Simplicity Suspension

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Simplicity Suspension

Postby Craigandvanessa » Sun Jun 24, 2012 5:55 am

Hi all,
Is there any benefit and can it be done, in fitting shock absorbers to Simplicity Independent Suspension?????
Thank you in advance
Cheers Craig
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Re: Simplicity Suspension

Postby Powerstream » Sun Jun 24, 2012 8:36 am

I suppose you could say that any correctly fitted shock absorber must add benefit to most suspensions but I have never felt the need for them with Simplicity .
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Re: Simplicity Suspension

Postby PeteS » Sun Jun 24, 2012 8:44 am

No.
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Re: Simplicity Suspension

Postby Mike » Sun Jun 24, 2012 1:08 pm

Why?
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Re: Simplicity Suspension

Postby Iron Mike » Sun Jun 24, 2012 2:40 pm

Craigandvanessa
It may well be possible to attach dampers to the A frames but looking at the action of the suspension it would make it very doubtful whether you could even come close to getting the damping correct. The front and rear axle are connected meaning that whatever is happening to one axle the opposite is happening to the other through the pivot point of the chassis.

Looking at the more heavy duty varieties the spring is so heavy for it's length that the word suspension as an isolating the load from the road, maybe almost non existent at high speeds. To the best of my knowledge, and I am happy to be corrected, these suspension types of rocking beam evolved from agricultural machinery in the '30's. They generally have extremely good oscillation between the front and rear axle, but having both axles rise and fall together requires enormous loads.

As you have obviously picked up, this massive amount of energy storage is undamped and when released goes up through the pivot point into the chassis.

If you must use this type of suspension, it is advisable to pay attention to your tyre pressures and speed on poor surfaces, as in reality the tyres will actually do most of the suspending work.

As a personal preference the more modern trailing A frame with coil or air springing medium are vastly superior in protecting the van and it's contents, which after all is what suspension is all about.
Iron Mike
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Re: Simplicity Suspension

Postby track0r2 » Sun Jun 24, 2012 3:19 pm

Speak to N P Haufe in Melbourne, the manufacturer of Simplicity suspension. Their advice the last time I asked was not to use shock absorbers with their suspension system.

Peter
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Re: Simplicity Suspension

Postby Anythingonce » Sun Jun 24, 2012 6:41 pm

Springs and dampers do very different things. Can't understand why damping (shocks) might be considered unnecessary?
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Re: Simplicity Suspension

Postby gaz42 » Mon Jun 25, 2012 9:17 am

The answer I have seen most often to that question is that leaf spring packs have a certain degree of self-damping built in due to the friction between the leaves as the spring flexes. That answer is usually combined with advice that the leaf spring pack should not be lubricated (between the leaves) because it reduces the friction effect.

I don't know the accuracy of either of those answers - I do know that my tandem van with Simplicity suspension is not prone to bouncing along the road like I see many single-axle vans doing on seeming pretty smooth blacktop, presumably because of lack of damping.
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Re: Simplicity Suspension

Postby avro » Mon Jun 25, 2012 11:57 am

I suspect that the reason that some say not to use shockers on Simplicity Suspension is that they would also damp the rocking motion so could actually cause the paired wheel to the one that is hitting the bump to lose contact with the ground. That is it would help the wheel hitting the bump, but have a negative effect on the other one in the pair.

Regards avro
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Re: Simplicity Suspension

Postby Sterling Sal » Mon Jun 25, 2012 12:06 pm

Iron Mike wrote:Craigandvanessa
It may well be possible to attach dampers to the A frames but looking at the action of the suspension it would make it very doubtful whether you could even come close to getting the damping correct. The front and rear axle are connected meaning that whatever is happening to one axle the opposite is happening to the other through the pivot point of the chassis.

