New product for PDS..Could this be the answer?

[terry hay]

A lot of people have argued the case for and against the PDS and continue to do so. One of the main problems I see with the PDS is the failure to adequately control damping progression through the majority of the stroke. As Ive mentioned before the needle really only cuts in when the shock is near to, or on the bottom out bumper. It is then we really notice an abrupt rise in the compressive resistance. Linkage shocks have a smooth progressive curve from the initial movement. I take delivery tomorrow of our first prototype telescopic needle. this needle is two stage with the inital stage retracting into the final one to give a housed length similar to the current needle design incorporated in the 04 shocks. The extended length however is dramatically longer creating the ability for the PDS shock to now develop a smoother progression similar to that of a linkage shock. WP has requested we send them one of our needles upon arrival for testing purposes. Could this be the end of the argument...who knows but seems good on paper. We've discussed a lot on this forum and I thought I would put this out there for discussion and welcome your thoughts an critique.
Terry Hay

 

[drehwurm]

Servus,

Haha, very funny coincidence. I was about to post a thread with almost the same topic after reading an announcement from Novation on KTM-Talk. Telescopic needles, Slide Valve - what's next? Triple piston PDS! I don't want to be negative, but it seems a little strange to me that everyone is scrambling to sell the wonder-cure to us PDS users right now. Hasn't the PDS been declared dead by the DRN community not too long ago.

Michael


Quote from KTM-Talk:
______________________________________________________

Pds spring issues solved. Why, How and When
1. The KTM spring has to have limited preload for breaking bumps
2. The KTM works best for the first half of the travel with straight rate
3. The KTM needs more than a straight rate for excelleration chop deeper in the stroke.

This means that a stiffer spring is required and that it has to be longer to be closer to staight rate for the first half of the stroke( like linkage). The Novation spring is just that. A pds 4 is way soft for 4 strokes if you weigh over 160 lbs. Why because it needs to much preload to hold it up. Thus the progression is virtually gone.

1. Stiff spring plus to much dampening means harshness/ Stiff spring with appropriate damping means proper preload and no harshness.
2. Straight rate spring does not have enough to hold it in the end of the stroke as to hold it up when generating a heavier load like eccelerating out of corners.
3. Standard PDS springs arent stiff enough and dont generate a more linkage style ramp up. Thus it hasnt been satisfiing to everyone. The ones who like a softer bike prefer a stiffer straight rate for less preload and less middle stiffness and the ones who want a stiffer middle use a progressive that is preloaded to much.

The Novation spring is one of a kind and our dampening is too. With the proper dampening system that will be the future to all suspension is here. Say goodbye to the shim stack as you know it and get ready for the news about how to have a bike that pleases everyone. If there is the proper low speed and the proper mid speed and the proper High speed on the shim stack then it has a solid base to work with. The problem is that our unique dyno allows us to see that a shim stack itself is incapable of this. Why? Because it doesnt have rapid controll. A shim by design flexes. How then do you make a shim be strong enough to hold the oil but not strong enough to create harshness. I now own this method. With our new patent pending method we are able to make the PDS better than linkage. All the way better than linkage. By plushness, bottoming, by breaking bumps, by seat launching, by low speed bottoming, and by rebound control. I cant explain the whole method and my phone is attached to my ear so I am triing to save some time and tell the world about our great new setup.

With this new controling method we can achieve the perfect specs for the shock and the bike along with the rider. It hasnt been done like this before and I believe it like drum brakes compared to disc brakes. Shims as you or we know are going to be like the great and wonderful drum brake method. It works a little and can be made to perform but it has its problems, and disc have fixed those problems. Which do you have on your bike now. Disc of corse because the system finally improved. Thus the shim cannot be stiff and plush at the same time or should I say the shim can get within 25% but not any closer than that of this new product.
You all probly think I am tooting my horn, OK, But wouldnt you all like to know there is a new product as soon as possible.

The new Novation Slide Valve is amazing. It can actually do two thing at once. Give the bike major mid speed control (more than 25%) and have less high speed control(25% less) Than a shim stack. Thats a 50% percent bennifit. I give credit to the shim stack in this way. If you have the maximum performance you can get good results. But good results are not going to be in the factory suspension. Great results and perfect suspension is the goal here.

