Aftermarket Air Bags Anyone ??

[jharrell]

Originally Posted by tripntx

I just downloaded iDynamics from google store.
https://play.google.com/store/apps/d....sdt.idynamics

Googling 'smartphone vibration sensor' led me to this page
https://www.sciencedirect.com/scienc...77705817340614

So, I opened the PDF, and started reading the 6 page paper, which led me to download the app from google play
https://ac.els-cdn.com/S187770581734...40d81eff882676

I am interested in running the app with minimum air pressure installed in bags, and then repeat with whatever air pressure my ears & butt dyno determine is best. It will be interesting to look at the recorded results across the same stretch of road.

Any advice on where my smartphone should be secured during the test?
I was thinking about taping my cell phone to drivers window or dash so I could easily stop and start the app.

I use Vibration Version 2 and later but is is for iOS only unfortunately.

It best to secure the device to the most rigid place you can including removing shock absorbing protective cases. You want to measure vibration in the structure of the vehicle and not dampened by thing like seats and cases and other isolators.

Taped to window or dash should be pretty good. I did kitchen counter because my wife was driving at the time for the vibration analysis. I have't done testing with suspension mods yet although now my interest is peaked again I may do it with the sway bar to have some fun.

[TeJay]

jharrell,

Please take another look at your post #74. Compare that to your drawing on post #77 above and compare to the bottom left picture. Your link is in the worst position to apply forces to a lever. It will exert the most force on the bushing as opposed to the actual lever.

The lever we are dealing with is the length of the arm coming out of the SB bushing not the length of the link. The link length is changed to alter or correct the steep angles created when the bottom of the link is moved 3" inward which also requires the SB to be raised up.

Changing the link length does absolutely nothing to the lever in question. You made a similar comment on another thread and I just thought you made a mistake. Now you're making it again so you must believe it.

When the link bolt is moved from stock to the inner position the lever in question is shortened 3". If the lever is shorter the same applied force moves or twists the SB less. That's why & how the SWAY control system works.

The CHF changes the length of the lever arm coming out of the SB bushing. Increasing the link length only places the angle closer to its stock position. Lengthening the link puts the angle closer to 90 degrees which allows the system to work more efficiently. If the link is made longer the system works more efficiently as you showed us with your drawings. And because the SB is not raised any with a longer link your wheels don't come off the ground as soon during leveling. Many, many posters complained about that happening throughout the CHF thread.

You showed us all how easier it is to apply forces if the angle is closer to 90 degrees. So why not make your applied forces closer to 90 degrees when being applied to a lever?

I'm aware of at least three RVs driving our roads who have three SB installed and none of them complained of increased harshness due to added SB's. Some have done the CHF and added even more SWAY control and still no harshness. If harshness is experienced I'm sure it's due to SB angles that are not close to 90 degrees. Did you not illustrate to us all how much more difficult it is to apply forces as the angles become less than 90 degrees?

[jharrell]

Originally Posted by TeJay

Please take another look at your post #74. Compare that to your drawing on post #77 above and compare to the bottom left picture. Your link is in the worst position to apply forces to a lever. It will exert the most force on the bushing as opposed to the actual lever.

NO that's not how it works my link is not in the "worst" position. The "worst" position is when the link and arm are at 180 degrees. The bushing always take all the force, they have to the force goes through them regardless of angle or lever length, it is impossible to apply force to the lever without applying the same force to the bushing.

Originally Posted by TeJay

The lever we are dealing with is the length of the arm coming out of the SB bushing not the length of the link. The link length is changed to alter or correct the steep angles created when the bottom of the link is moved 3" inward which also requires the SB to be raised up.

Changing the link length does absolutely nothing to the lever in question. You made a similar comment on another thread and I just thought you made a mistake. Now you're making it again so you must believe it.

The link length changes the angle, the effective lever arm length is the physical arm length multiplied by the sine of the angle. Link length most certainly changes the lever arm effective length as given by the well know mathematical formula which you seem to be ignoring. It changes the effective length whether you or I believe it. Maybe a teaching video will make it more clear:

https://www.youtube.com/watch?v=_HuxmF_1Z90

Originally Posted by TeJay

When the link bolt is moved from stock to the inner position the lever in question is shortened 3". If the lever is shorter the same applied force moves or twists the SB less. That's why & how the SWAY control system works.

That's how levers work, the shorter the lever the less torque is applied with the same force. The more the angle deviates from 90 degrees the shorter the effective lever gets, and therefore the less torque is applied.

