low and high speed damping

[InsideLineModels]

Originally Posted by MRD

The easiest way to make a piston with different bump and rebound is to have a piston with 4 holes in it with a reed valve on the top covering two of the holes. Going up the valve would be forced shut so only two holes are open, going down the valve opens and all four holes are open.

Its as simple as a disk of rubber clamped to the top of the piston using the c clip with only half of the holes in it that the piston has.

Easy peasy.

This is something that has been available on the Predator Shock absorbers for quite some years. I have to be honest, i've not played with it too much though.

I think the main use was in the front to slow the shocks on rebound to help stop the nose lifting on acceleration.

Kev

[The Pookster]

Originally Posted by InsideLineRacing

This is something that has been available on the Predator Shock absorbers for quite some years. I have to be honest, i've not played with it too much though.

I think the main use was in the front to slow the shocks on rebound to help stop the nose lifting on acceleration.

Kev

That was the original intention (I remember trying these with Richard Weatherley when he was developing the Pred in his back garden...), and to copy how road car dampers are set-up where there is more rebound to control the spring recoil force.

[JohnM]

Originally Posted by Apricot Slice

Are there any racers out there that would interested in more advanced shock absorbers?
(assuming of course that they would give you an advantage over the competition)

Whats the point? If it could be done, and If they worked that well, everyone would buy them, and then there wouldn't be an advantage

At least now, you can try/hope to get an advantage by setting your car up better then someone else.

[JohnM]

Originally Posted by InsideLineRacing

This is something that has been available on the Predator Shock absorbers for quite some years. I have to be honest, i've not played with it too much though.

I think the main use was in the front to slow the shocks on rebound to help stop the nose lifting on acceleration.

Kev

I'm sure that was something you could do on Supershot shocks back in 1986ish.

[Apricot Slice]

Originally Posted by JohnM

Whats the point? If it could be done, and If they worked that well, everyone would buy them, and then there wouldn't be an advantage

At least now, you can try/hope to get an advantage by setting your car up better then someone else.

Whats the point.. you said it :- "If it could be done, and If they worked that well, everyone would buy them"
Also it would be nice to be responsible for some technical advancement in a sport that i really dig.

[Chrislong]

Im with JohnM on this, well and truly.

Things like diffs - im for reducing maintenance/increasing reliability, going with gears etc (still tuneable though!). But for shocks, they should ALWAYS be tuneable.

If something was made, which was sealed, untuneable, worked everywhere and gave a massive advantage over what we have now (I don't see how btw, without re-writting rules of physics, cars handle great when setup well) - yes, we'd all have to use them to not be at a dissadvantage - but I personally would dislike that, and im sure many others would also dislike it. Id hope for the BRCA to not allow them - which id propose and attend AGM to vote on.

[Apricot Slice]

Originally Posted by Chrislong

Im with JohnM on this, well and truly.

Things like diffs - im for reducing maintenance/increasing reliability, going with gears etc (still tuneable though!). But for shocks, they should ALWAYS be tuneable.

If something was made, which was sealed, untuneable, worked everywhere and gave a massive advantage over what we have now (I don't see how btw, without re-writting rules of physics, cars handle great when setup well) - yes, we'd all have to use them to not be at a dissadvantage - but I personally would dislike that, and im sure many others would also dislike it. Id hope for the BRCA to not allow them - which id propose and attend AGM to vote on.

I think you kinda got the wrong end of the stick there mate. Maybe i didn't make the point clearly.

I'm pretty sure though that if you had a shock absorber that behaved exactly like the full sized ones do only scaled down, then it would out perform any shock with a simple piston with some holes drilled in it. (even one that is well dialed in)
okay, so you may have to re write the laws of physics or something to prove it. but hay, it a hypothesis. Lets not take things out of context.

Actually I would vote the same way. If some magic shock arrived on the seen that were very very expensive it would make the high end of the sport inaccessible. which is not.. well, sporting.

As i said earlier, I think a better solution is possible with less than half a dozen easily manufactured parts and be inexpensive.
The design is quite simple and would allow me to adjust the shocks in the same way as usual and have some additional options.
The only big difference would be using bump stops to cushion landings instead of using pack.

[MRD]

I think the general idea of adjustable rebound shocks has been lost in this thread. Somewhere along the line these magic sealed ultimate shocks have been drempt up that will walk all over standard shocks, this is pure fantasy. Even with adjustable bump and rebound the oils and pack would need to be changed depending on the track, all it would do is improve the current setup, so if you cant set up shocks for toffee then they wont help.

As far as cheating, whats to say what is and isn't? Big bores seem to be the big thing at the mo and at £80 they are pricey and out of reach of some racers so do we ban these too?

