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PostPosted: Sat Dec 03, 2011 8:31 am 
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As my front beam is now pretty close to being finalized I thought I would mention the details for other budding beamers ...

It is a highly unusual semi independent beam and I have never seen the design before and a bit hard to explain clearly.

Take a standard double ball joint upright and connect them together between the lower ball joints with a beam and run 2 radius rods forward (or rearwards) to the chassis for longitudal location.

From the upper ball joints also take 2 radius rods forward to the chassis also for longitudal location.

From the upper ball joints, short adjustable (for static camber) lateral location rods run direct to the beam (imagine a typical wishbone but the rear pivot meets the beam not the chassis).

Lateral location of the beam can be the usual suspects, Watts, Panhard rod etc, but I am using a trailing reversed A-arm (single pivot under the beam) which makes front roll center changes a 5 minute job.

Sounds complicated but it's actually very simple in layout and surprisingly light in weight. It gives me a 2 tyre beam flat footprint while allowing independent action of caster and caster induced camber in steer/pitch.


Black = uprights
Red = radius rods
Yellow = ball joints
Orange = beam
Blue = lateral link
Green = chassis

All the red and blue links are adjustable for length ie; lengthen the upper red rods for increased caster or decrease the blue rods for more neg camber. Easy to look at the drawing and think it's just 4 parallel equal length links but the lower red radius rods are shorter in length than the upper ones which gains caster in bump.


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PostPosted: Mon Dec 26, 2011 2:55 pm 
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Location: Charlotte, NC
cheapracer,
Have you built a model of the drawing you have posted there? Looks like an interesting design.


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PostPosted: Thu Dec 29, 2011 9:30 am 
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DTNeil66 wrote:
cheapracer,
Have you built a model of the drawing you have posted there? Looks like an interesting design.


Drawing is taken from the real thing, in fact I recently built 4 or 5 of them working out dimensions, when I make the last good looking finalised one I'll post it. :wink:


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PostPosted: Fri Dec 30, 2011 2:11 am 
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I don't know if you've mentioned this elsewhere before, but I'm curious how you've gone about mounting the steering components.

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PostPosted: Fri Dec 30, 2011 3:28 am 
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Driven5 wrote:
I don't know if you've mentioned this elsewhere before, but I'm curious how you've gone about mounting the steering components.


No I haven't, down to 2 systems at the moment, let you know in a couple of weeks.

Has been a bit of a bugbear actually and have tried quite a few different ideas, the difficulty is in keeping it simple.


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PostPosted: Fri Dec 30, 2011 9:23 am 
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Location: Connersville, Indiana
My stupidity is kicking in again. All I see are a bunch of interconnected rods of varying length. Seems like the hubs being located by lower control arms as well as a beam would lock everything in place.

Bill


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PostPosted: Fri Dec 30, 2011 10:00 am 
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BBlue wrote:
My stupidity is kicking in again. All I see are a bunch of interconnected rods of varying length. Seems like the hubs being located by lower control arms as well as a beam would lock everything in place.

Bill


Here you go Bill, this is full droop and full bump (exagerated of course for instructional purpose) - remember the green is the chassis and yellow are the ball joints .. also no lateral location device is shown.


Black = uprights
Red = radius rods
Yellow = ball joints
Orange = beam
Blue = lateral link
Green = chassis


Attachments:
beam plan view.jpg
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droop and bump.jpg
droop and bump.jpg [ 36.74 KiB | Viewed 1158 times ]
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PostPosted: Fri Dec 30, 2011 1:28 pm 
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It seems that if this system was used at the front of the car that active chamber correction would not be possible. A common solid axle condition.

It also seems that as the chassis rolls that the axle will become a gigantic anti sway bar. If the axle doesn't bend (more or less in the center) then the red arms will be in compression/tension and something else will have to give.

On my car the low mounted axle would interfere with the lower chassis tubes even sitting still. How would the axle move from above to below the chassis tubes?

