Dan Woods opposed coil front suspension

Does anyone currently build a setup like Woods' opposed coil/coilover front suspension? Any pics out there to show how it works? I love the look but sure don't see much like it anymore.

Steve

 

Think he's still building down in south Florida.
I'll see if I have his e-mail in my stuff,I'm sure he'll help you

 

If you need some pics, we can take some of the Ice Truck and send them to you. It's at the paint shop right now but I need to go check on it anyway.

Doc.

 

I haven't heard anyone mention that name in ages!

The way I understand it, you have bell cranks acting on the spring shackles at one end and on one end of a coilover at the other. You need the shackles because the travel paths of the bell cranks will be different from that of the spring perches. You also need a Panhard bar or some other means of positively locating the axle laterally.

Keep in mind that this set-up will give you no front roll stiffness. That means the car is going to handle like a 1F2R trike, which was basically the way the T-buckets the system was used on handled anyway. That is, serious lack of rubber at front compensated for tail-happiness due to too much rear roll stiffness, though I suspect that there might be oversteer at the limit.

The way to think about this, I'd suggest, is as part of a total suspension system which incorporates all kinds of other devices to do specific jobs. In particular it should be used in conjunction with some mechanism for controlling roll. For instance: how about DW-style systems at both ends, each using a Shockwave coilover-air spring? To keep the front clean the bell cranks can have offset arms so the bag sits behind the radiator. With the right bags that'd give a soft ride, but it'd give no roll stiffness at all; so there's another DW-style system between front and rear, only this time using stiff steel springs. There's an idea that might stand some elaboration.

 

Last I heard Dan Woods was on the Monterrey Peninsula and was building architectural ironwork. Think about the efficiency or lack thereof of your springs when laid at 90 degrees to their optimum vertical position.

 

Weasel, the efficiency of a spring depends not on its angle to the ground but on its angle to the arm acting on it. The bell cranks in the Dan Woods system can easily be set at the optimal effective angle, or preferably such that it reaches that optimum after an inch or so of bump. It's not rocket science.

 

This is the front set up as on the Ice Truck.

 

I'm sure I remember a Dan Woods system using an axle? That one has the bell cranks but it's an independent. It also looks like it has two coilovers with their fixed ends close together. Or, as does happen, have I been imagining things?

Edit: Here we go:

Axle and bell cranks, but two springs, not one.

Here's quite a good illustration:

It also seems to have elongated holes at the ends of the bell cranks instead of shackles.

For some reason I remembered it with a single "floating" spring in the middle.

 

Early Dan Wood's stuff had Ed Roth Style beam axles,
typically with one coil spring in the middle.

This later IRS is a better job !

 

Thanks for the info and pic - I'm really looking for how the opposed coilovers are attached at the center - any close up's of this area?

Thanks again,
Steve

 

Druid Princess, yes. That moreover had all the weight of the front half of the car on the centre of the axle, where the bending moment is the greatest.

 

here's Dan Woods business number and Address
Dan Woods' Designs
1341 A Dayton St
Salinas,CA. 93901
Phone 831 754-9646
fax 831 754-9648

 

with the panard rod for location probably still better than bell cranks with slots as axle location

 

Took these pics of Jerry Rogers T, a recently ressurected build in UK. All design and most of bild by Nick Butler, builder of Revenge, a ground breaking UK show rod in the 70,s. Has a slot in one of the bell cranks to allow for arc movement of bell cranks. Frction shocks are part of the bellcrank pivot.
Buitiful Jag rear, Borrani wheels and Kinsler injection too. Jerrys, saving his pennies for CHROME.

 

OOps, heres the pics

 

I disagree with that.
The springs are attached to the frame at the middle and don't free-float between the bellcranks so the suspension WILL offer roll resistance. The force is applied to the chassis thru the bellcrank pivot bolts just as it is when the car is bounced evenly...except the spring force won't be 50/50 between the two bell cranks as the car leans.

(Besides....tubular axle and radius rods = plenty of roll stiffness! LoL )

The other Woods style with one spring bearing down on the axle center is just showcar stuff!

 

Yes, indeed. You're absolutely right. I'd remembered the set-up incorrectly: though I'm still sure I saw (or perhaps read about - it was years ago) a Dan Woods suspension that had a single, "floating", horizontal coil-over. It could even be that I'd read an incorrect description. Whatever the case, it stuck in my mind.

 

Maybe you missed the point I was trying to make - so I'll try and be more specific: very simply put, when you angle a coil spring you have to compensate for the loss of spring rate. A vertical spring works at 100% of its rate but angle it 30 degrees for example and it is only working at 75% efficiency. To correct this you have to run a spring that is correspondingly heavier. So if you need a 300 lb spring mounted vertically, you will need a 400 lb spring if it is leaned at a 30 degree angle from vertical. This is for fixed mounting point springs. But yes, you're right that the bell crank ratio figures into the equation and one needs to know this ratio when calculating spring rates.

