What sevens have inboard suspension?
I'm actually asking a bit too late as all the suspension design on mine is now finalised, but thought I'd do a sanity check and see what
solutions the others have had!
Pavs
most Silva's
I think most MNR's too.
I think my colleagues robin hood has inboard suspension on the front too.
[Edited on 1/8/10 by irvined]
MK indy R.
Quantum Extreme...
Formula 27 (F27)
Sorry should've clarified...
What cars have FULL inboard suspension (i.e. Front and rear!)
Hi
Now ask the question Which manufacturers have developed an inboard setup THAT WORKS. The answer is non. Not even the freestyle Caterham setup worked
any better than the traditional outboard setup. And the Westfield FW400 setup was dropped on the final version after the inboard setup was found to
be no better just added extra weight.
Cheers Matt
Matt,
Well when talking front I'd say looks is a factor aswell. And most do get that atleast.
But would you mind reminding me (us?) what the real gain of inboard suspension would be when done right?
And what kind of things do most of them wrong?
Maybe a bit of a hijack, but what about the CCAR system that Dax supply... Any experience with it? Usefull?
[Edited on 1/8/10 by JF]
My own personal reasons for going to inboard suspension on the haynes roadster:
- The front wishbone shock mount to me looks like it gets loaded somewhat a lot in bending as the shock isn't outboard enough. Now given that
there's loads of locosts with the same setup I imagine the severity of the issue is limited, but it just makes me feel uneasy worrying about
whether the wishbone will bend over a big bump/pothole. Moving the shock bracket further outboard creates a problem in that a standard length damper
can no longer be used, and it increases the shock angle - more regressive spring rate...
- the regressive spring rate. At the angle the front shock is, unless you use some heavily non-linear progressive springs, you'll end up with a
softer suspension with increased travel. Undesirable, as far as I'm concerned (and therefore the only reason I went inboard on the rears)
- Finally, adjustment of corner weights/ride height without preloading the springs on the dampers seems like an advantage.
Wasn't for aesthetic reasons, as I actually think that the standard setup looks really good!
Having said all that, we'll see if it works or not once it's built!
whenever you start introducing more levers and bell cranks into suspension you start multiplying the forces on bits of the chassis. cant really see
the point to be honest. Just my opinion.
Did it front and rear on mine for various reasons, including getting shocks out of the way of the front driveshafts, playing around with different rocker arm ratios (hence 5 different shock attachment points on my rocker arms), and for fun.
Hi
Even if done right there is no gain what so ever to be had that's useful on a seven car or kit car. All it will mean is that the weight has been
increased and the cost of dampers needed to do the job correctly has significantly increased. Now look at all the problems that are / have been shown.
Chassis need to be increased in strength or you have the extra loads placed on the chassis leading to brackets falling off. Extra loads placed on the
wishbones leading to wishbones bending and push/pull rods failing.
The fact that it needs a minimum of double or triple adjustable with remote canisters to be used to gain proper control. And finally it makes the
cars much more sensitive to setup thus making every car setting individually for the individual drivers requirements and driving style. This of course
not to say it can not be done on an individuals car that is to be used and setup for a particular individual. But if spending that sort of money you
are past messing around with a kitcar and into the realms of something similar to a radical where the car is mainly to be used for track only.
Just tacking a chassis and cobbling up an inboard setup like all the kit manufacturers have just leads to many problems. Especially when they can not
be bothered to even sort out what spec dampers they need and just supply the same as they run on there out board setups and supply incorrect spring
poundage's.
The DAX setup has been proved to be a complete waste of time. Both the works cars that ran it have proved that it is far worse than the original
setups. with far quicker lap times on circuit. With much complaining to DAX.
Cheers Matt
Thanks Matt,
Although you're quite often a bit blunt, it's great that you share your knowledge on here. Well actually you're bluntness is more a
blessing then a shortcoming if you ask me. Nicely short and to the point, if only politicians knew how...
The Dax system always seemed way to good to be true to me. If it really was this great then why don't others give it a try aswell. When only 1
company uses something like this that they claim is as good as Dax does... then others would follow shortly... and clearly they don't in this
case.
Still like the concept of it though... a shame...