Originally Posted by TeJay

The CHF changes the length of the lever arm coming out of the SB bushing. Increasing the link length only places the angle closer to its stock position. Lengthening the link puts the angle closer to 90 degrees which allows the system to work more efficiently. If the link is made longer the system works more efficiently as you showed us with your drawings. And because the SB is not raised any with a longer link your wheels don't come off the ground as soon during leveling. Many, many posters complained about that happening throughout the CHF thread.

The CHF is about making the system work less efficiently, the less efficient the system is at twisting the sway bar the less sway will occur. I don't like using the word efficient because its not accurate, but I am trying to use your terms.

Originally Posted by TeJay

You showed us all how easier it is to apply forces if the angle is closer to 90 degrees. So why not make your applied forces closer to 90 degrees when being applied to a lever?

Because like moving the link further out to stock it makes the sway bar easier to twist increasing sway. I think it feels pretty good now and don't want to soften it up by leveling the connection back to 90. Nothing wrong with doing so your just doing a 3/4 CHF instead of a full CHF.

Originally Posted by TeJay

I'm aware of at least three RVs driving our roads who have three SB installed and none of them complained of increased harshness due to added SB's. Some have done the CHF and added even more SWAY control and still no harshness. If harshness is experienced I'm sure it's due to SB angles that are not close to 90 degrees. Did you not illustrate to us all how much more difficult it is to apply forces as the angles become less than 90 degrees?

Again the more difficult to apply force the less sway you have, this is the whole purpose of the CHF to make it more difficult to twist the sway bar. If you think it adds no harshness, then drill a hole as close as you can to the bar on the arm and connect the link there but keep the link at 90 degrees and tell me how its not harsh I guarantee you will have no sway.

[tripntx]

On my 2001 Tiffin Allegro Bay 36DB, the frame to top of u-bolt measurement is 4.75", and the bottom of bump stop to top of leaf spring is 3".

I installed the air bags today, but it was well after dark when I finished, so no air bag pics until tomorrow.

[WDW]

Wow what super technical knowledge! Not to be a PITA but why air bags over Sumos to improve the ride? Can you do just the front or do you have to do front and rear?

[jharrell]

Originally Posted by WDW

Wow what super technical knowledge! Not to be a PITA but why air bags over Sumos to improve the ride? Can you do just the front or do you have to do front and rear?

Air bags are adjustable, Sumo's are not they fulfill the same role as a helper spring by bolstering the existing leafs springs. Sumos do not have to be maintained, air bags pressure needs to be monitored and replenished periodically.

You do the front and or the rear depending on whether the front or rear or both needs more spring rate to provide you with a improved ride. I can't really answer that.

[TeJay]

If you've read this thread you know jharrell and I have different conclusions regarding the addition of air bags. I'm not the only one who feels there is some improvement with air bags.

ga traveler is a contributor on this thread. On thjis and other threads he's reported while he was a service manager at an RV dealership in FL they would drive the customers RV down a very rough state road in the area before they installed air bags and after they installed air bags on 12+ different RV's. They all reported a ride improvement after the install.

Did all 12+ have the same placebo result? Did they all feel since they spent $600 plus labor then it had to feel better? Draw your own conclusions.

All I can tell you is I added front AB's and the ride is softer. Next week I'll add the rear AB's. In the end it will cost us $650.

I didn't spend $7,000 for the Kelderman air ride nor did we spend $30,00 for a new DP and the ride in our opinion is a better.

It's a gas RV built on the F-53 chassis leaf spring suspension with solid front and rear axle. There's 1,000 and 1,000 and 1,000 of these F-53 RV out there. We are done and this is the best ride I can afford. It is what it is!!!

[tripntx]

Originally Posted by tripntx

On my 2001 Tiffin Allegro Bay 36DB, the frame to top of u-bolt measurement is 4.75", and the bottom of bump stop to top of leaf spring is 3".

I installed the air bags today, but it was well after dark when I finished, so no air bag pics until tomorrow.

Front air bags installed.
Measurement between bump stop to leaf spring as follows:

0 lbs air, 3 1/2"
10 lbs air, 3 3/4"
20 lbs air, 4 1/8"
40 lbs air, 4 3/4"

Believe I'll start out 70 lbs in the rear, and 40 lbs in front.

I use extended one piece (non-adjustable) aftermarket links with my CHF mod.

