Pull Damper/Re-Valving of Dampers

[blister]

Hello.

Thinking about different mounting solutions for dampers and bellcranks i found several interesting solutions which can be achieved with "reversely actuated" dampers. This means that if the wheel moves up (suspension is in compression) the rod of the damper is pulled out and vice versa. Of course you then need to adjust the damper curves or even better change the internals of the damper.

Has anyone experience with such solutions on their car or changing internals on their dampers?

[The Stigg]

Hi,

this kind of packaging solution is already present on nearly every F1 and Le Mans Car.
The problem is that you need to have some Through Rod Dampers which are amazingly expensive.

It' s not easy to modify the oil flow in a mtb damper so it could be actuated properly in the wrong direction. Take a CAD screenshot of a exisiting damper and find out how it realy works. Then you will see that there is a lot of work to do than you first thought it would be.

Best Regards
Andy

[flavorPacket]

it's easier to figure out a mechanical way to pull the damper closed than use a damper in extension. Without a through rod, the nose pressure will seriously affect the performance of the damper.

WWU did just this a few years ago, look for pictures.

[Pete Marsh]

UWA has in house developed pull type dampers on its current car (which was quite sucsessfull). They do allow for some neat solutions with mountings etc. They are not through rod type.

Pete

[blister]

this kind of packaging solution is already present on nearly every F1 and Le Mans Car.

I only know the RS Spyder and this car has indeed pull dampers on the rear (combined with Torsion Bar Springs on front and rear).

I also do like the UWA concept of this year. The forces are fed into the sandwich structure without bending loads etc.
I remember last year`s car of UWA which had push dampers, with the drawback that the pullrod angle on the front was a little bit big. Nevertheless the car was also very good.

But thanks for the help anyway.

[The_Man]

Hi,

I'm really sorry if this is a rookie question but please can someone explain how a "reversely actuated damper" may enhance car performance?

Thank you,
Mahek Mody

[The Stigg]

UWA has in house developed pull type dampers on its current car (which was quite sucsessfull). They do allow for some neat solutions with mountings etc. They are not through rod type.

Yeah I saw this kind of installation on a photo of your IHS-007 car.
I love it, mainly for brilliant packaging and load path opportunities. But its hard to justify such an effort for building completely new dampers that you need to have for such a system.
In your case things are a little bit different. When using a system like your H2 solutions for the stated problem are much easier to find.

For our indian guy:
Through rod dampers also have one other benefit in that they allow a range of installation options. Assuming the damper does not use coil over springs (i.e. torsion bars instead) the damper can be mounted both in compression (in bump) as with conventional dampers, when the two operating ends of the suspension linkage are moving closer. But also in tension (in bump) when the two operating ends of the suspension linkage are moving apart.
http://scarbsf1.com/dampers/damper_toyota.jpg"
Best Regards
Andy

[flavorPacket]

Originally posted by Pete Marsh:
UWA has in house developed pull type dampers on its current car (which was quite sucsessfull). They do allow for some neat solutions with mountings etc. They are not through rod type.

Pete

for the sake of newbies, let's be honest here, Pete. Double acting hydraulic rams are not exactly 'dampers'.

And blister, the Audi R10 and Peugeot 908 also use pull dampers. The first team to do it was Toyota F1 a few years back. Check scarbsf1 for some sketches.

[murpia]

Using a damper that extends in bump / compresses in rebound really only makes sense if you use torsion bars (or similar) as your spring. Moving to torsion bars is not a trivial change.

I think any team with the capability and resources to make a success of torsion bars should find it relatively easy to cope with the damper issue.

Blister: What type of springs did you have in mind?

I see no reason why a 'reverse' damper needs to be through rod, although a through rod design _might_ result in lower internal pressures and therefore easier sealing. Watch out for cavitation though.

Regards, Ian

[TG]

I agree with murpia on the use of dampers that extend in bump only makes sense with torsion bars.

You can use just about any damper (some dampers do have orientation limitations) in a setup where the damper extends in bump. Through-rod dampers aren't neccessary for operation. However, dampers that are not through-rod have significantly higher gas pressures and act as a spring and will oppose the spring to effectively pre-load the system. If you are adjusting the dampers properly where you are changing the gas pressure, too, you will always be changing the pre-load in the system. So long as you are taking this into account, you should be fine without through-rod dampers.

BTW, to any of the teams building your own dampers, have you looked at making a through-rod design? It wouldn't be too much more to manufacture and the additional seals are trivial in cost.

[B Hise]

As flavor packet said, the nose force will seriously compromise your car if put the other way 'round. Its not just preload. If you have your heart set on it, put the piston rod through the divider piston and pull it. Through shaft dampers have their own pros and cons as compared to canister style dampers.

Its a big project for a small gain in packaging.