Snowblower Snowblowers - Long chute or Short chute ?

755inNY · Dec 28, 2005

Excellent discussion.

Isn't it more than just long chute vs. short chute.

Doesn't both the diameter of the second stage impeller and the diameter of the chute come into play? It would seem to be an advantage to raise the height of the discharge point. But you need adequate force to get the wad of snow that high. It appears from the comparative pictures that the long chute snowblower also has a taller first stage opening. Does this mean the second stage impeller is bigger too? Are there deeper impellers (distance from the face to the back) with more blade surface area?

It seems that the long chute model pictured would be better at cutting back snow banks. The mouth is taller and the long chute will be better at blowing the snow over and beyond the pile.

Jeff

Steve_Miller · Dec 28, 2005

Mad,
Do you have any more pictures that you could post of your chute set up. I'd really like to modify mine to something similar. I just can't make out exactly how you've done it. This unless there is a patent or something /forums/images/graemlins/grin.gif.

Steve

Bob_Skurka · Dec 28, 2005

(
Doesn't both the diameter of the second stage impeller and the diameter of the chute come into play? It would seem to be an advantage to raise the height of the discharge point. But you need adequate force to get the wad of snow that high. It appears from the comparative pictures that the long chute snowblower also has a taller first stage opening. Does this mean the second stage impeller is bigger too? Are there deeper impellers (distance from the face to the back) with more blade surface area?
)

I'm not sure that I would agree with all your thoughts, but I think there are a lot of factors that come into play when looking at snow blowers that go beyond chute height.

The Fan (2nd stage impeller) speed is going to be dependant on the gearbox ratio and faster is likely better. There are different fan sizes and a larger fan will likely have a faster tip speed which would also help in expelling the snow up the chute. From the simple standpoint of a clogged chute, the shape of the transition from the fan to the chute is going to be critical, it will not only affect the speed that the snow can be expelled but also the amount of snow that can be expelled. Both the fan shape and the clearance between the fan and the housing are also going to be factors as well.

rambler · Dec 29, 2005

Most snow blowers I know of have direct drive fans - the gearbox only slows down for the cross auger. So gearbox ratio is non-issue - for the 2stage blowers I have seen. Large impellers for slow pto speeds, smaller impellers for fast pto speeds.

_The_ critical issue for snow volocity is clearance of the impellers to the shroud. Any leakage there is _the_ issue. Worn out blowers are the ones that have the impellers worn shorter & there is too big a gap. Any other consideration is small potatoes.

The snow going through the short chute pictured must make 2 sharp angles. This will make 2 severe (relatively) slowdowns, plus general slowdown of sliding along the flat surfaces between the angles.

The snow going through the long chute pictured will have the general slowdown of sliding along the flat longer area, and then a single, but stronger, slowdown of making the curved area - really multiple tiny angles of directional change.

Now, how does fluid dynamics work when you are shoving a granular such as snow, and it hits 2 sharp angles, or one curved section? Which is better? Does snow act like a fluid & you lose push as it leaves the impleller? Then the 2 sharp angles of the short chute may be more efficient.

Or are you more closely pushing a rope - each snowflake is packed onto the one above it, and you continue to push the whole column of flakes so that the impeller is imparting some force to the flakes several inches above the impeller? Then the round corner of the tall chute would be more efficient.

I suspect the answer will depend on how wet or dry, and how chunky the snow is, and the real answer is quite variable.

The short chute is much better at blowing the snow right back to the ground - in wind, or around buildings. Sticky wet snow may go through this chute better, but will not go very far, wet or dry snow.

The taller chute will be better blowing the snow up into the air. Light fridgidly cold snow, or blowing with the wind will make the snow travel much farther away.

I have seen much taller chutes with a hyd 'angle' control that tilts the whole fixed chute at the base of the chute. These are used for loading snow onto trucks.

I see the mechanics of the short chute working better in heavy wet or compacted ice snow, and the tall chute working better in light fluffy snow. But the tall chute gives you a better chance of getting the snow some distance away, while the short chute gives you more control of aiming the snow in tight locations.

--->Paul

Dmace · Dec 29, 2005

Excellent write-up Paul !

The fact of having a short chute in tight areas and a tall chute for throwing the snow farther makes complete sense.

