Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I was reading about the Clarence impeller improvement online today. It attaches a rubber gasket to each impeller blade ceiling it against impeller housing. Most who tried it seemed to report outstanding results especially with heavy wet snow. The only place where some reported it may not be effective were on units, such as the Honda, that reportedly have very tight clearances tween the impeller blades and the housing from the factory.

Ariens snowblowers are well-known for their high-capacity high capacity. Well most large snowblowers at 12 inch diameter impellers, the Ariens have 14 inch. That is over 16% faster speed at the end of the impeller blade. Does that give them a decisive edge?

So the question is: how important is the design of the impeller to the overall system performance? Are tight clearances between the impeller and it's housing critical? If so, which brands have the tightest ones? Is the diameter of the impeller critical? If so, did he Ariens and others with large impellers have a distinct advantage? The Clarence kit is inexpensive if you can install it yourself. Should everybody be installing these kits? TheToro has a unique impeller housing. Partially plastic, it has a return for excess snow to be returned to scoop. The effective Toro and edge or is it a disadvantage?

Toro: http://www.youtube.com/watch?v=ZTAAaT_sFss

This is 2010. We used a 480 frame/sec video from our camera. It was trivial since there was only 30° of movement between frames.

I guess this is 2010...

Friiy

friiy wrote:

Ouch, that hurts, more than the furnace door bearings. :) its late and I have no idea what you just said. 400 is 200, 3200 is 1600. Maybe I'll just a get high speed camera and forget about the strobe light idea. It's already Oct 2010, ferchrisssakes. I'm going to have another beer and call it a night.

At 30 degrees per frame means 12 frames per revolution, 480 frames per sec means 40 rotations per sec, 40 rotations per sec means 2400 rmp... 360/30=12, 480 / 12 = 40, 40 x 60 = 2400 rpm Now, just a question... is the impeller pulley larger or smaller than the engine pto pulley? If the impeller pulley is smaller than the pto pulley on the engine crank, then the impeller would have to spin faster than the engine.. ( the engine I think runs between 2800-3200 rpm).... Just throwing that out there.. Friiy

Friiy:

Engine drive pulleys are always smaller than lower driven pulleys.   Crank pulleys are generally right around three inches in diameter.  Driven lower pulleys are alway about 9.  When the drive pulley is a bit smaller the driven pulley is smaller.  The ratio alway very close to 3:1 in all machines.

DavidNJ in reference to Honda:
The engine doesn't appear to be anything special.

 

The GX series Honda used on snowblowers is special and a big part of the pricing on their machines.

 

DavidNJ:

What is equally interesting is that impellers between the Deere/Simplicity and the Ariens are signficicantly different in design. The Deere/Simplicity is a 4 2" L  sections welded to a 11" square plate with thin supporting ridges to the plate center from the blate. The Ariens is three U-section scoops, straight for 2" then tapering in for about 3" mounted on three pronged support plate.

This part is interesting.   There are 2 - 6 blades used on 9 to 16 in diameter impellers.  The impeller arm shapes vary widely between makers.  Each winter I have 5-10 machines around so can take out similar range hp machines and compare them.  These are generally 70’s through 2006 machines, my machines and all have been compression tested.  They’re around so I can take them out numbers of times in different conditions.  I clear two average driveways, 6 car widths of EOD, 200 feet of frontage sidewalk and 1000 feet of sidewalk up the street.  Beside the house there is a large cemetery so long trips can be taken through it or weave through the markers.  When conditions are good I do the above clearing and by a day or two after a storm have a couple of acres in the cemetery will all be covered with thrown snow. 

It’s been just about impossible to isolate any value to various impeller configurations.  Say for example comparing 2 824 machines with 12 inch 3 blade impellers with different arm configurations.  There too many other parts figuring in the total performance, auger shape, bucket shape, bucket outlet, chute shape & etc. 