 

Yes: but it depends on where you measure the angle from. In your example the force acting on the spring would be more like 87%, i.e. the cosine of 30°, of what it would be if the force were acting parallel to the spring's own axis. Be that as it may: what you say is perfectly true as long as the force acting on the spring is vertical. But forces don't always act vertically on springs. A spring might lie horizontal and still be 100% effective, if the force acting on it is also horizontal. One way of bringing that about is with bell cranks, as is the case with Dan Woods's various systems. The same principle applies at any other angle in between.

Motorbike rear suspensions use this principle to gain spring rate over suspension travel, by incorporating a linkage that gains angularity far more quickly than the swingarm does. The system can therefore be set at, say, 30% effective at ride height, but reach 100% at 6" of bump. It does this by arranging that the force acts some 75° off the spring's axis at ride height.

 

I think that most directly applies to a suspension where the spring unit is directly attached to the axle on one end.
With this DW setup the direct line of force changes due to the bellcrank. The spring is still being acted upon in a direct way, even though the spring is mounted 90* off vertical.
As you suggest...the bellcrank ratio is somewhat easier to play with than actually changing the spring angle (maybe even the actual rate up to a point) in this configuration.

It's a pretty cool design!

 

Just been cruising Woods front ends on a search engine, and need to put some details straight about my T. Nick Bulter has had nothing to do with this car. Original chassis, front and rear end are Wimbles work and design.
Take a look on TBucketeers to see how much it has changed and how much work has been put into it since then.

gerry

 

Now that is very much the sort of quality of form I'd want for my '31's weird suspension.

 

Go to it.
Takes a little more time and thought but its worth it in the end
Gerry

 

The thing you have to remember about these bell crank operated spring/damper systems is that while the spring doesn't really care about the motion ratio, the damper most certainly does.

What I mean by that is, if you have a very high (numerically) motion ration, say 5:1, the spring sees 1" of travel for every 5" that the wheel sees, and the spring will need to be ~5X as stiff as if it were mounted normally to carry the load. So long as the rate follows along, the spring couldn't care less how much travel it undergoes (without coil binding, obviously).

Not so with the damper. Dampers need displacement to do their job, so the higher the motion ratio, the less effective the damper becomes. At a high ratio like 5:1, you're getting well into open wheel racer territory (think Indy cars) for damper stiffness, just so that they will have some kind of effect on the suspension.

If you try to run dampers (shocks) of standard stiffness in a high ratio bell crank operated suspension, the ride is going to be very poorly damped indeed (think old work truck with 50 yr old shocks, running down a bumpy gravel road).

Just something to keep in mind when you're buying parts to integrate into the design. You must use dampers of sufficient stiffness to make up for the loss of travel.

At some point, the ratio becomes so high that the damper is not able to do any real damping at all, and your suspension will be essentially undamped (IE running without shocks). That's not good, so keep the motion ratio as close to 1:1 as the design can stand.

 

Thanks. That had been a concern.

 

No worries.

I love bell crank/push rod operated inboard suspension. All the rods and linkages. It would warm the cockles of Rube Goldberg's heart.

I came within a hair's breadth of doing a inboard push rod operated system on the front of my '36, but simplicity won the day. Maybe my next build. I'm kinda wanting to do an IRS on the next one anyway, so what's one more set of geehaws on top of that whole mess, right?

 

Dampers are a real problem for me. I have been looking for over 6 months for a pair that will fit inside the springs. They need to be less than an inch in dia, and no one offers them that small. Course they can make them for a small fortune, but so can I. I will try it with the frictions and if they are no good make a couple of oil ones.
I am aware of the small amount of movement on this set up so maybe something innovative!!!
Gerry

 

I think Ryan's point, which had occurred to me though I had no direct experience, is that there must be a bit of displacement before the damping valves inside the dampers can do anything. If there isn't enough stroke the fluid can barely open the one-way valves, never mind flow through controlled orifices from one chamber to another. If anything that argues for a larger diameter of damper body when the stroke is necessarily small - and that suggests placing the dampers somewhere other than inside the springs.

Is there room for dampers behind the radiator? Then you can have a second pair of bell-crank arms on an extended bell-crank shaft - or even put the springs (bigger ones) there as well. Torsion in the bell-crank shaft might become something to be aware of then, and one might go to a sleeve rotating on a stationary inner shaft welded to the frame; in which case the elegant way to do it would be circular-section frame rails, and before you know it you've built a whole new chassis

 

I'm lovin this thread because it requires more thinking than just how to use the catalogue index.

 

My thoughts are.
I need damping. This is off the wall but old RC cars used a piston with an O ring in a smooth bore cylinder. Dampers!.
I have little movement on the front end and the aim is to damp the movement of the axle. That is to stop oscillation and tramping. Now if we consider I have a 2.5 inch wide tyre on the front and a 18.5 on the rear then cornering is not its strong point. I just need to keep the tyre in contact with the pavement as much as possible.

No way am I going to start adding parts to that front end. Its been a long and difficult road to keep it as clean as it is. The bell cranks are on roller bearings (and yes I am aware that they are not too keen on restricted movement, Ill just replace them as and when they wear.)

So, we ll see how well the frictions do. I am a member of another forum (just for Buckets) and the view on friction dampers is really quite good from the guys that run them.

I have a few other 'original' problems that need to be though out on this T but more of that at a later date.

Dont you just love a challenge. I DO
Gerry