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Author Topic: Vacuum Wipers  (Read 3719 times)
JohnEd
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« on: July 27, 2010, 12:51:24 PM »

I have never heard anybody say anything kind about those old stock wipers.  Aren't they actually powered by the air system?  Did they ever work satisfactorily?  Back in the day I remember taking the old vac wiper motors apart and getting them working just fine by cleaning the crud out and oiling the seals.  I don't remember anything bad about them when they worked but is is certainly true that they needed service.  I sure don't want to ever beat a dead horse AGAIN so what is the answer....please.

Thanks,

John
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bigjohnkub
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« Reply #1 on: July 27, 2010, 01:46:50 PM »

Having worked on Heavy Equipment most of my life, I have became familar with these wipers. They are air operated, and adjustable as to throw. They will need periodic lubrication, but work really well when maintained. My 4905 and 4107 are no problem . My brothers Eagle had
scraped the side(drivers) of his front windshield. I adjusted throw and away went problem. If you repair, use a pure silicone lube( As Dallas
noted, Astroglyde works good.) Good luck
  Big John
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Big John  Tyler Tx PD 4903-188 & 4107
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kyle4501
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« Reply #2 on: July 27, 2010, 01:56:03 PM »

Damn, I thought the answer was obvious about why vacuum wipers went away. Guess not.

A vacuum system has a theoretical max pressure differential to work with of 14.7psi (~30 inches of mercury) which is a hard vacuum (so called because it is so hard to create  Grin )
The practical real world vacuum attainable is less than that & after a little wear & leaks, you find very little is left to work with.

However, in using compressed air, we are working with a minimum of 90 psi on our buses & we can easily design the wipers to work on much less than that (even with keeping the size small), so we can tolerate much more in losses before the system fails.

If you make a vacuum motor larger to get more surface area for the vacuum to work on (= more force), you have to have room for the larger size. Then there is the diminishing returns from the larger volume of vacuum required.
 

There isn't anything on the bus that works well if the proper maintenance is ignored! go figure.  Wink
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« Reply #3 on: July 27, 2010, 02:43:26 PM »

Possibly, I made a mistake. I presumed he was talking about air wipers, not vacuum. What busees had vacuum wipers?
  Big John
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Big John  Tyler Tx PD 4903-188 & 4107
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Lin
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« Reply #4 on: July 27, 2010, 02:50:52 PM »

My 1956 Oldsmobile had vacuum wipers.  As the pun goes, they sucked! 
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steve wardwell
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« Reply #5 on: July 27, 2010, 03:01:24 PM »

Big john, how do you adjust the throw ( width of swing) on the wipe? My wipers ether clash in the center or run off the outside edges
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Eagle Andy
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« Reply #6 on: July 27, 2010, 03:37:11 PM »

On my Eagle I took my motors apart and cleanned and used silcone, and they seem to work great, As far as the throw I have a varible speed switch so I can slow them down. Now if I haven't used them in a while and forget which way to turn the speed switch it can get a little crazy  Grin but for the most part they work good .
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JohnEd
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« Reply #7 on: July 27, 2010, 03:47:36 PM »

I meant "vacuum" as that is what I have experience with as a boy.  I was the "kid" that my uncles came to when they couldn't figure it out.  I assumed, correctly, that air pressure would be used on the bus wipers.  I can imagine that electrics would work better in some regards and I ain't no purest but the electrics were spendy and a lot of "fitting" seems to be involved.  Hence I was curious about the "repair" aspect of the air powered wipers.  The huge problem with the auto vacuum items was that they quit working on a hill where the vac was low.  Not a problem with air drive.

Thanks Big John
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"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
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« Reply #8 on: July 27, 2010, 09:40:31 PM »

Along the lines that busnuts inherit worn out coaches...

The wiper motors/assembly etc are often well worn out, and, hence, get a bad rap from busnuts.

Used to be swap to electric got you the intermittent feature, but there are delay systems available for retrofit for air wipers.

So, spend your cash and time however you want.

I'd love to put those electric wiper retrofit systems up against air wipers for clearing a proper snow storm and see which ones burn out...

oops, my bias is showing!

happy coaching!
buswarrior
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JohnEd
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« Reply #9 on: July 28, 2010, 01:27:42 AM »

Steve,

The "limit" on the vac wiper was located on the drive mech. There is a mech that changes the side of the "chamber" that gets the vac from one to the other.  That adj will change the place where it switches direction.  There is a adj for each side and that corresponds to center and edge return point.  I never saw a air pressure unit but they must be the same as the old vac units.  You need tobe conservative on setting the limit as when you operate them fast there is some inertia that isn't in them at low speed so they hit on high but are full scree on low.  You have to sacrifice a tad on loe for high to work.  Or it used to be that way in the "day".

HTH,

John
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"An uneducated vote is a treasonous act more damaging than any treachery of the battlefield.
The price of apathy towards public affairs is to be ruled by evil men." Plato
“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.”
—Pla
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« Reply #10 on: July 28, 2010, 05:23:54 AM »

Damn, I thought the answer was obvious about why vacuum wipers went away. Guess not.

They "Suck".......You are too damn funny!

Had to read it twice though


John,

I like my air wipers.

They maybe a little quirky...but part of the essence of the Bus.



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Jerry W Campbell
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« Reply #11 on: July 28, 2010, 08:48:27 AM »

Slightly off topic but, to compare air to electric, I was driving in a blizzard in the mountains in northern Mexico. The pucker factor was high. My wipers were keeping the windshield clear of snow. Behind me a couple of hundred yards was a new bus with an 8 ft tall windshield and bug antenna mirrors. He had a strip about a foot wide to see out of because his wipers did not have enough power to push the snow off.
Jerry
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Len Silva
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« Reply #12 on: July 28, 2010, 08:58:41 AM »

My 1956 Oldsmobile had vacuum wipers.  As the pun goes, they sucked! 

Did you mean 1946?  I thought vacuum wipers were pretty much gone by 1951 or so.  I'm quite sure my '55 Chevy had electrics.  Could be that my memory is just as bad as those wipers.
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« Reply #13 on: July 28, 2010, 09:11:33 AM »



My 55 Pontiac has vacuum but I think Chev got them before Pontiac.
I have a electric motor off a Chev that i am going to retro fit. "tomorrow"


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Lee Bradley
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« Reply #14 on: July 28, 2010, 10:47:13 AM »

A number of the more expensive cars kept vacuum systems through the 50s into the early 60s as they used a number of vacuum controlled systems on the car; heater and A/C controls, headlight covers, etc. Some of these cars also had double diaphragm fuel pumps. One side pumped fuel and other side pumped air out of a vacuum tank to supplement engine vacuum which pretty much disappears during hard acceleration. One downside of those pumps was when the vacuum diaphragm failed the it pulled oil out of the engine. One plus for air and vacuum wipers is their almost infinity variable speed adjustment.     
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