One thing that does not get mentioned much is the distance between the back of the auger to the impeller arms or the distance between the back of the auger to the housing.  Too short of a distance would restrict flow along the back of the impeller housing.  A big distance would require quite a bit bigger bucket from front to back and longer drive shaft.  More metal more expense.  Too great a distance and snow will just jam up.  There’s no one optimal distance either.  The design will vary with average ground speeds estimates, impeller size and shape, impeller speed, collection ability of the impeller arms, bucket outlet shape and chute shape.  One element is not optimal without considering the rest of the design.

Trying to isolate contributions by specific design area has been too difficult.  What seems to matter is the total design is important versus one specific thing being of more value.  A 4 blade impeller is not a given advantage over a 3 blade.  Arm shapes of various three blade machines are not necessarily better.  On the less expensive machines the arms will be flat.  They go from less wide to wide at the end on some and on others the same width for the length.  The more expensive machines generally have shaped arms but vary with no shape being better versus its contributing factor in the total design.  The arm shape may be important to how close the arms extend to the housing barrel with closer not necessarily being better.

Outside of the gross contributors of impeller diameter and rotation speed the other contributing factors are too much for the average person to get a grip on.  Even with having a bunch of machines and a lot of testing hours it’s been impossible to isolate factors.  The average guy knows his current machine, a few old machines that are outdated and he probably can’t recall specifics about the old ones.  Probably the only person who could make some interesting comments about these things is Snowmann.  He could probably write a very interesting post on just the bucket output size and shape and it’s influence on the rest of the design. 

trouts2 wrote:

Thanks for your answer. As engines, the Honda's are roughly the price of other small engines. They certainly have a brand name for reliablity; however I've never seem objective data on that and believe alot of it may be overflow from the earlier days of the automotive brand (mid-1980s to early 2000s).

As I understand it the auger has two functions: to break up snow and ice and to move it to the impeller in the center. Most are pretty open designs which seem to just gently encourage the movement. Most have a serrated edge on the outside; I've seen one that also has a serrated edge on the inside.

I certainly agree that it is impossible to calculate the impeller performance. A CFD model may do it, but just getting the dynamics for different weight snows and ice/snow mixtures would be difficult. In many cases the impeller seems to be the key; it determines how much snow is ejected. For heavy snow it would seem to be velocity of the snow at the edge of the blade, is the force enough to sheer the snow and cause it to eject. While a greater length of the blade may move more power, a shorter blade could be better in heavy stuff. A larger diameter at the same rotational speed would have more force. A higher rotational speed would have more force. A slower vehicle speed would reduce the volume of snow and those the load on the impeller. Too much to compare spec sheets.

However, other than Honda and MTD nearly every manufactuer  is using basically similar Briggs and Stratton engines. They also use nearly identical friction drives. So, the impeller could be the deciding factor on snow removal perforance (in contrast to ease of use or reliablity). Ariens has a 14" impeller, 15" tires (vs. 16"), and reported by someone in this thread 8% faster impeller speed on most others have you noticed and advantage with their models?

Another difference, not impeller, I've noted is the Honda and Yamaha have the upper edge of the scoop recessed from the leading edge; every other brand seems to have the upper edge even with the front of the scoop. When the snow is taller than the scoop, such as EOD, that seems to cause some to fall on the scoop. Do the Hondas work better in those circumstances? Do any other manufactures have similar scoops?

friiy wrote:
I had a feeling you would not have missed that little tidbit.  You are good, and diplomatic.  :)

aa335 wrote:

I did it in my head on the fly, it was exactly 24 frames. That would be 15° not 30°. However, didn't change the relevant calc which was 20 rev/sec.

DavidNJ wrote:  
Don't sweat it. 

trouts2 wrote:

Just came across this Ariens spec sheet: http://www.homedepot.com/catalog/pdfImages/04/04f00473-2321-4eb8-8447-31daba809102.pdf

It gives the impeller speed as flows on all 14" models. Note: the Subaru and the Briggs and Straton engines have different 'sheeves' that run the betls to the drive and attachment from the engine. Without knowing their diameters it is hard to say if the 4000 rpm is extra speed at the impeller.

  Impeller

Impeller Diameter - in. (cm) 14 (35.6)

Impeller Speed (RPM) 1010

Impeller Tip Speed -

ft/min (m/m) 3702 (1128)