And yeah I can really see the problem with the multiple linkages adding stress and possible play with inboards. Which you really don't want.
Personally I'd still want to give it a try really. I really like the clean look of just a pushrod instead of coilovers sticking out.
Couldn't be to bothered to do the rear, execpt if space would be an problem.
But then again I've always been to thick headed to go for the logical and sensible option.
Woah woah woah there Matt, I completely agree you can't just throw it together, but I don't think all your points are valid!
Bending loads on wishbones are all but ELIMINATED with pushrods, as you can put the pushrod right next to your bottom ball joint - wishbone then only
sees push/pull, no bending.
Yep, you need to add extra tubes to the chassis, and you add the weight of a pushrod, but it's not a massive increase, especially if it's a
locost build which is never going to be an ultralight.
And you do not need different dampers, if the suspension is designed to be used with the standard dampers, it'll work very well, and indeed
better as you can build in natural progressive spring rate. As for poundage, yep, mine will need different springs as I'm using a 1:1.2 rocker
ratio.
Just because some have cocked it up, doesn't mean it's not worth doing. As for cost, the only increase to me over standard outboard shockers
is:
- Four tubes (pushrods)
- Eight rod-ends
- Bush for rocker
- Rocker (made out of 3mm steel)
In the grand scheme of things, not massive, and I'd quite like to have the adjustability, particularly as the roads around here are more rally
than race!
quote:
Originally posted by procomp
The DAX setup has been proved to be a complete waste of time. Both the works cars that ran it have proved that it is far worse than the original setups. with far quicker lap times on circuit. With much complaining to DAX.
Mj Hoson bula best set up purdys own works realy well on race car Ali
Went to bed thinking about this and ....
What is to stop you from converting an existing locost (with front suspension mounts under the top chassis rail) to inboard via making a simple rocker
arm and shock absorber bracket welded onto some box in the middle of the empty space between the suspension units?
Ok, i appreciate there is some maths to do and this is Matts point that its not just this easy & the shocks are now in warm air flow & the box
is now put into bending with no triangulation.
But it just seems without the maths rather 'easy'. In my dreamy state i was even thinking of using a 1/2" rod end for the rocker pivot
& perhaps poly bushes for the other pivots (cause thats what is on the shock absorber now). If this makes no sense i'll draw something up,
photograph it and post it up.
quote:
Originally posted by ali f27
Mj Hoson bula best set up purdys own works realy well on race car Ali
Just because one person or company can't make it work or doesn't fully understand it doesn't mean it wont, if every one thought like
that we'd never get any development or advancement in technology
Isn't the fisher fury/syliva cars the most sucessful race cars in the class, they use it so it can't be bad.
In fact i'd look for which chassis has won the most races then start from there.
[Edited on 2/8/10 by franky]
Hi
No one is saying that it can not be made to work. What i have said is that for the application of a kitcar that will be seeing a bit of track use it
is just not worth it. As i said if you wish to pursue it and make it work well you are moving towards the territory of Radical type cars. If you are
looking at fitting it to a kit type car that will be seeing mostly road use then you are into a huge development with springs and dampers and the
whole front design that will be costing a few £'s. As you'll likely be needing to move towards something like double/ triple adjustable
Olin's / penske's Etc Etc. And if you look at what you are likely to gain as a benefit overall when finished you are on a hiding to nothing
as it's not like your trying to work with slow speed and high speed with huge down forces.
Sylvas with inboard suspension winning races. Well if you take any of the inboard setup strikers and compare them to a well setup Westfield then you
soon learn it a no no. The majority of true successful Inc the works Sylvas where converted back to outboard setup. Even the current RAW setup is
flawed and truly requires very expensive dampers and many mods to get it to work as well as a traditional out board setup.
All in all if we are talking 5-15K kitcars do you really need to go adding an additional 5-7 K of dampers to make it handel as good as the traditional
outboard setup. However if it's an individual with plenty of time and deep pockets then there's no problem just do it. But i think some are
not understanding just how much development it requires and just how sensitive the car / handling can become As i say fine if your developing a
Radical type motor for track use but for the average Kit that's being used on the road with some track work then the rules are keep it simple and
develop the overall package to be precise well setup with good handling.
