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Steve Hirano
Administrator
2 Posts |
 Posted - 01/04/2001 : 06:24:11 AM
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I've been hearing complaints about the operation and maintenance of air-powered service doors and would like to put together an article for School Bus Fleet Magazine on how to deal with these problems. I'd like to hear from anyone who has input on this problem. Thanks.
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cowlitzcoach
Advanced Member
USA
325 Posts |
Posted - 01/05/2001 : 5:50:57 PM
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The original design of the door control mechanism will have a greater impact on problems than most anything else.
Any accordion/scissor type door will inherently have more problems than other styles.
The door with the fewest problems and the easiest to fix problems has to be the Crown Safety Door.
Having an electric control over the air control means the door opens with the push of a button. A driver does not have to worry about repetitive stress injuries pushing a button, or at least not as much as having to pull hard on a knob.
If the air system is not kept as dry as possible, problems can occur in cold weather with mositure freezing and not allowing the door to open or close.
The only other problem is adjusting the pressure to open and close the door. Most of the magic in knowing how much or how little pressure is the right amount is determined more by guess and by golly process than anything else.
Mark O. |
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larrym
Active Member
USA
13 Posts |
Posted - 01/10/2001 : 4:00:49 PM
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We purchased a new bus in 1999 with an air-powered entrance door. This was the first time in over 30 years of driving school buses to have a powered door. The bus had air brakes so the air powered door rather than electric door was the way to go.
I have driven Charter Buses for several years and most of them have gone to air-powered doors. It makes it much easier on the drivers.
When we picked up the school bus I was surprised to find the way the air switching was done for the door. It had a machanical valve to operate the door. If you wanted to exit the bus and close the door you had to open the door, go on the outside of the bus and flip the emergency open valve and then get back in and put the inside valve back in the closed position, then back outside and flip the emergency valve and the door would close. As long as air pressure is up above 60# the door will remain closed. Not a very good method. When you make five trip a day with short breaks in between you feel like your going in circles to close the door.
On charter buses you have a toggle switch on the inside and one on the outside, flip inside switch and door opens and flip the one on the outside and it closes and vise versa.
I looked over the opeation and found two double throw switches and a 12volt MAC valve corrected this problem. The MAC valve replaced the manual valve at the drivers seat and all other safety valves remained the same. I mounted the inside switch in same location as manual valve and the outside switch inside the fuel door area. Locking the fuel door locks the bus.
I also had some problems with the door opening and closing too fast (sometimes on a slow student) but the flow control valves, at the air cylinder, corrected this problem.
All in all I would purchase another bus with an air-powered door, but I would make the above change.
So far I have not had any problems with cold weather opeation of bus, We have not been above freezing since Dec 15th. I think the air dryers they are putting on the new buses have solved the moisture problems.
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wagonmaster
Top Member
USA
2298 Posts |
Posted - 01/19/2001 : 06:04:51 AM
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Hey Steve,
We buy every bus with air doors because each route includes three different schools/trips, and thats a lot of opening/closing entrance doors. Its another small thing we do for our drivers that helps them out(Anything to keep our drivers) and this also allows us to use sufferers of carpal tunnel syndrome on bus routes that we would otherwise have to pay workers compensation to, for them to sit home. maintenance hasn't been a real problem either. Our '98 Carpenter units are the poorest design, but good maintenance keeps them rolling without too much extra down time. Amtrans New large door is as smooth as I've seen and, so far, trouble free. Thats my $.02!
Joe |
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wrenchmen
Senior Member
USA
115 Posts |
Posted - 01/28/2001 : 1:13:59 PM
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Preventive maintenance of the air brake system is essential to extend the life of air operated components....air tanks should be drained at every p.m., air dryer dessicants should be changed once a year, Air compressor intake filters should be changed { some air intakes are plumbed into the main engine air filter}...if the system is not maintained, oil and moisture will find its way into components and create problems....When checking an air operated door, first you should check the manual operation of the door and make sure there isnt a mechanical problem that is causing the door to bind and not move freely...hinge pins on "jack-knife" style doors slide out of the hinge and drag along the lower step..Older units might require replacement or re-sealing of the air door cylynder...Check the linkage at the top of the door connecting the door to the air cylynder, make sure it has not loosened and come out of adjustment and that it works smoothly...
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Ed Allandar
Active Member
USA
18 Posts |
Posted - 02/02/2001 : 11:47:09 AM
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Steve-
Our fleet of 350+ buses is equipped almost 100% with air doors. Maintenance has not been a big issue. Our inital lack of maintenance training created some problems. We started specing air doors in 1990. The first 5 years we purchased Waynes with jack-knife doors. We had a few valve and air cylinder problems, however most of our problems stemed from mechanics turning up the pressure regulator (you know more is always better) rather than finding the root of the problem, lack of lubrication, binding or incorrect adjustment. We ripped some hinges right off the doors. Since 1995 we been buying 25-35 Thomas's a year, 1997 we bought Carpenter's. Double out doors are definitely the way to go. Haven't been having much in the way of maitenance problems. Biggest complaint we get is the need for the next generation door. The driver has no ability to just crack the door, insuring no students disembark before traffic stops, or have the lights actuate but the door not open till students arrive on a cold windy day. Let's face it the door is open or closed. Lubrication, adjustment and a clean air system are key, two out of three are required on a manual door.
Ed Allandar
Rohrer Bus Service
717.957.5114
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Topic |
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Air-powered service doors
