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| Blooze Own: An F355 Six Speed N* Build Thread (Page 50/126) |
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Bloozberry
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FEB 19, 10:00 PM
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Thanks for the feedback fieroguru and FieroWannaBe.  I appreciate the encouragement since this stuff can be pretty tough to get motivated to work on.
I do have some rewards of my labor to share today though. With the previous discussions focusing on all the problems introduced by modifying the suspension, this post reveals the final solution to resolving the issues with widening, lowering, stretching, and re-shoeing the chassis. Remember, my primary goal was/is to make the car's stance look good, followed by minimizing the negative impact of this stance on performance. So, the three aspects of getting the right front stance involved:
a. moving the wheels outboard to suit the wider body of the F355 using wide track control arms;
b. lowering the car, but maintaining a reasonable ground clearance using a combination of 1.5" drop spindles and a 1/2" spring drop; and
c. filling the front wheel wells with the right size wheels: 215/45/17 tires on 17 X 7 (ET 47) wheels. The somewhat narrow front tires give an approximate ratio of 45% contact patch front / 55% rear in keeping with the weight distribution of the car. The rears will be 18" X 265 mm wide.
Knowing the final configuration allowed me to send the last set of suspension coordinates to Zac88GT for him to run through his Lotus Suspension Analyzer software. Having known from the start that drop spindles are an inherently better solution than simply using drop springs, I was initially quite disappointed when I re-plotted the performance curves and found this combination to be only marginally better than using drop springs. This new case is shown by the orange lines.
I knew there had to be a way to squeeze better performance from this combination, so I decided that the next most logical step would be to shorten the upper control arm to mimic the OEM ratio between it and lower arm. I started by lopping off 29 mm from the upper arms in my drawings, then asked Zac to run a few iterations shortening them even more in 1 mm increments until the best possible performance was achieved. The end result was to shorten the uppers by 35 mm. This of course will entail relocating the upper control arm mounts on the front crossmember 35 mm further outboard, but that appears to be a relatively simple affair after having confirmed the possibility on the actual crossmember.
The static benefits of the new front configuration include a 10.75 % reduction in scrub radius (from 40 mm to 35.7 mm), and an 8% reduction in the CofG height (from 495.5 to 456.5 mm);
Here are the final graphs depicting the kinematics including all of all the earlier configurations, with the final layout in green:
Front Camber vs Bump:
Result: within a whisker of the stock performance in jounce, and improved performance in rebound.
Front Camber vs Roll:
Result: identical performance compared to stock configuration (stock curve hidden by overlap).
Front Toe vs Bump:
Result: improved performance over stock by changing front oversteer in jounce to slight understeer (near neutral steer) up to 50 mm jounce.
Front Caster vs Bump:
Result: identical performance compared to stock configuration.
Anti-Dive:
Result: loss of 1% anti-dive over stock; slight gain in anti-dive stability
Roll Center to CofG Vertical Distance vs Bump:
Result: slightly improved stability and slight improvement in roll couple (1.5% reduction) compared to stock;
Roll Center Location vs Roll
Result: tighter roll center control and lower, improved roll center location compared to stock.
I consider the final configuration to have accomplished my primary goal of getting the stance I was looking for, and was pleasantly surprised that I didn't have to settle for simply minimizing the impact of these modifications. I hope this will be more than enough to satisfy provincial regulators that my new config meets or exceeds the OEM's configuration.
Next up: a break from graphs (altogether now: YAY!), and a return to the workshop to modify the front crossmember and shorten the HT Motorsports upper control arms.
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Bloozberry
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FEB 27, 07:58 PM
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As promised, this post is about getting the nose to the grinding stone, or more accurately, the grinding wheel to the crossmember. After a quick disassembly of the front suspension, it became a little easier to plan how to modify the upper control arm mount to move it outboard by 35 millimeters. Here's a close up of the area:
My first thoughts were to weld a couple box-like extensions to the existing upper control arm mounts on either side of the shock mount, like this:
This would probably have been the route I would have taken had I not been worried about the unwanted attention the obvious add-on might draw during the engineering certification phase of registration. Then it dawned on me that there might be enough room to simply relocate the OEM mount. The advantage is that it would appear very OEM. The disadvantage is that it would mean having to relocate the shock mount as well. I'm not worried about it affecting performance, just the extra work! So out came the safety goggles and the die grinder equipped with a cutoff wheel.
One thing I can tell you is that those factory welds penetrated very deep into the cross member. Using the cutoff wheel with 120 psi air pressure, it took me nearly 15 minutes of grinding per shock mount to work my way through the steel.
