A Tractor Snowblower Primer

 A Tractor Snowblower Primer;

Getting the Most Bang Out Of Your Snowblower Buck

It came to me this evening when I was explaining to a confused gentleman why I wasn't buying his snowblower after I showed up with my truck and trailer to look at it that there isn't much knowledge out there on snowblower parameters or dynamics. 

He had a 6 foot snowblower. It was in good shape and priced reasonably. I wanted a 6 foot snowblower. He couldn't understand why I wouldn't buy his. I felt I had to explain why to him. 

A snowblower is like an engine. Most people have heard the old engine adage, 'There's no replacement for displacement'. The very same goes for a snowblower. 

The width of a snowblower means very little when it comes to capacity. My 5 foot Lucknow blower on my 25 horsepower Mahindra 2525 would blow circles around the 8 foot Smythe blower on my 92 horsepower Cockshutt 1850. How could that possibly be? Not size. Capacity. 

There are several design parameters that affect a snowblower's capacity. 

1. Number of Blades on the Fan or Impeller 

2. Diameter of Fan or Impeller

3. Depth of Fan or Impeller

4. Throat Size of Chute

5. Single Auger or Dual Auger

6. Side Discharge Feature

#1:  Number of Blades on the Fan or Impeller: 

Most older, used snowblowers are going to have a 3 blade fan. They are okay, but if you want any real performance, you definitely want a 4 blade fan. Why? Because a 3 blade fan only unloads three times per revolution of the fan. A 4 blade fan unloads 4 times per revolution. All other things considered equal, that is a 33% increase in efficiency right there with only one small but very important upgrade. You can go one third faster with that blower on the same horsepower tractor. Always look for a 4 blade fan. It is your most important consideration beyond overall width. You can go from a 6 foot 3 blade fan blower to a 7 foot 4 blade fan blower on the same tractor if everything else checks out similar. 

Look for right angle scoops on the ends of the paddles to keep the snow in the fan when it gets there and good delivery to the throat of the chute. Another thing to watch for is a partial cover or shield over the upper left hand corner of the fan housing to keep snow from being shot back out of the fan housing by compression, and help direct it into the throat of the chute. It is a very small thing, but it adds to the overall efficiency by making sure almost all snow in the fan goes directly out the chute.

Some larger late model blowers have 5 and even 6 blade fans, but they are generally commercial grade, very expensive units. 4 blades is satisfactory for practically any homeowner. If you're doing commercial snowblowing, time is money, so buy a blower with as many blades on the fan as you can get for efficiency.

#2: Diameter of fan:

Now we are going to get into some Grade 10 algebra. Remember A = π × r²? There is actually a practical use for it, and a tractor snowblower is a prime example. Okay, let's try a theoretical purchase:

Let's say a blower you're looking at has a 24 inch diameter fan: A = π × r²

Area = π (3.14159265) x r² (12²) or 3.14159265 x 144 = 452.39 square inches. 

Now, take a 28 inch diameter fan: 3.14159265 x r² (14²) or 3.14159265 x 192 = 615.75 square inches.

So, for only that 4 inch increase in diameter, there is a 36% increase in area! That is a lot more snow moved. 

Another thing comes into play with a larger fan in a compound function: Tip Speed. 

A 24 inch fan at 540 RPM gives us a tip speed of 56.55 ft/s.

A 28 inch fan at 540 RPM gives us a tip speed of 65.97 ft/s. That's almost a 17 percent increase in tip speed, which translates into a 17 percent further throw at the same RPM. That's almost a 1/6th increase in the distance that blower will throw snow. 

So that 28 inch fan over a 24 inch fan will move 36% more snow and throw it 17% further. If it is a 4 blade 28 inch fan over a 3 blade 24 inch fan there is a dramatic increase in efficiency. Not even close to the same performance. Those two theoretical blowers may look very similar (say both 6 footers) but they will be night and day apart in performance.

#3: Depth of fan or impeller:

We have already discussed the importance of fan diameter. Depth is important as well. Not as critical as number or blades or diameter, but still important. Think of a snowblower as a pump; the more you can cram into it the more it can huff out. I know I compared a snowblower to an engine before, but that was for familiarization of the subject matter. It is really more like a pump; a snow pump. 

If you have an 8 inch depth fan on one blower and another blower with a 10 inch depth fan, the second unit has a 25% increase in efficiency. You can see now these factors really start to add up. No algebra needed; that's just plain old multiplication. 8 times 1.25 equals 10. If you upgrade from a 24 inch diameter, 8 inch deep, 3 blade fan to a 28 inch diameter, 10 inch deep, 4 blade fan, that blower is going to seem like a rocketship compared to your old blower!

