AUGER TO CASING CLEARANCE ????

   / AUGER TO CASING CLEARANCE ???? #1  

doxford jim

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Mar 29, 2007
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Location
British Columbia, Canada
Tractor
1959 MF-65 sold, 2007 Jinma 554 diesel.
Hi Guys,

I have an older 73" Allied-Farm King snow blower that works very well given it's age (1989 vintage). However, today I used it in what would have been perfect snow conditions and still found a lot of snow in the lower half of the auger casing - between auger and the back of the casing.

It got me thinking about the auger and casing clearance on newer snow blowers and what I have on my machine. I strongly suspect that the auger edges have worn down a lot and the result is a lot of snow left in the space behind the auger screw. I could be wrong of course, but to my thinking, the snow is supposed to be fed along the casing by the screw to where the fan / impeller picks up the snow and then it gets thrown out.

So, if any of you guys feel inclined, I would sure appreciate learning on what sort of clearance there is between the auger screw and the back of the auger box/casing - preferably on a newer blower. I would guess and say that 1/4" would be plenty to do the job properly.

If my suspicions are right and my auger clearance is indeed excessive, I have thought about bolting extra pieces to the auger spiral to close up the gap and move the snow along more effectively.

What do you guys think - is this clearance that important ? I think it is one that needs to be monitored - just like the impeller fan blades clearances. I have checked with the auger running and there is no "bow or distortion" and appears to run true. I also renewed the auger bearings just recently - the old ones were going south quickly (overheated and leaking grease).

Any input you guys might have would be appreciated - I am always happy to learn something new.

Thanks in advance

Jim
 
   / AUGER TO CASING CLEARANCE ???? #2  
I just went out and measured mine for you. May I remind you it was cold going from my warm house outside to my heated garage.

I have an inch and three eights from my auger to casing and one quarter inch from the fan to casing. This is on a 2008 Meteor

Clearance around the augers is not much of a consern.
Remember, the augers do not feed the fan. They only move the snow towards the center and the movement of the entire blower is what feeds the fan.
 
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   / AUGER TO CASING CLEARANCE ???? #3  
My auger-to-casing clearance is 3/4". My fan-to-casing clearance is 1/4". That's on a new (last fall) Bobcat 72" SB200 blower.
 
   / AUGER TO CASING CLEARANCE ????
  • Thread Starter
#4  
Hi Guys,

Thanks for the info - I really appreciate it.
My fan/impeller clearance is 5/8" - too much. I will be fixing that somehow this summer - maybe fitting renewable blade tips on each paddle.
The auger clearance I have to measure - but from what I recall, is close to 2" or there abouts. I will measure it tomorrow.
Here is a picture of my old blower and you can see the excessive clearance on the fan.
With the right PTO speed , it still throws a good distance around 30ft at 740rpm instead of 540 rpm.

Thanks

Jim
 

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   / AUGER TO CASING CLEARANCE ???? #5  
My fan/impeller clearance is 5/8" - too much.

Everybody says that the fan/housing clearance is super-critical, but I don't believe it. Bigger is better, and a closer clearance via longer fan blades will give you higher fan-tip speed, but other than that, I totally don't believe that the gap itself makes any difference. Within 10 seconds of running the machine, that space is filled with super-packed snow, making the gap roughly zero, and is as solid as steel as far as the fan is concerned. If I closed a gap from the outside using collar or something, I'd bet there would be no difference in performance.

I'd like to see proof to the contrary, if it exists.

JayC
 
   / AUGER TO CASING CLEARANCE ???? #6  
Jay - if you look at the surface inside the fan housing, it's polished bright with lots of sweep scratches. If it was packed with snow how would it get that way? The centrifugal force shoves the snow (and rocks, sticks, dirt, toys etc) against the outside until it gets launched up the chute. It rides hard against the inside surface and keeps it shiny clean. The only time I've seen a buildup in there is when the machine was much colder than the air temp and it temporarily froze on the surface until it equalized. Then it was gone.

No proof, but here's why I think impeller clearance matters. The impeller sections alternately fill with snow, then air, then snow etc. Impeller clearance allows back-leakage of snow and displaced air at the outside of the circle, right where it is most disruptive to tip velocity. The snow is fighting a local headwind at each tip. In a water pump it has more effect than in a snow pump. Snow is semi-solid and holds itself together a bit, helping to plug the gap. I agree the effect isn't large unless the gap is. Take care, Dick B
 
