| Author | Message | ||
| Sojourner (Jjimage)
Rating: N/A |
Pass post regard to four points air-bag lifting to level. Naturally it will raise more height if per say to add more air pressure to right or left front on higher ground plane then same side rear wheel at lower ground plane. What you are doing is bottoming out shock absorber or with-out shock will over stress (pulling) rear air bags, another word trying to lift rear tire off of ground of lower plane. Like I said in pass post, you are gambling when it will crack or trouble with window binding or door. Take a shoe box with top test. 1) 1pc shoe box with top = Coach body 2) 4pc of checkers (game of checker) = level ground surface 3) 4pc of checkers = wheel with tire 4) 4pc of checkers = air bag at maximum air pressure Put one (1) “wheel” checker plus one (1) “ground surface” checker under box at each corner to simulate rear duals and front wheels of your coach on flat table. Now you have a coach at lowest level (no-air in bags). Let say maximum air bag or shocks is bottom-out by adding “max air bag psi” checker between body and “wheel” checker. There you have it (with three checkers in each corner) of “All air up” four points manually. Now you want level your box (coach) in unleveled ground plane. To simulate this, you remove one left rear “ground surface” checker from “dual-wheel” checker. Now it causes uneven pressure of four points. Result will be that two diagonal points will have all or nearly the combine pressure (weights) of total coach weight. Another word the other two points will be zero or must less pressure (weight). Which mean, you are straining the body to twist. More so when it a rear engine pusher (heavier then front end) with one of front bag trying to level coach. That why all pusher use rear bags to side-level coach in parallel with pave surface while driving. It may not happen quickly but in time under these conditions it will eventually twist some or crack frame or LOOSEN RIVETS. Sure it will have un-even pressure points while driving over un-even surface but its body is engineer designed to with stand momentary flexing. Now there maybe better ways to explain the law of reaction, anyone is welcome. Clarke Echols…if he will, I believe he can explain it better. If you want a safe manual three points and still higher than air-bag lift in rolling area, go for four points hydraulic lift with equalizer. Equalizer means all four points is no-greater load than wheel on level surface. Sorry about the long details but I care about some of you not knowing what going on when using 4 points manual air set-up. If you already have “4 points-airs” then be sure both front air bags are at equal gauge pressure after rear is side-leveled. Coach body is in relaxing stage. For what it’s worth. Sojourn for Christ, Jerry | ||
| James Maxwell (Jmaxwell)
Rating: N/A |
A minor correction. All hi-way coaches do not side to side level with the rear air bags, they use the fronts, ie. Neoplan and as I recall, an RTS that I saw (don't know if that was original or not. My Neoplan has 1 leveler valve for 4 rear bags, 2 mounted outboard on tags and 2 mounted inboard of driver wheels; individual valves for fronts, with IFW suspension and independant tags, each. However, I agree w/you on the hazards of 4 point leveling. | ||
| John that newguy Rating: N/A |
And of course, the Eagle being of the same type integral frame/body design, never used leveling. Yet, with all the twisting during normal use, no windows fell out... | ||
| John that newguy Rating: N/A |
Say..... anyone know what happens to the bus's structure when it's jacked up and blocked? | ||
| Sojourner (Jjimage)
Rating: N/A |
About Neoplan with 4 points leveling, either they have flexible body to twist or over-structure designed build coach or uneducated structural chassis engineer. Then if it fast recovering air differential, it will drive squirrelly on wavy pavement. Flexible coach body will need four points leveling system. However it would not be my choice for motorhome. About jacking points, normally you only jack up enough to remove a wheel at factory jacking point. Which mean the OTHER same side wheel is still pressure on ground to booster your jacking. Sojourn for Christ, Jerry | ||
| Sojourner (Jjimage)
Rating: N/A |
Correct my pass post about "Flexible", I wasn't regarding to brand name's Flexible. I am regarding to coach that flexible if there is any. Sorry for confusion. Sojourn for Christ, Jerry | ||
| Brian (Bigbusguy)
Rating: N/A |
