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!