From: atrav (Original Message) Sent: 7/27/2002 11:19 PM
I'm reading the flatheaders online web page about the caster/camber topics, and bending the wishbone for castor change. I'm wondering if you have split wishbones,
transverse buggy spring up front (A-V8), and tie rod ends on the radius rods, if threading the tie rods in or out a bit would pull/push the axle to affect caster too?
I wonder how much the spring, shackles, and other bits would tolerate an axle pushed or pulled a bit off center?
Reading "How to Build a Traditional Ford Hot Rod" Bishop/Tardel, page 59, he states "The kingpin inclination of Lincoln spindles is different from that of Ford spindles.......Lincoln spindles are about 1 degree negative on the same axle, requiring some adjustment of the beam."
When he says 'kingpin inclination' is that caster? or camber? or what? left/right, or forward/back?
From: JWL Sent: 7/28/2002 12:53 AM
First, no, do not adjust the caster by "pushing" the axle forward and expecting it to pivot at the spring and add caster. It is possible (but not advisable in excess) to attach the rear tierod connection low enough to add a few degrees of caster. Otherwise it would be better to bend the axle outside of the perch bolts.
Kingpin inclination is not any of those things, except that if wrong, it can affect camber and more. This inclination thing refers to the angle of the pin from vertical. This angle (or inclination) is designed to coordinate with the spindle, wheels, and tires, so the centerline extended of the pin will reach a point on the road surface at something close to the center of the tire. When the wheels are turned, correct inclination assures proper upward force against the thrust bearing.
From: ole Sent: 7/28/2002 3:58 AM
When I did my track roadster, I added more caster to the axle by cutting a wedge from the yoke ends of the wishbone, bending the yoke backwards in the direction of the axle tilt in order to achieve the desired caster, then welding back at the new angle. Worked great! I also used a correctly angled shim between the spring and perch... rodnut
From: hotrodjack Sent: 7/28/2002 11:14 PM
Hey Rodnut...and anyone else who can help. First of all, I love the the "V cut radius rods and angle shim" idea for degreeing in the caster. I also understand that a lighter car needs more caster for the Akerman geometry and the toe-in to allow the car track straight at higher (over 50mph) speeds without a lot of wandering. My question is : how many degrees of caster would you recomend and, as you increase the caster, is it still OK to maintain 1/8+ toe-in or does the toe-in have to be decreased? I'm building a steel 27 rdstr on A rails w/39 flathead, split bones on the front (very similar to Rodnuts). Thanks HotRodJack
From: ole Sent: 7/29/2002 1:33 AM
These specs can be quite varied on the early Ford I-beam axles, depending on what source, and what year one is looking at. The recommended caster runs from 4 to 9 degrees+, with toe-in at 1/16" to 3/32". My '34 Ford spec book shows "axle tilt" (caster) at 8 3/4 dgrees with 1/16" toe-in. When I set up my roadster, I used about 7 degrees+ caster, with 3/32" toe-in. I used a suicide spring perch, which set the axle C/L several inches ahead of the front motor mounts, which would normally decrease the weight on the front wheels. However, the wheel base was 112", so the F/R weight percentage was probably very close to the 'A' set-up. With your axle at the stock 'A' location, I would set it at 7 dgrees+. Also, with this angle on the spring, and the split bones, etc, things tend to want to go into bind during suspension movements. For this reason, I use stock style rubber bushed shackles to allow some 'give'. I would not recommend using the more rigid 'poly' bushings that everyone touts. They are not forgiving enough. And be sure to use spherical rod ends or tie rod ends at your radius rod mounting points to allow them to rotate as needed... rodnut
From: JWL Sent: 7/29/2002 8:33 AM
You have touched on the technical reason I don't suggest using the angled spring. I know, I know, I know it has been done on MANY cars. But there is just no way to make the split bone legs long enough to prevent binding stress. If there is moderate travel it doesn't seem to be as big a problem with splits as it looks on paper. However, I think a 4 bar could be dangerous.
