Front axle/suspension questions

[Zandoz]

A few questions have come to mind, but first the basics of what I'm planning...instead of the typical spring behind and radius rod "suicide" set up, I'm planning on going with a spring over 4-bar configuration, with the lower shock mounts on the bottom end of the perch bolts. For upper shock mounts I was planning on using the forged F1 style mounts. Now for the questions...

• Is there any caster angle built in to the new axles sold by the likes of Speedway, Super Bell, Magnum, etc? I recently ran across someone who was selling actual Model A axles that he had dropped, and had 7 degrees of caster "built in". Until I saw that I'd assumed that all of the axles were straight, and caster was set entirely with the adjusters on the 4-bars or radius rods.
• Should the 4-bar frame end mounting points be perpendicular or could the upper bars be mounted slightly more rearward to have a bit of built in caster?
• From what I've seen, the lower shock mounts fastened with the perch bolt mount the shocks in front of the axle to the outboard side of the batwings. Would there be a problem with turning them around to mount the shocks on the back side of the axle, inboard of the batwings?

 

[TrackTV6]

I understand that camber is built into the Speedway Motors axle, but caster is set with the radius rods/hairpin. The radius rods should be as close to parallel as possible to keep them from having to great of conflicting arcs of travel leading to a bind. Whether the shock is in front of or behind the axle should have no effect on its rebound or compression rating, as long as the angle of mounting remains the same.

 

[Dirt-T]

Are you talking about a tube axel? When i used to build tube axels i pre set caster at 6* so bars would be ths same length.
I would talk so the MFG of the axel you will be using and ask .

 

[Lee_in_KC]

My Superbell tube axle has some caster built in. With both hairpin arms set to the same length (top and bottom), I get about 7 degrees of caster.

 

[Zandoz]

I understand that camber is built into the Speedway Motors axle, but caster is set with the radius rods/hairpin. The radius rods should be as close to parallel as possible to keep them from having to great of conflicting arcs of travel leading to a bind. Whether the shock is in front of or behind the axle should have no effect on its rebound or compression rating, as long as the angle of mounting remains the same.

One of the axles I'm considering is a Speedway 48" tube axle with 4" drop, but I believe it is actually made by Magnum. I tried going to Magnum's site, but it is under construction, and their catalog does not mention anything about caster.

If I do set up the 4-bar mounting points at a bit of an angle to build in caster, they would still be parallel...but like a parallelogram instead of a rectangle

 

[RESINATOR]

There is no caster built into the axles that are cast or forged one piece units.. or the tube type that have the axle ends (not bosses) welded at the inside of the spring perch boss to a curved tube. Superbell, Magnum, TCI, Chassis Engineering, SoCal and others that are similar will not have caster built in..
The manufactured tube axles that are bent tubing with kingpin bosses welded to the ends would just depend on the manufacture... We put about three degrees into the actual boss and the rest is made up in the brackets for the radius rods/4 links. If the axle has brackets welded onto it when purchased it should have the caster built in, if there is only a boss to attach a batwing or wishbone to the axle it will probably not have any caster.
The 4 link brackets, frame side, will have to locate where they line up with load. they normally have an angle with the bottom hole forward of the top.
The shocks/brackets rotated behind is no issue,unless they have the keyway,.. just be aware that the batwing will be there and the shock may limit the turning radius because of tie rod clearance. We use the same setup on our 1926/27 type chassis when using an I beam axle.

 

[Zandoz]

There is no caster built into the axles that are cast or forged one piece units.. or the tube type that have the axle ends (not bosses) welded at the inside of the spring perch boss to a curved tube. Superbell, Magnum, TCI, Chassis Engineering, SoCal and others that are similar will not have caster built in..
The manufactured tube axles that are bent tubing with kingpin bosses welded to the ends would just depend on the manufacture... We put about three degrees into the actual boss and the rest is made up in the brackets for the radius rods/4 links. If the axle has brackets welded onto it when purchased it should have the caster built in, if there is only a boss to attach a batwing or wishbone to the axle it will probably not have any caster.
The 4 link brackets, frame side, will have to locate where they line up with load. they normally have an angle with the bottom hole forward of the top.
The shocks/brackets rotated behind is no issue,unless they have the keyway,.. just be aware that the batwing will be there and the shock may limit the turning radius because of tie rod clearance. We use the same setup on our 1926/27 type chassis when using an I beam axle.