Needless to say, I wasn't looking forward to cutting the 5" long weld seam on the control arm mounts. There are a few obstacles to getting the perfect cutting angle; the first being the non-removable cross member alignment pin on the driver's side. The other obstacle is the return flange along the bottom edge of the crossmember which prevents you from cutting the vertical welds all the way down. The smaller the diameter of your cutting wheel, the closer you can get to the bottom.
These control arm mounts took a solid 1/2 hour to cut off per mount. They are some heavy suckers too. I haven't measured the gauge of the steel but they're at least 1/8" thick. Can you imagine the die pressure needed to stamp one of these out of a flat sheet?
Next, they'll need to be trimmed down in height to account for the rising angle of the cross member in their new location. (The eagle-eyed among you will notice the gloved hand in the last photo. Anyone living in Northern climes will know that you can't use a die grinder bare-handed very long in the winter if your compressor is not in a heated room. It gets soooo cold, it develops a layer of frost on the outside, no joke.)
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fieroguru
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FEB 27, 08:31 PM
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| quote | Originally posted by Bloozberry:
The eagle-eyed among you will notice the gloved hand in the last photo. Anyone living in Northern climes will know that you can't use a die grinder bare-handed very long in the winter if your compressor is not in a heated room. It gets soooo cold, it develops a layer of frost on the outside, no joke. |
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That's why I use an electric hand held grinder with a cut off disk... it gets warmer the longer you use it! I am also spoiled these days, my garage never gets below 50 degrees!
If you need any tabs or brackets off the 88 front crossmember, I have 4 of them on the shelf and one was involved in a roll over (bent lower a-arm mounts).
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Bloozberry
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MAR 05, 07:00 PM
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I heat my workshop too, but my compressor is in the basement, which I don't heat. Having it down there keeps the noise down but the downside is that the air is ice cold.
I was starting to have regrets about not choosing my first option to extend the UCA mounts rather than relocate the stock ones. It was a ridiculous amount of work to cut them off, and now I was looking at the prospect of trying to modify them so that they would remain at the same overall height, retain the 5 degree slope backwards for anti-dive, but mount them further uphill onto a surface that was sloped 15 degrees sideways. It might sound easy, but when you have a ruler and a level in one hand and a saw in the other, it suddenly becomes a bit more complicated.
The blue lines show the stock location of the UCA and shock mounts, and the red lines show where they need to be, 35 mm further outboard.
When faced with a task I'm not sure how to do, I often find myself cleaning my shop... that's part of the reason why it's taken so long for this update.  Once that was done, I started with the easy stuff like knocking down the old OEM welds on the cross member with my angle grinder... anything but address the challenge of modifying the mounts. Turns out it was a good thing. Something that was not at all evident when I drew my earlier drawings of the cross member jumped out at me while grinding.
With the UCA and shock mounts no longer obscuring the OEM design, it was clear that the outboard upper surface of the cross member (which is sloped 15 degrees laterally across the car), is also tilted backwards with a built-in 5 degree slope longitudinally (backwards). The OEM mount straddled both the straight-and-level portion and the sloped-and-tilted portion of the crossmember, so it was designed to account for this strange transition. By moving the UCA mounts outboard 35 mm, this places them entirely on the compound sloped surface, simplifying my life since I need only worry about retaining the original height of the mount, while accounting for the 15 degree lateral slope. The 5 degree longitudinal slope takes care of itself.
Here is a side by side photo of the two UCA mounts with the one on the left being the newly modified one:
So the only two operations that were needed were 1. eliminate the built in 5 degree anti-dive by first making the bottom parallel with the top. Then 2. shorten the overall height of legs since moving it outboard also forces it up the 15 degree slope. (Disregard the long legs at the extreme right and left of the photo, those aren't the legs I'm talking about.) Rather, the legs are the lower horizontal edges. Obviously the outboard leg (foreground) had to be cut shorter than the inboard leg (background) to account for the 15 degree slope of the crossmember. Confused yet?
So with the first mount trimmed just right, I test fitted it to the cross member and measured it for being level in the lateral (cross-car) plane, and for 5 degrees in the longitudinal (fore & aft) plane.
Here's what it looks like without the level:
A bit of tweaking with a file and my angle grinder, it was ready for welding.
Now on to the other side.[This message has been edited by Bloozberry (edited 03-06-2012).]
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fieroguru
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MAR 05, 08:25 PM
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Looking good! You are the master of measurement.
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Bloozberry
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MAR 08, 08:16 PM
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LOL. I'm not so sure about that Fieroguru... once I update the stock cross member drawing, it'll be version 3.
