Damping Technology

[F5 Dave]

For those interested but still at kindergarten level here are a couple of books worth the read that contain drawings with explanations.

These are aimed at general public but will progress you to primary school level. Captivating reading for the Christmas break, even all the MX sort of stuff in the first book is worth the read to absorb the style of thinking.

Both avail from Real Groovy (NZ based) or from your local shop on order. $50 well spent.

Eric Gorr's book

Kevin Cameron book

[Robert Taylor]

There are many ways of skinning a cat! A conventional ''single tube'' damper relies on shaft displacement to move fluid to create damping. The problem is that the damping reaction is actually not instantaneous, although there have been many clever ways of minimising delay in damping response.
A through rod damper such as the car specific Ohlins TTX40 and I beleive some high level Sachs ''builds damping'' instantaneously the very moment the damper moves. Ohlins TTX40 has independent externally adjustable high speed / low speed compression and rebound damping. The really cool thing about it is it comes with a valving reference program. On your pc you can input your current settings and it shows you the damping graph. You can then input your new desired settings and it will show you the new graph(s) overlayed against the original. Before you have physically made a change.This technology though does ideally rely on suspension data logging so you can interface what is happening, plus a high level of set up knowledge and experience.
The motorcycle specific TTX36 shock absorber is not a true through rod damper as it is difficult to fit into a ''given'' recess intended for a conventional damper. But it does rely a whole lot less on shaft displacement, confirmed by its 14mm shaft size. Of internal twin tube design it recirculates the oil internally through check valved chambers and has five times the flow rate through its external adjusters than a conventional displacement damper. Its much much more instant damping control means that the damping force on both compression and rebound is a lot softer, and I have confirmed this myself with comparitive dyno runs.
There is no textbook on this and it may be subject to some argument but it appears that with conventional shaft displacement dampers the internal shim stacks are more stiff than they ideally need to be, in order to maintain decent ride height control, and in especially the case of a superbike, adequate acceleration squat control. If damping doesnt occur right now but a few milliseconds later then effectively the train has already run away. Therefore a little more force is required to arrest it, whereas a lot less force would have been required to arrest it instantly. An added external HIGH SPEED COMPRESSION adjuster will allow the user to adjust its reaction to abrupt edge bumps because it is compensating for too much damping force. Essentially it is an adjustable DUMP VALVE to bypass the main shim stacks. Usually these are arranged in the reservoir ( Ohlins 46PRX / WP / Penske ) but the best result is arguably via a main shaft adjuster ( Ohlins TT44 ) or latterly on the high response adjusters on TTX40 / TTX36.
Because the TTX36 doesnt need anything like the damping force levels of a conventional damper there is arguably rather less need for external high speed adjusters, although these technically are now available as parts taken from the second generation of TTX40.
Also consider that many or most struggle to understand high speed compression ( let alone rebound ) adjusters and how they should be tuned. Cost is also another issue, its all very well to have the bells and whistles but are you going to implicitly understand how to get the best out of it and what will be the comparitive bang for buck ratio?
Some oem forks and shocks have external high speed adjusters but it is arguable that they are installed more for marketing than function. In the case of the R6 front forks the high speed adjusters have an abysmal to no response range if the low speed adjuster is more than 6 - 7 clicks out, simply because there is then so much bypass bleed happening that it lessens the pressure applied to the internal high speed spring and hat.
Because the design of the through rod / twin chamber type dampers means that you dont have the compression adjuster regulating flow into a reservoir the damper is inherently better ''pressure balanced'' internally than a conventional damper. A damper always has to have its gas charging pressure set just high enough to preclude cavitation. With conventional Ohlins 46PRX / WP / Penske / Showa etc that pressure has to be around 150 to 210 psi. More pressure equals more seal friction and that is not something to be unconcerned about. TTX36 gas charge pressure is 88 psi.
This shock is a new design and with ongoing development from Ohlins huge R&D facility it will just get better and better. Second generation test parts we fitted to Andrew Strouds race bike yesterday have certainly confirmed that.
At the coalface of working with this stuff it is highly interesting. Cowpoos was about yesterday to help ( and ask incessant questions, some of them actually sensible ) He will I am sure testify how much work is actually involved and I would like to recite his memorable quote ''its about achieving the perfect compromise''. I think we did a little better than that but all credit to him for such a statement.

[Robert Taylor]

Excuse my ignorance but how do the TTX cartridges differ? And can I be placed on the "I want some" short list please Robert.

Gas charged and same damping principle as TTX rear. That means they will be great!

[boomer]

And I still managed to Kick Stroudys arse yesterday!!

[enigma51]

DONE

I will lend you a set of forks all set up, totally built by RobT not ever touched since he last worked on them! ( If Rob wants them first for service reason's etc, A OK ) with full ohlin"s and Rob's Skill put into them for (a year ago give or take a month or 3 for these ones) for a week or so in January 08- OK ? They bolt in, no worries at all, In fact, I will fit FOC!

Then, swap them out for a set that I spoke about at the start of this thread, for you to try! And comment on.

