Model A Tudor aerodynamics?

I don't have a sound theory to advance, just the title of the thread was like having a rusty screw-driver jabbed in my eye i can't think of a bigger non-sequiter,.. perhaps "military intelligence" "british styling" or "italian engineering"

 

I was taught that if only one bar is used, it must be the front. If you don't have a bar in front, get rid of the one in the rear.

 

DItto^^^^Plus the Panhard bar being short. Combination of several things. What a ton of great info and posts on this thread! Plus chop it 3 to 4 inches. Still a cool ride.

 

OK y'all, here's the the next part of my experiment and a couple other things.
I've been taught a beam axle with split wishbones will act as a front sway bar. I'm sure there will be arguement about that. I used this as why I drilled thru paint to experiment with a rear sway bar.
As it stand at this moment, I have now put a preload on the rear coilover springs which I had not done before. I have removed the rear sway bar and cringe at damaged paint, I did it.
I haven't driven the car with these changes yet. Have been making other repairs and adjustments to my first hotrod experiment. I'm like a doctor, I'm still practicing, but this is my first subject built from rust and junk.
Y'all be careful how you handle your screwdrivers!! Thanks!!

 

I dont remember exactly how to figure roll centers, but my thought is with the really high cg of that car, then what seems to me to be a really high rear roll center because of the panhard bar placement vs. maybe a much lower roll center in the front it makes the rear want to roll side to side very easily.....just a thought

 

I believe very strongly that this is part of why the car reacts the way it does.
I also believe that if the top bar of the 3 bar suspension was centered, instead of toward the passenger side, the suspension would react in a different manner too.
Does that mean the rear suspension steers the car similar to a dirt late model with the left rear pushing forward BY DESIGN? My design.

 

Although I have an IRS and IFS in my 35 Chevy phaeton with front & rear sway bars, I experience it was well in string cross winds. Car is as aerodynamic as concrete block at 60mph. However the chassis weighs more than the body so the slightest cross wind buffets the car. I live with it, part of the experience.

 

yes i too cracked up when i read the thread title!

I thought ''It's a fuckin' square!... it has no aerodynamics!''

Sorry...

I hope you can sort out the problem. A friend was telling me how a semi up the clacker of his caravan would cause it to dance about and try to lift off... maybe it is related to the massive air pushed out by these rigs?


aussie

 

Yeah, aerodynamics = oversize brick.

As for your issue, my Tudor isn't chopped either.

I don't have an instability issue, but I do have to cross steer when I approach a tractor trailer with a box trailer (away from the truck when I approach the rear, towards the truck when I'm passing the cab),

I'm running a Parallel 4 Bar with a short Panhard and Coilovers.

I have a set of 350 Lb / In 12" free length coils on the rear (the shocks accomodate an 11" free length spring, it makes it "interesting" to install the springs).

I'm somewhat paranoid about breakdowns, so I bring parts and tools, along with oil and water with (food, luggage, parts for other projects...) hence the heavy springs.

So my suggestion is to try the heavier springs after you try unhooking the sway bar, as was suggested earlier.

I hope that helps.

 

The word aerodynamics and Model A sedan make me smile,,

The Model A has basically the same aerodynamics of a Barn!

With split bones up front you still need some sort of panhard bar or a dead man perch,,nothing feels as spooky as going through a series of curves at speed and having the front spring unload and get that quick bump steer feeling.

With Coil overs you need a sway bar,,do everything you can to make the car pleasent to drive. HRP

 

Glad to help some of y'all laugh!!! Yeah, I know a Tudor is as bad as a barn!
Anyways, down to what I've done.
I pulled the rear sway bar off because I felt it was making the car spring left and right all the time over the rear suspension, constant correction mode.
Previously I did not have any preload on the rear coilover springs. I now have 4 turns of preload on the coils. I also lowered them back down to the lowest position on the rearend housing brackets.
The car still has a bobble feeling in the ass, but I think it feels more stable than what it had been previously. FWIW, this is just with taking a jog on I-40 thru NLR where there are plenty of overpass bumps on the fresh concrete, lane camber changes, and traffic. I think it feels a little better. I also think maybe stepping up from 250 lb springs to a step or two stiffer might help.
I also have all the glass in the car and driving with windows closed,, which will also affect aerodynamics of a vehicle body designed to be driven at approx 45 mph tops.
I feel like I have made a step in the right direction without making major changes to the suspension SO FAR. I was and am still prepared to make a ladder bar setup to replace MY three bar setup and ditch the existing upper bar.
Next weekend I plan to drive it to the NSRA Appreciation Day at the Pulaski Tech College campus along I-30. My 20 mile route to it has a few bumps that show what the car does. I may make a loop thru the country afterwards to just see what it will do. So far, I think it's good.

 

Finally, have a better feel of what my car is doing and an another witness from the passenger seat that has built a few cars.
Here is the bottom line. My car has a neat rear steer capability that would be extremely good for a circle track dirt car because of geometry. I will be building ladder bars based on my pickup points on the axle housing and suspension mounts.
MY suspension bar angles cause the rearend to steer the car and cause the rear of the car to bobble without steering feed back. It's compounded because it's motion is free enough to rotate like a rock crawler 4wd would possibly want.

