I-beam axle set up- Leaned back how far?

[pikesan99]

Hi everyone...

A quick question... how far back does an I-beam axle lay back? Isn't it 6-8 degrees?

Thank you!!

[Unkl Ian]

Yes.
Back at the top.

[pikesan99]

Thank you very much!

Here's what I'm up to. The spring shackles are supposed to be straight up and down, right?

Thanks again!

[gettingreasy]

I really like the "hidden" quarter springs, cleans up the frame qute a bit. What if it's rocked back to far, say 12-15*?
-Jesse

[**DONOTDELETE**]

Steering effort increases with the amount of caster.

12 to 15 degrees of caster will drive great in a straight line but it will be a bear to turn. I've run as much as 12 degrees on a sprint car but I've had to use power steering to do that.

[Retroline]

Yeah,
Do you want a dragster or a drivable hot rod? 6 degrees is usually enough but more will help it pull in a straight line. I like the set up you are running. neat stuff.

[roadstar]

5 degrees is the rule of thumb around here.

Also keep in mind as odd as this my sound many people for get to set the chassis to ride height before setting up the proper caster. For example: If you set the car level on jack stands and put the front x member in with 5 degrees of caster built in and then put the car on the ground with big and little tires it may change back to zero. I have seen this done more than once.

[hatch]

Good point on planning ahead.

One thing to watch.... too much angle and a "three point turn" becomes a "nineteen point turn"...not cool when you are trying to do a fast exit at the strip club.

[tommy]

http://fototime.com/{F30BE534-54ED-435B-94CB-DEA566CFE6A7}/picture.JPG

1947 Motors Manual specs

[C9]

Neat CAD drawing.

Looking from here - unless you have other bracing not shown - it looks like the shock upper mount will flex and eventually break due to forces input from the shock.

Are you running shackles between axle and spring?
Similar to what would be seen on a standard solid axle/transverse spring arrangement?

Or just tabs welded to the axle for a single bolt through the tabs and the spring eye?
Sounds like the former if I read it right.

I'm curious too as to how the rear of the spring is clamped inside the frame.

Not trying to pick things apart, just curious about it all.

Curiosity or not, it's a good looking and clean front end setup.

Post a pic during construction and at completion if you would please.

[Harrison]

Is there any truth to the rumor that a car running bias ply tires needs a bit more caster that one running radials?

JH

[Mojo]

The car is a bit off topic, and the suspension is different, but I had a old 79 chevy that I dropped the frontend after rebuilding it. Well, I put the upper arms on backwards by mistake, and it gave it way too much caster... it was around 14 or 15 degrees. The car wasn't any harder to steer, it just drug the tires really hard while turning and backing up. One side of the front would tilt higher while turning too. It didn't pull the wheels straight any harder either. The car had power steering, but it wasn't any stiffer to steer.

I've had it at about 7-8 degrees before, and it didn't drag the tires, and the steering was actually a bit stiffer to steer. I think when it got to around 13 degrees, it kinda negated any benifits of additional caster...

[DrJ]

This is very interesting! since my '53 Motors repair manual, which goes back to '35 says +6-3/4º caster for '35 thru '48 and - 1/4º (yea, that's minus caster) for '49 thru '51 IFS.
I wonder why they changed specs? and obviously there are different opinions even in the old manuals.
I guess they changed the spelling from CastOr to the more contemporary CastEr somewhere in there too?
Our language is ever evolving...Especially the American dialect of English.


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http://fototime.com/{F30BE534-54ED-435B-94CB-DEA566CFE6A7}/picture.JPG

1947 Motors Manual specs

[/ QUOTE ]

[gettingreasy]

I think I measured it at 12* but that is with it sitting flat on the ground not at ride height(which should be quite rakeish). I'll have to measure it again when it's a roller and at proper ride height.
-Jesse

[DrJ]

If you set the ass end up 4-5º that should make it 8-7º which'll be fine.

[gettingreasy]

I still can't wait till I get it into being a roller so I can see what kinda crazy rake it'll sit at. This just eases my mind a bit cause I've been worrying about this very thing.
-Jesse

[SamIyam]

That's what people seem to say... 6-8 degrees. I set my Model A up at 7 degrees... and the BFD is lingering in at around 18 degrees...

The main thing that you want to do when you set up the caster is to make sure you set it before you weld in your front crossmember. To do this, weld a piece of steel, temporarily, to hold your frame rails apart. Mount the radius rods... and then set the caster. After that, bolt the crossmember onto the srping, slip it into place, and then weld. When done correctly, you should be able to unbolt the spring and jack the frame up without the spring bolt "popping" out of the hole... it sould go right back into place with little or no deflection.

If you do have to tweak it one way or the other, try to set it up so that you are popping it into the hole from the front. This is assuming that your radius rods are set up neutral and that they move the axle rearward when the spring collapses... but don't force it more than 3/16 of an inch into the hole.

When you have spring perches that bolt into the axle, like a stocker, it's kind of hard to set the angle of the spring. But when you do have the liberty of welding the spring shackle brackets onto the axle... you can set it up so the spring does not bind. I did this on the BFD by taking a straight edge from the hair-pin mounting bolt cl and running that line through about the center of the spring (non compressed). I then put a square in the straight edge and mounted the spring/shackles/perches paralell to that. I've given it a lot of thought... and (exagerated to make it more clear) say you have set the axle/spring/crossmember in at 20 degrees. The arc in which that entie assembly moves is not paralell to the direction in which the spring compresses. In other words, the shiznit will bind. Now I realize that the spring will diflect a little, as well as the shackles... so take this example with a grain of pepper. http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

Sam.