Cavalier rack installation question:

[Fireball]

The reason for big turning radius is faulty positioning of tie rod ends versus center of rear. It is called "Ackerman" steering principle. If you wish to educate yourself properly read this http://www.rctek.com/technical/handling/ackerman_steering_principle.html

and do it right next time.

[james curl]

If I understand the problem, it is that the rack does not have enough right/left travel for the length of the steering arms. The spindles never travel enough to hit the stops that limit the traverse travel. The Plymouth steering arms are longer than the Cavalier steering arms thus requiring a larger travel than the rack can provide. The Ackerman steering article is a good read but not applicable in this case. The rack was designed for a different geometry steering system.

[MiltYergens]

The Ackerman Principle is a function of the wheelbase and steering geometry. for example if one was swapping a Chevy Nova sub frame into a 40's Plymouth, and if the nova was even designed with this principle in the first place, then one would only compare the wheelbase of the Nova to the 1940's Plymouth.

I wonder if the Ackerman Principle is being used these days when considering trucks for example that come in varying wheel bases lengths.

Swapping steering gears for racks effects turning radius and bumpsteer. The Cavalier rack used on 1940's P&D's seems to quite aways to solve bumpsteer , turning radius is to question. and I feel good about Jame's answer about not using the lock to lock potential of steering and really how many times do we do tight U turns?

[james curl]

Almost ever time that you park in a parking lot that had 90 degree parking, especially if you have to park between two cars, or turning into a one car driveway on your right without going over to the far curb before turning.

[MiltYergens]

Sorry, I'm prolonging the length of this tread but I think we are the cusp of the issue here.

I understand that having the entire range of what was available in the stock recirculating ball sector is highly desirable but obtaining that lock to lock with effort and too many revolutions of the steering wheel is not.

The Cavalier works on these early Mopar suspensions because when installed, it conforms to stock tie rod pivots thus addressing the bump-steer issue.

The only way to get something approaching lock to lock steering with a the Cavalier rack then is to shorten the steering arms increasing the turning angle. How can this be done:

Are new shorter arms availableor can they be fabricated?

Is a stock arm available that is shorter that will bolt up?

Can the stock arms be cut and welded?

Will any of these methods be safe.

Yikes..answering two or all of these question (including the safety one) with a yes would make me feel better about making this steering swap.

[james curl]

The fellow from down under had a certified black smith do his and passed by an engineer, they are much more strict down under than we are. If we had to meet their standards there would be a lot less frame clips with their dirt dobber welds on the roads. They could be heated and re-bent which would shorten them and lower the bottom edge. Check the overall length of both arms now installed on your car. do not be surprised if you find one to be shorter than the other. I bought a set of dropped uprights with spindles installed and the arm reversed side to side. The straight one was re-bent to mimic the original bent one which was re-bent. One is shorter than the other. I heated and re-bent mine trying to clear the lower pivot boss on the lower A frame. After bending re-heated both bend areas to cherry red, wrapped with two or more layers of foil then wrapped two tee shirts around then with some more foil and buried in 6" of sand all around and allowed to cool over several hours to room temperature.

[Andydodge]

James & Milt.......as mentioned in these posts the problem with using a rack & pinion in place of a steering box, as such, is that in most cases, certainly the racks that I have played with, the rack & pinion does NOT have the same throw or extension of the tie rod as compared to that from the standard style steering box, which is why I had to have the steering arms on my car shortened...............shorter arms results in the pivot point where the tie rods attach being closer to the kingpin pivot point, therefore allowing the rack to move the steering arm further out and as a consequence providing a tighter steering circle.........or a return to something approaching the original arc........frame clips are basically a big no no here in Oz tho some have been able to convince the consulting engineer that this type of modification can be o/k.........the modification that I had done to my steering arms 35yrs ago would even with x-rays & other paperwork be very hard to get passed now........andyd

[MiltYergens]

