Hugh Paterson
|
| posted on 12/11/03 at 09:41 PM |
|
|
Inboard suspension on the front
Whos tried building their front suspension with inboard shocks similar to the F27 setup then? Would like to swap notes
Shug
|
|
|
|
|
pbura
|
| posted on 12/11/03 at 10:31 PM |
|
|
Shug,
Bob MacLeod has kindly put complete plans for inboard shocks on Mike Polan's site:
http://members.rogers.com/7builder/Downloads/BobsShocks.html
Steve Graber designed his own setup using bike shocks:
http://www.newtier.com/graber/mid-engine/Front_Suspension_Cradle/index_2.html
Dozracing also had an inboard shock kit on his website, that was designed for a standard chassis, but it has disappeared from the online catalog. I
recommend emailing him for pictures and a quote.
Sorry if I left anyone out!
Hope this helps,
Pete
Pete
|
|
|
Hugh Paterson
|
| posted on 13/11/03 at 01:05 AM |
|
|
Cheers Pete, I like the pushrod version, the adjustable spring platforms are a brillant idea simply done
Shug.
|
|
|
Alan B
|
| posted on 13/11/03 at 12:49 PM |
|
|
quote:
Originally posted by pbura......Sorry if I left anyone out!........
Yeah, me...:
More on...
http://www.desicodesign.com/meerkat/Manufactured%20parts.htm
|
|
|
MikeR
|
| posted on 13/11/03 at 03:00 PM |
|
|
lower unsprung weight (i think)
better aerodynamics (I've been told it makes quite a difference)
Looks sexy (very important!)
|
|
|
pbura
|
| posted on 13/11/03 at 03:18 PM |
|
|
Alan:
Damn!  I knew I was forgetting someone.
Some splendid workmanship on those upper shock wishbones, too 
Syd:
Advantages of inboard coilovers are:
1. Can be made to rise in rate (or remain constant) as bump increases. Springs mounted on the wishbones decrease in rate as the suspension
compresses and the shock angle increases correspondingly.
2. Forces are applied directly to the end of the shock/spring, rather than at an angle, so springing and damping is more efficient.
3. Benefits in decreased unsprung weight and wind resistance as Mike mentioned.
Keeping the shocks out of the spray is good, too!
It's a great setup, but some extra work, obviously. It's one of those things, along with a Mumford link at the rear, that I'm going
to wait and see if I feel like horsing with at that stage of the build.
Pete
Pete
|
|
|
Spyderman
|
| posted on 13/11/03 at 04:23 PM |
|
|
Just a couple of minor corrections!
Having inboard shocks does not reduce unsprung weight! The wishbones still weight the same from chassis to wheel, plus there is a pull or push arm to
add to the equation. There is also more material that has to be accelerated up and down due to the inboard section. The shocker is still attached to
the suspension and is part of it.
It actually adds some weight overall, but it's major improvement in spring rate control more than compensates for this.
The forces through the shockers can only be direct along it's length unless it is fixed in more than one place each end. However the forces at
the mounts are more direct. Unless this is what you meant Pete?
Syd, I think your trig is rusty! It is a falling rate that a normal outboard setup gives.
Also the extra stress and forces going through the pivot is only what would be applied to the original shocker mount in an outboard setup. So actually
you are distributing the loads better across the wishbone mounts instead of into the centre between the mounts that is unsupported.
Aerodynamic forces start to come into play at anything above 30mph, so anything done to improve air flow will have an effect however minor.
Terry
Spyderman
|
|
|
JoelP
|
| posted on 13/11/03 at 06:28 PM |
|
|
just a thing that occured to me whilst pondering this one, i think that unsprung weight should maybe actually be worked out as angular momentum,
mainly because the rocker bone might balance itself if unconnected and not apparently have any weight (only mass), even though the wheel may feel
lighter it may have more mass to move.
Thinking back to the beginning, a low unsprung mass is desirable so that the wheel can respond faster to road undulations. on a standard set up it is
easy to work out unsprung mass cos its all mostly in the same place, at the centre of mass of the hub. With complex inboard setups it is easier to
calculate total mass and then work back to the actual inertia at the hub, which can be compared like for like.
