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View Full Version : Refining the Disk Damper Design


glider
2012.02.18, 01:19 PM
I have been testing a modification of the disk damper that is giving excellent results on my Kyosho Dnano and I think will work as well on my Mini-z. Here is an image of the design. A detailed review is available at my blog. I would appreciate any input regarding the design and whether anyone thinks it is re-inventing the wheel.

http://dnano-mini-z.tumblr.com/post/17757843529/in-search-of-the-ultimate-rear-damper-system

color01
2012.02.19, 03:51 PM
I like the idea but I'm sorry to report it's definitely not new -- it's been done several times before in 1/12 pan cars, cutting oil reservoirs inside the damper plate to hold more oil. You bring up an interesting way of going about it in that your disks are proportionally large, as well as the holes, so what you end up doing is keeping the surface area roughly the same as a smaller disk damper but increasing the oil volume. I agree with you that this is a good thing to do.

I have often wondered about the implications of having the base plate be only as large as the disks -- theoretically, you lose damping as you move away from the resting suspension position -- but on the other hand you can, as you noticed, keep the damper cleaner for a very long time. I feel like this is a compromise you are correct on. I raced a 1/10 F104 yesterday with a small disk damper and didn't have to clean the damper at any time all day long. I couldn't really feel any obvious loss of damping in turns.

What I see potential issues with is the use of Lexan as the damper disk material -- correct me if I'm wrong but Lexan exhibits considerable amounts of creep, i.e. once you tension the disks they are going to bend inwards (towards concaveness) and you will find the disks over time riding on the inside edge of the center hole in your damper plate. I don't need to point out to you how bad that is if/when it happens. If I recall correctly (again, feel free to correct my numbers) Lexan's static/dynamic friction coefficients are not as close together as Delrin's or Teflon's, so your design may suffer from stiction if you have a higher spring tension. Though you may not need that tension for dNano, you certainly need the spring tension for Mini-Z and even more for larger scales like 1/12 pan. The combination of Lexan's flex and stiction makes it difficult to scale your concept up to larger cars.

If you decide to build one of these for Mini-Z, try to get oversized Teflon or Delrin disks instead of Lexan -- I just can't imagine how you're going to keep Lexan disks flat without making them way too thick to be useful.

HammondCheese
2012.02.19, 05:58 PM
I've actually been giving consideration recently to tuning the dampers by shape/size. Am I crazy or on a set up that has a central shock with damping as well as the damper plate, there is already a degree of fore and aft damping - so what you're mainly needing the damper for is to damp lateral movements from the T plate..... Do we have any experts in friction here? But my guess is an oblong plate oriented correctly would reduce the damping in one axis (or grooves/holes in the damper plate running in one direction to decrease contact area along that axis - or alternatively a different layout to prevent movement except laterally- hmm this is starting to sound like a tri shock...). For the non circular plate option I guess some change like a notch (or square holes) would be needed to keep it oriented in the right direction.

If that could be made to work correctly it would at least give independent (somewhat) damping rates to the fore-aft and left-right axes.

Then again any improvement might be so minor its not worth the effort. Has anyone tried something like this?
Thoughts?

glider
2012.02.20, 12:04 AM
Hi Brian, Thanks for your well thought out comments!

"I have often wondered about the implications of having the base plate be only as large as the disks -- theoretically, you lose damping as you move away from the resting suspension position -- but on the other hand you can... keep the damper cleaner for a very long time"

Yes, the way I have set up my Dnano minimizes this issue. A good part of resolving this point is to make the disc oversize such that the resulting mismatch with the base plate caused by the movement of the disc is reduced on a percentage basis. Additionally, perhaps the phenomena you describe can be turned into an advantage as one can modulate it. If you offset the disks to a position behind the base plate so that they become more aligned as the suspension compresses one should get progressive damping rather than the diminishing damping you cite.

