Don't know much about the subject. However how big in diameter are bags?

Ralphy

Last edited by Ralphy (11/21/2013 1:52 pm)

I'm trying it like this. I have no experience and it's a long ways from trying it out. Using the lower shock bolt for support bracket and retaining the shock on the front side. Think I will need a way to overcome some give in the bushings of the shock and make the set up more solid.

These sleeve type bags came with the van body when I bought it. I don't think they they are an overkill by any means. Definately need a swaybar on the rear as it acts like a Weeble when aired up. Just figured if it doesn't work the way I like ,I'll go back to the coil overs. Right now it also has air over leaf springs up front. That's a little weirdness unto itself also. 

Hi guys,

I've been working in CAD a bit to make a plan, please shoot at this one:



The lower picture is the front view, with the dampers. The top one shows the air bags, unit seen from the rear. The centre of the purple pivots should be a hefty axle taking all torque of splitting the damper and spring forces.

[EDIT] BTW, with the current standard dimensions and my chosen wheels, overall width will be 1.800mm. I think I will need to cut down the arms and axles a bit... [/EDIT]

Cheers,

Hugo

Last edited by HugoW (11/25/2013 3:55 am)

The air bag shown in the installed view is called rolling lobe air bag not sleeve. Air bag is a commonly used slang and is not accually wrong however the correct term is air spring. The part of the air spring  mounted to the lower control arm in the first images is the piston. That type of air spring rolls over the piston as it extends and retracts. The technical drawings show double convoluted air springs. Just thought some terms needed to be explained.  I see more wrong names used for air springs than correct. Another point of intrest is most airsprings have virtually no friction.  Good shocks should always be used to prevent a ride quality that would make a kangaroo motion sick.  No insult intended, just thought you might want to know.  Nice drawings Hugo W but in the drawings with the airsprings, how would you fit a differential in there? Air shocks are designed to assist springs.   When used in place of springs, their life span is dramatically reduced. I have seen both rolling lobe and convoluted air springs built on shocks that looked quite sanitary. Typically rolling lobe airsprings have a smaller out side diameter than convoluted's do when compaired for equal lift. The rolling lobe design on average will also will provide more travel than convoluted airsprings.  The only convoluted air springs with three or more convolutions are only  available in sizes too big for light applications. I have yet to see three convolution springs smaller than 10" od. over the counter. There may be a smaller one on some salesmans desk but that would be a sample.   The big problem I have with air springs in a performance application is when you lower the ride height by dumping air the springs get softer. This gives the vehicle a mushy ride that is way too soft to go around corners effectivly. If this were a perfect world the air springs would get more firm as the air pressure was reduced to lower the ride height. This would translate to good lateral accelleration.  The bright side of this is that rolling lobe air springs are affected least by chenge in ride height by change in air pressure.  That is  providing you are not resting on the internal bump stop on the piston. Rolling lobe air springs have a basic design flaw that catches up with them sooner or later. The way the spring rolls up and down on the piston, rocks and road debris will get trapped between the lobe and the piston. This debris will slowly eat through the soft rubber bag and eventually ruin the air spring. Contact with suspension/frame and road debris are the most common causes of failure for every type of air spring.  They tend to like zero contact with anything. I have seen smoothe plastic air brake lines eat through air spring bellows. Zero contact!

Last edited by tyrellracing (11/25/2013 3:00 pm)

tyrellracing wrote:

Nice drawings Hugo W but in the drawings with the airsprings, how would you fit a differential in there?

 
The idea is to fit the bags behind the dif. And the shocks in front. I will make a top view drawing as well, when I get to it.
 

tyrellracing wrote:

The big problem I have with air springs in a performance application is when you lower the ride height by dumping air the springs get softer. This gives the vehicle a mushy ride that is way too soft to go around corners effectively.

tyrellracing wrote:

The bright side of this is that rolling lobe air springs are affected least by change in ride height by change in air pressure.

 
Eh, no. With equal load, the height of the spring is determined by the amount of air in the spring. Not pressure. Pressure is a result of the surface area of the air bags (the top and bottom disk, in my case) and the load. So unless the Mrs. stuffs her beauty-case in the back of the truck, the pressure in the bags stays the same regardless of ride height. Vice versa is true, too. If I don’t change the ride height and the Mrs. puts the case in the back, the pressure in the bags is adjusted, not the ride height. I worked a lot with these valves:
 

 

(Not my car, pics googled)

I used three of them, one in the centre of the solid rear axle of the vehicle, and one per front bag / wheel. So the front is kept level with the road. The rear is only on the correct total height, not necessarily the right height per wheel. These I have always used in full load applications, not as assists to coil or leaf springs.