Re what was mentioned regarding the Haynes setup. Well your always going to have problems with that type of design because there is no design. Take a
basic look at the tracks and wheelbase and ask does it resemble anything that has proved to work. Nope it just way way to big purely so it can use
standard production parts with no modification. It's a cheap design for a bit of road cruising rather than a setup that's designed to get
round corners quickly.
Cheers Matt
quote:
Originally posted by procomp
Re what was mentioned regarding the Haynes setup. Well your always going to have problems with that type of design because there is no design. Take a basic look at the tracks and wheelbase and ask does it resemble anything that has proved to work. Nope it just way way to big purely so it can use standard production parts with no modification. It's a cheap design for a bit of road cruising rather than a setup that's designed to get round corners quickly.
Cheers Matt
quote:
Originally posted by procomp
Sylvas with inboard suspension winning races. Well if you take any of the inboard setup strikers and compare them to a well setup Westfield then you soon learn it a no no.
Hi
there's just too much loading placed in to the one area of the chassis. Even the ST setup with bearings was useless. Not to mention the chassis
constantly needing to re straightened when the car is subjected to a jarring from road surfaces.
Cheers Matt
Ahh .....
I remember here reading ages ago that the forces can be quite huge. Hadn't thought of that.
(ok, i'm now conceptually picking your brain Matt / others whilst waiting to take the doggy to the vets as it appears he's eaten something
he shouldn't and has a blockage - don't ask how i found this out, but cleaning up hasn't been fun).
If i had my lever ratio 1:1 would it still get the huge forces? Say the lever was 20cm long. In the exact middle i had my pivot rose joint. Exactly
8cm from the pivot at either end I had the push rod & damper pivots. If i go over a bump now - would the pivot point and the shock chassis
mounting see any greater force than the shock was mounted directly to the chassis?
You'd have twice as much force at the pivot as at the ball joint as the lever as half as long.
That makes sense to me but i'm not too good at teaching 
Have an FBD:
The force applied down from the chassis must be twice the force applied up from the pushrod (assuming its in equalibrium at the time!)
Hi
In basic terms. Yep it will place more load on the chassis how much more will be down to angles of pushrods and dampers. As well as the spring
poundage differences required for the different setup. The Sylvas are not far off a 1-1 ratio but haven't got specific details to hand at the
mo.
You will also suffer pivot problems such as those on the sylva setup.
Cheers Matt
What pivot problems?
My cunning dream plan was to use a 1/2 inch rose joint as the pivot, this would be mounted in the box that formed the pivot. As rose joints are used
to taking suspension loads, they are great at having things turn around them and can take up a slight amount of missalignment they seemed ideal.
Later this morning it also occurred to me they have no ability to stop my pivot twisting, so now its two rose joints, one either side of my existing
suspension pick up point and a crush tube where the shock would normally go.
As the weight on the chassis doubles on the existing shock pick up, we've got three choices,
1) replace that section with thicker steel.
2) limit the engines to bec's (if the existing mounts can take P&O anchors and V8's then a bec will give things an easier time
3) drive it till it starts to fatigue and add extra steel at the weak points.
p.s. stupid thoughts stop in 1 hour
[Edited on 2/8/10 by MikeR]
when i went searching for a kit car to buy i looked at the kit car race series. With raw and sylva chassiss seeming very competitive i considered that
the only way to go. The coil overs on my raw are nothing special at all. Shorter throw with different springs and thats it. This is a tried and tested
chassiss that has had years of development and setting up. Buying a a raw buys you that tried and tested setup.
Refering back to op and changing or building an inboard thats where all of the above comments are very relative and i agree to a certain extent. I
think that if you want to build your own inboard setup then give it a go. It sounds like you would enjoy the work and testing. Something else to be
proud of when its finally going around the track.
Hi scootz will get photo up of mj hoson bula cheers Ali
Hi
Don't underestimate the loads present. there where a few sylvas modded to use rose balls either side of the pivot. Lasted less than 1000
miles.
bi22le. Now having done a fair bit of work on the RAW strikers with in board suspension with dampers and anti roll bars Etc. Can you tell me which of
them is running a chassis that is as it was when it left Raw unmodified. And running less than 2k worth of dampers upfront.Cause that rules out all of
the cars that have competed in the 750. championships. ?