I have some steering arms from a mid 30's Mopar (I believe these used straight axles). It seems circa 40's Mopar independent suspensions were derived these straight axle systems be cause the "uprights" have attached to them what appears to be the end of a straight axle. With the kingpin assembly attaching the pivoting spindle. Then it stands to reason that the early steering arms attach in the same way and are at the spindle dimensionally similar. The difference is these arms are 1 1/2" shorter. I am attaching a drawing from memory that shows the difference between the two arms. The two additional drawings show the angle each steering makes if the constant Cavalier rack is used I am assuming 6 1/2 " total movement in the "center of that rack. as you can see, with stock "40's" arms, there is 54.84 degrees of total movement. and with then "36" arm ( 1 1/2" shorter) there is 67.71 degrees movement. How many degrees is lock to lock and does the 76.71 number exceed it?

[teardrop puller]

MiltYergens

that is super. Thanks a lot

kai

[MiltYergens]

my last sentence.. How many degrees is lock to lock and does the 67.71 degrees exceed it? ....I guess the stops are easy to determine on the upright / kingpin/ axle spindle assembly.

[james curl]

I think that I will be working on my 48 this week. I can pull one front wheel, place a piece of poster board under the spindle and use a plumb bob to lay out the travel to determine the number of degrees travel a stock P-15 has. After I have done the deed I will post my results here on this thread, hopefuly tomorrow evening.

[teardrop puller]

thanks James

yo espera

kai

[james curl]

As promised yesterday, I jacked the car up and put it on stands. Pulled both front wheels. Place two 2' X 4' pieces of Masonite end to end and Xed at the junction points so that I could place them on the patio after marking just as they were under the car. Using a plumb bob,as close to the pivot point of the spindles, had to guess where the extended centerline of the spindle bolt would intercept the bottom of the steering arms. Marked the pivot points on both sides and the end of the spindle in the straight ahead position. Plumb bobed the steering pitman arm points and marked them on the Masonite. Rotated the spindle for full right turn, spindle on drivers side traveled 29 degrees, spindle on passenger side traveled 33 degrees. Turned the drivers side spindle for full left turn. left side spindle traveled 40 degrees and right side spindle traveled 28 degrees. Part of this can be contributed to the difference in steering rod lengths and steering arm lengths. I measure 6 13/16" on the left side steering arm and 7.00" on the passenger side steering arm length. I measured the amount of travel required to go lock to lock on both sides at 3 5/8" both ways. So in conclusion, if your rack has a total of 7 1/4" of travel you should be able to go lock ot lock.

[james curl]

I just measured the bolt spacing on my 48 spindles and it is 2.00" not 2.25" like my 41 Dodge and 37 Dodge axle and spindles.

[MiltYergens]

The "short arm" from the circa 1936 then works for 1941's but not later 40's cars.

[cattmann]

I have some steering arms from a mid 30's Mopar (I believe these used straight axles). It seems circa 40's Mopar independent suspensions were derived these straight axle systems be cause the "uprights" have attached to them what appears to be the end of a straight axle. With the kingpin assembly attaching the pivoting spindle. Then it stands to reason that the early steering arms attach in the same way and are at the spindle dimensionally similar. The difference is these arms are 1 1/2" shorter. I am attaching a drawing from memory that shows the difference between the two arms. The two additional drawings show the angle each steering makes if the constant Cavalier rack is used I am assuming 6 1/2 " total movement in the "center of that rack. as you can see, with stock "40's" arms, there is 54.84 degrees of total movement. and with then "36" arm ( 1 1/2" shorter) there is 67.71 degrees movement. How many degrees is lock to lock and does the 76.71 number exceed it?

Milt I have PM ed you

[Dave72dt]

Since the rack should travel the same distance from center either way and you're getting x degrees travel with half of the rack's total travel,  double the degrees to get total for either length  steering arm.

[fstfish66]

so  i guess  the early  steering arms, may be the answer ??

[MiltYergens]

http://p15-d24.com/topic/35780-please-identify-steering-arms/

[Smokeywolf]

Its very nice to see some technical drawing

Handy for getting copy's reproduced