All of the tube axles I've considered have forged ends that include both the spring and kingpin bosses. After seeing the dropped old axle with caste built/bent in, I hoped the new ones would have the same...it would make things easier.

Moving the lower 4-bar mount hole slightly forward is exactly what I was talking about. I was considering a 7 degree angle forward, which would pit the lower hole about a 1/2" forward

 

[RESINATOR]

The other thing you may need to do is to make sure the spring perch is set to 7 degrees or so ..if that is not possible then you need to use the adjustable spring perches so you will not bind the spring when the axle is laid back.

 

[Zandoz]

The other thing you may need to do is to make sure the spring perch is set to 7 degrees or so ..if that is not possible then you need to use the adjustable spring perches so you will not bind the spring when the axle is laid back.

I had planned on angling both the perch and the upper shock mounts to correspond with the angling of the axle.

 

[Dirt-T]

I had planned on angling both the perch and the upper shock mounts to correspond with the angling of the axle.

also angle the pad for the spring.

 

[Buster]

I used speedways 48" tube axle with the spring behind and had problems finding away to mount shocks. My perch is 5deg angle on frame using hiar pin radius rods and axle set to 6deg caster. I fially used a set of 1934 shock towers welded inframe after locating where shock needed to be mounted. I then drilled upper batwing bolt hole out to 1/2" max and made bolt to hold shock in place in lower position and used shock studs to fit shock towers. NOTE: shock towers will need to be cut to fit and welded in place. I then used a set of 10" gas shocks with shaft extended all the way out to find shock travel to get proper fit and angle. You must have all wieght of engine and tires on the frame when doing this to get correct fit. Only difference should be you are using a four bar instead of hair pins which gives you a better way to adjust if needed. I on hand will need to take complete hair pins off to adjust. Also take note of angle of shock, this affects the effienecy of shock, no more than 20deg angle. My car drives great at low speeds and highway speeds needed very little adjustment. Had a little bit of problems with toe end not staying put. Also I'm using traditional sterring.

 

[Zandoz]

As the plans stand now, with the 6 1/2" F1 shock mounts and 12 3/8" mounted length shocks, the shocks would be at around a 16 degree angle. The shocks are spec'd at 4 1/2" of travel. The F1 mounts, perch pad, and frame ends of the 4-bars would be at 7 degrees.

Another question that has come to mind is just how much travel I can reasonably expect out of the spring over axle configuration? I'm aiming to get all I can, and at this point I wouldn't be able to get the F1 mounts any higher. On the other hand if the 4 1/2" travel is more than needed, it would make things easier mounting them lower with shorter shocks.

 

[RESINATOR]

Once everything is set, you should have about 2 1/2" to 3" of down travel and at least an inch of up travel.
In most cases you should have a fully extended shock when the motor and transmission is out. To simulate the load without the motor (spring under perch style) use only the main leaf for set up with the chassis weight on the suspension. It is still best to use the longest shock you can, and use all the components you will be using when doing the mock up.

 

[Zandoz]

Once everything is set, you should have about 2 1/2" to 3" of down travel and at least an inch of up travel.
In most cases you should have a fully extended shock when the motor and transmission is out. To simulate the load without the motor (spring under perch style) use only the main leaf for set up with the chassis weight on the suspension. It is still best to use the longest shock you can, and use all the components you will be using when doing the mock up.

By down travel do you mean down travel of the frame, compressing the shock...or do you mean down travel of the the axle, extending the shock?