Last edited by HugoW (11/26/2013 1:38 am)

I worked at a spring shop for years and have seen people make every mistake possible.  I have set up bell crank linkages on suspensions before. The bellcrank can become a torsion spring and fail if the input rod is too far from the spring down the pivot axis. When set up this way the bellcrank can fatigue and fail with prolonged use. I still like the entire concept of bellcranks to reduce unsprung weight. My personal discovery in their use was, there is a lot more involved in their application than just throwing it together because it looks right. I have had the rod that is loaded in compression between the LCA and the bell crank catistrophically fail. I broke a few bell cranks before I stopped making them from aluminum. These parts take a serious beating when you hit a pot hole. Strength of materials and performing some static summation of forces would be a good place to start. Just eye balling the design will get you in trouble. . Pull rods are more difficult to set up but fail far less often.  I had the impression that the images of the Air spring on the jag IRS were more of a study than a final design.  I am well aware of how to set load leveling valves and what they do. Are you aware that if you jack up a vehicle with air springs with out shocks or limiting straps, there is a very high likelyhood you will explode the air springs? The load leveler valves have a built in time delay plus they cannot dump air fast enough to prevent air spring failure. I have seen a Kenworth dump truck blow up all eight air bags by dumping the pay load and not hitting the manual air dump valve.  Load levelers would make the system use too much air if they were allowed to dump air every time the vehicle hits a bump. Most designs have an adjustable delay to prevent that from happening. The valve you posted looks like one of the non adjustable types but it will still employ an aprox. 3-5 second time delay. Even with the valve dumping as fast as it can, due to restrictors the release is typically slower than the fill.  This delay keeps the system from making any changes in the springs for say three seconds. if the arm returns to the home position before the three seconds is up no change ocurrs. if the arm does not return to its home position in time, a change will be made in air pressure. One of the things the web site you got your image from probably did not disclose. 

The air ride system you posted is a typical conversion package. The thick monoleaf is called a "Z" spring and  will attach to the front spring eye hanger. This type system was intended to convert from leaf  to air spring. The "Z" springs are used by air ride on the 1 to 5 ton conversions. The Z tapers from the axel th where they wrap it in a eye for the front mount. This configuration would twist the axel housing when articulating if the "Z" springs were not tapered. The taper allows some degree of give. This design also uses a panhard rod and that is a failure point of the system. The U bolts will not allow the springs to pivot on the axel housing yet since the panhard rod demands the axel housing to move in an ark. The two lincages are not compatable and the U bolts will work loose in a short period of time. That is the flaw in the Air ride design. Other truck manufacturers use this same system and they all suffer erosion of their spring perches due to twist of the "Z" spring as the axel is shifted side to side by the panhard's ark . It is impossible to get U bolts tight enough to prevent this from happening. In a perfect world this would not be as common of an issue but most vehicles that use air will have leaks. Leaking systems will bleed off over night. The load leveling valve will sometimes hold but usually will not. They were not designed to hold air from escaping back to the resivor. When the vehicle looses all of its air the axel will settle on the frame. Not good!  Either the pan hard or the U bolts must fail when it binds. The "Z" springs are brutally tough and typically never fail.  I have also seen the front spring hangers torn off the frame in 1 ton truck applications. A watts link would have solved this but we were not allowed to change their design because it would void warrenty.  I have installed hundreds of Airide systems in new trucks and then had to deal with the headaches of bad designs comming back to haunt me.

Nealing systems were my speciality. I got pretty good at making them work. Still like the Wabco stuff we used back then. We built some pretty wacky protos and used to race them on the narrow roads behind the factory, "to test stuff". Too bad the company went bust, pure missmanagement.

And I was the only person in the comany the could drift (like counterstear oversteer action) with an articulated bus. Ours had the drive in the rear section, pushing the rest. I did so unvoluntarely one morning when the roads had iced up, but it sure looked good the bystanders told me. I was happy to get out and have a cup of tea...

