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PostPosted: Sun Jun 10, 2012 11:06 am 
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I've read this post from the beginning with fascination and forgive me if it was already stated but what advantage is there in independently controlling the caster? It doesn't seem as it would make a significant change in camber for cornering.

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PostPosted: Sun Jun 10, 2012 11:39 am 
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...and here's a side view of the caster gain in bump. I hope it's now established that this caster action is totally independent of the other side ..

Attachment:
LH caster 1.jpg
LH caster 1.jpg [ 62.18 KiB | Viewed 667 times ]


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LH caster 2.jpg
LH caster 2.jpg [ 58.97 KiB | Viewed 667 times ]


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PostPosted: Sun Jun 10, 2012 4:38 pm 
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I think I understand how most of your system works. As the axle goes up the spindle rotates the top to the rear creating more caster and as the car is turned you will get some camber gain. It looks like by attaching the "camber rod" to the front of the main beam it looks you will get some more camber gain. How is the main beam restrained laterally and from twisting?

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PostPosted: Mon Jun 11, 2012 12:15 am 
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Well spotted on the camber rod motion, you're clevererer than Gonzoracer thinks ;-)

Until I start doing some driving/testing I don't know if the camber rod will be in front, behind or on top (it was on top but got moved to make way for another system that has since itself been moved again) - it is also adjustable at the top by moving the trailing arm longitudinally by adjusting the front and rear heim joint stick out.

Also well spotted about the main beam lateral and especially the twist movement which I doubt many would realise, you're a clever lad. That's taken care of by an A-link, not shown. The tip of the "A" is mounted below the beam (and of course necessarily at a different height to the lower link's mount) and is 5 minute adjustable with spacers to change the front roll center height. Of course the other advantage with that is the RC doesn't move.


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PostPosted: Mon Jun 11, 2012 8:39 am 
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Yo, Cheapracer-
Quote:
Well spotted on the camber rod motion, you're clevererer than Gonzoracer thinks ;-)


Let's not be startin' trouble in here, OKKK??? I've been reading and mindin' my own business in here (mostly). As they say in Da Hood, "If you don't start nuthin, there won't be nuthin!" :mrgreen:

Keep up the good work, MYTF, keep ol' Cheapy straight! (Like his axles) 8)
:rofl:
:cheers:
JDK

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PostPosted: Mon Jun 11, 2012 1:39 pm 
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GonzoRacer wrote:
Let's not be startin' trouble in here, OKKK???


Well ok then, but where do I start it?


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PostPosted: Mon Jun 11, 2012 2:28 pm 
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Jim Hall tried that solid axle business to. The only way he could get rid of the gyroscopic precession was by adding a joint mid axle. Of course he was talking about a really skewed sprung to unsprung ratio and a really flimsy monocoque chassis. The Lotus 6 had a solid axle split in half I think. This might actually be easier to mount.


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PostPosted: Mon Jun 11, 2012 11:13 pm 
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vroom wrote:
Jim Hall tried that solid axle business to. The only way he could get rid of the gyroscopic precession was by adding a joint mid axle. Of course he was talking about a really skewed sprung to unsprung ratio and a really flimsy monocoque chassis.


I presume you are refering to Sam Posey's Caldwell D7, a car with some poor understanding of basic engineering and steering. It's failure is often blamed on it's front beam but people don't mention it was a low budget front runner that led races beating McLarens, Lolas and Chapparals etc. Caldwell had the right idea but some poor methodoligy.

The Welsor was not only an underpowered but front running Clubman car in Australia, it won the Clubman Championship one year with a much simpler but very well engineered beam.

Lotus, ie: Chapman's last effort to improve mechanical grip was a double beam'er (1968 Lotus 58) but Clark had just been killed, Hill didn't like the car after just one test drive and all teams had a new full time task on their hands - aerodynamics and wings. Note Ferrari mid 70's tested a DeDion on their F1 car and the drivers loved it but it also lost out too the all important aero as it interfered with diffuser airflow.

