Terry, I'm liking reading through your thread. I can truly appreciate the work your doing. I only wish I had more time to work on mine. Keep up the good work and keep posting away. Your build has me sucked in now.
I also enjoy this thread very much.. the car is simply awesome.. hope i would start my project next month. For now I made a foam bodywork of the Manta Mirage in 1:4 scale just to see how it works and how it would look like, think I'll drop some photos of it next week.
I greatly enjoy threads like this, and I suspect as you go through the "Head Scratching" process you will get the results you are looking for.
I had a question as I looked at your photo with the superimposed lines thru mounting and pivot points, I was wondering what size tire width you will use, and with that question in mind why you set your instantaneous center as short as you have it?
I would anticipate quite a bit of camber gain with the setup you have, and I would think that you would need to extend that instantaneous center if you want to use a fairly wide tire.
Re-setting the center means re mounting the upper arm and I realize this is a lot of work, but it would create a larger radius at the hub face, less camber gain, and make you issues with rack position easier to deal with.
I would anticipate very little roll in your chassis, and therefore not a great need for lots of camber gain, especially with wide tires.
One other question I had was whether your frame rails, and wishbone mounting points are parallel or tapered? This will affect rack position and adds another dimension to the dynamics as you cycle thru your travel.
I am not trying to throw a wrench into the gears, just adding some input from my experience.
You are in the ball park, and small changes now can make all the difference to acheive your goal. The final position of your rack pivots may not look correct, but if it works that is what really counts.
Not trying to be critical here...your build looks great and I look forward to when you get it where you want it.
Keep posting photos and many here on the forum will add input to help.
Great points Phil. This is a process in which I take in as much data, tips, suggestions, wisdom, and advice, and use these factors to come up with the best result. This is also why everything is either tacked in place, or only Cleco'd in place until I have it set in my mind on a final configuration (If I sat it down on it's own weight, it would mimic the "Blues-mobile" as it falls apart). I'm soaking it all in, and it's taxing my grey matter more than I can comprehend, so notations are getting lengthy on each part or parts. It is very possible that the arms will be a couple of inches longer than their current configuration, and this will move the I.C. out further. Again, all good comments.
Oh, and the arms are tapered relative to a side view.
My latest challenge is the rear arms. I've considered rear lower arm attachment points that are parallel to the chassis centerline, and horizontally flat in a desire to eliminate any rear toe-out. But also recognize an up-angle to the front, plus an move slightly outboard for the front link's mount would also provide the slight toe-in (compressed side) as well, plus anti-squat attributes. This would mimic the 40, which is very compelling.
Just can't wait to see your project finished Terry. Unfortunetely I have no time for now to start my work.. Two weeks ago I just made a scale model (1:4) of the M8b just to see how it would look like. It took me something like 7 hours to measure the dimensions and carve the shape in the foam. Here's a picture of it:
On my stock car I used a magnetic laser level stuck to the rotor for bump steer. Set it at ride height, put the dot on the wall and cycle the suspension and see which way it goes. Not as accurate as a true bump steer guage but it does a pretty good job.
Based on tips you guys have provided, I've implemented one of a couple of planned changes. I dropped the pickup point of the lower front arms to gain ride height on the front (with the use of the smaller 15" front wheel/tire combination), but mainly to increase my IC. Yes, it changed the bumpsteer characteristics, but that has also been resolved (no photo of the changes yet)
I'm finally to the rear suspension and replacing the original tubing to better accomodate the trailing arm suspension. In the photo below, the OEM tubes are tinted red. Everything surrounding those tubes are the new tubes that will eventually replace the red tubes. As soon as I'm satisfied with the postioning and the pick-up placement, I'll cut out the red tubes and reinforce the new tubing.
Looking good. I see you are busy with the Sawzall. I have a question on the relationship between the forward and rearward mountings for your radius rods, I can't see your upright so I was wondering if there is some anti-dive built in there?
keep on plugging away.
What took 45 days to do on the driver's side only took 2 days on the passenger side in finishing up the rear suspension. It looks pretty gruesome right now, but once everything is where and like I want it, I'll pretty the uprights up some, put a little make-up on them, and they should look fine. Basically, it's a 6" tube (to mount the hub and house the CV), welded to two 1 1/2" square vertical tubes. Then I triangulated (not shown in the first photo, but seen in the second and third photo) the upper and lower extensions
So, my wife is walking out in the garage and takes a photo of me as I’m drilling holes and fitting panels…
Little did she know (little did I know) how precarious the support on one side of the frame was. Remember, this is on a rotisserie. So, I’m drilling away, and all of a sudden it started rolling on the axis with all of my shi++ headed south. It was like the movie “Poseidon Adventure”. My boat capsized big time. My wife is upstairs on the opposite side of the house and heard the commotion. So with camera in tow headed swiftly to the garage to see this. I don’t even remember how out got out of this without a scratch, but I did...absolutely amazing. Anyway, now I’ve got to pick up all my rivets, screws, tools, parts and pieces that are spread out all over the floor. Oh well, I needed to get back to the undertray again anyway, so I guess I’m there a little quicker than I expected. Notice the battery upside down and held in place with the master cylinder reservoirs. It would have gone all the way over if not for the squirrel-cage fan that it bent up on its way over.