Cheers Matt
Er nope. . . .
quote:
Originally posted by procomp ...the Westfield FW400 setup was dropped on the final version after the inboard setup was found to be no better just added extra weight.
Well, my first post for many months, if not even years on here so if I am out of touch and wrong, apologies in advance!
The obvious answer to the question about a seven with full inboard suspension is the Caterham CSR - at £42900 fully built it is not exactly locost
however, but does show that it can be done, at a price! All reports suggest that it drives very well.
When I get round to working on mine again I will be doing inboard rocker arm suspension, I have made the appropriate parts on the chassis for it, and
will eventually make the wishbones. One thing I haven't decided is the ratio to use on the rockers, but have figured (I think) the mountings and
everything else. I can't remember but am pretty sure I posted some pictures on here when I originally made that part.
People love reinventing the wheel, don't they? If it makes people happy, why not? However, I don't see the point in trying to turn a 50's era fun car into a modern single seater, which it isn't and never will be. Creativity doesn't have to have a point though.
quote:
Originally posted by andyps
The obvious answer to the question about a seven with full inboard suspension is the Caterham CSR - at £42900 fully built it is not exactly locost however, but does show that it can be done, at a price! All reports suggest that it drives very well.
Most of what Matt says is very correct.
But, the biggest mistakes I see are in the design of the rockers themselves. Inboard with rockers was developed in the open wheelers to cut down drag,
improve polar moments, and packaging.
In racecars the inboard setup works well, because the amount of wheel movement is usually kept to near zero in droop, and no more than 40mm or so in
bump. When you get to the movements needed for a road car, the size of the rockers needed is astronomical compared to a racecar. The small rockers
udsed by most amateur builders end up producing all sorts of undesirable effects at their limits and beyond.
As a final note, what's wrong with a properly designed outboard setup, with properly designed wishbones and coilover pickup geometry? Caterham
have been doing it for years.
Cheers,
Nev.
Whats wrong with trying something for yourself instead of simply doing the very same thing over and over again.
If everyone had always done that, we probably wouldn't even exist...
Sure could be that most 'amateur' inboard setups are inferior to 'pro' outboard setups. But most of those 'amateurs'
might never even notice the difference... As they're not pro racing drivers. They might never even drive a single mile on a circuit.
So who gives a f*ck if it's not as good as X. As long as that 'amateur' is happy with the result....
quote:
Originally posted by JF
But most of those 'amateurs' might never even notice the difference...
Well might have come accross a bit grumpy, but my point is... Live al little and try something. Experiment. Because really... why else would you want to build your own car when you can just buy a standard tintop...
quote:
Originally posted by Volvorsport
inboard
quote:
Originally posted by ceebmoj
quote:
Originally posted by Volvorsport
inboard
Why would an inboard set up be mutch worse than an out board set up? Also can you point out the problems in the above set up? found the thread through a serch so was suprised my the resurrection.
[Edited on 5/4/12 by ceebmoj]
Given that it might not be material effishent, can a rocker set up ever be efisent in that way ? Do the benafirs of
1. Rising rate suspention with the corect
Rocker.
2. Using a lager % of the shock travel
3. Moving the actuater point on the bottom wishbon closer to the balljoint and Moving another thing out of the air stream
and any othere things i dont know about make it worth wile
quote:
Originally posted by ceebmoj
Given that it might not be material effishent, can a rocker set up ever be efisent in that way ? Do the benafirs of
1. Rising rate suspention with the corect
Rocker.
2. Using a lager % of the shock travel
3. Moving the actuater point on the bottom wishbon closer to the balljoint and Moving another thing out of the air stream
and any othere things i dont know about make it worth wile
I have always wondered why kit manufacturers use inboard for a much more simple reason.
They all appear to place the shock directly behind the radiator. So what happens as the hot air flowing out of the radiator heats up the oil in the
shocks? Surely the viscosity changes and the damping alters?
I know shock oil is meant to be quite stable but since expensive shocks and small bike shocks have remote reservoirs to prevent this. What happens to
our cheapo Protec or Gaz shocks?
