David Jenkins
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| posted on 19/6/07 at 07:37 AM |
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A query on inboard shocks...
A fellow forum member and I were standing in front of the MK chassis at Newark, looking at the inboard shocks. We started to discuss why manufacturers
have started fitting them to 7's, and struggled a bit... I thought of a couple of reasons, but they're unconvincing...
1. They're out of the rain and dirt - but they're now getting hot behind the radiator, and they probably still get wet and
dirty.
2. Reduced unsprung weight - marginal, I would have thought, as the steel pushrod probably doesn't weigh a lot less than the bottom half
of a shock absorber.
3. Reduced wind resistance - as the typical 7 has the aerodynamics of a house brick, this won't make much difference.
4. Bling value - possibility!
Anything I've missed, that may justify replacing a very simple solution for something quite complicated?
David
BTW: This is NOT a pop at MK - there's enough of that going on elsewhere - but a genuine question, as other makers seem to be going that way.
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JoelP
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| posted on 19/6/07 at 07:40 AM |
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i think its entirely bling value, though using pull rods can help you bring the centre of mass lower and reduce the polar moment (ie towards the
centre).
IMHO it raises the unsprung mass, but that turned into a can of worms last time so i shalln't argue the point!
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tiger7
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| posted on 19/6/07 at 07:53 AM |
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Inboard shocks only remember me of fitting a Pinto engine in my Tiger Cat, a touching issue. 
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smart51
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| posted on 19/6/07 at 07:58 AM |
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MNR talk of rising rate with inboard springs and falling rate with outboard. I'm not clear on this but I think it means that for small
suspension movements, the springs are soft, giving a nice ride, but the more the body rolls (or drops) the firmer it gets, giving good handling.
edit: people on here always say that the seven has terrible aerodynamics as if you'd be mad to even consider improving them. Why? Surely if
inboard dampers, wraparound cycle wings and nose cone shape can improve aerodynamics then why not?
[Edited on 19-6-2007 by smart51]
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Agriv8
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| posted on 19/6/07 at 08:00 AM |
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All to do with 'rising rate' against 'falling rate ' I belive.
The way I understand it is that the more angle you run your coilover at the less affective it is, You then need to add a beeffier coil spring to prop
the front end up, add the desire to get wider fron track ( cornering stability ) you are going to make the problem even worse.
Oh nearly forgot an added bonus is on the MNR system you can change your ride height without haveing to wind the coilover spring in.
To give you an idea of how well it works I am running 125 lbs springs on the front of my inboard V8 ( a little soft for the track ) but perfect for
the Cr4ppy roads arround here.
It May be bling but it is function over form sure Marc will be along to put me right.
regards
Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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SaveTheDodo
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| posted on 19/6/07 at 08:01 AM |
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Wind resistance plays a significant part in having inboard suspension per se - remember an open wheeled F1 car in 1962 (Lotus 25) did'nt have
much better aerodynamics than a 7, and this was stated as the reason for switching to rocker arms. I believe Jeremy Phillips also introduced his
rocker arm type suspension for the same reason.
However the switch to pushrods came about because the increased forces in the ground effect and big wings era were bending the rocker arms - I
can't see this reason applying to 7alikes!!
Credit where credit is due - the original idea for rocker arm suspension apparently came from the Clairmonte brothers who commissioned a special from
Lotus that was originally intended to have the number 7. The wheel has come full circle!!
Andrew
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David Jenkins
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| posted on 19/6/07 at 08:18 AM |
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quote:
Originally posted by smart51
edit: people on here always say that the seven has terrible aerodynamics as if you'd be mad to even consider improving them. Why? Surely if
inboard dampers, wraparound cycle wings and nose cone shape can improve aerodynamics then why not?
Slightly off-topic - but I don't believe that aerodynamics are relevant on a 7. For me they are about acceleration and cornering rather than top
speed.
Other people may have different opinions - it is allowed  - but my car is used for blasting around local roads most of the time, so wind resistance
is not very important to me.
After all, some of the cars with inboard shocks have a typical 7-style windscreen - you may as well have a parachute dangling from the back of the
car!
Now back to in-board shocks! 
[Edited on 19/6/07 by David Jenkins]
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SaveTheDodo
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| posted on 19/6/07 at 08:22 AM |
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David,
At road speeds they may be bordering on irrelevant, but remember these manufacturers are in the business of making track day and race cars -
aerodynamics are significant for these.
Cheers
Andrew
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David Jenkins
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| posted on 19/6/07 at 08:25 AM |
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Agriv8,
If there is a technical benefit for inboard shocks then that would be a good reason to have them... if they improve the spring function, or increase
the adjustability, then that is A Good Thing.
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nitram38
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| posted on 19/6/07 at 08:48 AM |
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I will be running compressor driven Airbag spring bilstein shocks on the Motaleira.
I will be able to raise or lower the car from 0-6" with a running height of 3".
Apart from not having a big shock in the airstream, the main advantage to me is ride height adjustment.
The shocks optimum setting is 13.5", so I will mount a dummy rod in place of the shock and make my pushrods the correct length in relation to
the running ride height of 3".
I also intend buying carbon csr cycle wings which according to catering van, stops them lifting.
Using wilwood calipers instead of the rover calipers saves 3kg per wheel.
All these "little" things help gain a bit more speed and suspension compliance.
Aerodynamics may not mean much to a road going car, but if you track or compete, then very small gains make all the difference.
I have seen cars with little bits of plastic placed all over the suspension/protrusions to help them win.
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Agriv8
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| posted on 19/6/07 at 08:51 AM |
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I have come up with another way to explain it better ( possibly ! ).
