Jesus-Ninja
|
| posted on 17/1/08 at 11:46 AM |
|
|
Uaing upper wisbones to lever inboard springs
Is this an option? As far as I understand, things are best used in compression or tension.
By using extending one of the arms on an upper wishbone inboard, such that it acts downward on a spring / shock, is it asking a single component to do
too much?
Or is it just that it needs engineering in a different way to handle the bending loads?
Has anybody any first hand experience of such a system?
|
|
|
|
|
nib1980
|
| posted on 17/1/08 at 11:48 AM |
|
|
It is doable, I believe that the formula 27 is like this (someone correct me)
But I think personnaly it requires some carful engineering, and If it was a better of doing it why has't F1 adopted it? they still use push
rods i believe?
|
|
|
tegwin
|
| posted on 17/1/08 at 11:51 AM |
|
|
Doing this is a very very common thing on quite a few cars...
F1 cars of the past have used this system but changed in favour of pushrods to allow rising rate, antidive/antisquat to be controled.
The car that springs to mind, is Kurt's mid engined mini...that has upper A arm lever type shock mounts...
|
|
|
hughpinder
|
| posted on 17/1/08 at 11:59 AM |
|
|
See the onyx mongoose, sylva riot ....
|
|
|
02GF74
|
| posted on 17/1/08 at 12:05 PM |
|
|
quote:
Originally posted by nib1980
It is doable, I believe that the formula 27 is like this (someone correct me)
yep - top wishbone is single box with pivot bush about half way - other end acts to compress spring/shock.
photo shows plan built i.e ancient but I believe it is similar in principle on current model.
 
escort mk2 rack?
|
|
|
StevieB
|
| posted on 17/1/08 at 12:15 PM |
|
|
Sriker does the same thing too, but the upper wishbones are much more meaty than standard items and, as said, the geometry needs to be well thought
through
|
|
|
Jesus-Ninja
|
| posted on 17/1/08 at 12:27 PM |
|
|
quote:
Originally posted by 02GF74
yep - top wishbone is single box with pivot bush about half way - other end acts to compress spring/shock.
photo shows plan built i.e ancient but I believe it is similar in principle on current model.
How is location of the top of the upright controled, given that the upper wishbone is a single arm? Is control of caster under breaking, for example,
an issue, as the upright tries to "revolve" around the same axis as the wheel.
Is it simply very strong and well located inboard - I'm guessing it pivots on a long(ish) shaft rather than a short shaft. Certainly a spherical
bearing wouldn't work!
|
|
|
nitram38
|
| posted on 17/1/08 at 12:31 PM |
|
|
If you go this route, you will have only the spring seats to adjust ride height.
If you use a rocker or cam with a pushrod set up, you will still be able to adjust ride height but without changing the spring rate.
To make the rocker/bone setup work, you make have to experiment with different springs to get it right.
|
|
|
Jesus-Ninja
|
| posted on 17/1/08 at 12:39 PM |
|
|
quote:
Originally posted by nitram38
If you go this route, you will have only the spring seats to adjust ride height.
If you use a rocker or cam with a pushrod set up, you will still be able to adjust ride height but without changing the spring rate.
To make the rocker/bone setup work, you make have to experiment with different springs to get it right.
I have coilovers which provide adjustment of the length of the unit independently to preload/spring platform. 
|
|
|
nitram38
|
| posted on 17/1/08 at 12:48 PM |
|
|
Then I can't see any problems.
If you design the set up as normal unequal "A" wishbones for your desired camber change, then use the top bone mounts as your pivot
point, all you have to do is extend an arm to your shocks.
Remember that a 1:1 ratio will require the arm to be the same length of the wishbone. So ensure you have enough space.
You could change the length of the arm, but you would have to change your shock/spring rating too.
Remember also to build in some sort of strengthening to stop the bones bending.
[Edited on 17/1/2008 by nitram38]
|
|
|
britishtrident
|
| posted on 17/1/08 at 12:48 PM |
|
|
Rocker wishbones put much larger loads into the chassis. Although this can be engineered round a lot of manufactures and home builders don't
understand the implications and as result both the wishbone and the chassis deflect elastically a lot more and in effect act as an undamped spring.