RebecaLynn wrote:
I have seen where a few hot-rod style cars have either ran split front axle ( 2 with off sets to line up the front spindles) also have seen where they have cut a tube style axle in the center and mount both halves at a cent pivoit point.

vroom wrote:
The Lotus 6 had a solid axle split in half I think. This might actually be easier to mount.


I see, so according to you guys a double A-arm is actually a beam cut into 4 pieces?


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PostPosted: Tue Jun 12, 2012 11:01 am 
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Have you ran numbers on the anti/pro dive geometry that the links will create under braking. It's a creative solution indeed and really is turning the traditional beam axle into more like a 5-link type suspension.

What is your plan for lateral location? (It appears converging lower links correct?)
I think at this point your at or over the weight of a dual a-arm suspension (same number of links/pivots and you don't seem to have lateral location complete) with a higher unsprung weight than the dual a-arm would have (I know you are going to disagree but you have the same upright, 4 fore-aft links, your beam, and a pair of camber links an optimized dual A-arm setup will weigh less, possibly not much but it will be less). Not saying this is bad just that it's part of the compromise you will have.

The same variable Caster can be achieved with a dual A-arm by having non-parallel inner pivots. It's rare to see it on non-strut type suspension which have basically the completely oposite camber curve of what you are developing so I'll be interested to see how it reacts when in use.

If I ever get around to building my Subaru 360 Autox toy I'm planning to use front and rear Beam axles so I'll be paying attention to your design and specifically what you find when you put it on all 4 wheels and get some testing.

Beam axles have their advantages but historically in front suspension applications these have not outweighed their disadvantages. I do agree with your premise that perhaps the racing world flew by the beam axle before it's development was complete.

Our FSAE team had begun developing a Beam axle for our car and couldn't come up with any solid reasons that it would be better than a dual A-arm and knew we would suffer during the design competition for it. It's a technology the establishment has deemed inferior so your road to prove otherwise is an uphill one.

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PostPosted: Tue Jun 12, 2012 12:07 pm 
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o.k. now we've got all the excriment out of the way,

1. you don't seem to have a side to side location for the axle (beam)
can you find room for a three point pivot for the beam instead of the two front lower arms?
this will, "i think" give the same control over the bottom of the spindle whilst controlling lateral movement.


2. the solid track rod, how does this work when the spindles change their distance appart when the camber changes?

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PostPosted: Tue Jun 12, 2012 12:39 pm 
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i do understand what you are doing and i do mean doing not trying to do,

on droop the top spindle ball joint moves out and forward, on compression it moves in and back, while the bottom remains static apart from the arc of the lower arms.

is it feasable to replace the top link and the link from it to the beam with a top "a" arm to do the moving for camber changes, picking an arc position where the a arm is parallel to the beam in droop, shortening the distance on compression, thus pulling the spindle into neg camber.

or move the link from the axle/top link to the top link/chassis

on an independant front the movement in the lower ball joints is far less important than the top ball joint for camber changes, in your setup, you have just taken this lack of importants to the extreme.

or have i got it completely wrong?

is camber change a necessety of the forces pushing the chassis straight and the loss of grip which would ensu? if so, then the chassis should, i feel play a part in combatting those forces by acting directly on the camber gain

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drag racers lament

oh to go down to the strip again where the blacktop meets the sky
all i ask is a small block and some fuel to make her fly
with slicks a smokin pushrods pokin next round i'll get a bye

she's up on song the shift was strong in the finals to boot
it's back to the pits and take it to bits and don't forget the shute
the final round was good and sound so come on give me the loot


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PostPosted: Tue Jun 12, 2012 7:13 pm 
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john hennessy wrote:
i do understand what you are doing and i do mean doing not trying to do,

on droop the top spindle ball joint moves out and forward, on compression it moves in and back, while the bottom remains static apart from the arc of the lower arms.
The top ball joint can't move in/out because the lower ends of the camber links are mounted to the axle on both sides. From what I can determine he's going to depend on the change in caster to change the camber when turning. That will take some judicious placement/lengths of the trailing arms etc etc to induce the correct amount of change for various conditions.

I am wondering what the affect on straight line tracking will be when the wheelbase changes (independently) from side to side as the wheels move up and down. Certainly Ackermann is going to be affected.

