Note the pictures included are a mock-up from scrap to test the theory and not indicative of my typical standard of finish! (Some people don't understand mocking-up!). The Bex Steerlink, bit of a mix of Hoekens and Pantograf linkage priciples. Advantages; bump steer completly eliminated, light and simple, steering ratio easily designed for quicker steering using a standard production rack, variable steering ratio (ideal slower at center and faster as more lock applied). 2,3,4 and 5 are floating pivots while pivot 1 is the fixed pivot. Links A,B,C and D must aproximately meet the formula; A/A+B = C/D For example A 100mm, B 50mm, C 400mm and D 600mm therefore 100/150 = 400/600 (3/4 = 3/4) - there is virtually no limit to these combinations. Lengths of A and B will determine final steering ratio (over the rack's final ratio), for example, longer A and/or shorter B will decrease advantage (slower steering) and of course shorter A and/or longer B will make steering faster (and heavier). Examples 1 and 2 are sample lengths and example 3 has the drag link moved away (we hit a bump!) demonstrating the theory of no lateral movement of the all important pivot 5. Example 1 dimensions are the actual pictures below. Examples show all joints at 90 degrees but there is no problem at quite large angles, I have tested AB link up to aprox 45 degrees (to the drag link) and pivot 5 still travels perpendicular to the drag link in bump/extension. This is certainly an advantage for mounting. Links C and D must be generally parallel to each other although not required to be parallel to the drag link and all 3 should be aprox. on the same plane. Fixed pivot 1 may (or may) not require a single plane pivot to stop lateral fall ('T' bush or twin hiem joints etc). Pivot 5 will only travel in a strait and perpendicular line for so long before eventually link arcs determine direction change, this is totally dependent on link lengths and I have no formula yet to determine that but pivot 5 stays straight for a suprisingly long time and there should be no need for stupid link lengths to achieve your goals. Example 5 is alternate design but is weaker if you want steer ratio increases. There is no example 4 as nudity was involved. Oh, and for what it's worth, the mock-up works very well, as you can see it's almost directly steering the the drag link and if you are happy with the amount of travel your rack offers then you can almost apply all of the rack's travel to drag link (although it can never be 1:1). This setup gives me 2 turns lock to lock using a steering rack that otherwise would be 3 turns. No reason why you couldn't use a steering box as the medium also and it doesn't matter if it's mounted vertical or horizontal, you can see mine tilts back about 60 degrees. Anyway, maybe none of you need it but I see many discussions about steering systems for beams so I thought I would throw this in - and remember, Bex is better!
This echoes what I was thinking quite recently. It's vaguely related to my firewall-mounted rack and diagonal link idea, which you can see here. I'd gone through a vertical rack on the firewall and a vertical rack alongside the radiator in the process: I might still find a use for the latter. I'm having a little trouble seeing where everything fits in in your photos. I need something to give me an idea of context. Have you got any more photos?
Not till I go back to the shop tomorrow or the day after. The underside picture is taken from the left side of the car (front of the car to your left) and the other picture was taken standing up, standing directly in front of the facing towards the back. The racks pinion is actually sticking through the (wall'less) firewall and the 2 support tubes you see run from the firewall to the front. The drag link, 30mm tube, is in front of the beam, 50mm tube. HTH below .. and you will be interested in my unique beam front end I'll post next week.
I like it. But it requires a method of axle location that likewise gives near-pure vertical motion, i.e. a Panhard bar would defeat the object. I'd certainly like to see what you've done. Is this a rear-engined vehicle?
Any investigation of how "kickback" affects the system? Normally a WOB link like you have there needs to be constrained to a single plane of motion. It seems like vertical motion of the axle would cause the WOB "rocker" (A/B) to twist. Just curious how it reacts when the forces are reversed (drag link TO rack)? I used one of these years ago as a lateral locating link on a beam axle, and found that there was a small (but unacceptable in my application) amount of deviation unless the rocker was held to a single plane of motion. Then again, I didn't have time to really sort it out, so I gave up and went back to a panhard bar...
Yup a friend of mine pointed out I had invented the already existing WOB link - albeit for a different application. I have looked at a few on the net since and in my opinion most do it wrong using a basic 50/50 setup rather than getting the 'D' link as close to pivot '5' as possible - IMO. Anyway, they should all be using the Bex Link! I can't see any issues with a bit of offset during vertical motion (you may have missed that there will be offset movement as the drag link draws closer to the beam as lock is applied too), it's not enough to make any variations of note. Kick back is as normal ie: increase the ratio advantage and you will always feel more kickback. I don't want to use a Panhard rod with matching tie rod in this application, one reason is lateral axle movement but more importantly is I want aprox 2 turns lock to lock using both standard steering arms and standard rack. Anyway, I just like being inventive and up for a challenge as well
Just bear in mind everything is flopping around (the beam's lateral link isn't fitted either) so pay no attention to odd looking angles ...
You're doing nothing to satisfy my curiosity! Intriguinger and intriguinger. Is that a front axle located by trailing links?
I hope it's located laterally by a WOB or Watts link. Those angled trailing arms could cause a TON of bump steer with panhard angle.
A-ha, he says! As the chassis has been locked down on the jig while I have been cobbling up and understanding this steering setup, I have only had access to limited axle roll. Today I popped the chassis out of the jig and put it up in the air enabling me to get full axle roll. I discovered that 'Pivot 5' needs to be close to the roll center height (preferably a little above) otherwise you do get some roll steer as the RC and 'Pivot 5' are rotating on different fulcrum points. This would be fine for a fixed RC fulcrum such as Watts link, A-link etc. but maybe not so good for RC's that move in height such as a Panhard rod.
I'm a bit wary of introducing steering control other than hugging one of the axle locating links - especially if I've gone to a lot of trouble to locate the roll centre outside the physical car! Any progress on the beam thread?
Well I believe this is the way for me and should have it sorted out either way today. Simply put, it's never been done before, it's WIP and understanding/resolving issues is part of the game. Scotty will be beamed up within a couple of days.
The Jalopy Journal
