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Learning how to build Lotus Seven replicas...together!
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PostPosted: Sun Apr 27, 2008 1:06 pm 
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Mid-Engined Maniac

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I can't tell if the A-arms you made above are tops or bottoms. Due to how they're constructed, there is no adjustability once installed. Said another way, the angle of the A-arm is permanent set by your weld angle. Since the inboard mounts are also welded, it's impossible to move the outboard point at all. Will camber and toe be adjusted via other links?

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PostPosted: Sun Apr 27, 2008 9:53 pm 
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Always Moore!
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THAWA wrote:
I spy an RS. I want to say it's an 06-07?


Good eye. 2007 2.5i...for some reason 2.5RS was translated into 2.5i in 06 (maybe to save a nickel by eliminating a letter after the 2.5?) Either way, I enjoy it as a daily driver and its great in the snow.

Randy, I re-read your post...I think I was answering the wrong question in my first response; theres enough deflection in the actual rod-end. From my cad model, the front lower arm needs about 8 deg of deflection each way and the front upper needs about 13 deg each way.

The cheap-o 2-piece rod-ends I'm mocking up with will allow 17 degrees as they're mounted. Summit also sells a similar 2-piece rod-end but in chromoly and with a teflon liner that I'll probably use on the final car. If I need a few more degrees, I can also do a little work with shimming the rod-ends in the mount.

Good eye KB; all of the arms that are built that way are lowers. For the uppers, I've made threaded adjusters (essentially a grade 5 bolt with the threads chopped off and a female thread drilled and tapped in place) that allows camber to be adjusted without disassembly.

As far as orienting the bolt goes, I'm still on the fence if I want to go vertically or horizontally (fore/aft) for the upper arms. I really like the horizontal approach since it allows for caster adjustment in the front along with more travel.

For toe, I plan on using a separate toe-link that will attach to the steering arm on the rear upright - much like what it had when it was a front upright on a Protege. The toe-span isn't too bad but the big downside is this design requires readjusting toe and bump-steer any time I make a camber change (the fronts are the same).

The easiest way to avoid this would be to have the line of action of the toe-link colinear with the arm when viewed from the front/back but I couldn't find any steering racks that were the correct length for the front and theres no way I could get the Protege upright to safely work like this on the rear. Maybe on the next car.

The toe-link won't levitate on the actual car like it is in the screen shot below (and the halfshaft will also line up). :)

.....I hope. ;)

Camber adjusters:
Image


Attachments:
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File comment: Front upper and lower arms (uppers have camber adjusters)
DSC02826.JPG
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PostPosted: Mon Apr 28, 2008 10:55 pm 
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Always Moore!
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I got the 4 vertical tubes cut and tacked into the front subframe tonight.

Hopefully I can get some mounts for the upper arms in place by the end of the week. They have the potential to be really time consuming.


Attachments:
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PostPosted: Mon May 05, 2008 10:20 pm 
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I decided to tackle the back half of the transmission tunnel and some other cockpit stuff instead of getting upper front arm mounts in place.


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File comment: I added a gusset so the hoops wouldn't hang off of the edge of the frame.
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PostPosted: Mon May 05, 2008 10:24 pm 
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Next car, I'd like to design the frame around some pre-bend hoops. It might be tough with a 7 due to width but it would be really easy with a middy....

I'm lucky enough with this car that the leg hoop won't hit the pavement unless the front half of the car gets ripped off; its more for stiffness so I'm not as afraid of cutting and piecing together.


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PostPosted: Thu May 08, 2008 9:33 pm 
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Always Moore!
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I've made some progress on the cockpit area and the front half of the frame.

I'm going to need a cart for the welder soon...its table space is slowly disappearing. :?


Attachments:
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PostPosted: Thu May 08, 2008 10:33 pm 
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Is that Molsen Canadian? :?

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PostPosted: Thu May 08, 2008 10:42 pm 
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That it is eh?

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PostPosted: Fri May 09, 2008 1:14 am 
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Watch it Yankees! There are enough Canucks here that we could cause some civil unrest!

..or atleast show some mild discontent... :D


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PostPosted: Fri May 09, 2008 6:45 pm 
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I'm Canadian but I have no problem saying it: Molson sucks.

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PostPosted: Sun May 18, 2008 12:02 am 
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Always Moore!
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I'm sure we can work something out then....wanna trade some Iron City or Milwaukee Beast for Molson? ;)

Back on the topic of locosts....I went shopping today and ended up coming home with a transmission. I'm picking up something to go in front of it next weekend. I figured it was a bad idea to try fitting a 4A-GE in the trunk or back seat of the Subaru.

I'm hoping the 4A-GE service manual has something in the electronics section covering the sensors on the transmission. I need to figure out what they do (plus each time I look at the transmission, I find another sensor thats camoed by dirt).

Anyone have any good tricks for cleaning 21 years worth of grime from parts? Right now the transmission smells like an old basement.

The front suspension is also on. I just need some shims to keep the rod-ends from sliding axially on the bolt and a few parts need a little clearancing to keep stuff from hitting under full bump/droop.


Attachments:
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PostPosted: Sun May 18, 2008 1:40 am 
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Hi Andrew,

Great build log. Can I quiz you on the front suspension's inboard front mounts upper and lower? I can see that under the big load case - braking - they will be in tension and lie in line with the suspension load, so no problem there. But under cornering load wouldn't they see an out of axle compression, which introduces cantilever loads at the chassis connection? Did your FEA indicate that the displacement would be trivial?

Cheers,
James

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PostPosted: Sun May 18, 2008 9:59 am 
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James,

I'm trying to cure myself of the notion that suspension loads are infinite, everything must be perfectly triangulated, and everything must be made of 1.5" x .125 wall tubing. Those "borderline-cantilevered-too-far-brackets" caught my eye too, so I did a quick calculation*. At full bump roll cornering at 1.5G, the lower front bracket has a downward component at the heim centerline of about 75 lbs. No problem. If he manages to slide really badly straight sideways with full roll and hit a curb and manage a 6G hit it would be 300 lbs downward. That might (?) be enough to start bending, but the roll bar might be a bigger concern at that point.

Upper arms see only about half the load lower ones do, so less concern there.

*Caution: My calculator is 23 years old and I aren't very smart. My results may not resemble reality and depending on them may result in death and dismemberment or worse. Your mileage may vary. Don't blame me.

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PostPosted: Sun May 18, 2008 10:30 am 
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Always Moore!
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SCD is about right on. Under steady state cornering of 1.25G (a little conservative), the forward leg of the front lower arm sees 1300lbs of force in compression.

When the arm is level at ride height, its inline with the bracket (so compression only). At 2.5" of full bump, its about 7 degrees above horizontal so the vertical component is about 150 lbs; at 3" of full droop, its about 13 degrees below horizontal so about 300 lbs of vertical force.

The droop case is unlikely though since no normal driving situations are going to cause the tire to be fully loaded and in full droop.

If the droop case were to occur, there would still only be 3500 psi of stress at the weld from the bending load (so essentially nothing).

While I'll admit the second case is a little is less than ideal in a design, its also a 2"x1"x0.125" bracket. I'm still going to do some gussesting though since the tubes the brackets attach to are less robust. I feel its no better or worse than some of the "U" arm brackets I've seen where half the bracket is overhanging the tube.

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PostPosted: Sun May 18, 2008 4:28 pm 
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I know I'm rusty at force calculations, but I can't figure out how you got such a high number for the compression force in one leg at 1.25G. Did you miss a division by two or am I messed up? I double checked with a graphical force digram and an equilatral sling equation...

Image

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