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Author Topic: Original bus heat blower speed  (Read 3278 times)
steve5B
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« on: January 22, 2008, 03:23:42 PM »

 
  Hello everyone,

   I have a 1975 MC-5B shell heat ducts have been removed, I was wondering is there a switch that can be installed to lower the 

   blower speed? It's either on full (will run you out) or you have to turn it off.  Can't keep it a constent temp!


  Thanks for any impute!


   Steve  5B........
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« Reply #1 on: January 22, 2008, 03:28:54 PM »

Origninally, there was a temp sender in the bus that would open and close an electric valve that would allow freshly hot coolant into the heater core and that is what would controll the heat.  Fans were on or off.  I have not heard of a way to slow that monster motor.  It uses an awful lot of juice.  I bought a large truck heater box, core and 2 speed fan to replace the original system.  I'd love to hear of a way to do this electrically.
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Glenn Williams
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www.threemenandatenor.com
1968 MCI 7 Ser. No. 7476 Unit No. 10056
8v71
4 speed Spicer
Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #2 on: January 22, 2008, 03:30:40 PM »

Hi Steve,

No, they only have one speed. But, you can fabricate a sort of reastat or simular to ramp it down.

i'm sure one of our members will come up with an idea on how to build one..

Good Luck
Nick-
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steve5B
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« Reply #3 on: January 22, 2008, 03:41:42 PM »



 Hey Nick,

 I was thinking a rheostat also, when the heat runs were in place for the windows it worked fine, when removed .....downhill from there..............Thanks!


Steve 5B............
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« Reply #4 on: January 22, 2008, 06:04:28 PM »

BIG Rheostat!  Have you seen how big the ones are for the defroster?  You may need a second bus for one for that motor! Cheesy
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Glenn Williams
Lansing, MI
www.threemenandatenor.com
1968 MCI 7 Ser. No. 7476 Unit No. 10056
8v71
4 speed Spicer
Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #5 on: January 22, 2008, 06:45:35 PM »

Here's a thought..

What if we could just have a battery switch to drop the voltage down to 12v to lower the speed.

I'm not sure if that would overheat the motor or not but, that would give us two speeds...??...??

Any thoughts?

Nick-
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Sojourner
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« Reply #6 on: January 22, 2008, 09:29:02 PM »



http://www.busconversions.com/bbs/index.php?topic=6954.0
Look for diode series voltage reducer.

Or if you want 2-speed switch:
1)   1pc SPDT center-off switch at 20a rated
2)   8pcs Diode at 3a x 200v or higher voltage, the better protection from damaging spike voltage.
Solder or terminal strip all diodes in series to make a 6 volts drop (each are .7volt drop) from one of two outer switch post to motor. Connect 25 amp fused power wire to center post. The remaining post wired to motor which is high range.

How to identify the diode polarity:
http://www.allaboutcircuits.com/vol_3/chpt_3/1.html

Nothing fancy or complex and low cost and work every time.

Very good price for less then 50 cent each:
http://www.mouser.com/Search/Refine.aspx?Ntt=511-BYW98-200%09

Radioshack cost 1.59 each:
http://www.radioshack.com/search/index.jsp?kwCatId=&kw=diode&origkw=diode&sr=1

FWIW

Sojourn for Christ, Jerry
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Tony LEE
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« Reply #7 on: January 23, 2008, 01:35:34 AM »

Simplest way is just to restrict the air flow to something close to what it was originally by severely reducing the cross sectional of the outlet ducts between the blowers and the floor outlet.

Might be best to restrict it closer to the motor to reduce the air noise inside the bus, but the engine noise might mask it anyway. Try it by shoving a block of foam down to block say 3/4 of the area on each side.
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Nick Badame Refrig/ACC
1989, MCI 102C3, 8V92T, HT740, 06' conversion FMCA# F-27317-S "Wife- 1969 Italian/German Style"
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« Reply #8 on: January 23, 2008, 03:20:06 AM »

Hi Tony,

Good Thought! The only problem when you restrict air flow on squirrl cages is they tend to speed up and may get even louder.