I still say if you try to level with the rear only and have the front with air at the same PSI . How is the bus not going to have a twist in it when you lower one rear corner and raise the other. And leave it that way for days or more when parked? I think what Jerry is saying: "If you already have “4 points-airs” then be sure both front air bags are at equal gauge pressure after rear is side-leveled " Well that will not work if your bus is leveled in the rear from side to side . You will have your front air bags at differnt hights if you look at the gauges when you lower the right rear you let out air and the right rear PSI goes down as so does you bus now your bus is leaning to the right. But here is where he is wrong . The right front air bag is comperssed trying to push the right front corner back up and the PSI is higher. So what you end up is RR at a lower PSI and RF is at a higher PSI and you bus will be in Which mean, you are straining the body to twist. Now with a 4 point. Put the same PSI on both RF and RR and a lower of higher on the LR and the LF no twist the bus leans and you leveled side to side. Some people keep talking about the 3 leg stool. Well my bus has 4 legs , Wheels on all 4 corners. I would like to see there bus that like the 3 leg stool with the one front wheel in the center. Im not trying to sell any thing so my posts are from what I have installed and know works. 3 point will work but I think 4 point works better and will put less stress on you bus. I would go out and get some air PSI numbers when leaning my bus but Im redoing my dash and front floor and my air system is partly taken apart. But I will get some numbers and will go the the local scale and see how the wieght changes on all 4 corners when leaning using a 3 point VS 4 point. If any one wants a clear pic of my air schamatic and any info send me a email Il send it. Its a all air switchs and air lines no electric valves.  Brian 4905 Klamath Falls | ||
| t gojenola
Rating: N/A |
Brian, If I may jump in here, I think you may be missing one important concept. In the factory installed three point system, the two front sides are actually only one system. This is because the right and left bags form a single volume of air. If the left rear system leaks down, the whole bus will lean to the left but the pressure in all the front air bags will be the same, as will the weight registered on each front tire. Air simply flows from one side to the other to equalize. If the bus is parked on a very uneven surface the situation could arise where one of the front sides could go all the way down to the bumper while the other was still suspended by the air bags. In this situation, and only in this situation, would any twisting effect be present. In your weight test to be you will find that with three point leveling, under normal conditions wherein all air bags are actually suspending their respective parts of the bus, that both front tires will register identical weight. Any deviation from that will be due to whatever differences are present in the axle and its components. I do like the design of your leveling system and will likely employ something very similar for three point leveling on my 4106. regards, tg | ||
| Brian (Bigbusguy)
Rating: N/A |
Tj, Yes your right the factory system is tied togther and the the air PSI will balance out from right and left. What I did not explain very well is with air if one side is compresed there is less volume of air with and the other one is lifted up its acting like a air tank . The bags will try even out and the compressed one will push down more then the uncompressed side trying to level them self out. And if I could go to the scale to get some weights you would see but I will have to wait for a little while until I can drive it. Ether way 4 point or 3 point I dont think you will bend or twist any thing so 4 point is not any worse the the 3 point in making the coach do somthing it was not made to do . The 4 point just will give more travel.I agree with a 4 point system if you want to try you could air up the RR and the LF and deflate the LR and RF would be some thing I would not want to try but would it dammage the coach I think no. Not any more then going up the drive way at a angle my doors and windows dont pop out. If someones bus if flexing that bad there is more wrong with it then a level system. But with both systems if you over inflate the bags or over extend the travel you can dammage somthing. Any way go 3 point or 4 its easy to do with out lots of sharder valves wires or relays just a simple little valve I use the KISS system. Try this eBay number 7944040722 would be nice but the price is way out there Brian 4905 Klamath Falls Oregon | ||
| Sojourner (Jjimage)
Rating: N/A |
