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jkaz
10-28-2009, 11:08 PM
Thanks to everyone for your interest in the Penske 7800 FSAE shock, especially those who have bought damper sets for your car.

Between phone calls, e-mails and the recent FSAE workshop in Detroit, people are asking a lot of the same questions about dampers and the Penske 7800 shock. To make it easier for everyone, we have put together a list of the mostly commonly asked questions, and will post them on this FSAE forum.

Please feel free to post any questions, ask for clarification, etc, etc. We will gladly answer your questions.
You can also write to us at FSAE_Shock@kaztechnologies.com

Thanks,
Jim Kasprzak
Kaz Technologies
jkaz@kaztechnologies.com


FAQ: I haven’t heard about the Penske 7800 FSAE shock. Where do I get information?
All the information about the new Penske 7800 FSAE shock is on the Kaz Technologies website, www.kaztechnologies.com (http://www.kaztechnologies.com). Below is the list of information:
Penske 7800 FSAE Shock Products Brochure
Penske 7800 FSAE Shock Technical Brochure
Penske 7800 FSAE Shock Order Form
50mm Stroke Damper Blueprint
50mm Stroke Damper CAD file
75mm Stroke Damper Blueprint
75mm Stroke Damper CAD file

FAQ What are the disadvantages of tuning your motion ration to achieve the desired damping?
There are several disadvantages, all related to the reduction of stroke by reducing the motion ratio. With a motion ratio of 1:1, the range of shock displacement on a FSAE car is approx. 1 inch, with typical velocities up to 5 in/sec. This is already a small amount of displacement, and relatively low velocities for a shock. With these small displacements, you have a small volume of oil moving through the valving. As you reduce the motion ratio, you reduce the displacement, thus reducing oil volume moving through the valves. Even worse, you reduce the velocities of the shock. This reduction in velocities and displacement means you are only using the low speed or bleed portion of the valving. This is not a very effect use of the shock, and, in this low velocity range, the adjusters in any shock are not very effective. So, what you want to do is use motion ratios of 1:1 or greater to get the best performance from your damper. If not, you will have a hard time making effective use of the dampers.

FAQ- Can I order the Penske 7800 FSAE shock in different lengths?
There are both 50mm and 75mm stroke versions available. The 50mm version allows for direct replacement with many of the mountain bike shocks currently used by teams. The 75mm version allows more flexibility when designing your motion ratios. Also, if you want to switch the length of your shock (say to change your suspension design for the next year), you can purchase replacement rods and tubes to convert the shocks without buying entirely new units.

FAQ- Is there a lower cost unit available?
We have been receiving many requests from teams for a lower cost shock. We are currently working with Penske to develop a lower cost version of the shock. This "lower cost" version will use the same external construction, but will not be adjustable. We are also investigating upgrade kits that would allow teams who are budget conscious to purchase the lower cost units, then purchase the parts upgrade them to adjustable units at a later date.

FAQ- Is performance data available for this Penske 7800 FSAE shock?
We are currently finalizing the valve codes for the four stock compression and rebound valving codes. We have spent time minimizing the hysteresis and maximizing the adjustment range for each code. We will be publishing the data for each of the four stock compression and rebound valve codes in the near future. One of these valve codes will be a good baseline for your FSAE car. The damping selection for your car is part of your suspension design and optimization process. We ask you to provide your vehicle’s specifications with your shock order so we can verify that your valve code selection is appropriate for your vehicle.

FAQ- How did this shock come into existence?
The design and development of the Penske 7800 is a joint project between Kaz Technologies and Penske Racing Shocks. The shock was specifically designed for FSAE cars. The shock includes special design features such as changeable canister orientation and clockable canister. The design uses pistons and valving from the Penske F1 line of shocks.

FAQ- Can a team rebuild or revalve this damper themselves?
Yes,. As with all Penske shocks, the 7800 FSAE shock can be rebuilt and revalved by teams with minimal tools. All tools and valving parts are available from Kaz Technologies. The Penske design does not need an "evac and fill" machine to rebuild. Kaz Technologies also provides both rebuild and revalving services for your FSAE shocks.

FAQ- Can we change the reservoir orientation or clocking ourselves?
Yes. The assembly orientation of the bridge dictates the reservoir orientation. You will need to be able to disassemble the shock and reassemble with the desired orientation and clocking.

FAQ- Can we order replacement parts for this unit?
Although we hope that you never have to, yes you can order replacement parts for the shock. There is a bill of materials (BOM) print for each of the shocks These list part numbers for each of parts in the shock. We understand that things happen and replacement parts need to be ordered.