#4: Throat Size of Chute:

There's a limit when it comes to efficiency. 'What goes in must come back out'. That's a rule of hydrodynamics. A bottleneck anywhere in the system will spoil your outcome.

If you have a whopper of a fan but there's only a small diameter chute, you're going be pulling your hair out in a big snowfall or especially heavy, wet snow. That sucker is going to plug. And you're going to mutter things under your breath or maybe right out loud that you normally wouldn't while you're trying to break up that solidly compacted slug of snow with a broomstick, a shovel handle, a wrecking bar, or your bare hand shoved up or down the chute to the shoulder. A large diameter, free-flowing chute will deliver that column of snow without plugging, almost no matter how wet and heavy the snow is. Once again you get into the π × r² thing. I was looking at a conventional (back up) blower because the inverted (drive ahead) blower that came with our tractor when we bought it isn't practical for going between our buildings. The blower we have has a 13 inch diameter chute. The blower I looked at has a 10 inch diameter chute. 

That blower: π (3.14159265) x r² (5²) or 3.14159265 x 25 = 78.5 square inch chute opening. 

Our blower: π (3.14159265) x r² (6.5²) or 3.14159265 x 42.25 = 132.73 square inch chute opening. Huge difference! That 3 inch diameter increase resulted in an opening 69 percent larger! That is a whole lot less likelihood for plugging. 

You may not have realized it before, but in snowblowers, math is everything. Keep in mind, some blowers have a triangular gusset inside the chute for top of the blower chamber strength, which creates a bottleneck. Pass that blower by or cut the gusset out and add reinforcing members elsewhere on the blower body. That blower is going to plug when the going gets heavy. The biggest chute in the world is no bigger than it's smallest passageway. 

These first four parameters really work together to make or break a snowblower. Just because it looks nice doesn't mean it will blow nice. Some blowers suck! Pardon the pun but it's true. Any decent welding shop can turn out a functioning snowblower. They just build it around a gearbox and PTO shaft and some bearings and roller chain. And therein lies the problem. Just because they can build it doesn't mean it will be a performer. If the design considerations are done right; if it wasn't just built, but planned, it will blow snow powerfully and reliably in all conditions. And you won't have to abuse your tractor to get the performance you want; your carefully selected blower will deliver that performance. 

There is one way of sidestepping throat size and that is number of blades on the fan. Very modern design blowers with 5 or 6 blades can have a smaller throat size. That is because there is a smaller charge being sent to to the chute each time. 

Knowledge is power in many things, and snowblowers are definitely one of them.

#5: Single Auger or Dual Auger

The old saying goes, 'Two heads are better than one', and, while the same does hold true for snowblower augers, it's not as critical as fan and chute parameters. Those are crucial to performance. One auger generally is fine. Two augers only comes into real importance if your property is prone to deep drifting, or if you are a commercial contractor. If the snowfall or drifting itself is deep, a dual auger snowblower is preferred. Especially if the drifting creates a hard pack; the dual augers will chop that up and break it down into a suitably consumable medium for the impeller. If you are a commercial snow contractor and you are always pushing your blower to the limit, you need dual augers to keep the snow moving into the impeller instead of being pushed back behind you into a pile that is sure to slug and break a shear pin. That's really about the only consideration; depth of snow or all out performance. A super performance commercial blower is going to be a 5 or even 6 blade huge, deep fan, with a whale's throat chute, and dual augers. And it's going to be massively heavy for impact and debris resistance and at least two to three times as expensive as a typical homeowner's snowblower. Just make sure it has a good diameter auger nearly up to the center of the fan. It should be equipped with noticeable solid paddles or shovels at the center that go almost right to the ground to fling the broken up snow into the impeller. No paddles or shovels means less effective delivery of snow to the impeller. Look for sturdy construction of the auger flighting, with solid attachment to the center tube. Skimpy spiral auger bars and spacers are a sign of an overall poorly built blower.

#6: Side Discharge Feature:

This is a very rare feature on privately owned tractor snowblowers, but it results in Ultimate Performance. A hydraulically operated rolling gate in the fan housing can allow the snow to bypass the chute and directly exit the impeller at the nearest side. The impeller doesn't have to carry the snow as far, and there is no restriction or 'hysterisis loss' of the length of the pipe of the chute. Just like there is more pressure and volume coming out of the length of a 50 foot garden hose versus a 100 foot garden hose, there is more pressure and volume coming out of the side discharge gate versus the top of the chute. You can't direct the snow plume; it goes straight out the side. That's it. You can't place it where you want it but you can sure get rid of it. If you have ever seen a snowblower on a railroad locomotive, you have probably seen a side discharge blower. Or an airport runway snowblower truck. Very impressive performance. It is a rare feature on a farm tractor snowblower, but one for sure to put a smile on your face. 

