MC9 cooling blower fan dampers- are they needed?

[Zeke1]

Hello, I just bought a new pair of squirrel cage blower housings for my 1987 MC9, and they have swinging dampers on the bottoms, that would be under the blower wheels when installed. My old setup didn't have these. What are they for, and do they improve the efficiency of the blowers? I can't find anything about them in my manuals. Thanks for your help!!

[tekebird]

the dampers close when cooling is not needed.


they are a HP saving device as a Squirel Cage fan uses no energy if it is not pushing air, it just freewheels.

so the only HP needed to spin them is the HP it takes to overcome the friction in the drive system for the fan.

they were somewhat problematic  Most have been removed at some time or another

[Busted Knuckle]

Zeke1 sounds like Doug has wrapped it up in a nutshell!

Now if you wish to do away with the lower flaps. I'd be more than happy to pay for the shipping on them so that they wouldn't end up laying around in your way!   BK 

[Zeke1]

Am I correct in assuming that if the outside thermostatic louvers are not installed, that the dampers are not going to close anyhow, and therefore not needed?

[JackConrad]

Am I correct in assuming that if the outside thermostatic louvers are not installed, that the dampers are not going to close anyhow, and therefore not needed?

Yes, you are correct.  Without the actuators, the flappers will not close.  Jack

[gumpy]

Am I correct in assuming that if the outside thermostatic louvers are not installed, that the dampers are not going to close anyhow, and therefore not needed?

Not necessarily. They are controlled by the same shutter stats, but they are separate circuits. However, if your bus didn't have the cold weather package, you probably don't have the actuators anyway, so they're basically useless. Bolt them in the open positon and forget about them.

[buswarrior]

Hello Zeke.

Depends on where you are going to be operating the coach.

If you have some winter operation ahead, you will want some part of the shutters and or dampers working in order to maintain engine operating temperature.

You won't be able to get any heat out of the defroster or coach heat, if still equipped, without running the coach hard, and it will cool quickly when in traffic or stopped.

If staying where the air is above freezing, it doesn't matter, and in the desert, all the obstruction you can remove from the airflow to the rads is a bonus, strip it all away.

The "economy" aspects regarding horsepower consumed by the fans are a fine academic discussion, but from what I've watched, a practical myth. Drive alongside the old two stroke dogbus out on the highway in winter, and the system is open while underway, closing in relation to how cold it is when you exit the highway and take the load off the engine. So don't worry about losing fuel mileage with the system active, it isn't closing anyway.

The damper doors seem to be the more problematic of the two, the return spring in the air piston gets tired and won't pull the doors all the way open. Even an inch shy of full travel will cause an overheating condition in warmer weather.

In my MC8, I pulled the pins for the air pistons on the damper doors, left them hanging until I feel like removing them, so the damper doors are fully open, and I keep the shutters working. I find this is a suitable compromise. The fans are fairly weel obstructed on the intake side, and as a busnut rarely does the extensive idling to keep the coach interior warm like the previous owners did in seated coach trim, I don't need the complete isolation of the radiators that the system provides when working in concert.

A big Webasto coolant furnace ensures a speedy warm up under any and all Canadian conditions...

happy coaching!
buswarrior