FAQ- Will Kaz Technologies sponsor our team with a set of shocks?
Unfortunately, we are a relatively small company just beginning to sell this product. Currently the sales volume is just not enough to support team sponsorship. However, we are providing free shock seminars at each of the events we attend, and will soon begin publishing a series of technical papers on shock absorbers and suspension tuning that will be available on our website.

MalcolmG
10-29-2009, 05:13 PM
Hi Jim, I have a question about the damping curves you have on your website

Why is the low speed compression damping so much more aggressive than the rebound damping? This year was the first year I'd worked out damper curves for our car, and while I was researching it I found that the majority of race cars and all the FSAE damper curves I found (designed by teams) had higher rebound damping rates - the argument typically being that on the compression stroke the system is absorbing energy, and on the rebound stroke you're trying to dissipate this energy. What's the reason behind your different approach? I'm assuming it probably has something to do with improving response to vehicle body motions in fast-changing transient situations like slaloms?

Also, the knee point on the compression curve is around 20-30mm/s, which also seems lower than where I've seen most (usually between 50-100mm/s).

At the moment our team is probably looking to buy new dampers in 2010 and obviously yours are near the top of the list, I'm just keen to get a better understanding of why the standard valvings are how they are.

Matt N
10-29-2009, 07:07 PM
I don't see any info in previous posts, or on the Kaz website, referring to the springs they are offering with the dampers. Eibach ERS 36mm springs seem to be available in pretty high rates exclusively (F3 applications). Not only that, but if anybody wanted to explore the sub 1:1 motion ratio idea (more than 1 inch damper to 1 inch tire) they would likely want rates well below 150lb-in. What range of rates is available, what are rate tolerances, and are any further details about spring manufacture available?

Matt

jkaz
10-29-2009, 08:40 PM
This is in reply to MalcolmG's question.

You are correct. Typically, you will see rebound to be greater than compression. However, because the transitions for FSAE cars are at low vehicle velocities, there is not a lot of lateral force early in the corner to load the outside tires. So, we have made the decision to be aggressive with the low speed compression control. This helps the cars be responsive in transitions and on turn-in. We have also lowered the compression knee to make this more effective.

You will note there are 4 standard compression and 4 standard rebound valve codes available for the Penske 7800 shock. You can choose any compression and rebound code to obtain the damping characteristics you desire. In other words, you can mix and match the standard compression and rebound codes to obtain the damping characteristics you desire for your vehicle.

If you do not like the characteristics we have chose, you can make your own! That is the advantage of the Penske shock. You can tune the curves in the shock yourself to your desired characteristic. Or, we can develop a custom valve code to match your specified control forces.

Jim Kasprzak
Kaz Technologies
jkaz@kaztechnologies.com

jkaz
10-29-2009, 08:52 PM
This is a reply to Matt N's post.

We are currently finalizing our spring designs and supplier to fit the Penske shock. We plan to make springs available for the shock in 25 lb/in increments from 100 to 250 lb/in, and 50 lb/in increments from 250 to 400 lb/in.

Jim Kasprzak
Kaz Technologies
jkaz@kaztechnologies.com

MalcolmG
10-29-2009, 10:16 PM
Jim,

Thanks for the response, I certainly wouldn't claim to "not like" your damper curves, I don't have the experience to have a personal preference yet. Has the approach you've taken been tested/proven at all? I know you worked with an FSAE team on developing them, and I guess I'd be interested to know what sort of scientific testing was done - but realise this is probably information the team may not want shared

jkaz
10-29-2009, 11:07 PM
Reply to MalcolmG

We have used this approach on race cars many times. We also used this approach on the FSAE car that was used to test the Penske dampers last season. We found this damping approach to improve the response of the vehicle in transitions, and the vehicle to be more responsive on turn-in. This is all I can reveal. We do not share team data.

Jim Kasprzak
Kaz Technologies
jkaz@kaztechnologies.com

MalcolmG
10-30-2009, 01:34 AM
No worries, I appreciate that. Might give it a try on our Konis and see how it effects our car.

Crispy
10-30-2009, 09:25 AM
25 lb/in increments? That seems a little coarse. Are there any other spring suppliers, or does the damper require a special size?

jkaz
10-30-2009, 09:26 PM
Reply to Chris

25 lbs/in is the increments we chose to supply for the Penske damper. If you want springs in finer increments, you can have springs made for the damper by other spring manufacturers such as Eibach or Draco.

J.R.
11-01-2009, 08:01 PM
Penske seems to have a different idea of what their 7800 series is:

http://www.penskeshocks.com/fi...00_Series_Manual.pdf (http://www.penskeshocks.com/files/7800_Series_Manual.pdf)

A lot of teams use these dampers, why did you pick this number? Seems like it will only cause confusion.

rkraft
11-02-2009, 01:13 AM
J.R.,

The part number designation came from Penske's design office.