BTW, contrary to appearance in picture, the bump stop does not touch or interfere with the air bags.

-

[Rossi6998]

Nice... Appreciate the pictures and measurements. I always wondered what type of difference you would get when you increased air pressure.

[jharrell]

Looks like my front is 6 3/4" Frame to top of U-bolt. Bump stop is 3 1/4" so 3 1/2" travel to bump stop.

Yours definitely seem low at 4 3/4" frame to u-bolt, your bump stop is much smaller too. I believe they went to longer more progressive stops in 2008. Not sure if they increased travel at some point.

Around 6" makes sense for my 550lbs inch leaf springs it take about 6" of compression to support 3500 lbs two springs 7000lbs which is my axle rating. That gives the spring 12" of travel with it sitting right in the middle at rest.

[jharrell]

I went ahead and raised my front end off the ground using jacks and measured to see how far the axle can droop and if the CHF limits it. I know not very safe, I typically make it a rule to stay out from under the MH when only the jacks are holding, but this is for science.

Results 10 1/4" from u-bolt to frame or 3 1/2" down travel.

I am not sure if the CHF is limiting down travel its close but the link angle is still not to a full 180 degrees with lever arm, the shocks may have hit their limit first. One side of the sway bar is making is making contact with the leaf the other is not, this did not make sense to me until I remembered the track bar.

The factory track bar is set to center the axle at normal ride height, as the axle moves up and down the track bar pivots creating an arc causing the axle to shift side to side. As the suspension went down the track bar pulled the axle to one side causing the sway bar to make contact on one side and not the other. Incidentally this is why Watts linkages are preferred over track bars they don't pull the axle side to side when the suspension moves up and down. Another concern if your changing ride height with air bags. When changing ride height in Jeeps more than a couple of inches with lift kits adjustable track bars or modified brackets are used to properly center the axle.

Tomorrow I hope to have the time to undo the CHF and check down travel again and see if the CHF is limiting down travel and by how much.

[tripntx]

Just returned from a 20 mile round trip highway test drive.

42 psig in front bags
70 psig in rear bags

8 mph direct crosswind onto side of MH

The ride is different, but better for me.
Wind didn't cause sway, or bad push like it did before.
It was easier to drive with the crosswind, and I was able to maintain lane. Pre-air bag crosswind driving had MH moving from center line to shoulder line continuously. Post-air bag install was easier.
Road imperfections are still felt, but not as harsh as before.

Suspension feels firmer and springier at the same time.

I'll wait until after I have driven it several hundred miles before say much more about it.

[twinboat]

Originally Posted by jharrell

I went ahead and raised my front end off the ground using jacks and measured to see how far the axle can droop and if the CHF limits it. I know not very safe, I typically make it a rule to stay out from under the MH when only the jacks are holding, but this is for science.

Results 10 1/4" from u-bolt to frame or 3 1/2" down travel.

I am not sure if the CHF is limiting down travel its close but the link angle is still not to a full 180 degrees with lever arm, the shocks may have hit their limit first. One side of the sway bar is making is making contact with the leaf the other is not, this did not make sense to me until I remembered the track bar.

The factory track bar is set to center the axle at normal ride height, as the axle moves up and down the track bar pivots creating an arc causing the axle to shift side to side. As the suspension went down the track bar pulled the axle to one side causing the sway bar to make contact on one side and not the other. Incidentally this is why Watts linkages are preferred over track bars they don't pull the axle side to side when the suspension moves up and down. Another concern if your changing ride height with air bags. When changing ride height in Jeeps more than a couple of inches with lift kits adjustable track bars or modified brackets are used to properly center the axle.

Tomorrow I hope to have the time to undo the CHF and check down travel again and see if the CHF is limiting down travel and by how much.

Attachment 236583

Attachment 236584

Attachment 236585

Attachment 236586

That side to side movement is more pronounced with the shorter rear track bars.

Having them attached high above the axle centerline also causes them to limit sway.

[jharrell]

Originally Posted by twinboat

That side to side movement is more pronounced with the shorter rear track bars.

Having them attached high above the axle centerline also causes them to limit sway.

That's why I prefer sway bar bracket mount rear track bar on the F53 to diff mount as it allows a longer arm.

Ah yes raising the roll center, I always forget that when talking about the advantage of a rear track bar, it might be just as important as locating the axle on a MH and why adding a rear one has such a noticeable effect.

Its also another thing to consider when raising the ride height with air bags