Cowl steering question

Ok guys I've done several searches, and learned everythin from how to reverse a covair box to the easier to use mopar unit which doesn't require reversing (which incidentally is the box I ended up getting).

My question is mounting the box, does it have to tie into the frame? Wouldn't a sturdy subfloor, under dash support structure be enough?

Need some help on this as I'm about to start on the subfloor on my A, but need to know about tying into the frame first....

Of course pics would be great, but if not I'll settle for opinions and change.....

Thanks,
Harris

 

Fatigue. Sheet metal will fail eventually. You might get lucky, but why not work out a mount that bolts to the frame at the very least?

 

I second that. It will be worth the trouble, IMHO.

 

Hook 'er to the frame...............

 

Look at Dreadman's build!!
Bolting to the frame can also look nice!!!
And it's the safer way for sure...

 

Cool, just trying to figure out how to do it?

 

Yup, it needs VERY solid mounting. If it flexes you will have vague steering, and something will eventually fatigue, crack, or break.

 

Check this out:
http://www.jalopyjournal.com/forum/showthread.php?t=297314

 

Here's a pic I shot at GNRS. Looks like a Mopar box.
Maybe somebody here knows the car and can fill in the details.

 

There are basic rules to steering and Lot's of folks on here choose to ignore them because it makes for easy building. Better driving is what is you are seeking so with this I ask you to look carefully at this picture.

Although much care has gone into the construction of the steering ,one of the basic laws of steering have been ignored .
The Drag ling from the pitman arm to the steering spindle MUST be parallel to the radius rod .
Why? . Imagine two arms ,one is moving through an arc. The arc is the axle moving up and down.
Imagine the second arm ,in this case the drag link.
it too is moving in arc on it's end. BUT it is moving in a different arc because the arc is beginning and ending on a different plane.
Result?
The top arm will be shortened AND lengthened as the bottom rod moves up and down .
What happens when the top rod is shortened?
The steering either kicks out of your hands on every bumpOR the car steers itself.
The last scenario is where your car heads off the road or into another car at speed.
Some here may think a little kick is oK in a car they build themselves,But what if someone else drives your car and doesn't know about this, having been bought up driving powersteered Asian econobombs with their dead steering?
You prepared to pay some lawyer for the pleasure of fighting a law suit when it is found the steering had a life of it's own and they lost control and died ?
The rules for correct steering geometry were arrived at 100 years ago so why do it wrong?.
Do it right .

 

Good points Dirtynails. To correct the problem in the photo you posted, let us assume the steering box stayes were it is. If the split radius rod is raised to mount on the chassis and the steering arm is bent or replaced with a higher drag link mount location would that solve the problem? Correcting the castor would be a given.

 

Along with running parallel to each other, to work properly, the drag link and radius rod should be of equal length as well.

 

Here is how I did it on my Track T:

 

The simplest way which worked for me was to have tubing (a roll bar) bent into a "U" an have it sit right behind your firewall. Weld in some diagonal struts towards the A pillar onto the roll bar. Weld tabs on the tubing where it meets the floor and have it removable. Now you have a sturdy spot to mount your steering box and brake pedal assebly.

 

Nonsense.I hate to break it to you , but what you just described is why nearly all cowl steering hot rods have bumpsteer . A cowl steering set-up is not a 4-bar . The parallel theory pushes the pitman arm back as the axle moves on the arc established by the wishbone.
Imagine a straight line drawn through the rear pivot of the wishbone and the ball on the front of the drag link. The ball on the pitman arm ( drag link ) should be on this line . If you look again, you'll see THAT is how the 100 year old steering was done .

 

Has anyone actually measured the bumpsteer with a cowl steering setup?

 

Yes , I have built working models to prove all this . The problem is that it is difficult to do it right without having a very ,very long pitman arm . Also it is a popular misconception that the bone and drag link should be parallel , so most guys don't know they're doing it wrong .

 

Back to your original question , yes it really should be fastened to the frame .If not , you really gotta brace the crap out of it as stated above. FYI , I know the sprint car boxes are very popular because they look cool and mount fairly easily , but I believe you'd be happier with the Duster box . It will correct itself back to straight better than a Schroeder box on an identical car with the same caster . Your arms will be less tired after a long trip .

 

Actully the drag link should not be exactly straight, it should only be straight in the center of the typical suspention travel, and All radius rod cars set up push-pull steering have some bumpsteer and this limits it to the smallest arc

Anouther factor is radius rod angle and length because that may cause the axle to move closer or farther away from the bottom of the arc of the pitman are

 

I dont have cowl steering on my car but my drag link is no where near parallel with the wishbone and it steers fine.