Other things to consider:

Chute rotation:

There are 5 kinds of chute rotation: Manual crank, manual hoop, electric winch, hydraulic winch, and hydraulic motor. 

The manual hoop style is the most trouble free of all. It is just a big hoop shaped handle attached to the chute that you swing either way like a boat's rudder. They are not seen very often anymore. 

The manual crank style is very common. A hand crank is worm driven to a toothed sprocket on the bottom of the chute. Look for a solid gear on the crankshaft at the base of the chute, not one made in a spiral out of round stock. Those are cheaply underbuilt and do not hold up well. Some manual crank styles have a cable wrapped around the crankshaft and the chute. They work very well and are easily changed up to hydraulic or electric.

Electric winch chute rotators are typically installed on small blowers for compact tractors. They generally work well, but can be a little slow, and anything electrical can be subject to poor connections. The same controller as an electric winch or dump trailer is installed on the tractor. Instead of up or down, the function is left or right. They can be winch style with cable or a direct drive motor onto a toothed sprocket.

Hydraulic winch. This is the most common chute rotating mechanism in older blowers. Like the electric style, a cable is wrapped around the base of the chute and each end is attached to each end of a large bellcrank that is controlled by a hydraulic cylinder or ram. They are powerful, simple, and work very well. 

Hydraulic motor chute rotators are very smooth. The same toothed sprocket as manual crank or some electric designs is attached to the bottom of the chute and geared to a hydraulic orbital motor. They are precise and smooth in operation. Winch style rotators can be a bit jerky in action but hydraulic motor ones are very predictable and can be moved in small increments. The design is very tidy as well, taking up very little space on the blower itself and almost unnoticeable. 

A chute with the sprocket on the bottom is easily convertible to any kind of rotator.

Three Point Hitch Attachment:

Look for an integrated design in the 3 point apparatus. If it is all bars and pipes and tubes and braces bolted together, it probably isn't very strong. If it is built of wide steel plates welded together like the framework of a box blade, then it is well engineered and will last. 

Overall Body:

The weakest part of a blower is the unbroken span across the top of the back. Look for at least a folded edge if not a peice of square stock or angle iron welded in to reinforce that span. All your strength is there; however rigid that section of your blower is however rigid the rest is; that's your weakest link. Make sure it is as strong as possible. The top is best to be the same depth as the sides. If not, there should be strong gussets from the top extending out to the sides. The side plates should be thick for strength. If they don't look stout, the blower definitely isn't sturdy. They should extend at least close to the full size of the auger to not lose snow out around them.

PTO Shaft:

Look for a good shield on the shaft. The new, self lubricating plastic shields are actually much better than the old steel ones. They will spin and prevent a deadly snag much better than the old steel ones. Please don't put them to the test though; Shut the tractor completely off before you check or service anything around the PTO shaft or the auger. There are gravestones all across North America and Britain and Europe six feet above people that lost the fight against a spinning Power Take Off shaft. You don't want to add your own to that list. Countless more somehow survived but are maimed for life. Don't be a dummy. I had a guy come into my shop that slipped when he walked behind his idling blower. He had about 30 fractures from going around the auger several times until the tractor actually stalled, saving his life. Shut the darn tractor off, okay? It only takes a moment to preserve your life and it only takes a moment to ruin or end your life. Spend that moment right.

Some PTO shafts have a push pin to lock onto your tractor's PTO output shaft. They aren't bad if they are in good shape. A better style has a pull collar on the front universal joint. You just pull back on the round collar with both hands while shoving it onto the tractor's shaft. They tend to be much easier to manage when it's cold. Check for an easy to change shear bolt on the rear of the shaft where it attaches to the blower. It should have a grease fitting for when a shear takes place so the shaft doesn't wear metal on metal until it stops. Some blowers have a shear bolt on the auger drive. Make sure it is easy to get at rather than having to pull shields off to do it. 

Hydraulic Spout or Deflector:

Those are a nice feature. You have more accurate control of where the snow goes. You need two hydraulic remote circuits on your tractor to run one of these. You can blow the snow up and over a building roof or a vehicle, or direct it down to avoid a window or a delicate tree. You can load a truck or a dump trailer with snow you want to haul away for disposal elsewhere. It is very nice to have, but less popular on homeowner level blowers versus commercial ones. 

That's it. Now you know. Buy the right one for you and make the white stuff fly...