I asked a couple of manufacturers this question at a show last year. I was basically told to bugger off.
thought i'd do a little 'internet research' and managed to stumble across this....amazing work
http://www.kirkhammotorsports.com/book_aoe/aoe_12.pdf
certainly not locost!
quote:
Originally posted by scootz
quote:
Originally posted by procomp
The DAX setup has been proved to be a complete waste of time. Both the works cars that ran it have proved that it is far worse than the original setups. with far quicker lap times on circuit. With much complaining to DAX.
Hi Matt
Is that just their in-board option or the CC&AR thingy that they offer?
does someone have pictures of the front suspension of the mirach ?thanks
quote:
Originally posted by rdodger
I have always wondered why kit manufacturers use inboard for a much more simple reason.
They all appear to place the shock directly behind the radiator. So what happens as the hot air flowing out of the radiator heats up the oil in the shocks? Surely the viscosity changes and the damping alters?
I know shock oil is meant to be quite stable but since expensive shocks and small bike shocks have remote reservoirs to prevent this. What happens to our cheapo Protec or Gaz shocks?
I asked a couple of manufacturers this question at a show last year. I was basically told to bugger off.
I thought about going inboard with my front suspension, but didn't in the end. Here was my reasoning:
The pros were:
a) Looks nicer.
b) Allows creation of really neat/small and light anti roll bar
c) Easy to set up for rising rate, but you can also do this if the suspension is outboard (not to the same degree though) - just put the upper spring
mount point so it is outboard somewhere between:
1. the arc drawn with its centre on the lower arm chassis mount and the 'drawing' end on the lower arms lower shock absorber mount, and
2: the point where a tangent to the shock absorbers lower mount does not pass through the upper mount point at maximum bump (otherwise the rate will
start to drop)
The cons were:
a) Gain in aerodynamics from putting the shocker/spring inboard offset by the fact they are still in the airflow behind the radiator(less because the
air is slowed by the rad though), and extra introduced by the push rod and lever.
b) Extra cost for bearings and rod ends
c) More parts to fail/maintain
d) Extra metal for shocker mounts inboard
e) Extra strengthening of upper chassis bracket/rocker mount required.
f) Exponential increase of 'wheel rate'and spring poundage if inner arm is shorter than outer
g) You will need double adjustable shocks at least so more £££
h) Shockers are in the hot air flow from the rad, which isn't especially good.
i) little experience in setting them up properly to draw on, seemed like even the 'proper' companies had design problems like rapidly
wearing pivot bearings/problems getting a good ride, chassis rails bending......
Just my thoughts when I did my early design decisions.
I'd still like to do it though, and may do if I build a second car!
Regards
Hugh
You missed the pro of less unsprung weight
Also some of the cons can be easily negated by good design:
Gain in aerodynamics from putting the shocker/spring inboard offset by the fact they are still in the airflow behind the radiator(less because the air
is slowed by the rad though), and extra introduced by the push rod and lever.
I think the engine thats sat right behind the shocks would be alot worse!
Extra cost for bearings and rod ends can be designed out
More parts to fail/maintain
Exponential increase of 'wheel rate'and spring poundage if inner arm is shorter than outer
not with good design
You will need double adjustable shocks at least so more £££
why?
[Edited on 11/4/12 by loggyboy]
Ah yes, I did consider the unsprung weight at the time, but I forgot to mention it. I believe its traditional to consider half the weight of the
shocker/spring as unsprung - I couldn't decide if the unsprung weight actually goes up since the pushrod/rocker and half the shocker/spring
weight are on the 'wrong' side of the spring and still need to be moved by the spring and damper relative to the chassis, to keep the wheel
in contact with the ground.
Mines a midi/rear engine which I forgot to mention, so the engine thing didn't figure in my design I suppose!
I don't see how the extra cost of rod ends and bearing can be designed out, as in one case you need them, and in the other you don't!
The exponential increase in wheel rate etc can only be designed out by having a 1:1 arm ratio, hence my caveat "if inner arm is shorter than
outer ". I couldn't get a packaging setup that allowed better than (inner
uter) 1:1.2 in my design, but I could have gone for a setup with
the shockers offset front/back to avoid overlap I suppose.