Most tuners have and are getting good results and I give all of them a big applaud for beating the shim stack and building pistons to perfom better. It is a hard job to do, Trying to make everyone happy, that is by finding the best for the customer. The problem is with shims are that When building one for a woods guy you have to get rid of some bottoming and with moto guys you have to live with some harshness. Especially with the PDS. Thats all I hear with suspension is its to plush or its to harsh. After saying all this, I say it is possible to have both ends of the spectrum met.

Bladder Facts
1. Bladders are made of rubber and a we all know Air goes thru rubber. This spring make sure to add air to your tires in the bicycle tires. Now add heat and rubber expands.
2. Bladders can break
3. Bladders do not make it easier to rebuild a shock.
4. Manufactuors make bladders because the are cheaper.
5. After 3 rides 10-20% of the nitrogen moves into the shock where the oil is. Thru the rubber. Thus creating some plushness.
6. Bladders cause some DNF's in races due to breakage.
7. If you get a leaky shock seal you can lose your oil and cause the bladder to break.

The Oil/Air separator piston is used to do just that. It is located on the other side of the Adjuster of where shock valving is. Now the adjuster is doing its best to slow the shock down by creating a whole bunch of resistance. And the Piston or bladder is on the other side of this adjuster. HMMMM. Try slowing down a vehical moving in neutral and have someone behind you with an air hose, helping. Is the air going to help you any. It may help 1/1000000, but not in a bad way. It is trying to slow down the same way the adjuster is. By adding resistance. An air piston is easy to work on and reliable as can be. If it had a bad type of friction it would not be the way to go but think of it this way. It has 150psi+ behind it and the pressure varies a little between shops. It takes a whole whoppen 1/2 a pound to move when cold and so if anything you could vary your air pressure to 149.5 psi. Ha Ha.

I think I have finally said enough. So in responding, ask questions and I will do the best I can to explain. I am trying to be polite. I wish everyone to find a way around shim stack insuficiantcys. Pete Russell/Novation Racing.

Quote End

 

[marcusgunby]

Very interesting, something the pds cant solve is rebound issues, the pds uses a very stiff spring and the rebound has to control that, the heat from a shock IMO comes from the rebound side not compression, so how does the oil cope?? it doesnt:( it breaks down faster and the shock gets faster still, and you are in a vicous circle of fast rebound and hot shocks.

be interesting to hear the theory behind the novation system, however one tuner i trust above many others has tried the fork setup, and it was reasonable but didnt match a well valved setup.

 

[terry hay]

I don't know what the Novation guy is on - but I wan't some

 

[bclapham]

Originally posted by marcusgunby
so how does the oil cope?? it doesnt:( it breaks down faster and the shock gets faster still, and you are in a vicous circle of fast rebound and hot shocks.

are you sure you didnt mean VISCOUS circle- that would have been a nice play on words! :laugh: :)

 

[Jeff Howe]

Me too! It's been awhile since I've had a good mind altering experience.

 

[KiwiBird]

It seems that the development on the PDS internals is reaching fever pitch. By the time I get new base valves, mid valves, Ti springs, PDS pistons, needles, bumpers, bladders and subtanks I wonder if I shouldn't just get a bulldozer to run ahead of me and be done with it :laugh:

 

[Jeff Howe]

Hey Terry, have you ever tested with straights and different length/density bottomout bumpers? I thought I remembered you mentioning that once and was just wondering if you had done anything with it.

Though this does not apply directly to PDS, I tried this approach on snowmobile front A arm setups and it makes a world of difference. The bumper was double in length and apparently perfect in density. I no longer have a hard bottoming feel at all with it. Best ride I have gotten out of that sled yet.

 

[marcusgunby]

Kiwi all that to get by without a few links LOL.

 

[bclapham]

so what happens if the bubble bursts and they go with a linkage- will it take another 5 years to find a decent rising rate and valving???

 

[marcusgunby]

bruce thats not a problem, as when the japs get a good working system they change it anyway, then it takes 3 years to get back to the good setup.

