, get parts and materials ordered, get some parts machined and fabricated (there are things I just cannot do in my garage), and get to the final square for mocking everything up.

 

[Rttoys]

I thought he was Racer O ?

 

[Sebnuts]

Guess I'd better update my build log, its been a while, and I have accomplished a few things. I completed the anti-dive geometry changes to the front suspension by moving the forwardmost UCA and LCA mounts - upper raised 3/4 inch and lower dropped 1/2 inch. This changes the instant center of the front control arms to increase anti-dive from a nil geometry (arms are parallel) to about 18% - UCA angle is 4.5 degrees and LCA angle is 2.5 degrees. Changing the mount locations to get to the ideal 20% was limited by the physical characteristics of the DF frame. For reference - road race chassis are typically between 25-35% and performance street cars between 15-25%.

What are you using for your brake bias, wheelbase and CoGH when doing your calculations?

 

[Desert Sasqwatch]

The brake bias will be a variable until the balance can be achieved in the car, but based on the weight distribution for front (35%) and rear (65%) and comparing like vehicles (Atom), I'm using 60/40 front and rear for now. This is also loosely based on the experience of several builders who have installed the brake bias valve and are having much better braking force, but this figure will probably change. The Goblin frame forward moment is somewhat less than other vehicles, especially front engine platforms.

I have the extended (now standard) wheelbase track frame at 97.5 inches, this will not change with the new rear suspension. The COG is based on a couple measurements made by other builders - four corner weights and then jack up the rear to specified height to get front weights, The COG has a calculated height at 20.5 inches above the datum ground plane (based on a 6 inch ride height at the COG position in the frame) and nearly centered over the fuel tank (3 inches aft of the upper fuel tank support bar). The position of the COG will vary somewhat with the options being installed and other accessories and modifications.

The changes in UCA and LCA angles - from the stock parallel mounts and zero anti-dive - puts the front instant center intersection point within 4 inches of the base of the b-pillar and between 2.5-3 inches above the bottom frame tube from rough measurements. I still need to re-run the strings for an accurate instant center point to get a precise anti-dive calculation.

The rear suspension is still in the works and I have not yet finalized the UCA/LCA mount locations or angles. I've been researching the anti-squat geometry for the double control arms - versus a McPherson strut - and it seems there are different schools of thought on how much (%) is required for a mid-engined platform. Most race cars shoot for 90-100%, but this can cause lift/jacking issues on the street since roads are far from flat, smooth and no pot holes. Most information I'm finding for mid-engine street cars is anywhere between 50-80%. Since there is very little experience with the Goblin with a UCA/LCA setup (only one builder that I know of) this is going to be a shot in the dark, especially since I'm not using the Cobalt subframe. Thus the reason I am making everything fully adjustable for caster/camber/toe and UCA/LCA mount heights to allow variation of the control arm angles.

 

[Sebnuts]

I've been going back and forth on optimizing the strut setup or doing a multilink UCA. An optimized strut would be absolutely sufficient for my use, but I'm leaning toward doing a multilink UCA for fun anyway.

From what I've been able to find, like you said, the rear/mid engine production cars (Fiero, MR2) run around 60% anti-squat.
I found one website that claimed the stock Porsche Cayman GT4 has 108% anti-squat.
I wish I could find more information on the Elise, the early versions were nearly identical to the goblin as far as weight and weight distribution goes. I recently read an article that said the Elise does not use anti geometry in the front, but does use it in the rear (it did not specify the amounts).

For my build, I'm thinking of shooting for 20-30% front anti-dive and 40-50% rear anti-lift with a 60/40 brake bias. For anti-squat in the rear under positive acceleration, I'm looking at the 60-80% range.

 

[Desert Sasqwatch]

A few photos of how the rear UCA/LCA is progressing.

 

[ah.b.normal]

To your loss of speed holes, It's still holeyier than thou. (Ba-dummp-paaa) Your car is so holey I thought It was running for Pope-mobile! Robin: "Holey Swiss Cheese Autos, Batman!" Hey! Are those holes to let the water Out?, or IN? And we can't even see the Black Holes you installed because they are gravity wells. ("holeyier than thou", I crack myself up!)

 

[Desert Sasqwatch]

Mr. Chapman - build in lightness. Racer X - the lightest thing in the world is a hole. My engineering brain - add speedholes to anything not critical structural.

 

[ah.b.normal]

Mr. Chapman: making things holey, I've seen his work. I confess a little concern about drilling holes in my stuff. I ain't no engineer, I'm more of a contraptioneer.

 

[Desert Sasqwatch]

I'm waiting on some more materials before I can make more significant progress. But in the meantime, I did pick up a new tool - good enough to bend up to 1 inch tubing, which is something I need to get my rear suspension arms fabricated.

Also needed a place to store it, and since I have some wait time, I built a storage box from scrap wood I had laying around.

Hopefully I will have an update on the rear suspension build soon.

 

[Tinkles]

Improving my suspension geometry is something that has been on my mind, but that is an area where my knowledge lacks.

 

[Desert Sasqwatch]

There are (edit) 3 of us - that I know of - who are delving into a full UCA/LCA rear suspension design and fabrication to replace the Cobalt subframe, LCAs and struts. @Sebnuts is getting close to having his design and fabrication complete, he will probably have his done before I have mine completed. @Orion24 is also making progress too. We have been collaborating on ideas and using @Dale E inputs to help guide the ideas. We have very similar tube subframes and somewhat similar mounting schemes for the UCA/LCA mounts. The major difference is he is reusing the Cobalt hub uprights and I will be using a custom milled piece similar to the DF front hub uprights - this is the long pole in the tent for me.

 

[Desert Sasqwatch]

So I redid the filler plates on the b-pillar, didn't like the first set I had welded in a while back. These are not really structural, but provide an enclosed space to install some overhead speakers at some point. Will likely grind off the welds flush and fill the seams, but they do have a 'ratrod' look to them I kinda like.

 

[Jareth]

I like it.

 

[Desert Sasqwatch]

Fabbeb up an aluminum roof panel from a 'recycled' road sign - it was sitting beside a dumpster. Working the dents out of it and will have to strip the orange off. Plan to line with rubberized sound deadening - every little bit will help.