The double adjustables I suppose is hearsay as I have no sound design reason for saying it - I just spoke to almost anyone I could running inboard
setups at trackdays/hillclimbs/races and it seemed everyone had already changed to them or thought that they needed to!
Regards
Hugh
quote:
The double adjustables I suppose is hearsay as I have no sound design reason for saying it - I just spoke to almost anyone I could running inboard setups at trackdays/hillclimbs/races and it seemed everyone had already changed to them or thought that they needed to!
Regards
Hugh
twin40, As I said, I didn't have a sound logical reason to see a requirement for the 2 way adjustables - it may just be a symptom of things not
really working and people thinking more adjustment=better! It was about 4 - 5 years ago too, so not as many inboard set ups were around in actual use.
I believe its very difficult to set up 2 way adjustables optimally.
The effect of the lever ratio is quite significant. If you have a certain weight on the front wheel, you need a certain spring poundage to resist that
weight. The shorter the inner arm is relative to the outer, the higher the spring rating will be to resist that weight (think of it as equivalent to
moving the shocker mounting point on the lower wishbone closer to the chassis by that ratio o an outboard setup). The 'wheel frequency' goes
up in inverse proportion to the square root (e.g shorter = higher frequency) of the lever length and the spring rating, so if you have a lever ratio
of 2:1 your spring will have to be twice the pounds rating and the wheel frequency will go up by a factor of 8! (this is all from memory so it may be
worth checking in a suspension book like staniforth or similar). I'm not an expert - these are just my conclusions from my own design. From
memory a wheel frequency of 60-80 was normal road car, 120 about the comfort limit , with full on race cars 200 up to about 400. I'm sure someone
with more practical design experience will correct me soon enough!
Regards
Hugh
quote:
Originally posted by hughpinder
twin40, As I said, I didn't have a sound logical reason to see a requirement for the 2 way adjustables - it may just be a symptom of things not really working and people thinking more adjustment=better! It was about 4 - 5 years ago too, so not as many inboard set ups were around in actual use. I believe its very difficult to set up 2 way adjustables optimally.
The effect of the lever ratio is quite significant. If you have a certain weight on the front wheel, you need a certain spring poundage to resist that weight. The shorter the inner arm is relative to the outer, the higher the spring rating will be to resist that weight (think of it as equivalent to moving the shocker mounting point on the lower wishbone closer to the chassis by that ratio o an outboard setup). The 'wheel frequency' goes up in inverse proportion to the square root (e.g shorter = higher frequency) of the lever length and the spring rating, so if you have a lever ratio of 2:1 your spring will have to be twice the pounds rating and the wheel frequency will go up by a factor of 8! (this is all from memory so it may be worth checking in a suspension book like staniforth or similar). I'm not an expert - these are just my conclusions from my own design. From memory a wheel frequency of 60-80 was normal road car, 120 about the comfort limit , with full on race cars 200 up to about 400. I'm sure someone with more practical design experience will correct me soon enough!
Regards
Hugh
Everything you have mentioned is as valid for outboard as it is for
inboard. phelpsa
Sorry if I've made it sound more complex - I was hoping for the opposite.
It's true that the rising spring rate and higher wheel frequency also occur on an outboard set up - but only if you move the shock absorber
mounting point closer to the chassis pivot point, and this is unlikley to be chosen, as almost all designs anyone is likely to copy have the mounting
points as far outboard as possible, and also this is where the tubes join and it makes the easiest to fabricate arm design - I dont think Ive ever
seen one with the mount half way along the arm, but I'm sure people will immediately provide plenty of pictures! On the other hand, a lot of
people don't think about a 20% difference in pivot lengths as particulaly significant, but it needs at 20% stronger spring and a 70% higher wheel
frequency! (This is not quite accurate - as you move the pivot point inboard the spring becomes less inclined to the vertical, and this reduces the
spring strength a bit).
Sorry - I've had to look up my original notes/calculation to find the frequency units - it was cycles per minute! I'm not sure why - Hz
seems a much more natural frequency to use for me (I think the calculations came originally from the Staniforth book).
Regards
Hugh