Other than all that ........... what is the advantage of using this system over upper/lower A arms or even a pre 1949 Ford set up?

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PostPosted: Fri Dec 30, 2011 1:58 pm 
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olrowdy_01 wrote:
It seems that if this system was used at the front of the car that active chamber correction would not be possible. A common solid axle condition.

It also seems that as the chassis rolls that the axle will become a gigantic anti sway bar. If the axle doesn't bend (more or less in the center) then the red arms will be in compression/tension and something else will have to give.

On my car the low mounted axle would interfere with the lower chassis tubes even sitting still. How would the axle move from above to below the chassis tubes?

Other than all that ........... what is the advantage of using this system over upper/lower A arms or even a pre 1949 Ford set up?


It doesn't need camber correction because the 2 tyres maintain a flat footprint. It has total roll freedom, those yellow dots are ball joints.

In steer condition the system provides total side to side independent dynamic caster and caster induced camber change ability while maintaining 2 flat footprints, that's the whole point of it and only one other system (and a race championship winning one at that) that I know can do the same - please see picture at bottom of that cars system ...

The red radius rods in the flesh are of different lengths and do not need to be parallel as with a true beam, on mine top longer than lower to provide caster gain in bump/pitch.

The red radius rods in the flesh are of different lengths, top longer than lower to provide caster gain in bump/pitch independently side to side.

Beam clearance is through design, it's up to your imagination.



The picture below is one of my first test of that other car's system, forgive the square tube and general ugliness, that's what prototyping is all about and why I don't generally show experiment pictures, people start to think that's your work standard, it's not (I just threw out 5 or 6 rusty old test beams laying around yesterday in fact). Note the full roll ability through pivoting in the center. Note the caster gain on the full bump and caster loss on the full droop.


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PostPosted: Fri Dec 30, 2011 2:06 pm 
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..and the other way ...


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PostPosted: Sat Dec 31, 2011 12:25 am 
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Location: Charlotte, NC
Cheapracer,
My thought would be a steering rack mounted to the axle. Could a center steer rack would work possibly? If you could isolate axle movement from causing unwanted steering input, not sure how much if any there could be?
Other option would be to use the sprint car type steering rack or steering box with drag link to spindle. I'm sure you have considered those already, very interesting, keep up the good work.

Don


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PostPosted: Sat Dec 31, 2011 1:34 am 
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DTNeil66 wrote:
Cheapracer,
My thought would be a steering rack mounted to the axle. Could a center steer rack would work possibly? If you could isolate axle movement from causing unwanted steering input, not sure how much if any there could be?
Other option would be to use the sprint car type steering rack or steering box with drag link to spindle. I'm sure you have considered those already, very interesting, keep up the good work.

Don


Thanks Don.

Beam mounted rack does incur an unsprung weight penalty and while I'm not a big worrier about unsprung weight it can certainly get to a point of damaging grip - small specialized lightweight racks are not to be found here is the other issue but it is certainly a good option for street cruisers.

The speedway arrangement won't work for me as I pivot from out front ie; trailing link radius rods and the speedway steering is leading link - the different arcs are not compatible.


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PostPosted: Fri Jun 01, 2012 11:07 am 
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Driven5 wrote:
I don't know if you've mentioned this elsewhere before, but I'm curious how you've gone about mounting the steering components.


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!

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PostPosted: Fri Jun 01, 2012 11:34 am 
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Clever. It seems to me that this would still experience some amount of bump steer during non-uniform suspension movements liek one wheel bumps or as body roll angle changes...Or am I thinking about some part of it the wrong way?

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PostPosted: Fri Jun 01, 2012 12:27 pm 
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It seam the easiest way to se-up steering would be either a single or two-way hydraulic cylinder. Much like they use for raised trucks and off road buggies.

As the only part going from the main chassis to your steering / axle set-up would be a pair of hoses.

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