Jerry, Thanks! that will do it.. My blower is 24v, couldn't I try and drop it down to 12v?

Nick-
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Jerry32
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« Reply #9 on: January 23, 2008, 07:04:46 AM »

I think what you need is a pulse width modulation motor control. Maybe you could find one on ebay that would do the job.  Jerry
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Tim Strommen
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« Reply #10 on: January 23, 2008, 09:10:15 AM »

I agree with Jerry,

I think this topic came up about a week ago at a different voltage, with the same set of answers... (use this link).

If you need a PWM circuit, and can't find a suitable one on the e-place - we can come up with one (in fact that seems like an idea for this board - where would we put scematics, PCB layout files, parts lists, and pictures etc. for free "open source" designs?).

Cheers!

-Tim
« Last Edit: January 23, 2008, 09:13:39 AM by Tim Strommen » Logged

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1984 Gillig Phantom 40/102
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« Reply #11 on: January 23, 2008, 12:11:11 PM »

I agree with Jerry,

I think this topic came up about a week ago at a different voltage, with the same set of answers... (use this link).

If you need a PWM circuit, and can't find a suitable one on the e-place - we can come up with one (in fact that seems like an idea for this board - where would we put scematics, PCB layout files, parts lists, and pictures etc. for free "open source" designs?).

Cheers!

-Tim


Tim, on the Help board would be a good place. A topic could be dedicated to just such animals.

Richard
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« Reply #12 on: January 23, 2008, 02:26:34 PM »

Hey Richard, in that case - I'll design a PWM controller for free/open-source use and post it there (in a day or so).

I'll include the schematic, parts list (with prices and sources if I'm allowed), a board layout file (ExpressPCB - they are cheap and fast) and the source code for the PWM pulse generator Microprocessor.

The design will be for a low-side switched (that is, the ground leg of the motor is switched - not the "+" supply), 12-24VDC supply with a 20Amp-surge load.  In the microprocessor code, I'll put in some basic spread spectrum stuff (using a pseudo-random-number-generator, with optional external "entropy" via a broadband white noise generator) for better EMI/RFI performance.  For giggles, the design will support a 10K-linear potentiometer, I2C, and auto-baud-detecting multi-rate RS-485 control (the latter two for direct digital control and feedback).

Cheers!

-Tim
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Fremont, CA
1984 Gillig Phantom 40/102
DD 6V92TA (MUI, 275HP) - Allison HT740
Conversion Progress: 10% (9-years invested, 30 to go Smiley)
Tony LEE
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« Reply #13 on: January 23, 2008, 02:46:01 PM »

"The only problem when you restrict air flow on squirrl cages is they tend to speed up and may get even louder."

yes, but the original air system with the vent holes along the windows is also very restricted, so restricting the duct to approximate that condition  is not going to introduce any more noise or fan speed than would have been there in the original setup.

May actually work well enough to satisfy the OP's requirements and is very cheap and doesn't require a soldering iron or a computer to do it.
« Last Edit: January 23, 2008, 02:51:30 PM by Tony LEE » Logged

Brian Diehl
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« Reply #14 on: January 23, 2008, 03:45:05 PM »

Hey Richard, in that case - I'll design a PWM controller for free/open-source use and post it there (in a day or so).

I'll include the schematic, parts list (with prices and sources if I'm allowed), a board layout file (ExpressPCB - they are cheap and fast) and the source code for the PWM pulse generator Microprocessor.

The design will be for a low-side switched (that is, the ground leg of the motor is switched - not the "+" supply), 12-24VDC supply with a 20Amp-surge load.  In the microprocessor code, I'll put in some basic spread spectrum stuff (using a pseudo-random-number-generator, with optional external "entropy" via a broadband white noise generator) for better EMI/RFI performance.  For giggles, the design will support a 10K-linear potentiometer, I2C, and auto-baud-detecting multi-rate RS-485 control (the latter two for direct digital control and feedback).

Cheers!

-Tim

Tim, I'm looking forward to this!  I like to dabble a little bit in electronics and wish I understood it much more than I currently do.  Thank you so much for doing this!
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