On an inboard setup the spring and shock is working through a vertually constant line while the suspension arm travels from full droop to full
compresion.
in an outboard setup the shock is working at 'diferent angles' while going from droop to compresion.
There are other ways arround this ( have a look at Dax for instance ) they run the coil over more vertically on an outboard setup by moving the top
coilover mount out from the chassis
Just re-reading that I have almost convinced myself that I know what I am talking about
Regards
Agirv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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short track 123
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 posted on 19/6/07 at 09:07 AM |
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There is also the advantage of less unsprung mass with inboard shocks + the aero. And if your design allows you could put them much closer to th
C/G.
Every little bit helps. 
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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nitram38
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| posted on 19/6/07 at 09:10 AM |
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quote:
Originally posted by short track 123
There is also the advantage of less unsprung mass with inboard shocks + the aero. And if your design allows you could put them much closer to th
C/G.
Every little bit helps.
I have said this before and got shot down in flames! I'll get my coat...................
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Agriv8
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| posted on 19/6/07 at 09:15 AM |
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quote:
Originally posted by nitram38
quote:
Originally posted by short track 123
There is also the advantage of less unsprung mass with inboard shocks + the aero. And if your design allows you could put them much closer to th
C/G.
Every little bit helps.
I have said this before and got shot down in flames! I'll get my coat...................
I agree
but as a safty precaution.
A My coat is aready on.
B My parashute is strapped to my back
C I have my fireproof Grunndies on
regards
Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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3GEComponents
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| posted on 19/6/07 at 09:16 AM |
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I think what Agriv8 is trying to say that with normal outboard mounted units, as the suspension compresses the effectiveness of the shock is
reduced.
With inboard, cam actuated systems this doesn't happen, you can tune the rocker to give a rising rate which works wonders for suspension.
One thing that has yet to appear on kit cars, as far as i know, is stable platform dampers, these are big in the off-road scene in the States, and
mountain biking, where the shock is stiff to move until a large bump force happens, the point at which this happens is controlled by air pressure and
so adjustable to suit needs.
Could work wonders for handling, just think flat stable car where the suspension only moves when it hits a bump, Mmmm..........................
[Edited on 19/6/07 by jroberts]
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swalf3
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| posted on 19/6/07 at 09:46 AM |
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Inboard Dampers
Another advantage of pushrod or pullrod suspe n.sion is that when you alter your ride height you don't need to redo the corner weights.The main
advantage that has already been mentioned and explained is the adjustment to rising rate .This is all the more important if you widen the track, as a
result the angle of the shocker to horizontal is reduced so is the rate of springing in bump. Winston
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JonBowden
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| posted on 19/6/07 at 10:01 AM |
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quote:
There is also the advantage of less unsprung mass with inboard shocks
This won't make much difference. If the rocker mechanism has a 1:1 ratio, then the moving mass of the damper still has to be moved by the same
amount. The only way to use this to reduce the unsprung mass would be to use a rocker mechanism that caused the damper to move by a smaller amount
using a stiffer spring and damper. Even then, the the push/pull and rocker mechanism will add to the unsprung mass.
Jon
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nitram38
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| posted on 19/6/07 at 10:36 AM |
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quote:
Originally posted by JonBowden
quote:
There is also the advantage of less unsprung mass with inboard shocks
This won't make much difference. If the rocker mechanism has a 1:1 ratio, then the moving mass of the damper still has to be moved by the same
amount. The only way to use this to reduce the unsprung mass would be to use a rocker mechanism that caused the damper to move by a smaller amount
using a stiffer spring and damper. Even then, the the push/pull and rocker mechanism will add to the unsprung mass.
Good job mine is 2:1 then !
1" travel on my shock gives 2" ride height change.
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David Jenkins
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| posted on 19/6/07 at 11:22 AM |
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oops! I seem to have inadvertently opened one of these...
It was an honest question, though...
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Agriv8
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| posted on 19/6/07 at 02:08 PM |
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Naa - Just like everything else in life everbody got their views on a given subject.
Nothing wrong with a little livley debate.
regards
Agriv8
Taller than your average Guy !
Management is like a tree of monkeys. - Those at the top look down and see a tree full of smiling faces. BUT Those at the bottom look up and see a
tree full of a*seholes .............
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locostv8
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| posted on 19/6/07 at 04:13 PM |
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One nice thing about the rocker system is that you can change your effective spring rate by changing the rocker ratio.
http://wrangler.rutgers.edu/gallery2/v/7slotgrille/hssss/
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MikeRJ
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| posted on 19/6/07 at 09:43 PM |
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quote:
Originally posted by locostv8
One nice thing about the rocker system is that you can change your effective spring rate by changing the rocker ratio.
The downside being you also change the damping at the same time.
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JoelP
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| posted on 19/6/07 at 09:47 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by locostv8
One nice thing about the rocker system is that you can change your effective spring rate by changing the rocker ratio.
The downside being you also change the damping at the same time.
i was gonna say that but im tired of arguing about inboard shocks!
However, i really like the rising rate aspect, makes a lot of sense.
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locostv8
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| posted on 20/6/07 at 06:20 AM |
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I'm using R6 coilovers which are adjustable and rebuildable/rrevalveable and CHEAP. With shipping I have less than $200 in 8 coilovers.
[Edited on 20/6/07 by locostv8]
http://wrangler.rutgers.edu/gallery2/v/7slotgrille/hssss/
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short track 123
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| posted on 20/6/07 at 05:50 PM |
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If you put a set of scales under the wheel with a block supporting the chassis and remove the bolts from the shock is this unsprung weight ?
If so.
If we repeat this with push/pull rod set up how come we get a lower weight.
I could be wrong but is mass not weight?
I did think that the force it takes to compress the shock is a separate issue.
A crude experiment but it does seem to work.
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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