Another point is that as one wheel moves up (as in the latest pictures) the axle rise on one end will cause both wheels to change camber in relation to level ground. That is a normal action of a solid axle.

If I had a 46" long axle on my car using this system a 1" rise of one wheel would amount to ~1.25° camber change. In the extreme case shown in the pictures (what looks like 4" of rise) that would amount to 5° of camber change on my car.

[edit]
After reading this thread by cheapracer I think he's probably got the following comment about binding corrected by the placement of his trailing arms so they don't bind. viewtopic.php?f=5&t=13741&start=0
[/edit]

Since the trailing links have to angle out from the chassis (to clear the tires in turn) to the uprights (and they are different lengths) it seems that there would be a tendency to bind at extreme wheel travel up/down when all the links are mounted using rod ends.

As an example, if the trailing links were parallel to the axle there could be much less up/down movement because of the arcs the links have to travel through. It would appear that the axle would be under pressure to become shorter or bend.

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PostPosted: Wed Jun 13, 2012 7:12 am 
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nocones wrote:
Have you ran numbers on the anti/pro dive geometry that the links will create under braking.


I was doing this for some time before computers came along and anyway, all systems are quickly and easily adjustable; not enough dive, undo that bolt and throw a spacer in....
BTW, no disrespect meant to people who do "run the numbers" and I put my hand up for computer roll center calculators making my life easier (although in this car's case you can physically see the roll centers).

nocones wrote:
It's a creative solution indeed and really is turning the traditional beam axle into more like a 5-link type suspension.


In lateral kinemetics, it is 100% beam.

nocones wrote:
What is your plan for lateral location? (It appears converging lower links correct?)


I'll merely quote myself from a post above;

"That's taken care of by an A-link, not shown. The tip of the "A" is mounted below the beam (and of course necessarily at a different height to the lower link's mount) and is 5 minute adjustable with spacers to change the front roll center height. Of course the other advantage with that is the RC doesn't move".

The bottom of the A's legs share the same bolt as the lower trailing arms so you see a 'W' from above.


nocones wrote:
I think at this point your at or over the weight of a dual a-arm suspension (same number of links/pivots and you don't seem to have lateral location complete) with a higher unsprung weight than the dual a-arm would have (I know you are going to disagree but you have the same upright, 4 fore-aft links, your beam, and a pair of camber links an optimized dual A-arm setup will weigh less, possibly not much but it will be less). Not saying this is bad just that it's part of the compromise you will have.



I have never claimed it to be lighter than double A-arm merely claiming it to be a lightweight beam. It is however lighter than a production car's double A-arm but then again it is handbuilt.

i only disagree about unsprung weight, it is overated and one only has to go to a historic race meeting to see the lap times 60/70/80's sedans will turn with their huge uprights, brakes, discs and usually a massive live rear axle up back.

What I claim is the meager difference is more than offset by the gains.

Also note that manufacturers these days are also piling on unsprung weight (5 link and double BJ systems) looking for superior wheel control.

nocones wrote:

The same variable Caster can be achieved with a dual A-arm by having non-parallel inner pivots. It's rare to see it on non-strut type suspension which have basically the completely oposite camber curve of what you are developing so I'll be interested to see how it reacts when in use.


I am chasing caster for 2 reasons, braking stability and camber gain to offset the camber loss suffered from KPI in turn.

Maybe "camber gain" is a misnomer and a bit confusing and people are thinking the top of the wheel will splay inwards, all I am chasing is to keep the wheel perpendicular to the ground at all times (+ whatever necessary camber for the tyre's best performance).

All I am doing is countering positive camber gain due to the fore-mentioned KPI and outside tyre compression/inside tyre extension. I am not countering body roll as that has little effect on a beam's camber unlike how it is all critical on a typical IFS - I can literally have 30 degrees of body roll and the beam's 2 wheels will not be effected, put 3 degrees on a typical IFS and you got problems.


nocones wrote:



Beam axles have their advantages but historically in front suspension applications these have not outweighed their disadvantages. I do agree with your premise that perhaps the racing world flew by the beam axle before it's development was complete.