For simplicity of working stuff out i would personally call the spring weight negligable compared to the hubs weight and forget it. You cant really
add on half the springs mass cos its not evenly distributed, the adapter end will be heavier cos of the seat and thread, and i guess the damper fluid
as well. On the inboard designs this end is on the car and hence is sprung, on standard designs it is on the bone and is not sprung. Whilst i
wouldn't imply this is necessarily important or enough to make a difference, it is technically true.
Sorry if that was all drivel. I personally think inboard is nicer though having read this thread i accept it doesnt really reduce unsprung mass.
|
|
|
Hugh Paterson
|
 posted on 13/11/03 at 07:03 PM |
|
|
Top mounted pushrods
Alan, Neat job on the top mounted pushrods on the upper wishbones, I take it the adjustment for the ride height is on the pushrods/locknuts.
Shug.
|
|
|
chrisg
|
| posted on 13/11/03 at 07:25 PM |
|
|
Would this work?
Impressive Drawing follows
Just an idea.
Cheers
Chris
Note to all: I really don't know when to leave well alone. I tried to get clever with the mods, then when they gave me a lifeline to see the
error of my ways, I tried to incite more trouble via u2u. So now I'm banned, never to return again. They should have done it years ago!
|
|
|
Alan B
|
| posted on 13/11/03 at 07:28 PM |
|
|
Shug, yes correct, or even swap them out for shorter/longer ones.
Syd, my number one reason for doing it was none of the reasons mentioned....
Basically, because it is the bottom end of a McPherson strut I wanted to put the main load path in same place......through the top of the upright,
rather than loading the lower ball joint in way it was not designed.
I know many converted strut applications are bottom loaded, but I preferred not to go that way....just my choice
And, Ok it is cool too...
|
|
|
Alan B
|
| posted on 13/11/03 at 07:32 PM |
|
|
Chris, yes sure it would.....pretty much F1 style really...
|
|
|
Hugh Paterson
|
| posted on 13/11/03 at 07:38 PM |
|
|
Chris, yes I know of a car locally that uses somthing VERY similar
Alan we considered top mounting the pushrods on u know what but dont have enough space under the bodywork, at least on the front.
Shug.
|
|
|
sgraber
|
| posted on 13/11/03 at 07:41 PM |
|
|
Aside from the fact that it looks the business.... --- I feel the need to point out one of the major reasons that I built my inboard shocker
design.
The Hub/Upright that I used is originally McPhereson Strut. It was designed to carry loads from the top mount through the strut. The lower balljoint
was never intended to carry the weight of a car. Granted, my car may be 1,000Lbs lighter than the donor. And the lower bj may never fail when
subjected to this increased weight loading, but why take the risk?
Besides, I think the design I came up with is simple, lightweight, and allows for a great deal of adjustment. Not only height, but rate by use of
simple bellcranks. And who can argue with fully adjustable dampers (off a 2002 Yamaha R6) for only $20 each!? Yet, it's all untested. So my
mileage may vary. Time will tell won't it?
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
|
|
|
Hugh Paterson
|
| posted on 13/11/03 at 07:56 PM |
|
|
Steve. A lick of paint and it will look the mutts nutts, now if you had the wishbones in Airflow..... Aero-tube would look cool too (Jaw drop factor)
but it still looks good. Do you have an estimate of all up dry weight yet?
Shug
|
|
|
JoelP
|
| posted on 13/11/03 at 08:08 PM |
|
|
all true, i didnt mention i was very impressed with all the designs done. And the adjustment thing is pretty cool. Would've liked to do it
myself, mebbe next time eh?!? have to get better first...
|
|
|
sgraber
|
| posted on 13/11/03 at 08:28 PM |
|
|
Thanks Hugh. I humbly agree. The geometry was inspired greatly by Alan B. I now have SusProg3D, but have not yet run the numbers. Too lazy...