For the main leaf only simulation, I'm assuming that would be done with some kind of spacers between the main leaf and the perch, correct? This brings up a couple of other questions I've had. My motor and transmission will be considerably lighter than usual...both combined weighing less than a SBC motor alone. The springs I've seen for the 48" axle spring-over-axle configuration have 5-7 leaves. I've assumed that I'd have to leave one or more leafs out, but I have no clue how many. That combined with not knowing how much the springs will deflect under the load they will end up with, has left me not knowing how tall to make the front perch. I know that there are spacers for fine tuning, but I'd like to get close.

Another thing I've considered is going with one of the mono-leaf springs...possibly with one leaf added for a bit of extra support/insurance. The only reasons I'd consider this is because of the light weight of the engine/transmission. I just don't trust the mono-leafs with more weight on them.

 

[Dino]

Bill i missed what motor your running .Can you refresh my memory. Keeping a eye on this post do to i will be doing mine soon thanks.

 

[Zandoz]

Bill i missed what motor your running .Can you refresh my memory. Keeping a eye on this post do to i will be doing mine soon thanks.

A GM 60 degree V6 with a 700-R4 transmission. The 60v6 is around 350 lbs...a SBC around 575 lbs.

 

[RESINATOR]

Sorry, I should have been more clear. By down travel, I mean the suspension compressing such as hitting a bump or a dip. The frame will travel down, then it will rebound up past the original ride height. The up travel is the amount the frame will rise from the original ride height, this is as important as the down travel because you will get a harsh ride and possibly damage the shocks and brackets if there is not sufficient up travel.
The main leaf simulation is the main leaf only! this sort of gets you in the ballpark of where your car will settle to with the rest of the weight on the car (engine, trans, radiator and fluids) and is only an estimate. The best way is to have everything set up that you will use, but that is sometimes difficult and maybe dangerous when doing mock-ups.
When we build a non-production chassis, we only tack weld the frame brackets (a good tack weld, in multiple places) untill we tear the entire assembled car down. This way we can change things if necessary, and something always gets changed.

 

[RESINATOR]

Now for your spring..none of the springs from the various manufactures have the same spring rates. Start with the assumption that you will be using all of the leafs, they are easy to remove later if needed.
We use the Monoleaf springs because they look cleaner (if thats the right word) than a multi-leaf on these cars where they are out front for all to see, it's a preference that may change from car style, But to use the Monoleaf and add spacers may take away from that look.
As far as the weight difference, that is around the weight of putting one of your friends in the car with you (although he might not be sitting up by the engine) and you wouldn't change the spring if you didn't take him along every time.
If a spring breaks, you will still have your shocks and other components to stop the frame from hitting the ground, I would hope! I have seen both fail, although, a multi-leaf may give you a bit more notice/warning..assuming you check your leaves for cracks often.

 

[RESINATOR]

Example.

 

[Zandoz]

Now for your spring..none of the springs from the various manufactures have the same spring rates. Start with the assumption that you will be using all of the leafs, they are easy to remove later if needed.
We use the Monoleaf springs because they look cleaner (if thats the right word) than a multi-leaf on these cars where they are out front for all to see, it's a preference that may change from car style, But to use the Monoleaf and add spacers may take away from that look.
As far as the weight difference, that is around the weight of putting one of your friends in the car with you (although he might not be sitting up by the engine) and you wouldn't change the spring if you didn't take him along every time.
If a spring breaks, you will still have your shocks and other components to stop the frame from hitting the ground, I would hope! I have seen both fail, although, a multi-leaf may give you a bit more notice/warning..assuming you check your leaves for cracks often.

Thanks for all the info! I'm learning a lot here.

My main reason for considering a mono-leaf configuration is the fact that my frame is going to be very low (my target is the bottom of the frame being as close to 6" off the ground as possible), and I'd like to minimize the height of the front perch. The secondary reason is that a mono-leaf would minimize the unknown of the height of an unknown number of leafs. What do you think of the idea of adding an insurance leaf to a mono-leaf?