Freestyle Pushrod Front Suspension Conversion

[Peter Carmichael]

Ah, Graham I hadn't thought of that.

 

The mass of the bellcrank is sprung, but the rotational inertia of the bellcrank is not. The damper is similar in design and size/weight to the normal damper, but as the suspension movesits piston (which is unsprung) moves further/faster - therefore more effective unsprung mass. The pushrod is additional unsprung mass.

 

Edited by - Peter Carmichael on 11 Dec 2002 18:08:19

[MikeE]

?????????

 

Surely the pushrod is unsprung mass????

 

The way I see it is that an increase in the unsprung mass is a negative effect because:

 

when the wheel is forced upwards by an undulation in the road the wheel (and all the other unsprung components) have a momentum which the spring has to fight against to force the wheel back down onto the road.

 

So if you increase the unsprung mass then the wheel will take longer to make contant with the road again (all other things being equal).

 

So this new push rod is connected directly to the lower wishbone. When the wishbone rises so does this pushrod and thus this contributes to the momentum.

 

Or am I missing the point completely?

[Peter Carmichael]

Mike, you aren't missing the point. I just mistakenly hadn't typed 'un'. I have edited my posting to correct this.

[Morls]

The cost of the conversion seems much more reasonable for anyone considering an upgrade to wide track and new dampers from a basic set-up. And if, as previously posted on Blatchat, this is just part of a package of aerodynamic improvements, then the reduction in lift / drag might be the equivalent of many (expensive) horsepower.

 

I can see Dave Edmands' point about the penalty in mass, (particularly on a car developed with sprints and drag racing in mind), but if the aero benefit was only half that of removing a screen then the benefits over 100 would soon negate the loss to 60. Based on reports that screen removal is worth 10bhp, and a typical Caterham, (if not a BDR700), would need 3bhp to maintain the same power-to-weight ratio with another 10Kg. (OK this ignores braking and cornering disadvantages from the additional mass).

 

And as for the ride / wheel control benefit of rising rate suspension (as could be engineered in using a rocker arm). Anyone who has ridden a modern bike with rising rate rear suspension, then got back onto a falling rate suspended machine (albeit one with more sophisticated dampers) would instantly feel the supple response at small deflections (for a given level of control under cornering) that the modern method of damper location gives.

 

 

 

Mark

 

☹️ My Caterham Silver Jubilee No. 7 is for sale ☹️

[Lawrence_Z]

Effective unsprung weight USW .....is I suppose

the unsprung weight x the leverage to the wishbone fulcrum.

could we counter balance wishbones to produce zero USW ? or would it be double?

 

If the damper is inboard of the bellcrank, then some of the damper weight is transferred to the chassis at the bellcrank. The effective USW is reduced.

I suppose the dampers should be near horizontal to minimise their weight contributing to USW

 

If the bellcrank system increases the damper effectivness to 1:1(ie similar to the rear),

then surely the leverage of the USW must be reduced to 1:1, so the effective USW must be reduced?

 

Lawrence

 

[Lennie]

Hi guys. Thanks for the interest in our project. The current state of play is that we are waiting for Arch, who are being great in helping us, to deliver the wishbones hopefully all before Christmas. I will endeavour to answer some of the questions raised.

 

Graham has asked about the anti-roll bar. We envisualise having it inboard, mounted to our old style alli blocks, in the original mounting position. We think we will mount them on roller bearings and have the arms going forward at 90 degrees to pick up on the rockers with adjustable links, similar to the rear anti-roll bar links. This will mean that the bar will not only works more efficiently through 90 degrees, it can also be adjusted along the arms for stiffness, with no preload on the car. The set up is not fixed to the chassis with the header tank bolt but has four arms mounted to the suspension pick up points and front alli blocks. We are not sure of the weight of the final package against the existing set up. For instance, the new roll bar should be considerably lighter, and Avo have some super sexy alli dampers that we may have as standard. The aero efficiency of our set up should not be overlooked as in the wind tunnel the dampers did really strange things to the air and this set up allows us to investigate more radical aero dynamic aids which would be a waste of time with the dampers as they are. Someone said “what’s the point, the car has got the aero dynamics of a breeze block”. That is precisely the point. While you are always looking for more bhp, the aero dynamics give you something for nothing and if that comes with better handling, so much the better. One other small point is that SVA are asking questions about the dampers, hence all the silly bits of rubber around the adjustors you can see at the factory. Can I repeat that Gary and I are not making any great claims about this system, we only wish to produce our interpretation of a system we have been wanting to try for a long time. Gary and I are looking forward to testing the car when it is ready but we don’t want to be tied down to dates, prices etc. It will be ready when it is right and I can only let you know the price then. Can I offer an open invitation to anybody to come and see us. We are five minutes from Brands Hatch and 15 minutes from the Caterham factory. The demo car is there in a million bits but if you are interested it may help you to see how the system works. Obviously, give me a ring to make sure we are there – the kettle is always on.

[fordy]

Len,

 

as I am getting the super sexy ali dampers for my otherwise standard de dion set up, I am wondering if I would be able to use these in the future on the inboard suspension setup.

 

Or are the springs and dampers from the 2 different systems different?

[Lennie]

Fordy that is a definite maybe. Because the shockers are working much faster it may be that we have to adjust the valves but as you can rebuild the shockers that should not be a problem. You may also need spherical joints but they can also be added later. The only thing that may stop us is the length because the new system allows us to us smaller lighter units. i promise that if you do go for pushrod we will do you a very good deal on part exchange.

 

 

[Tight fart]

Let me know if you have any vgc cheap second hand units.

 

T.F@O.F

www.p1spot.com

[fordy]

thought that might turn out to be the case.....

[Julian Thompson]

Len - has a car run yet with the new suspension?

 

I have delegated your suspension system as my Christmas present to myself so I'd like to know where we are!

 

Cheers!

 

Jue

[Lennie]

Julian, we don't have a car running yet with the new suspension. Arch are fabricating the new wishbones for it; we spoke to them Friday and we should have them before Christmas, hopefully. Avo is happy to re-valve the dampers and the spring rate we have already calculated, so that should not be a problem. We therefore expect to have the car running early in the New Year - I will keep everyone posted on developments. You are welcome to come to the workshop when the car is running and have a test ride. We are booked on a track day at Avon Park in the second week of January but this may just be a little too early for testing.

 

Having read the latest issue of Car magazine about the new Mazda RX8, evidently we have also reduced the "yaw inertia" by bringing the weight from the extremeties into the middle of the vehicle to improve the agility and we didn't even know we had done that!!!

 

Regards

Len

[mr_ed]

Have you seen the Radical NikLink system where the tops of the dampers are on rockers that are interlinked by a pushrod. Its an antiroll system that looks rather neat.

 

Strikes me as it'd be quite easy to add to an inboard suspension system such as yours, although I believe Radical have it patented.

 

Cheers,

 

Ed