Looking at the more heavy duty varieties the spring is so heavy for it's length that the word suspension as an isolating the load from the road, maybe almost non existent at high speeds. To the best of my knowledge, and I am happy to be corrected, these suspension types of rocking beam evolved from agricultural machinery in the '30's. They generally have extremely good oscillation between the front and rear axle, but having both axles rise and fall together requires enormous loads.

As you have obviously picked up, this massive amount of energy storage is undamped and when released goes up through the pivot point into the chassis.

If you must use this type of suspension, it is advisable to pay attention to your tyre pressures and speed on poor surfaces, as in reality the tyres will actually do most of the suspending work.

As a personal preference the more modern trailing A frame with coil or air springing medium are vastly superior in protecting the van and it's contents, which after all is what suspension is all about.
Iron Mike


Good reply Iron Mike.

I notice Jayco don't use shockies on any of their tandem axle vans, including "Outback" models, with rocker-roller suspension. Your post makes sense as to why!

Do they use shockies on thier Simplicity Suspension? I don't know, but I don't think so. Seems to only be the single axle vans.

Cheers,
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Re: Simplicity Suspension

Postby Muizek » Mon Jun 25, 2012 1:16 pm

Sterling Sal wrote:

....Do they use shockies on thier Simplicity Suspension? I don't know, but I don't think so. Seems to only be the single axle vans.

Cheers,
Sally


On a Jayco Outback Expanda fitted with Simplicity tandem suspension as an option no shockies were fitted
Ray

Disclaimer: I dont profess to be an expert
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Re: Simplicity Suspension

Postby Iron Mike » Mon Jun 25, 2012 3:06 pm

To all
A limited reply to some of the points raised. Yes, leaf springs do have a degree of self damping but unfortunately most of it is on the compression stroke where it makes the spring stiffer without any weight carrying advantage. This is often why leaf spring vehicles have a rather rough ride. The place where the damping is needed is on the extension stroke but as the weight on the spring is decreasing so is the friction between the leaves and therefore the damping. Thus is why leaf springs have a catapult effect when there is no damping applied. The reason many caravans are revered to having good towing characteristics is nothing more than they are virtually suspension-less. The springs being simply too short and stiff to give any degree of flotation over anything but the smallest bumps.

I'm always bemused by the off road caravan mob as their suspension is often much stronger but nothing else, especially when the 4WD mob understood and embraced the logic's of long travel, well damped suspension to protect there vehicles and it's contents from damage 30 years ago.

The advent of a number of local manufacturers producing really good coil and air trailing arm set ups in about the last 5 years is the best thing to happen for protecting the van and it's contents for many, many years.

There is a gentleman called Collyn Rivers, who is a research engineer/writer and should be considered a national treasure by all caravanners. If you google his name, his selection of books will come up. If you go to the left hand column and click on articles there is a vast array of information. The very last one is called "Why wheels fall off". I would advise every single caravanner who has any interest in this area and all should to read and understand this article. If everybody did the many questions and misunderstandings which arise in the suspension area would stop.

Happy reading
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Re: Simplicity Suspension

Postby KGB » Mon Jun 25, 2012 3:18 pm

Our last caravan was a Golden Eagle with Simplicity suspension had shockers, it was not a tandem though.
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Re: Simplicity Suspension

Postby Motherhen » Thu Jun 28, 2012 10:54 am

In keeping with the advice given in this thread, the word from the manufacturers is

Our position on shock absorbers on Simplicity is that we would advise against fitting them.
They are not needed and will hinder the performance of the suspension rather than help it.
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Re: Simplicity Suspension

Postby Gone Bush » Thu Jun 28, 2012 11:08 am

I suspect that the difference in impact on the van from Simplicity or trailing arm, coil/shock suspension is minimal when dealing with a heavy van.

If a van weighs 3500kg or more, each type of suspension has to be very strong to support that weight over harsh terrain. I suspect that this strength in the suspension means that corrugations will be felt in the van no matter what type is used.

As mentioned, tyre pressures and speed become more important.
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