If they could make these magic dampers then they would come with the top end kits so its a bit of a mute point really

[Apricot Slice]

okay MRD, so you think the idea of improving something floored is ridiculous and that i am a cheat.



If there is anyone interested in the development of shocks that work better than what is currently available or have something constructive to say, please let me know.

[James]

Are you going to make some?

Would this hi/lo business affect how a car generates mechanical grip through its roll centres? You need the body to roll in order to do this so how would a system treat the forces this would be applying? fast or slow? And if if there is a transit point between hi/lo where the shock stiffens/softens would this affect how the roll centre works?

The only way to know is to try it, ask any R/C company in the world - its great on paper but things can be totally different when tested on the track.

I'm all for innovation though..

[MRD]

Originally Posted by Apricot Slice

okay MRD, so you think the idea of improving something floored is ridiculous and that i am a cheat.



If there is anyone interested in the development of shocks that work better than what is currently available or have something constructive to say, please let me know.

Wrong end of the stick mate, I'm saying its NOT cheating. Please re-read my post

I am sayin that people worried that there will be an all conquering shock have nothing to worry about as it isn't going to happen, what will happen is that there will be improvements to standard shocks that will make them better but will still need setting up properly.

I used the big bores as an example of improvements that are happening right now which are expensive but still aceptable, in reponse to people that say expensive tuning options are cheating and shouldn't be allowed.

I'm all for improvements in the hobby.

Like I said, re-read my post.

[Apricot Slice]

Originally Posted by smOkin

Are you going to make some?

Would this hi/lo business affect how a car generates mechanical grip through its roll centres? You need the body to roll in order to do this so how would a system treat the forces this would be applying? fast or slow? And if if there is a transit point between hi/lo where the shock stiffens/softens would this affect how the roll centre works?

The only way to know is to try it, ask any R/C company in the world - its great on paper but things can be totally different when tested on the track.

I'm all for innovation though..

I have some designs that i think will be effective. whether i actually go balls out and commit myself to making parts and a test rig depends on if i can manage it on my own.

you have got some good questions there... blimey! where do i start.

first of all, slow speed.(slow speed damping is what we have on the standard shocks) that is the main part of the damping that is responsible for the pitch and roll effects on the chassis.
too soft and it gets wollowy and too firm and it gets bouncy and you lose the weight transference and traction etc. so somewhere in the middle keeps the tire where its supposed to be and maintains feel and response.
(typically 'pack' is incorporated into the shocks as its a very effective way of surviving landing impacts but has detrimental effects to the handling at speed when traversing bumps for obvious reasons.)

the slow speed damping would incorporate heavier damping on the rebound stroke. something like 60/40. (many full size cars have twice the damping on the rebound) its a starting point.
this 60/40 ratio is designed to maintain spring compression so that the 'average' ride height is maintained even wile the suspension is waggling up and down over ripples n stuff.

high speed damping. basically this is the opposite of pack.
imagine you are going at speed and you hit a bump. the wheel shoots upward at great speed as it goes over the bump, this fast movement makes the shock 'pack' and too much energy, too quickly, is transferred to the chassis.
this situation will unsettle the chassis and raise the average height and over continued bumpiness will have the buggys wheels off the ground.
high speed damping relieves the shock of this massive load by backing off with the damping effect and allows the length of the suspension to comply with the offending bump and maintain chassis equilibrium.

bump stops would have to be used in the absence of pack to survive heavy landings.

the aim is to improve ride height stability and to keep the tyres in contact with the ground. and if the shocks allow this, then the handling results should reflect your setup.

of course, the theories have to be tested. I would make a test rig to do this. i couldn't rely on my driving skills as they are not too good. i would have to find someone good to do track testing for me.

[Matt Airbrushing]

Thanks for such an informative post Apricot

So this could be acheived on an RC car with some sort of pressure relief valve for high speed damping? Either on the piston or as a bypass from one "side" of the shock to the other.

Very interesting thread

If you could make this work then it wont result in uber dampers that work everywhere but would make damper tuning much more complex.

[James]

high speed damping. basically this is the opposite of pack.
imagine you are going at speed and you hit a bump. the wheel shoots upward at great speed as it goes over the bump, this fast movement makes the shock 'pack' and too much energy, too quickly, is transferred to the chassis.
this situation will unsettle the chassis and raise the average height and over continued bumpiness will have the buggys wheels off the ground.
high speed damping relieves the shock of this massive load by backing off with the damping effect and allows the length of the suspension to comply with the offending bump and maintain chassis equilibrium.

I like this ^^

bump stops would have to be used in the absence of pack to survive heavy landings.