Those Toyota uprights and brakes are way heavy! I can't remember the weight of that entire assy off the top of my head, but it would be
possible to lose 15 to 20Kg by using ali uprights and Wilwood ultralight calipers. It's all about money though. And the fact that I have so
little of it... 
I am confident that the total up weight of the car is going to be in the 600Kg range.
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
|
|
|
ned
|
| posted on 14/11/03 at 10:14 AM |
|
|
this is a pic of the racecar i mechanic on during the year. When we go to different circuits we change the spring rates accordingly. one way to do
this is to change the rocker ratio by moving the hole that the push rod mounts to on the rocker. This changes the wheel weights and hence the
springing. Has anyone done the calculations for the inboard suspension design on this thread for the wheel weight to see if it is equivacable to the
standard shock mounting position?
I understand the mounting angle of the shock is unimportant ie whether vertical or horizontal, but is the angle in relation to the rocker itself
something that requires consideration?
here are a couple of pics of the setup i'm familiar with:
beware, I've got yellow skin
|
|
|
locoboy
|
| posted on 14/11/03 at 10:39 AM |
|
|
Ned is that a hill climber?
ATB
Locoboy
|
|
|
ned
|
| posted on 14/11/03 at 11:06 AM |
|
|
nope, its a 'Nemesis' built by gpcmotorsport ( http://www.gpcmotorsport.com ) for the nationalsupersports series (
http://www.nationalsupersports.com )
Vauxhall 16v xe based, 230bhp spec engine on carbs. slicks, wings, carbon bits, data logging, blah, blah, blah. not quite locost!
Ned.
beware, I've got yellow skin
|
|
|
JoelP
|
| posted on 14/11/03 at 11:52 AM |
|
|
looks nice, must go like greased cod off a frozen shovel! The angle of the spring to the rocker will affect the spring rate if it changes leverage,
and also if it is rising or falling rate as someone mentioned earlier.
|
|
|
Alan B
|
| posted on 14/11/03 at 12:49 PM |
|
|
Syd...no offence taken at all....all your points were valid and good questions raised........in fact you summed up my main reason quite
well..."top load the bj in a low front car"......as you say there are other ways (as per Steve for example).....healthy discussion is
good
|
|
|
pbura
|
| posted on 14/11/03 at 12:59 PM |
|
|
Syd,
Here's a little music for you:
You're right!
In the traditional setup, the upward force of the wheel in bump is transformed into rotation of the wishbone about its chassis pivot. The wishbone
and shock become more perpendicular through their travel, as you pointed out. I'm glad you brought this up, because it adds support for a
system that is much simpler to build.
Still, it's possible to design the inboard system so that spring rates increase dramatically in bump. I think I would prefer that they stay
constant, myself, because changes in relative stiffness between front and rear during accelerating or braking could lead to some screwy handling.
Also agreed that overall weight will increase a few pounds with the inboard layout, but I think that a typical inboard layout will improve the
unsprung to sprung weight ratio.
Ned brought up a huge potential benefit of pushrod/pullrod systems, of being able to tune your spring rates if you have extra mounting holes in the
bellcranks.
So, as with all things Locost, you pay your money and you take your chances.
Pete
Pete
|
|
|
Alan B
|
| posted on 14/11/03 at 01:07 PM |
|
|
Just a small aside on this topic.
Before I bought my MR2 for a doner I was looking at many FWD cars plus the Pontiac Fiero.....had I got a Fireo (which was quite possible) then I would
have had a conventional front end as the Fiero is extremely Cortina-like......
Just shows how your design decisions can be driven by seemingly trival factors like what doner car you see in the paper first...
|
|
|
Bob C
|
| posted on 14/11/03 at 01:08 PM |
|
|
Interesting thread - a questions springs to mind - how do folks make that crucial hinge eg top wishbone inner on Alan B's pictures.
Bob C
PS I was a bit disconcerted by Alan B's reliance on the beam strength of 1" sq tube where the 2 dampers bolt but I note a general lack of
triangles so I guess they ain't been put in yet...
|
|
|