I like said before; If you already have “4 points-airs” then be sure both front air bags are at equal gauge pressure after rear is side-leveled. Coach body is in relaxing stage. “then be sure both front air bags are at equal gauge pressure” is performed like original system accept done manually. Factory equip a line connect both L & R front bags to a TEE to balance air pressure differential automatically. If you mean it will change psi at either front bag after you increase or lowered either rear bag….You are correct…..that my point about using 3 points instead of 4 points. Why go to trouble back & forth to front balance using 4 point. Save wasted time and fewer parts. Another word, three air psi gauge and three valves over the automatic road leveling system. Your drawing is good. Just now I read that Brian last post quote “The 4 point just will give more travel” unquote. Yes it lifts more BUT YOU WILL HAVE TWIST STRESS IN THE PROCESS. Do your self a favor, do the shoe box test as per first post. Trying to save future problem. Reminder…air leveling for rough camp ground terrain may be not enough adjustment to level unless wheel over board shims or better yet go for 18 inch hydraulic equalizer. http://www.equalizersystems.com/mh.asp No commission from them. Enough said from me. Wish you well! Sojourn for Christ, Jerry | ||
| Jon W. Rating: N/A |
We have had a Prevost since 1990 and they have leveling at only three points, using the rears for side to side leveling only. You can raise or lower the coach with the front or rear airbags, but you can only adjust the level side to side with the rears. I hope I explained that so it is understandable. There have only been a few occasions in the past 14 years where we had inadequate range of adjustment, and as a result we were forced to be a little out of level. The system is so simple and requires no additional componentry except for a few Norgren valves that it is an excellent means of leveling. Unlike jacks, if the ground will support your tires, you can level the coach with no boards or supports to prevent jacks from punching into the blacktop or soft dirt. You can detect some movement as you get in or out of the coach, but once inside you would never know you are supported by air as opposed to a rigid hydraulic jack. As far as worrying about flexing the frame, I have never seen any evidence of the shell flexing despite having often levelled the coach by fully extending one side air bags, while collapsing the opposite side. That may be attributable to the fact that only "three" points are used for leveling. Even if the front air bags are fully extended, as soon as one of the rear airbags is extended further, the coach will lean so instead of the frame being forced to twist, the air pressure in the front bags is increased as the low side bag collapses in response to the raising of a rear bag. Air bag extension is mechanically limited by the suspension components. The ride height valves that are operated independently of the leveling system, and are used over the road operate using exactly the same principle, except instead of leveling with respect to the horizon the ride height valves level with respect to the road surface. | ||
| gg04 Rating: N/A |
Done flamed once so might as well make another post. Had this same discussion 8 or 9 years ago think it was on Zane's board...I got talked into doing the testing.Buses used were a GMC 04 and 05. Go borrow or rent a set of portable scales,Run a string line down both sides of the coach from bumper to bumper using a body detail to aid in straightness,On level ground level coach front to rear,write down weights. Then raise one side let it down then the other...writing down weights...check the string lines for twist on all phases..2 move the bus to side ways on a incline..Scales must be leveled first before putting weight on..now do the same thing again...do this with three point and four point...I'm running four point...do the test and see what you think..Theory is great but does not always work in the real world...gg04 | ||
| Brian (Bigbusguy)
Rating: N/A |
OK gg 04 , What did your tests show? Id like to know. I will do the tests but will have to wait Im in the middle of redoing my coach. What Im going by is in leaning my coach using the rear with the front set as factory (3 point) And when checking the slope in the floor the front had less then the rear until I also lowerd the front on the same side and the trist went out it was not much but there was some. My plan was to drive to the scales and park the Right Front wheel on the scale and lower the right rear and see if the weight goes up down or stays the same I will leave the front set as a 3 point using the factory leveler control and staying off the axle bumber stops. And I think most coaches have some flex built in them if not things would crack . I guess we will need to have what the low rider cars do at there car shows and see who's bus can hop the front wheels off the ground , lean over the most and who can twist there coach and pop out the windows and doors  Brian 4905 klamath falls Oregon |