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Q65A
Age: 66 Joined: 17 Apr 2007 Posts: 1769 Location: Central NJ
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Posted: Fri May 25, 2007 8:10 pm Post subject: Retarder & Interlock Info |
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From the JG website:
Retarder
Later model buses are equipped with a brake retarder system. The purpose of this is to give you additional braking power. However there are a couple of things to keep in mind. Under normal conditions you must operate your bus with the retarder in the “on” position. When the road surface is wet or icy the retarder must be placed in the “off” position. If the retarder is left on under these conditions you significantly increase the chances of putting your bus into a skid. There is a pilot light on the front left of every bus equipped with a brake retarder. It works on opposite logic.
Light on = Retarder off.
Light off = Retarder on.
By operating your bus with the retarder in the wrong position, you run the risk of getting a violation.
INTERLOCKING BRAKES
All of our buses are equipped with a modified interlock system. The interlock does three things when it is applied. It locks the brakes, bypasses the accelerator and opens the rear exit doors. Always apply the interlock when opening the doors in a bus stop. Once the interlock is engaged it is unnecessary to keep your foot pressed on the brake. In fact keeping the brake pedal pressed can be dangerous as you may disengage the interlock prematurely when the exit doors close. Just rest your foot on the brake pedal. This will also protect your knee and ankle from injury. When parked do not hold the bus with just the interlock. Only a breaker controls the interlock, if the breaker pops your bus can move. Always engage the parking brake. |
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Bill D
Joined: 17 Apr 2007 Posts: 332 Location: Waterbury, CT
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Posted: Mon May 28, 2007 5:24 am Post subject: Re: Retarder & Interlock Info |
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Q65A wrote: | From the JG website:
Retarder
Later model buses are equipped with a brake retarder system. The purpose of this is to give you additional braking power. However there are a couple of things to keep in mind. Under normal conditions you must operate your bus with the retarder in the “on” position. When the road surface is wet or icy the retarder must be placed in the “off” position. If the retarder is left on under these conditions you significantly increase the chances of putting your bus into a skid. There is a pilot light on the front left of every bus equipped with a brake retarder. It works on opposite logic.
Light on = Retarder off.
Light off = Retarder on.
By operating your bus with the retarder in the wrong position, you run the risk of getting a violation.
INTERLOCKING BRAKES
All of our buses are equipped with a modified interlock system. The interlock does three things when it is applied. It locks the brakes, bypasses the accelerator and opens the rear exit doors. Always apply the interlock when opening the doors in a bus stop. Once the interlock is engaged it is unnecessary to keep your foot pressed on the brake. In fact keeping the brake pedal pressed can be dangerous as you may disengage the interlock prematurely when the exit doors close. Just rest your foot on the brake pedal. This will also protect your knee and ankle from injury. When parked do not hold the bus with just the interlock. Only a breaker controls the interlock, if the breaker pops your bus can move. Always engage the parking brake. |
I have heard differing opinions regarding the use of the retarder during wet or slippery conditions. When we first operated retarder equipped buses, I tried to get an answer as to why the retarder should be turn off under certain conditions. The best response was from our Nova service rep who stated that under certain, rare conditions, if the bus was decelerating from a high speed with the retarder engaged, and the transmission downshifted, there could be wheel lock up. The policy to shut the retarder off was seen mainly as a protection from liability in case of an accident or injury. In practice, I have found it safer to leave the retarder on in slippery conditions. With the retarder on, as you begin depressing the brake pedal, only the retarder engages, and the bus can be slowed down to about 2 mph without the brakes actually being applied. When the retarder is shut off, only the brakes are slowing and stopping the bus. Since most buses have self-adjusting brakes, this increases the chances of the front wheels locking up on a slippery surface, as the front brakes are adjusted snug. Before we operated buses with self-adjusting brakes, our practice was to keep the front adjusters backed off slightly more than the rear during the winter months in order to decrease the chance of the front wheels locking up. The newer buses, equipped with ABS, do not require the retarder to be shut off under slippery conditions, and many transit authorities have eliminated the pilot lights and shut off switch in the driver's area.
I also find it interesting that it is recommende not to have the foot brake applied when the interlock in engaged. While in most cases the bus will not move, the interlock system usually only delivers 50 to 60 psi of air pressure to the brake chambers. We have found that on some of our steeper hills, this is not sufficient enough to hold the bus from rolling back.
Bill Dobkins |
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Pineywoodsbus
Joined: 26 May 2007 Posts: 68
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Posted: Mon May 28, 2007 5:24 pm Post subject: |
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Doesn't NYCT instruct that the retarder be turned off in summer, because using it causes the engine to overheat (I think this was an Orion V specific problem).
This is not done at LI Bus, which may account for all the probs they have in summer. |
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