[ajbcc2]

I have finished mounting a 87 Dodge Omni power steering rack in my 34 Ford frame. Because i am using the origional lincoln 460 that has the power steering pump mounted off of the crank behind the crank pulley I mounted the heidts power steering control valve to cut the pressure and put the excess back into the resevoir...
Looking at the Heidts valve you can see the upper right port not connected...that goes to the power steering pump (as soon as the motor is in)... and the lower right hand port that is the return to the resevoir...again connected when the engine is in....
The rack is not seen from the front keeping that old style dropped axle look and is hidden pretty much under the engine...so i just thought you all might 've wanted to take a peek...

 

[Deuce]

You will find that a rack, mounted like you have yours ( to the frame ) does not work well in real life driving conditions. When the suspension moves up and down ... BOTH the front wheels will want to change directions. Both will point either inward or outward ( depending on the chassis movement UP or Down ).

Just a old mans opinion.

 

[ajbcc2]

I understand that, but hotrods with antique suspensions still have there draw backs..no matter what steering unit you have..I beleive that a vega unit , the mustang two unit and the cross steer unisteer will have some bumpsteer too as all do not pivot at the same points (tierod vrs "A" frame /straight axle)There will always be some sort of bump steer unless the system you use has the axle or A frame ,pivot from the same point as the tie rod pivots...the old straight axle racing design that pivoted in the middle of the axle inline with the tie rod was near perfect...but anything else..there will be some...i opt for this unit as I dont like the mustang units infront of the axle blocking its veiw...but thats just my opinion. :mwink:

 

[powerrodsmike]

You will find that a rack, mounted like you have yours ( to the frame ) does not work well in real life driving conditions. When the suspension moves up and down ... BOTH the front wheels will want to change directions. Both will point either inward or outward ( depending on the chassis movement UP or Down ).

Just a old mans opinion.

It's not just an opinion, but a quick study of simple geometry will show that with any vertcal movement of the axle, you will get wheel alignment changes. What most folks refer to as bumpsteer will be the lesser of the 2 issues that you have created.. If the suspension has very little travel and minimal body roll... it might be drivable.

I'm not trying to discount your efforts, but there is a reason that people do not put frame mounted racks on straight axle cars. Any benefits you would normally get from a rack and pinion will be overshadowed by the effects from misalignment.

The bumpsteer and toe changes you will experience will be much greater than any other system.

The commonly used straight axle using cross steer and any type steering box, there are no alignment changes, only varying degrees of bumpsteer, which can be easily fixed with a panhard bar..

Good luck.

Later, mikey

 

[ajbcc2]

hmmm.. cross steering still has bumpsteer as you say..but it sounds like you are saying that a panhard will eliminate bumpsteer..I dont believe that because a panhard as you know,only prevents side movement of the axle which does prevent steering direction change ,but,not the up and down of the suspension travel...which I think will still allow bumpsteer because the short tierod or the longer cross steering rod on a vega box do not pivot at the same point as the axle which is the center of the spring therfore still allowing tire direction change..again I agree with you its simple geometry.

 

[powerrodsmike]

hmmm.. cross steering still has bumpsteer as you say..but a panhard only prevents side movement of the axle which does prevent steering direction change ,but,not the up and down of the suspension travel...which I think will still allow bumpsteer because the short tierod or the longer cross steering rod on a vega box do not pivot at the same point as the axle which is the center of the spring therfore still allowing tire direction change..again I agree with you its simply geometry.

The pivot points of a standard panhard bar and drag link as installed on a car with cross steer are so close to each other that the arcs they swing in are almost concentric. Panhard( or "track bars) were offered in the ford catalogs to counteract bump steer by keeping the axle in lateral alignment with the frame mounted steering box. Much of the bumpsteer actually came from the shackles swinging around and not the linkage arcs created by suspension movement.

Like I said, if you don't have much suspension travel, your system might be drivable. Your definition of "drivable" may change when you get it on the road.

later, mikey

 

[NEW INTERIORS]

The pan-hard bar will only stop the axle from moving side to side..

 

[ajbcc2]

well then i guess i am installing a panhard mounted from a point aligned with the center of the spring to as close as possible to the steering arm/tierod connection...this should swing the same arc as the axle in its suspensional movement. this will eliminate the shackle side to side travel. as far as the "bump steer..your right we will see how far off the tie rod arcs are compared to the axles..
On the vega box though..this panhard that is close to the same arc as the drag link..makes sense...little arc differance equals little change in push/pull on the steering arm ...but what about the shorter arm from the pitman arm to the other steering arm?..that arc must be decisively different than the axles..there must be tremendous conflict going on in that system..a panhard holding same arc as the draglink , but the draglink is connected to a steering arm that is connected to a shorter arm that has a very different arc than the axles.ones trying to change and the other is trying to not change.
Also I was thinking that this radical tire direction changing (from the front axle travel) is only going to occur when the suspesion is going from one extreme to the other. How often is this going to happen?...driving over a washboard surface for sure....I am thinking that for normal driving with the suspension moving slightly or floating it will be fine. A torsion bar added to the front and back will only help too...thanks for the input guys..every little bit helps.. :thumbup:

 

[ajbcc2]

Its Alive!!!!

hey good news...Igot my 460 started today..put up a temp firewall of plywood, screwed on the solenoid,ignition resistor, wired up the coildistributopr with the pertronix unit I bought over ten years ago, dumped some gas down the carband...voila!....didnt runit long as I dont have a emp gauge hooked up but it starts right up...I have been waiting since I was 12 to have a coupe and now it has just taken a giant step closer to reality. .

 

[ajbcc2]

front end bump steer

finally got the car on the road and it drives awesome. going down the road you can take your hands off the wheel and it tracks straight as an arrow. no shimmy or pulling to either side. going over bumps produces no pull to either side also...I am very pleased with the system.

 

[sedanbob]

I have a manual Omni rack in my '33 sedan, with MII-style IFS. I like that it mounts behind the front crossmember. Because the pivots on the rack line up with the pivots on the control arms, there is no bump-steer. It drives and handles fine.

 

[ajbcc2]

power sterring rack in a 34 ford frame

cool, my front suspension has minimal travel top of front spring to under side of frame is just under 2". This may be a big help in bump steer as there is very little arc travel when tracking over a bump. As one side rides up over a bump, the wheel assembly tries to get closer to the ctr of the vehicle. The solid mounted rack arm cannot move into the rack on itself which causes a conflict. This conflict may cause premature wear at some point,but for now it prevents bumpsteer.:mwink:

 

[ajbcc2]

Steering rack update

I have 8300 miles so far on the hotrod...and the only direction change that i have noticed when cornering on a bumpy road is that the rear axle seems to hop up then out a bit....possible cause too stiff a rear suspension...but the front end holds straight and true...