Then, try the gear I will be working with next year, again FOC, and you have your say man, a bumps a bumps as you know I am sure

I do and have sold all 3, so, why not

sweeeet sounds like a deal to me

[enigma51]

And I still managed to Kick Stroudys arse yesterday!!

Dont forget jimmy's ass you kicked

[boomer]

Dont forget jimmy's ass you kicked

Everyone kicked Jimmies ass... remember.....DNF's Don't count!

[enigma51]

Well from the weekend i can only say that a 1098s with ohlins felt great around puke no bumps upset it even forgeting that there is no slippery clutch and getting the rear wheel to bounce like a rabbit did it feel out of shape.
but then I was not pushing it (it aint mine) so cant really comment.

So the following is my feeling on ohlins on a 1098s

I felt it could go faster just didnt feel fast on it even though i was doing similar speed through some of the corners and can actually see the speed. I was doing 178 where you straiten it up at the top of the hill and on the 750 I was doing 188 and 200 average by the end of the day. The left right up the hill did not feel bumpy and neither did the sweeper or the groove on the back straight where the 750 was getting a bit loose.

The 750 stock feels great for me the only time i feel like I needed ohlins is when i was behind boomer up the hill (puke) and he was throttling through the bumps with no rear wheel spin and no bouncing about. The ohlins was much nicer to his rear than the stock shock on the 750 granted we have different riding styles.

[JD Racing]

A through rod damper such as the car specific Ohlins TTX40 and I beleive some high level Sachs ''builds damping'' instantaneously the very moment the damper moves..................

There is no textbook on this and it may be subject to some argument but it appears that with conventional shaft displacement dampers the internal shim stacks are more stiff than they ideally need to be, in order to maintain decent ride height control, and in especially the case of a superbike, adequate acceleration squat control. If damping doesnt occur right now but a few milliseconds later then effectively the train has already run away. Therefore a little more force is required to arrest it, whereas a lot less force would have been required to arrest it instantly.

These statement that there is no damper lag in a TTX shock can only be true if there is absolutely no free bleed in the system, unless you run your TTX shock with the adjusters closed this can't be true as there is a continuous free bleeed path through the compression and rebound needles therefore the further out you run your adjusters the greater the lag.

Is instantaneous damper response strictly necesary when you have 2 big ugly spring elements in the whole system one of which needs a bit of free time to key in to the pavement surface. I have never had a big problem with shocks squatting under acceleration and certainly not to the extent that I felt a complete re-design of the whole shock was necessary.

[cowpoos]

These statement that there is no damper lag in a TTX shock can only be true if there is absolutely no free bleed in the system, unless you run your TTX shock with the adjusters closed this can't be true as there is a continuous free bleeed path through the compression and rebound needles therefore the further out you run your adjusters the greater the lag.

Is instantaneous damper response strictly necesary when you have 2 big ugly spring elements in the whole system one of which needs a bit of free time to key in to the pavement surface. I have never had a big problem with shocks squatting under acceleration and certainly not to the extent that I felt a complete re-design of the whole shock was necessary.

there is instant resistance though...at some level?

but if you have a softer valving spec...by not needing to have such a agressive spec for anti squat of a thousand....would that not net more side grip?

[JD Racing]

For there to be resistance the shock needs to move a sufficient volume of fluid through the bleed to create a damping force, the volume of displaced fluid in relation to the area of the bleed is large but you will still get some lag.

Many factors determine squat under accleration, c of g, swing arm angle, swing arm length, gearing, sprocket sizes, spring rate, fuel mapping, rider body positioning and style to name a few. If you look at the shock and how it builds damping it's more than possible to tune out squat without having to touch the main stack.

With the TTX you significantly reduce the amount of variables within the system to produce damping force, this makes it very difficult to isolate specific problems.
With a normal shock it's possible to tune for good grip without having to resort to stiff damping on the main stack. The forces fed to the shock associated with finding grip are not of a significant enough amplitude to generate damping from the main stack, with regard grip on the edge of the tyre, swing arm and chassis flex have a more significant influence.

[Mental Trousers]

With the TTX you significantly reduce the amount of variables within the system to produce damping force, this makes it very difficult to isolate specific problems.

Everything else makes sense except for that. I thought fewer variables means isolating problems is easier.

[boomer]

Everything else makes sense except for that. I thought fewer variables means isolating problems is easier.

less variables means there is a lesser ability to isolate a specific issue; all potential specific issues are now consolidated..which prevents identifying the specific issue

analogy.. the more probes or reference material the greater the ability to pinpoint an issue.


Fewer variables could mean less maintenance


give me

[boomer]

The 750 stock feels great for me the only time i feel like I needed ohlins is when i was behind boomer up the hill (puke) and he was throttling through the bumps with no rear wheel spin and no bouncing about. The ohlins was much nicer to his rear than the stock shock on the 750 granted we have different riding styles.

if nothing else, the shit sure does look good whilst making me look good too!

[Kornholio]

if nothing else, the shit sure does look good whilst making me look good too!

God knows, you need as much help as you can get

Merry Xmas.............