From: hotrodjack Sent: 7/29/2002 11:14 PM
Thanks Rodnut. That's exactly the info I was looking for. I am using the rubber bushings and tie-rod ends for the very reasons you mention. What bothers me though, is that JWL doesn't approve of this setup (and I really respect his opinion).What are my alternatives? Heres my setup: Stock A crossmember w/stock A spring (minus 2 leaves and reversed eye main) 2 1/2" or so (not quite 3") vintage MorDrop axle, split 34 bones and 600X16s. Rear has a stock A crossmember and spring mounted behind a 40 rear The bones are not split ( but I been thinkin' about splitting them) and mounted on the 32 t-tube w/ 750X16s. The frame is a stock A w/a 36 X member grafted in (it's plenty stiff). The car has a pretty good "rake" and it's obvious that the caster is at 0, -2 degrees the way it sits now. I have the threaded bungs welded in the bones, and the tie-rod ends are in, but I don't have the mounting plates on the frame yet. I figured there loction would be determined after the front end was degreed in. So if I shouldn't "angle shim the spring and V cut the radius rods, what would you suggest? I could angle the front crossmember but I don't believe that would be any more productive than the shim. I also have another un-cut 34 wishbone that I could use. this would eliminate some of the "binding" problems, But, because of the cars "rake", I would have to use the wishbone to "push" the axle ahead to degree in the caster...and bind everything up again. Any suggestions...or am I just worrying too much? LIFE WAS SO MUCH EASIER BEFORE I FOUND THIS SITE...YOU GUYS GOT ME THINKING TOO MUCH. Thanks HotRodJack
From: ole Sent: 7/30/2002 3:08 AM
I really wouldn't worry about it. I spent several months drawing up all of my suspension and frame details to scale before I built my car, and this front suspension problem is not overly significant. I scratch-built my chassis from 2x3 tubing, using an NOS 'A' rear cross member. The front suspension will not travel far enough to cause any kind of major problem. It ain't perfect, for sure, but you will really never notice it, and my car handled and tracked just fine. Building a car like this requires a lot of compromises. There isn't any free lunch here. Your tire sizes are also identical to what I had on my car. As for the rear rake, are you using a reverse-eye rear spring? You can also go with longer shackle side plates. I made them for my roadster. I mocked up the front axle caster in order to figure the amount of wedge to remove from the bones. After modifying them, I attached them to the axle, set up the axle to the chassis and clamped the mounting plates to the frame with c-clamps so that I could get the caster just where I wanted it before welding them to the frame. Do this welding LAST, so that you can check full lock tire clearances, etc. I used a '37 I-beam axle with a top mount spring and had to place the bone mounting plates on the inside of my frame rails, with the tie rod ends to the inside of the plates in order for the bones to clear the tires at full lock. You may also need to make some other adjustments. Also, feel free to email me with any other questions you may have with your project. I'm not saying that I have all the answers, but I have been there, and done it, successfully... rodnut
From: JWL Sent: 7/30/2002 8:01 AM
Nearly all truck alignment shops can correct caster/camber problems in beam axles which then allows perpendicular spring mounting and alignment.. However, as I said, vehicles with moderate travel don't seem to cause enough problem to worry about. I am just "PICKY".
From: ole Sent: 7/30/2002 2:23 PM
Yes, I thought about 'twisting' the axle ends to achieve the needed caster, but for me, the logistics of hauling the car to a COMPETENT shop were just too complicated. I also don't trust anyone to do work for me, because I'm also more than a bit fussy, and the job is usually (9 times out of 10?) not done to my satisfaction - to say the least! Not to mention that it just plain bothered me to think of bending the ends of my nicely drilled and polished I-beam!
There are some expensive adjustable s/s perches available that could be used, but again I did not, and still do not, feel that the problem was/is significant enough to warrant them. Plus, I didn't want anything visible on my car that was of a modern design- the car was built to look like it was right out of the 40's. The Model A perches and OEM type shackles were perfect for that... rodnut
From: hotrodjack Sent: 7/30/2002 11:37 PM
Thank you very much JWL & Rodnut for taking so much of your time to help guide me in the right direction. It is greatly appreciated. Also, Rodnut, thanks for the email offer of help...you'll probably be hearing from me. I too (like rodnut) am building this '27 to be as close to a "truely traditional" early post war roadster as possible, using no aftermarket (post 1952) parts. And, it is also an attempt to use up some of this Early Ford "junque" that has managed to find a home in my garage over the years. The roadster will probably end up being just a "scoot around town" car with roughly a 200 mile range ( the wifes hair is a concern here) but I still want it right. Your responses have been very helpful...like the lock to lock front tires hitting the radius rods. Can't figure out how I missed this...but I did, they WILL hit if I mount the bones on the outside of rails. And, like Rodnut, I'm too chicken to let some Truck Garage crank new caster angle into my vintage MorDrop ... . Been thinkin' about lettering up my 39 pickup as an old HotRodJack's Svc. Station truck (it's flat black w/apple green steelies) and flat-towing the roadster on longer runs to shows out of town (sort of a "going to the races" theme). Have questions about flat-towing a car with closed drive shaft...but will start a NEW TOPIC as this one is getting kinda long. Also curious about opinions using split bones on front but not on rear with a very rigid frame (will also NEW TOPIC this). Thanks again guys...I love this site! HotRodJack.
From: atrav Sent: 8/7/2002 9:44 PM
I'll add my thanks here too! I didn't think of the tire clearence issue, that'll be an excuse to mount tires a little earlier.
My conclusion on caster and camber with the I-beam axle is, I'll wait until everything is mostly assembled and weighted down, then measure and see what needs to be done before I really worry too much, yet!
There is a local place that I'd 'kind of' trust to bend an axle, they at least listen to me and let me be right there. They do specialize in heavy duty trucks though.....
From: 32tom Sent: 9/21/2002 9:41 AM
The king pin inclination was way off on this old axle. I was able to correct it by "walking" the axle back to the right angle with a torch. Basically warping the axle with heat and then stress relieving it.
I'm running a stock wishbone. I don't think anyone ever split the bones to run a flathead with the stock axle loction. They split them to clear the OHV8's. Then it became cool looking.
I hope everyone has seen that old factory picture of a 34 coupe(?) with the left front and right rear tires on big blocks.12"?18"? The right front and left rear are still planted firmly on the ground.
The ones I did split I bolted the spring and axle in the frame to find their neutral (no bind)location and then modified the bones to hold the axle in that neutral location. If the axle wasn't modified like mine, the alignment specs should come out pretty close. Like JWL says it can be dialed in from the spring perches out.