Formula SAE Dampers

[Maurini]

I helped to design the suspension for our Formula SAE car last year and had trouble making a damper selection. The final choice was Ohlin NT44 with remote reservoir which were clearly "overkill" for the application. These became a real packaging nightmare, and will likely be impossible to package this year because we are moving in the pull-rod direction.

Does anyone have any recommendations to compact and adjustable (minimum 2 way) dampers suitable for this application. My preference would be to use dampers with remote reservoirs, but I have reservations about using Mountain Bike dampers.

Your thoughts would be appreciated...

[Notso Swift]

My preference would be to use dampers with remote reservoirs

Why?
Needle and seat design makes adjustment less linier.
Or do you need to remote mount the reserviors due to packaging/limited space in the mounting area, so you would rather take up more space over all, but are willing to do so because you move the weight around.

[Maurini]

The remote reservoir restriciton is due to packaging issues. We are trying to reduce the size of the rear box, and with the pull-rod suspension we need as much flexibility as possible.

[ss_collins]

not a direct answer for you but this may help

http://www.racecar-engineering.com/c...notebook_3.htm

fair bit on damper location (with pics)

[Mackmot]

I strongly believe that the handling of the car is too important to be more bothered about the packaging and aero of an FSAE car.

Keep the quality dampers and set up your car well.

[Seljak]

finding the right damper for FSAE is a massive task. there arent alot of decent dampers avaliable for the application

we started with fox vanillas but they had problems with repetability, they were prone to overheating. The new fox vanillas have pro pedal which is crap for fsae and need to be rebuild as soon as you get them which is annoying. We ran pullrod with fox vanillas in 02 and 03 with great success. Winners of autocross in australia.

The last two years we have run penske 7800 dampers which were heaps better than the vanillas. The only problem with them is the are not externally adjustable, it takes a good hour to do rebuild them. Another problem we found was that each shock was completely different and it was practically impossible to find matching pairs. They are not that large and can be easily packaged for pullrod suspension, we ran it in that configuration in 2004 and pushrod in 2005.

This year i bought ohlins ST-44's, they are a good shock. our dyno testing has showed great repeatability and we found matching pairs. They are externally adjustable and have a big range of adjustment which saves us alot of precious tuning time. They are quite large and heavy but its well worth it. not good for pullrod but definetly good for pushrod suspension.

There are alot of dampers to use, have a look at what some other teams are using and talk to a decent suspension tuner for some advice. Remember that we run fairly low damper velocities compared to normal circuit racers so some dampers will not be suited to fsae application and finding small dampers for packaging is an even bigger nightmare.

cheers,
fil

[shiny side up!]

Quite a few teams acutually build their own shocks for FSAE. Usually those are not externally adjustable, so it can take a while to rebuild them, but once you get them sorted it makes it worth while from the packaging point of view without sacrificing handling. If you have access to a shock dyno, it makes the process of tuning / rebuilding that much quicker if you already know what in detail what an adjustment will do.

[Mech-Aero]

Our FSAE team is using ROMIC mtn bike shocks this year. They're a huge upgrade from the fox vanillas we used in the past.

[Smokes]

Ask the Pace mtb company as they may be able to come up with a custom solution for a fsae shock

[Hitech]

You eventually learn in motorsport that there is only one way to do things if you want to be successful, and that is to do it right.
Dampers are so fundamental in the package that you need to use the best you can find applicable to your application. Forget mountain bike shocks, they are much too light duty for car applications, even for FSAE/f.Student. Aviod the Spax/AVO end of the market if you can, good dampers are used by successful teams for a very good reason. Good luck with the car!

[ss_collins]

http://www.racecar-engineering.com/c...notebook_4.htm

is the correct link (apologies)

[R59]

Talk to Koni.

They'll sort you out.

[flavorPacket]

Originally Posted by shiny side up!

Quite a few teams acutually build their own shocks for FSAE. Usually those are not externally adjustable, so it can take a while to rebuild them, but once you get them sorted it makes it worth while from the packaging point of view without sacrificing handling. If you have access to a shock dyno, it makes the process of tuning / rebuilding that much quicker if you already know what in detail what an adjustment will do.

To my knowledge, we and Cornell are the only teams with completely custom dampers with independent compression and rebound adjustment, though Cornell's are not really externally adjustable (honestly we have some work to do here with the next generation, but our adjustment mechanisms do work, to varying degrees). ETS's dampers are very nice (hi/lo spd compression), but their guy Benoit openly admits that he used someone else's internals.

In response to the original poster's question, it seemed that RMIT had a fair bit of success with penske 1/4 midgets, if you're looking to buy. Unfortunately for us, our design judge was more interested in IC heights and roll camber than completely custom dampers (no bitterness here...), so from a design perspective I don't think you really gain as much as you need to put in to make quality dampers. They definitely performed on the track though, and excluding R&D time, were much cheaper than even the vanilla RCs we used previously.