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   / AUGER TO CASING CLEARANCE ???? #7  
The auger to housing clearance on my brand new 24 inch Murray snowblower starts out at about 1 1/2 inches nearest ground level, and decreases higher in the housing to 1/2 inch. The fan to fan shroud clearance is 1/4 inch. I have the skid plates set at their maximum height of 1 3/8 inches above ground level, as measured on level concrete. I was most worried about shearing the auger bolts in my dirt and gravel driveway, which has nominal 3/4 inch crushed rock mostly imbeded in the dirt. Some recently added gravel was still loose on the surface. I worked for 2 hours clearing my 400 foot long driveway, and the snowblower picked up quite a few rocks and spit them out ( it's easy to hear happen), but no rocks got wedged in the auger or fan. I had to conclude that the high skid plate setting was important, and the clearances built into the machine were well thought out, to provide good snow removal but without jamming and shearing auger bolts. I also suspect, however, that different designs that use different widths, rpms , augers, and fans might use significantly different clearances to achieve overall good performance. If you can document for certain that a lot of wear has occurred, then perhaps doing some rebuilding might help. The bottom line is whether the snowblower still seems to throw enough snow without any other problems. When I finished using the snowblower, I noticed there was plenty of snow packed into the auger housing, but it was clearing a nice path and throwing a lot of snow, so I was satisfied. There is one thing I see that will be important ; I need to do any work with my snowblower in the driveway before I use the tractor and blade, since I tend to uproot a lot of gravel and dirt with the blade, even if I'm trying to be careful. The snowblower is good for getting the snow up over the embankment along one side of my driveway.
 
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   / AUGER TO CASING CLEARANCE ???? #8  
No proof, but here's why I think impeller clearance matters. The impeller sections alternately fill with snow, then air, then snow etc. Impeller clearance allows back-leakage of snow and displaced air at the outside of the circle, right where it is most disruptive to tip velocity. The snow is fighting a local headwind at each tip. In a water pump it has more effect than in a snow pump. Snow is semi-solid and holds itself together a bit, helping to plug the gap. I agree the effect isn't large unless the gap is. Take care, Dick B

I'm sure the snow moves in there, but I'd bet that it doesn't clear every rotation. Don't know - never looked. I try to never be on that side of the blower while it's turned on (skeered).

Here's an experiment for someone with nothing to do and a hunger for science. Take a blower with a 1/2 fan/housing gap and make a pass, and measure throw distance. Then extend the fan blades to reduce the gap to maybe 1/8" (something easy, like tacking on some filler pieces of steel) then make the run again and see if the distance increases measurably.

JayC
 
   / AUGER TO CASING CLEARANCE ???? #9  
My auger has about 2" gap all around. This lets things wrap up nicely without bending the auger or jamming it. For example, 200 ft of 3/4" hot water rated hose fits perfectly on one end.

The fan/impeller clearance is pretty wide on mine, but even wider on the neighbours. Theirs won't throw snow as far even with same diameter fan at same rpm.

The gap does not stay lined with ice or snow in dry snow conditions. I have seen it under wet snow followed by freezing snap get filled and fills the gap around about 2/3 of the fan.

In dry snow it stays clear and seems to provide a leakage path but also lets rocks fit through.
 
   / AUGER TO CASING CLEARANCE ????
  • Thread Starter
#10  
Well, I got to measuring the auger/casing clearance. I have what appears to be 1 3/4" clearance - which is in line with what all you guys seem to have.

I also used the blower again yesterday to clear up the recent snow - not a lot,but areas of drifting was significant. I did manage to bend backwards, one of the yellow "added wings" - :mad::mad::mad:. I had left them without any bracing so they would be sacrificial - but didn't expect them to bend that easy. It had to be a very large chunk of ice frozen into the ground. I did get off the tractor and had a good look and all I could see was snow and ice. I guess I gets to make a couple more new wings but add the reinforcing to prevent the wings bending easily - can't win for losing eh !

Incidently, the time before last that I used the blower, the **** tractor engine was smoking and vibrating like crazy. I thought I had at least one fuel injector sticking - just a guess on my part. Uh -oh - injector replacement in sub zero temperatures ain't fun.

Yesterday, prior to using the tractor I dumped a good dose of fuel treatment (Power Service ? ) and then topped off from the same jerry can ( I store the fuel in 20 litre plastic fuel containers). You would not believe the difference the fuel treatment made. The first minute or so it smoked and vibrated while using the dry unlubed winter diesel. Then the lubed diesel got throught to the fuel injectors - the change was amazing. Within a very short time the engine settled down, quit smoking and purred like a kitten. A lesson learned - the winter diesel is much too dry and needs help to prevent injector needles sticking. I ordered a couple of spare injectors anyway - but that experience has made me realize extra lubrication is needed for the fuel injectors when using winter diesel.

Just thought I would mention the fuel treatment as it really does make a big difference.

Thanks

Jim
 
 
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