 

[bclapham]

it sounds like the Japs spend too much time looking what everyone else is doing and not at what they are really trying to achieve, with swapping the rates all the time. at least no one can say KTM were doing that

 

[marcusgunby]

I think KTM have swapped there rate once-they moved the shock further back on the swingarm, probably went from 11% leverage to 12%:)

 

[terry hay]

Guys
I put this thread here to get your opinion and/or critisisms and you've just started rambling. Tell me what you think.
Shocknut
I have tried the straight rate with mixed results. My preference is to use a modified straight rate (progression added) for the best results but this is time consuming and hardly economical. I have used XR650 BO bumpers with good results. Especially for SX. I suggested this in the thread where Jeremy did a big end and I guess all rationale went out the window.
Terry

 

[drehwurm]

Servus Terry,

Sorry, I didn't want to start a "rambling thread", but telescopic needle sounds just as excotic as a slide valve. Hard to comment on without any additional info. For me "telescopic" means sliding which causes abrasion or even "can get stuck" - how long will this telescopic needle last before needing replacement or service. For me this sounds like putting a service intensive item in a "not really easy" to service shock. At least those were my first thoughts after reading it.

Michael

 

[bclapham]

Terry:

have you got a digital camera? you can easily take a pic and post them here- remember a picture paints a million words- then if we have seen what we are talking about then the ramble factor could be less! :)

 

[Jeff Howe]

Before I can go any further I need to know how you are accomplishing the collapse of this needle. Is there a spring involved? If so, how is it rated to correspond to internal pressures? In other words what controls the timing of it's collapse.

 

[svi]

What happens if the needle sticks? Very few people get their shocks serviced as often as they should.
A lot of shocks compensate for the loss of fluid viscosity due to heat by using a high expansion coefficient needle rod, is this an issue?
How will the nitrogen pressure in the shock effect the needle?

 

[terry hay]

Ok
First of all I don't see the needle getting stuck as a problem due mainly to the amount of overlap assisting alignment and the fact that the outer tube will expand at a higher rate than the solid inner needle. Wear should not be a major factor given the constant lubrication and the type of material used. The collapse of the needle will be controlled by the contact of the end of the needle with a turcite bush located above the adjustable rebound mechanism. A bleed will be in the bush to ensure oil flow through the rebound circuit is constant. The extension of the needle could be controlled by either a spring or simply a port at the bottom of the outer needle employing the positive pressure above the secondary piston to ensure the extension of the inner portion. All this is good, but so far your thoughts pertain to the logistics rather than the theory. What do you think of the concept?
Terry

 

[drehwurm]

Servus Terry,

Well, it is an enticing idea - in theory. I guess it all depends if you can create a valving on the secondary piston and needle profile to give the desired progression curve. What about some facts - numbers, dyno graphs, ...

Michael

 

[svi]

Terry,
With regard the concept I would spend my development dollars on designing a link and use a regular shock in the place of the PDS. Many companies designed links and dampers to replace the rotary damper on Suzukis. It seems to be that the cost to modify a PDS is getting to be that expensive that this must be a viable option.

 

[Muzza]

When someone finally gets the PDS working properly, they will hopefully be able to sell the concept on to WP / KTM and you'll be able to buy a "working PDS" off the shelf with your next KTM and not spend megabucks going around in circles with tuners who can't agree on anything much at all.....

To be honest, I for one don't really want another linkage bike - it takes a whole 3 minutes to pull the shock from the Katoom, and there's one more pain in the a$$ job (lubing linkages) that is needed.

If some of the frantic activity that is going on with the likes of Terry Hay, MX-Tech, Precision Concepts & Novation produces a working PDS then the world (the KTM world at least) will be a much better place.

Just don't take too long guys, because the KTM linkage rumours are already flying.....

Muzza

 

[terry hay]

There are so many people out there now with KTMs who would like a nicer shock without spending the world to get it. A new needle will be cost effective and simple to install. Ron Jacobs from KTM in Holland is keen on this idea and sees the potential. Perhaps it's not so far fetched and perhaps its possible to achieve a similar effect to that of a linkage shock. We test next week. I'll keep you posted.
Terry

 

[marcusgunby]

Anything that mimacs the rising rate of a good linkage , is a good thing IMO.I beleive the problem with the pds is the spring rate/damping doesnt rise like on a linkage bike.It has small progression in spring rate and a huge rise in damping for a small change in travel.

 

[terry hay]

Well I now have the new needle. 30mm longer than stock with a taper that should ensure a smoother transition. Hopefully this will at least get us a step closer.
Terry