There has never been a beam like this and some classes of car can not be beaten using beams although attempts have been made, Supermodifieds being the prime example - sure they only turn left but so were all the IFS's that challenged them and failed. They now only run beams due to wall impacts that were leaving IFS bits all over the track whereas a beam can often be driven back to the pits.

nocones wrote:
It's a technology the establishment has deemed inferior so your road to prove otherwise is an uphill one.


Indeed I'm not silly, I could so easily build a double A-arm with F1 style pushrod inboard shocks blah, shiny bits, blah, and there is no question I would make more sales but I don't care, this is what I want to do and it very much serves as a test bed/foundation for a planned future model.


nocones wrote:
Our FSAE team had begun developing a Beam axle for our car and couldn't come up with any solid reasons that it would be better than a dual A-arm and knew we would suffer during the design competition for it. It's a technology the establishment has deemed inferior so your road to prove otherwise is an uphill one.


The Welsor split beam would be a killer in FSAE, better and simpler than mine but i also had to shoot for longevity, the Championship winning Welsor did not need to travel for years with no maintenance and keep clients happy otherwise I would have gone the Welsor route.

The only thing I can knock about the Welsor beam is the roll center is very high in the middle of the Watts/beam so it was a bit understeery. As you can see the anti dive was quickly adjusted by changing the height of the leading links...

David Seldon, the Welsor driver, drew these for me.. the beam was 2 pieces with simply a tight piece of short water pipe welded into one half of the beam and then located in the other half by the Watts linkage bolt passing through and slotted to enable rotation - not a setup that's going to last many years on the road!


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PostPosted: Wed Jun 13, 2012 7:27 am 
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olrowdy_01 wrote:

when the wheelbase changes

1" rise of one wheel would amount to ~1.25° camber change.

It would appear that the axle would be under pressure to become shorter or bend.




For all intensive purposes;

There is no bind, I've clearly demonstrated with a video of 6" of longitudinal movement.

There is no camber change, it's so simple to see that the upper and lower BJ's are connected and triangulated to the same beam for goodness sake. There is a gain in camber in steer only because the upright pivots around the non-vertical caster, there is no mechanical camber gain due to roll or bump other than a minor, almost irrelevant chord length change of the camber link during the change of caster.

There is no wheelbase change that isn't also relative to most other available systems, the 2 caster pictures comparison above proves that. A BMW with McPherson struts and BMW's typical short IRS trailing arms would have more wheelbase change than most vehicles, certainly more than mine.


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PostPosted: Wed Jun 13, 2012 11:34 am 
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cheapracer wrote:
olrowdy_01 wrote:
when the wheelbase changes

1" rise of one wheel would amount to ~1.25° camber change.

It would appear that the axle would be under pressure to become shorter or bend.
For all intensive purposes;

There is no bind, I've clearly demonstrated with a video of 6" of longitudinal movement.

1. I didn't mean that the camber would change due to wheelbase changes alone. And certainly not in straight line travel. Those two quotes come from different points I was discussing.

2. I haven't seen a video of all the trailing links connected to the axle.

3. I did edit my post that the thread where you explained the links connected to the rear axle should also apply to the front axle. Perhaps your reply was before I edited my post?

I meant that the camber change happens to both wheels simultaneously (in relation to the level ground) when one wheel is moved up/down wheel due to lateral axle angle changes while the wheel moves up/down.


There is no camber change, it's so simple to see that the upper and lower BJ's are connected and triangulated to the same beam for goodness sake.
I did point that out in the first sentence of my post.

Please, don't be so overly defensive of your system. I understand you've probably had to "discuss" the whole concept with disbelievers for some time before you posted the info here and it can be frustrating when you know something works and others can't grasp it. As you have pointed out your system is unique and it takes some time for people to wrap their minds around multiple virtual arcs etc moving around at the same time.

I'm sure you've thought of this but if you used a yoke on one or both lower ends of the camber links that would retain the axle from twisting. Of course that adds more weight.

About unsprung weight on the sedans. Those cars probably weigh more than twice what a Locost does and many Locost builders tend to use pretty heavy brakes etc (me included). So the unsprung weight ratio should affect our cars more than the sedans.

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