"If you decide to build one of these for Mini-Z, try to get oversized Teflon or Delrin disks instead of Lexan -- I just can't imagine how you're going to keep Lexan disks flat without making them way too thick to be useful"

On my Dnano this is being overcome by making the plates thicker, and by having a very small diameter solid titanium damper post that allows for a very small base plate "post hole". There is no reason traditional materials can not be used but I do find the clear lexan to be an attractive way of gauging the amount of oil in the reservoirs. While I agree with your general point that Lexan is not ideal in terms of its strength particularly as cars get larger, it may not be the enormous problem your suggest for a Mini-z, perhaps because there are other more significant limiting factors that exist with the current standard. For my Dnano in actual practice I am getting more responsiveness due to the huge reduction in grit and the smooth smooth damping. To minimize the issue one could route out a pattern in the lexan to lighten it and impart a strength profile that would keep it flat. But yes other materials may be better yet, and perhaps one can even see enough through thin white Delrin or other materials to make this a non-issue.

Brian Cunningham
http://dnano-mini-z.tumblr.com/

glider
2012.02.20, 12:48 AM
Just to clarify regarding your point about the change in contact surface occurring with disc movements. If you look at my current setup forward movement of the disk actually roughly results in no change in contact surface due to the way the disk enters into the collar region of the base plate. For side to side movement there is a very small loss in the contact surface, which could be eliminated by further increasing the size of the disc. So if one desired the whole effect could be greatly attenuated by design.

Cheers,
Brian
http://dnano-mini-z.tumblr.com/

doug01n
2012.02.24, 12:32 PM
We don't use any oil in the DDS system in our carpet track. My best setup untill now includes a PN 90mm mount with Atomic teflon disks, soft springs and a PN dual spring damper over it.

No rubbing on the DDS system, just springs working softly, and the tail is heavy planted.

With this setup, I have to use Atomic 10 tires at the front and 7 at rear. I wouldn't change the plate to achieve better dampening or performance.

glider
2012.02.25, 09:36 AM
Hi Doug,

It is interesting that you are having good success with no damping oil on a carpet track. In essence you have a low friction based damping system using light springs and teflon. I can imagine you can achieve a light responsive setup this way but you will have a certain amount of stiction that will become aggravated if you need to tune your set up with stiffer springs. I can understand how that could be an advantage over a system that becomes gritty but do not think it would be an advantage over an oil based system that is smoother and does not become gritty (although I am guessing that very high carpet track dust/debris may be the huge factor driving your choice). In a way your experience may reflect the problems that plague the standard disk damper system.

I would still say the jury is out on whether you might get an advantage with the system I am describing. By dramatically reducing the surface area of the base plate, increasing the supply of lubricant, and protecting the system from dust by using over sized disks you should get a more responsive plate with less stiction and that functions with both stiff and soft springs. I am currently putting together another blog piece on my latest iteration and experiences with this setup here http://dnano-mini-z.tumblr.com/

doug01n
2012.02.27, 10:55 AM
I agree with you, glider, but at the Galpas carpet, the DDS oil gets too much dirt of the track (tiny pieces of the carpet) too fast. Just 3 laps and the car is a mess... So, we always try to reduce maintenance to run more and less box work!

Atomic-USA
2012.02.27, 11:19 AM
The local racers and I are having good results using the new Atomic White Teflon discs. Little to no oil is needed. Extremely smooth. AR-135-TF

http://www.egrracing.com/shop/images/addition_atomic/AR-135-TF_inst.jpg

TheRinger
2012.02.27, 12:36 PM
The local racers and I are having good results using the new Atomic White Teflon discs. Little to no oil is needed. Extremely smooth. AR-135-TF

http://www.egrracing.com/shop/images/addition_atomic/AR-135-TF_inst.jpg

I use these teflon disc on just about all of my damper systems now and they are way smoother then any I ever use. I use either losi 171/2 shock oil to kyosho 1000wt gear diff grease with them and just smooth. Unfortunetly I have never raced a carpet track so I know nothing about them but I say there worth it.

Atomic-USA
2012.02.27, 03:31 PM
Carpet or RCP it doesn't matter. Some RCP can be very smooth while a carpet track may still be bumpy depending on the floor underneath. The teflon discs get the job done. Note: Atomic teflon discs do not have groove on the under side of the discs.

glider
2012.02.29, 10:09 AM
I will give these teflon disks a try on my Mini-Z when I return to the states. I was getting good low friction using teflon tape on the base plate together with Delrin disks which contain a small amount of PTFE. Hopefully these are even better.

I am curious to hear other users describe how often they need to replace the Teflon disks. Over time my Delrin disks have embedded dirt and gone off. Can the Atomic disks be refreshed by sanding them down?