 

I have built a pair of ladder bars and have pulled the upper forward bar of the three bar out. On jackstands, the body feels like it doesn't roll as easily. I'll put a pic in of the left bar after I get done with the picture hokey pokey.
I think the car on jackstands feels like it has less body roll ease than previously. I am in need of getting another pair of rear tires and registration renewal before I can test out my work. A separating tire and license plate being two days out of date are recipes for unneeded expense, so Miss Chevious sits on jackstands in the waiting.

 

Okay, here is the new bottom line.
The suspension you see above has a design problem, I did it. If I had put the upper bar in the center, it may have worked just fine. If I had put another bar forward from the left side too, it may have worked just fine. Without either, the upper bar location causes rear steer and causes the ass of the car to upset.
I have replaced all the forward bars with my homebuilt ladder bars. Pictures after I can get the fnbucket to work for me again. The car finally drives as well as a slight bump steer, solid axle car will. I'm happy with no body bobble with uneven road changes and weird transitions. I will not have to study the road at speed as much as previous to know how the car will react.
NO MORE FEELING OF THE CAR WANTING TO TAKE OFF AND BICYCLE ON THE LEFT SIDE TIRES!!!!!!!!!!!!! It might could use a front sway bar, but I can drive through that or slow down a bit.
Thanks to the guys that helped me think through this problem. Thanks to the guys that asked questions. I have learned a lot more about suspension fab by my doings and mistakes.

 

For what it's worth a three link with the upper link offset work's just fine.Ford ,Mercury ,and lincon ran three link's with offset upper for year's . I have a three link on my RPU and it work's great very stable.Your geometry might have been off but ther's nothing wrong with a three link.From the picture I'm looking at I would say your upper bar was way to long. JMO and glad you got it fixed.

 

I'm a grasshopper. The experiment still continues as I feel like the panhard bar needs to be longer at the rear of the car as the front does not have one.
I had one OH SHIT moment with a lot of bad possibilities.

 

The OH SHIT was with me and my sons. The car went into Weeble movement after having made my new ladder bars to hook to the existing four brackets. Look again at the short panhard bar that is close to 18" center to center. Short panhard, rotation.
In progress of making a new panhard bar from old A stuff and a little bit of my half or quarter assed lathe work. I can burn in a damn good weld most of the time.
Next experiment is with the ladder bars with the soon to be finished 32 1/2" center panhard bar.
Pics at 11 like on the news from Terre Haute, we're not on your time, we're on ours.

 

I agree, sounds like the bar is too big

 

I built a longer panhard bar from an original bar that was part of the Model A brake system, tabs from scrap plate steel, three tubing bungs from leftover round bar stock that were part of a cut to fit big truck torque rod kit, and a piece of 1 5/8" X .120 tubing for an Atro Engineering bushing for a Peterbilt sleeper lateral control bar.
I built a pair of ladder bars from 1 1/4" x .120 driveshaft DOM tubing using the same Pete bushings and 1 5/8" tubing at the rear and bungs for 3/4" heims made from what us truck associated folks know as Budd inner nuts.
The original panhard was about 18" CL to CL, new just over 32 1/2" CL to CL I believe this here is the real source of correcting the body/frame bobble over the suspension.
I drove over road irregularities at 80 that would've had me white knuckled coming down from a previous 65 at the other side, now no problem
Pictures of what I made in a little bit. Takes a hokey pokey for me to be able to do.
My bucket has a hole in it, can't buy more beer!!!
http://s274.photobucket.com/albums/jj268/patrickmoran1966/

 

Yah, that is like "military intelligence" or "jumbo shrimp".

 

Finally another chance to make a long drive in the car. I drove from North Little Rock to Conway for the first short leg, and then up to Harrison AR and back to NLR. Part of the drive up and the drive back also included about 80 miles or so of hard rain on a twisted road.
Highway 65 has some rough places in curves, smooth curves, uphill and downhill curves. I was pleasantly surprised that the car handled sooooo much better and my 16 year old son commented about it too.
I have a feeling that my previous three bar rear suspension also had some contribution to the front end wanting to screw up because I have been across some of the same road irregularities that caused my front wheels to bounce up and down making the radiator wave left and right and breaking the support rod bracket. I hit one section of interstate at above the speed limit and didn't receive that problem.
I love the howl of the wind under the visor, thru the overlapping doors, and under the open windshield!!!!

 

Glad your drive was pleasant, Patrick. And thanks for the cordial visit when I stalked you a week or so ago. I never thought about how it would appear to a rodder when a uniformed cop gets out of a car behind him.... I was a bit sidetracked by the Model A.

 

Damn sure took me by surprise for a bit. And I have friends on PD around here.
THANK YOU! I was damn glad it wasn't the kipper coppers on the damn cell phones that heard my pipes while they were passing me as I was trying to behave my ass.
Beer thirty is usually after 6pm. If the garage door is open, have beer because I have mine.
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