The damper will also run hotter.
However it has two advantages the coilspring damper unit can sit at a more upright angle and move in a 1:1 ratio with the wheel.
The other advantage only applies to open wheel cars --- less drag.
Used by Lotus on the 24/25/33 and some 70s F1 cars.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
lsdweb
|
| posted on 17/1/08 at 01:08 PM |
|
|
Here it is on my single seater - link (Pre BEC conversion btw)
Note the rockers are not equal either side of the pivot - it's a2:1 ratio (roughly)
There's an aerodynamic advantage but also a weight penalty!
Wyn
|
|
|
02GF74
|
| posted on 17/1/08 at 01:25 PM |
|
|
quote:
Originally posted by Jesus-Ninja
How is location of the top of the upright controled, given that the upper wishbone is a single arm? Is control of caster under breaking, for example,
an issue, as the upright tries to "revolve" around the same axis as the wheel.
Is it simply very strong and well located inboard - I'm guessing it pivots on a long(ish) shaft rather than a short shaft. Certainly a spherical
bearing wouldn't work!
As you can see from photo, the chassis is doulbed up - reading what BT says - is there for strengtrh - I wondered why.
there are two brackets underneath, bolted to chassis with a tube/bush arrangement.
If you are dead interested, I can take photo; there may be one in my archive.
|
|
|
Jesus-Ninja
|
| posted on 17/1/08 at 01:39 PM |
|
|
quote:
Originally posted by 02GF74
quote:
Originally posted by Jesus-Ninja
How is location of the top of the upright controled, given that the upper wishbone is a single arm? Is control of caster under breaking, for example,
an issue, as the upright tries to "revolve" around the same axis as the wheel.
Is it simply very strong and well located inboard - I'm guessing it pivots on a long(ish) shaft rather than a short shaft. Certainly a spherical
bearing wouldn't work!
As you can see from photo, the chassis is doulbed up - reading what BT says - is there for strengtrh - I wondered why.
there are two brackets underneath, bolted to chassis with a tube/bush arrangement.
If you are dead interested, I can take photo; there may be one in my archive.
Well, I wouldn't go out and start snapping just yet...
Amongst a list of options, one I am considering is a rocker arm, but use a tension arm running backward to the chassis to control hoizontal movement
of the top of the upright.The rocker would still have to be beefy enough to resist bending in the vertical plane, but there should be much less
loading horizontally.
|
|
|
lsdweb
|
| posted on 17/1/08 at 01:48 PM |
|
|
I forgot to say the single seater arrangement has two rockers with adjustable push/pull rods for adjustment, independent of the spring platforms.
Wyn
|
|
|
MikeRJ
|
| posted on 17/1/08 at 02:43 PM |
|
|
Note that using the transit drag link end in conjunction with the rocking wishbone arrangement is not a good idea at all. The Sylva Striker uses
either a Metro or (i think) a Vauxhall Viva ball joint depending on age.
|
|
|
Jesus-Ninja
|
| posted on 17/1/08 at 03:03 PM |
|
|
quote:
Originally posted by MikeRJ
Note that using the transit drag link end in conjunction with the rocking wishbone arrangement is not a good idea at all. The Sylva Striker uses
either a Metro or (i think) a Vauxhall Viva ball joint depending on age.
I'll would be using a rose joint between the upper rocker arm and the upright. The rose joint will mounted vertically on the upright, with the
rocker arm bolting through it, such that the joint end doesn't experience any bending.
|
|
|
britishtrident
|
| posted on 17/1/08 at 04:57 PM |
|
|
Metro ball joint has a lot going for it in this situation.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
Syd Bridge
|
| posted on 17/1/08 at 06:01 PM |
|
|
Are you trynig to make the front end as heavy as possible?
This would be a good start to that end.
Cheers,
Syd.
|
|
|
Dingz
|
| posted on 17/1/08 at 07:41 PM |
|
|
Here is a shot of the (early) Robin Hood inboard setup.
 
Rescued attachment top susp.jpg
|
|
|
