Hope everyone had a good Thanksgiving. Warning on a long post about steering/swinger geometry.
I made new swingers to correct the steering geometry, but didn't really understand what I was doing so had to trash them. I have scoured forums and the internet without really finding a "Start to Finish" on getting zero bump steer as well as how to size and design the swingers on a dual swing steering system. The closest I got was "typically swingers are 9-10" long with the upper link 2-3" up from the bottom". There were great posts by
@ChristianEwing and
@85Yota on locating swingers with adjustable mounts (multiple holes) until they found the sweet spot.
I found WeaselMotorsports through Instagram and he had a great cardboard diagram that got me on the right track, he also went out of his way to send me a several minute video explaining how he achieved zero bumpsteer. I was pretty lost until then so I'll share what I've learned so far on the subject, feel free to correct me or add any tips to aid in the process.
From what I understand, the length of the swinger is chosen both by desired pivot location (where the top of the swinger is mounted) and leverage/throw of the steering. Beam mounts are usually 5-7" below the frame. To achieve zero bump steer, the beam mount should mirror that of the bottom link of the swinger so they swing in the same path. Designing a short swinger (5-7") would locate them below or very low on the frame as well as require more travel of the steering box to achieve a desired steering throw. The longer the distance between the pivot and the far link mount on the swinger, the less travel that is required out of the box as the far end has to travel faster. Same as spinning something around on the end of a string, the far end will be traveling farther/faster in relation to where your hand is. This is a Class III system with the pivot/fulcrum at the mount, effort/force on the middle link mount, and the load on the bottom link mount.
I decided on a 9" swinger (top pivot point to the bottom link mount hole) and the spacing of 2.5" from the bottom link hole. For every 1" the middle link pivot moves, the bottom moves ~1.4".
From there I needed to locate it on my frame. Ranger frame rails are not at all square in regards to inboard/outboard, so I drew up my frame in CAD (not necessary but definitely helps) and located my beam mounts based off measurements and overlay pictures. Because of this, it was very apparent that my driver side mount must be mounted closer to the frame, and vise vera for the passenger side to keep them correctly referenced off the beam mounts. Not using CAD is pretty easy, but we will discuss that once the bottom swinger link mount is aligned with the beam mount.
I stopped off at a hardware store and found 1" long bushings that had an OD of 3/4", and an ID of 1/2". This would fit into the 3/4" hole of my beam mount and continue to hold up the heim inside so I can still cycle the beam, and allow a 1/2" all-thread to be put through the center. You can cut the all-thread to length and tighten to the beam mount, with the bottom hole of the swinger being mounted on the all-thread. To clear straight tie rods, I found that a 6" spacing, from outside edge of beam mount to outside edge of swinger, worked to place the swingers. I took some 1" metal strips and cut 1/2" holes and cut them long. I overlayed them onto the 9" template I had and tacked them to each other at an angle that would easily clear the frame. From here, the beam/steering swinger pivots were on the same plane and now I needed to locate the top pivot off the frame.
I used CAD to do this part and found that the top pivot sat 1 1/4" inboard of the hole of the beam mount to clear the amount of travel I needed. When actually designing the mass of the swinger, you will need to calculate how much it needs to move in order to clear the frame. Based on the length of what I believed my steering rod mount on the knuckle will be, to get my desired steering angle the bottom pivot needed to move a total of 3.5". You can get more technical with that portion, I honestly just held a tape measurer with a piece of PVC pipe resting on the steering rod mount on my knuckle and measured how far it moved once it was at my desired steering angle. If your swinger contacts and you do not want to trim the frame or take any more material off the swinger, move the pivot farther outboard of the frame until it clears and match on the otherside. I took a 48" T-Square and placed it on the ground and aligned it with the beam mount. I swiveled the swinger until I was 1 1/4" inboard (just used a separate tape measurer) and tacked on a temporary mount to allow it to swing.
I'm tossing my D44 Knuckle setup and waiting to have my new kit mounted to start messing with the steering rod mount. Would love to hear some tips on that mount, I understand that how it will mount will naturally give it negative Ackerman since it has to point inboard to avoid hitting the wheel. Other than that, I can guess the height on the knuckle will effect the bumpsteer if its not inline with the center of the two points of where the beam attaches to it, and the length will effect the speed of the knuckle turning (anything geometry wise this changes as well?)
Thanks everyone!
It’s slow progress but will be worth it