The first control arm mount took me 3 hours to cut off and modify, the second one took 1.5 hours: amazing how experience saves time. Both mounts are now ready to be welded back onto the cross member, but I'm holding off until after the control arms are fully modified. I want to build up the assembly, place the knuckle at zero camber, then weld the mounts so the control arm mounting bolts are centered in the slotted holes in the mounts. I also want to be sure there will be enough room for the shock to pass through much smaller hole in the cross member now that the mount encroaches in that space.
So, on to the control arm shortening! The first step was to make an accurate drawing of the final config for my files, and to help in making the jig to weld it all back together:
Obviously having moved the mounts outboard 35mm meant that the control arms would have to be shortened by the same amount. So I built a small jig just to mark exactly where the fish-mouth cut would have to be, then clamped the first arm into my chop saw to cut as close to the bushing housings as possible. I have to admit I had a moment of doubt as I started the saw... seemed crazy to be chopping up a nice new shiny part. Then I let her rip:
Once all four bushing housings were amputated, I chucked them up in the vise and cleaned off the old welds with the angle grinder. These puppies got HOT.
By the time I was finished the last one, the first one had cooled off enough to hold it to the belt sander for final dressing and preparation for the new welds (the tapped holes are for grease nipples):
The next operation was to build a rigid jig on the drill press table to make the fish-mouth cuts in the correct location, and at the correct angle to ensure the concentricity of the two bushing housings. That first involved finding the centerline of the drill and transferring it to the table. Then I used a thick plate of aluminum to raise the arm off the table so I could cut all the way through the arm without cutting into the table. Then I clamped two guides that would center the 1" tubes of the arm in line with the center of the drill. Finally, I made a steel block with a 1" semi-circle cut out of it to serve as a clamp to hold the arm to the table at the correct depth:
The last thing I needed to do was to set the angle of the entire table to compensate for the slight angles that the control arm legs meet up with the bushing housings. The curved leg meets up at 1 degree, and the straight leg at 5 degrees. Here you can see my angle finder resting on the table.
The bushing housings are 1.5" in diameter, so that's the size of the hole saw needed. Here's what the finished cut looked like:
And here's one arm ready to be mounted in the re-welding jig:
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Bloozberry
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MAR 10, 07:42 PM
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To re-weld the control arm bushing eyelets back onto the arms, I had to make a small jig out of some 1/4" steel plate, some angle iron, and a piece of exhaust tubing. After tacking the angle iron onto the plate as a back-stop for the bushing eyelets, I transferred the key dimensions of the shortened control arm onto some masking tape stuck to the steel plate. This gave me the exact location for the ball joint in relation to the two pivots. After bringing a short piece of exhaust tubing to a local muffler shop to have them expand it to the correct diameter, I tack-welded it to the sheet metal plate to act as the ball joint alignment pin, like so:
Once the three control arm pieces were clamped in place, I tack welded them together. I couldn't complete the welding right away since the jig didn't allow access to the back side of the arms while clamped in place:
My little Fourney 100A MIG welder is OK for non-critical stuff, but doing this job right called for the help from the local certified welding shop. His Miller 200A MIG made quick work of joining these parts together again, with nicer, deeper welds than the HT arms came with originally.
Once the smoke settled, I cleaned up the burnt off paint with a wire wheel. I had to grind one small nugget from the inside diameter of one bushing eyelet since the weld penetrated right through. No biggie. At least I know it won't come apart on the road!
Lastly, here's an overall view of the shortened arm. A little primer and some new paint and it should look like the new piece it is, only better. 
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cptsnoopy
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MAR 10, 08:53 PM
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Substantial and Purdy!
Charlie
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Bloozberry
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MAR 11, 08:23 PM
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With the upper arms shortened, I mocked up the entire front suspension again by temporarily clamping the upper control arm mounts onto the cross member in the new location. I wanted to do this for two reasons:
1. verify the final position of the upper control arm mounts and adjust them if necessary since I wanted the arm bolts centered in the mount slots with the knuckle at ride height and zero camber; and
2. cycle the suspension through its range of movement to check for any interference issues.
Part 1 was a piece of cake and everything worked out as planned, but I found when cycling the suspension that there was interference between the shock absorber body and the underside of the UCA mount in the last 1/2" of jounce. This wasn't really a surprise so I had a solution already planned out that I'll get into in my next post. For now, it was time to rejoin the UCA mounts back onto the cross member in their new location (I just love the welding photos):
Once again, I tack welded the mounts in place but for these major structural joints, I went back to the same shop that did the control arm welding to finish the job. Here's a smokin' hot, half completed joint (mmm the smell of burnt powder coating )
And here's the cleaned up final weld:
Next up: addressing the shock absorber problem.
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LaFierte
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MAR 12, 01:17 PM
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