low and high speed damping
 

Hi all,
Does anyone have an interest in hi and low speed damping?
And got any ideas why manufactures have not come up with anything yet?
Apricot Slice

Our shocks at the moment have adjustable high and low speed damping... ?

err.. is that a question or a statement?

I think it's been done yet, RPM used to make "2stage dampers", and at the moment there's the popular high end brand GHEA, who makes the 'tapered pistons' for several 1/10 en 1/8 kits, for the same purpose (low in, high out)

http://www.rpmrcproducts.com/faq/pistons.htm

http://www.ghea.se/index.php

http://www.oople.com/forums/showthre...t=29087&page=5

It's a statement, the question mark was in case I had picked up the wrong end of the stick and you had meant a difference in the car speed or something like that.

Any r/c shock out there reacts differently in high speed and low speed damping due to the laminar and turbulent flow of the oil.

I have seen the rpm pistons. you can use them as they state in the instructions to give more damping on the bound stroke and less on the rebound. this will help out on landings from big jumps. It will not improve handling though.
Fitted up side down it would act like typical low speed damping on a full sized car shock.



""It's a statement, the question mark was in case I had picked up the wrong end of the stick and you had meant a difference in the car speed or something like that.
Any r/c shock out there reacts differently in high speed and low speed damping due to the laminar and turbulent flow of the oil. ""

Yes, of course. the flow of oil passing through an aperture at different speeds has different reactions.
Take for example a B4 shock, or even a Tamiya Hotshot shock absorber which has a valve in it.. its all low speed damping.
Please take a look at the link to understand better the term high and low speed damping.
http://www.blackartdesigns.com/id4.html

A few have tried staged springs also, thats never really seemed to catch on though.. yet

Nothing about at the moment that I know of that allows you to tune high and low speed damping independently.

There are pistons about that allow you to adjust bump and rebound independently, such as Ghea and RPM.

I'm just starting to work on this for the RC world starting with proper damper dyno characterisation of all the current different damper pistons out there, will take a while to get results.

I assume you are refering to something like the platform damped shocks used on mountain bikes - which actually originated on real offroaders. These use variable pressure valves on the pistons to make the shock massively stiff (due to being over damped) to slow compression forces (such as those in cornering or accelerating) , but can be very soft and smooth for fast impacts (such as a bump).
Perfected it would allow you to set the car really soft for riding over bumps, without fear of it pitching and rolling into corners.

Basically the technology is simple enough that it could be fitted into an RC sized shock, but it wouldn't be possible to fit external adjustments (as on mtb shocks) and it would have to be a sealed unit (no oil changes) so ulitimately its not as good as we have now.

What I'm talking about is shock absorbers that work as they should.
Shock absorbers that allow the wheel to ride over the bumps and dips and maintain ride height and keep the tire in contact with the ground. Shocks that will bound rapidly without pack or over resistance to cope with the big bumps at speed without launching the car skyward.
So yes. like mountain bike shocks, racing car shocks etc.

If some sealed shocks appeared, as if by magic, on your car, (shocks that perform as their larger brothers do) it would be highly likely that they would out perform the competition in all situations anyway and negate adjustment.

External adjustment and sealed units pressurized with gas would not be manufacturable and be extremely complex. not to mention wildly expensive.

But however, there is a way of doing it cost effectively and maintaining the ease of use.

This sounds very interesting. Are you testing just competition shocks. Any particular scale?
What kind of equipment do you use to test them?

I'm going to be testing an AE shock with bleed cap with a variety of pistons, AE, 1,2,3, LOSI, Ghea etc and oils to measure what the real differences are rather than any conjecture.

Will be done on a full size Roehrig damper test machine such as this:

http://www.roehrigengineering.com/Pr...r-research.htm

How about something like the British Leyland Hydro-spastic? With a single oil reservoir, it'd be nuts, crap, oh and nuts.

It is possible to create a shock absorber from magnetic fields rather than oils, and the possibility is endless. But for me some of the enjoyment comes from the tuning of things like shocks, to remove this would remove it as a tuning factor, and remove any reward for making the car handle extremely well.

I will be interested to see the results. especially the comparisons with with the larger bore shocks.

Will you be testing for durability also?

Personally I like innovations and new stuff that makes things better and faster.

You could take existing real car technology.
Put a solid piston in, have a valve (or 2 stage/twin valve set) at each end of the shock, adjust them to activate at different pressures. Run a tube from top valve(s) to bottom valve to create oil loop. This means you could have fast and slow bump and rebound. Not rocket science.

Probably more advancements to be made with the delevopment of a diff unit that could do away with the slipper assembly rather than such over engineered suspension. Micro Hydradrive that replaces idler gear????

I would like to see a diagram of that.

doesn't have to be over engineered. I think it could be done with less than half a dozen easily manufactured parts.

er.. what is a micro hydredrive?

is a viscous coupling. Actually that would have to be on the layshaft gear rather than the idler.

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. :lol:

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)

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.

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.

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

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.

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.

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 :lol:

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



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.

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.. :thumbsup:

:lol: 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.

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.

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 :D

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

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?

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.

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?

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.

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!! :)

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.

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.