Dual drag links

I first saw it on a tractor. I subsequently wondered if it might have a hot-rod application. Then I saw it on Foose's P-32, and that got the creativity going again, especially as regards the possibilities for rack-and-pinion steering. Is anyone else running dual drag links and no tie rod?

 

bttt

Nobody?

 

We're pretty stoopid, remember? You got a pic?

 

Here you go:

Like I said, a drag link on each side, and no tie rod.

 

I can't get the dual drag link-rack and pinion concept??

 

neat idea, not only does it have bump steer, but it also has bump toe!

 

IIRC there were a few early indy/race cars as well as some high end luxury cars that ran dual drag link and some also had a tie rod.

Redundant at the time but kind of gimmicky today. And a bit more complicated than most would care to tackle correctly. I do like Fooses' take on the concept, very well thought out.

 

LOL, what's funny about that statement is that on an IFS bumpsteer IS bump toe...

Street Rodder mag did a whole detailed drawing and picture set showing how this system works. It is well done and I don't see it bumpsteering much if any.

 

Schroeder steering box under the dash, behind the firewall has a pitman shaft going horizontally to both sides.
The two pitman arms travel in opposing directions making the two fore & aft draglinks travel, one fore and one aft.

Used in early race cars I believe.

No tie rod required.

 

Was it called a rack and pinion?

 

Not to my knowledge.

I doesn't meet the definition of R&P since it's more or less a standard steering box with two pitman shafts.

At least the one I saw was....

 

yeah, it gets the benefits of IFS with a solid axle

 

I would love to see pics of the steering box setup, but it looks to me like the same concept behind go-kart steer but the drag links push front to back rather than left to right.

I realize I am over simplifying things here.

 

Gorden Schroeder built the Blakely Oil Spl. champ car in 1951 and utilized "Duplex" steering and IFS:
http://www.schroedersteering.com/History-BlakelySpcl.html

 

What little potential for bump steer i see could be lessened if the drag link pivots at the same ht & closer to the radius rod attachment point on the frame. So that the drag link pivoted at the same rate as the radius rod.
Looks clean. There is probably a reason we don't see it more often. What do you think Ned, there is a reason you dumped this on us. Whats your thoughts.

 

I think the only reason we don't see this more often is because its WAY complicated and it looks like it was a nightmare to package. But it is a very elegeant solution to the problem Chip was having getting the car that low and still being able to steer it.

 

Something I've been looking at. It's certainly possible to set it up for negligible or no bump-steer. I think Foose's set-up is more complex than it needs to be, as IIRC there are two bell-cranks under the firewall area plus a linkage to a steering box. That's where I think a rack and pinion can simplify the installation, at least to be equivalent in complexity to conventional set-ups.

The advantages of the steering happening mainly in the region of the firewall are:
1. Safety, as a short steering column far from the front of the car is less capable of spearing you;
2. Weight distribution (a bit), more stuff in the middle of the car and less on the end;
3. Ergonomics, more options for a column angle of your choice;
4. Further simplification, as the need for lots of u-joints in the column is eliminated;
5. Packaging, as you don't have to design around the lateral, longitudinal, and vertical displacement of a tie rod; and
6. Clean looks.

I think the last-named two were the primary considerations with the P-32. 1-4 apply almost equally to normal cowl steering.

I'd like to see what prior art there is, especially variations that haven't occurred to me - mainly just because I think it'd be interesting. I think it has potential.

 

Seems to me that packaging the double pitman shaft steering box on center, under the dash isn't much more work than setting up a single pitman shaft steering box with cowl steering.

Both pitman shafts run horizontal.

 

Believe it or not I can't see the whole picture of the Foose Mobile but I can't imagine that bump steer would be an issue it really isn't that far from the trailer to the display.

That said any chance you can send me a copy of the article? I'd be interested in what they had to say. Maybe something worth looking into for a high end sports car-esk '27 T roadster.

 

I'm still trying to figure out how you can drive two sector shafts from one worm gear, assuming that cowl steering boxes use worm and sector gears?

 

IIRC from that same Street Rodder article - I've got it somewhere - Foose's set-up is a single pitman arm box with a linkage to a "tie rod" running under the cowl area. It's basically cross-steering moved back.

What I'm thinking is replacing all that linkagery with a rack and pinion mounted over the bellhousing.

 

Tripped across this thread after starting a new one yesterday regarding somewhat the same subject.


Here's one answer to the above. Use two worms and worm wheels.

The key reason for the arrangement here is so that both right and left Pitman arm shafts are on the same center line through the box. I have seen only one other race car box and it had offset shafts like the Ford 8N tractor.