hwp
Platinum Member
Glowplug said:Don't you think the gearing and fan size have something to do with it. Sure the PTO spins at 540 RPMs but that doesn't mean the fan has to spin at the same. Now, as far as if they do or not, I can't say. But I just can't see a double auger snowblower with a 34" fan tossing snow aside at only 6'. When I was looking into these snowblowers I did a search here. One of the threads from a couple of years ago talked about how the casing around the fan would affect the throw. One person had commented that the casing had worn some on his and there was a slightly greater distance between the tips of the fan blades and the casing. When this happened his blower would only throw snow 75 feet! He put a liner in the casing to decrease the distance and once again he could throw snow 100'! I think that was a 3ph PTO-driven Provonost blower.
The "throw distance" is primarily determined by the tip velocity of the impeller blades. Every two-stage snow blower I've seen had a direct drive to the impeller, i.e. impeller velocity = PTO velocity. Tip speed = rpm x 3.14 x impeller diameter (in inches)/12. There seems to be some concensus among the experts that a tip speed is about 5000 feet/min is optimal. This will result in a throw of about 100 feet under ideal conditions. This may be great in rural environments but not in urban ones. A second factor that affects the "throw distance" is the gap between the impeller and the drum. If the gap becomes too large there will be significant leakage between the impeller blades and the drum which will have the effect of reducing tip speed. My snowblower was made by a small manufacturing company and I was able to talk to the owner/designer. He advised me to try to keep the gap between the impeller blades and the drum at about 0.020" for optimum performance. A quick way to check this is to put a dime at the bottom of the drum and see if the blades will carry it to the point of discharge. If the gap becomes too large, the blade tips can be refitted to the drum by adding weld to the tips and then grinding them to the appropriate clearance. Sometimes the blade tips get so worn that adding weld is not practical, in which case inserting a sleeve inside the drum may be an easier fix. I did this to my snow blower because the blades had not been maintained by the previous owner and the gap between the blades and the drum was too large to repair with weld. One problem with adding a sleeve is getting it perfectly round - this can take time but it can be done. I have found that I need to regap the impeller blades about every 100 hours of use.
Back to the example given, a pto velocity of 540 rpm and a 34" diameter impeller will result in a tip speed of about 4800 feet/min - close to "ideal". My snowblower has a 20" impeller and I run it at about 1000 rpm giving a tip velocity of about 5200 feet/min. If the blades are properly gapped then in really dry snow I get close to a 100 foot throw which is OK because I have the space to do so. The wetter the snow the shorter the throw, in part because more energy is used in dislodging the snow from the impeller blades. Most walk-behind snowblowers are built for urban use limiting the maximum desired throw so have a lower discharge velocity.
I am biased in favour of snowblowers but there are times that I use my dozer blade for moving snow. If the snow is dry enough and not too heavy I sometimes use a rotary broom and it works very well but wouldn't be appropriate for the specific situation. Having said all the above, I would think a blade would be the best bet since the amount of snow requiring removal is relatively small and probably fairly wet. One advantage of using a blade is that you don't need a cab!