I very much dont like this ^^

the aim is to improve ride height stability and to keep the tyres in contact with the ground. and if the shocks allow this, then the handling results should reflect your setup.

I like this ^^


Something that strikes me is the reference to full size cars, but you dont often see full size vehicles jumping 10 times their own height regularly on a race, the useable stroke on a full size car will be very little methinks compared to an R/C car, i would imagine the forces are exponential too ? Will the hi/lo work on such an extreme action?

[Matt Airbrushing]

I dont see why not.

It depends on how clever the shock design is.

The bump stops dont have to be solid, you could use secondary springs that are only used at the extremes of suspension travel, although this would negate some of the advantage of the high speed damping.

At the moment you are having to ballance damping between jumps, bumps and roll, so its all a compromise.
If you could set low and high speed damping you will still have to compromise, but you will have more options... and the possibility of a better setup.

[MRD]

The nearest thing I can see to 1/10 off road in the full size world is proper short course trucks, they seem to handle very large drops with an element of stability in the bends so maybe this scaled down would work?

[Matt Airbrushing]

Originally Posted by MRD

The nearest thing I can see to 1/10 in the full size world is proper short course trucks, they seem to handle very large drops with an element of stability in the bends.

Paris - Dakar rally trucks also face big drops and need good high speed handling.

Im not sure if these vehicles have anything unusual in terms of suspension setup, I wonder if we can find any technical information.

[SlowOne]

Fascinating thread. Couple of things to throw in the research...

First, it isn't the height the car gains that counts, it's the energy that you are trying to dissipate. Despite the height, the videos I've recently seen of Off-Road cars seems to show that, despite the height, the landing is quite soft, as you guys try to catch the downslopes of jumps and land the car like an aircraft. In those situations the spring/damper isn't doing a great deal of work.

Second, the main reason that this has never happened before is because whilst we can scale the size of the cars, we can't scale the Laws of Physics. All the ideas from full-size shocks rely on oils working in large spaces with large strokes, whereas we work in small spaces with short strokes. The basic characteristics of the oil remain, so, for example, the reaction time is slower relative to the movements of the suspension for our cars than a road car.

I tried the idea MRD wrote about with small flaps on piston holes back in the day. It did alter the compression/rebound ratio, but despite all sorts of testing, we never could get it to react fast enough, and eventually we abandoned it. I remain sure that the first person/company to crack a variable rate damper will sell their product like hot cakes, as it will improve handling and roadholding.

However, there will be no silver bullet, nor product monopoly - if there were only one killer way of doing it, there would only be one damper for all road cars, race cars and bikes. Since changing damper suppliers is a regular feature of race teams and road car manufacturers, it's clear that there is a lot remaining to be developed in damper world. There is constant change in the damper market, so once this is started, it will be the same in off-road RC. You might want a better damper, but be careful what you wish for!!

[Apricot Slice]

Originally Posted by smOkin

bump stops would have to be used in the absence of pack to survive heavy landings.

I very much dont like this ^^



Something that strikes me is the reference to full size cars, but you dont often see full size vehicles jumping 10 times their own height regularly on a race, the useable stroke on a full size car will be very little methinks compared to an R/C car, i would imagine the forces are exponential too ? Will the hi/lo work on such an extreme action?

Bump stops V's pack
because pack is effective for the most part of the piston stroke its effectiveness is hard to beat for a smack down landing.
It is something i have thought quite a lot about and have come up with various ideas like broaching the side walls inside the shock body to give variable damping but am not sure about the manufacturability of this.

your mention of not seeing full size cars doing massive jumps is a good point.
at tenth scale though, impacts from massive jumps are not nearly as destructive.

you can see quite a meaty bump stop nugget towards the end of this vid
these things take quite a bashing.
http://www.youtube.com/watch?v=3N-YOLjZg-8

Some folks mention the difficulty of setting up more complex shocks.
sure, it would make things more complex.
but its child's play compared to most normal motor sport.

personally i like all the technical challenges in r/c racing and would hate to see something dummed dowm because it might be difficult to understand.

[The Pookster]

Without question RC dampers could be much more advanced in terms of how the damping forces are achieved and in what direction. I also think it would not be too difficult to make some real gains on the track as it would improve the handling/large jump/bumpy track compromise.

But this needs to be developed carefully using real data as a guide and using real road/race car damper experience. Not wishing to upset anyone but it is plainly obvious on this thread that no-one has this understanding. I feel in a position to say this as I'm currently employed as a steering/handling technical specialist for a major car company.

Lastly, gains that could be made with the dampers would be at the expense of complexity, i.e. the number of options and interactions of damper internals would be so complex most racers would struggle to get a good balance. Sometimes keeping it simple means you get slightly less performance but for more of the time.