Hugo

Last edited by HugoW (11/26/2013 1:34 pm)

Hi all,

just changed the topic name, as I have plenty more questions and don't want to start just al many topics. OK next question. I have been drawing the suspension to fit the width of the truck / frame:





The top is the original width, the bottom is narrowed 200mm / 8 inches, half on each side of course. This seems quite a lot to be cutting out. It also required repositioning of the suspension pick up points, as shortening only between the dif and the pick up points would change the ratio (arm of the force). So, I think I will fabricate new LCAs, just to be done with it. This also means I can move out the dampers / springs / whatever I chose to use a but. And that in turn means I can makedrive shafts using 1410 weld yokes and 3" tubes.

So, eh, OK, major rework of the unit, but that was to be expected. Bit disapointed Jag didn't design the unit so it would fit a 1929 Chevy truck... They should have known sooner or later I would try...

Please shoot at the ideas, mention the gremblins I overlooked, etc.
Cheers,

Hugo

Last edited by HugoW (11/28/2013 8:43 am)

tyrellracing wrote:

I am guessing that your set up has the shocks mounted in their stock location at presant.

 
Nope:

HugoW wrote:

It also required repositioning of the suspension pick up points, as shortening only between the dif and the pick up points would change the ratio (arm of the force).

 
 
BUT, STOP THE PRESSES:
I was just offered 4 rims of the style I like for 50 bucks. Yes, 50 total for four. They are 7 inch wide, 15 diameter, Jag bolt pattern, ET 27mm. So, that is 27mm less to shorten. My IRS unit is about 60”/ 1.524mm wide flange-to-flange. Fitting these rims, the outside dimension will be 60” + 7” – 2x27mm (are you still with me?) = 1.650mm = 65” wide. Sounds pretty good to me!
I was previously calculating with 10” wide wheels, but these 7” ones with a little wide tires on it should give a nice look, I think.

[img]http://i.marktplaats.com/00/s/NzY4WDEwMjQ=/z/SlkAAOxyTjNSkNdT/$_85.JPG[/img]

Please tell me my calculations are correct. This would mean no shortening of axles, LCAs, or anything. Hurray!
 
Cheers,
 
Hugo

Last edited by HugoW (11/29/2013 6:21 am)

Nothing like a good case of Attention Deficit Oh Shiny!

303Radar wrote:

Nothing like a good case of Attention Deficit Oh Shiny!

 
Amongst other things, sure! I'll google what it means, my English runs out, here.

I am not very good at planning, things get more clear once I gathered parts and I assemble them. Once I fitted the rims to the axle, I saw widening inwards was no option. So I need to widen them outward, and therefor I probably need to narrow the axles. Once the thing was assembled in front of me, it was so much more clear what to do.

Cheers,

Hugo

Last edited by HugoW (12/03/2013 7:39 am)

Ah, oh, well, no. The shiny-ness has nothing to do with it, actually. They will be powdercoated. But they are the type of wheel I wanted, and dirt cheap. I found Attention Deficit Disorder on WIKI by googling; yes, fit's the bill.

On topic; both LCAs are off. I am very happy with how this axle comes apart, it was obviously well maintained. All nuts and bolts were really tight, but ones losened it all slid apart easily. I will clean the LCAs tomorrow and see about the square tube possibility. I'll try to get some pictures of the details and maybe a sketch of the idea.

Cheers,

Hugo

Last edited by HugoW (12/03/2013 7:44 am)

Hmmm, little response to that... Bummer.

Anywho, today I went back to the IRS and fit two rims. Then I alligned the LCAs and axles as per driving conditions, and measured. I was a bit surprised by the findings, but checking the rims shows they are 8",  not 7. And the offset is slightly different than quoted. I redrew the IRS in CAD to show the proper rim dimensions and rim distance from the center, and the distance between the upright and the centre of the axle. I am glad I did not make any cuts, yet...

I don't think the rims are a bad buy. They are the model and diameter I wanted, and the inward part is as close to the upright as it could be. Widening inward is no option, so that part is perfect. I do want to enlarge to 10", so I only need to add 2" to the outward part.

When tearing apart the lot I made a very nice discover. Although a bit dirty, the brakes are near mint. They seem to be overhauled only just before the IRS was removed from the car. Yeah! I carefully cleaned them and put them in bags.

All is now in pieces in boxes and plastic bags. I hope my truck will finally arrive, we're about 6 weeks past the original due date now. I know all reasons, but I like to see the thing and start taking measurements for the sub frame I designed.

Cheers,

Hugo