Thanks

Bob_Skurka · Dec 29, 2005

( Large impellers for slow pto speeds, smaller impellers for fast pto speeds.)

Paul, not trying to argue, but I've never seen that. So that leads me to a question. Are you saying that a smaller impeller fan is used at 1000pto speed and a larger one is used at the more tradiational 540pto speed?

The impeller fans I measured out were all within a few inches of each other, the smaller units having fans of about 18" to 22" and the larger units having fans of roughly 20" to 24". It seemed to vary more by brand than anything else. For example: "Brand X" would use 18" fans in their smaller blowers and 22" fans in their larger blowers, but Brand Y used 20" and 24" fans respecitively.

Here is a whole thread about a long chute blower that simply couldn't blow wet snow. It simply clogged the chute. It looks to be the very same blower that is in the first picture of this thread. Snowseb's clogging snow blower thread

MadReferee · Dec 29, 2005

( Do you have any more pictures that you could post of your chute set up. I'd really like to modify mine to something similar. I just can't make out exactly how you've done it. This unless there is a patent or something )

I have the Pronovost Puma factory hydraulic chute rotator. The hydraulic chute deflector uses a Chief cylinder and is exactly the same as the factory setup only 3 times cheaper.

jimgerken · Dec 29, 2005

>The position proposed in the original post was >that the snow in the long chute would actually >pick up velocity as it travelled up the chute. That >is simply not possible. It would encounter both air >friction and friction from the sides of the chute >and both would act to slow it down.

Well, here's another theory. The snow is being propelled by the impeller lifting it, as we all understand. Bu have you noticed that, when the blower is lifted, the fan is moving a large amount of air, as a fan would? And if snow can be picked up it will fly out along with this airflow. So, it seems possible that the snow COULD pick up speed in the chute, because it is still being accelerated to the speed the airflow is moving after leaving the fan. Worth considering anyway.
One other thing I will add, to help spice it up. When I finished building my first protoype chute for my home-built blower, it gave an output of two distinct columns of snow! This chute was actually a rebuild of an old smaller-blower chute, to save a bit of fabrication time. When running, it can be seen that there are two snow columns. See it in this video, near the end of the video:
http://media.putfile.com/Snowblower-Prototype-Testrun-2005
To change this to one stream of snow, I had to close up the lower open front side of the chute (like a bib), and widen the upper end a bit by prying it apart. I feel the longer the chute, the more drag, but also it helps shape the snow more uniformly into a single stream and so maybe will result in a longer throw, as the snow will stay together longer. As the snow stream begins to diverge, the distance shortens. This is also shown by the way the heavier wetter snow will throw further than the super dry light stuff. The dry snow doesnt stay in the solid stream as well, so air causes it to fly apart and slow down. OK, that's enough snow theory for today.

JoeL4330 · Dec 29, 2005

Let's start over: if exit speed from either length chute is the same, then snow that exits higher (i.e., from longer chute) will go further. [the higher the mountain you are on, the further you can throw the ball]

And, the snow will exit at the impeller input speed ...or, it would back up in the chute.

So, if the impeller speed is the same for either chute, and thus the exit speed is the same for either chute, which would throw further?

Disregard the first part of my previous post, it had to do with the gun barrel analogy after all gas expansion was completed.

Bob_Skurka · Dec 29, 2005

JoeL, lots of IFs there, but IF all the IFs are the same, then I'd agree with all you said. But the original post was asking for advantages and I was simply pointing out that people with short chutes seem to be able to thow wet or dry snow, but people with long chutes have difficulty with wet snow clogging. No matter what, I'd buy another short chute unit again and would shy away from a long chute. To me it is more important that the blower actually work when there is snow on the ground, rather than only working in some snow conditions but not working in others. So if the taller chute can potentially throw snow a bit farther, I guess it doesn't offset the problem of the clogging chute.

But to further the discussion, my short chute blower has a fan diameter of about 23.75 inches but the tall chute model pictured has a fan diameter of 21.25 inches (if I did my research correctly). So actually my tip speeds are going to be higher IF we run them at the same RPM so my snow will theoretically exit the blower chute at a higher velocity which may negate the fact that it is thrown from a chute that is 12" shorter (again lots of IFs and variables there) Not sure that any of it adds up to any advantage other than mine doesn't clog up in heavy wet snow, slush or powder. Thoughts?