Snow Attachments some thoughts on my snow removal options

[KennyG]

I read an article by a mechanical engineer working for Schultz - farm equipment manufacturer - paint all their equipment lime green.

The main point I got out of the article - its not so much the rotational speed of the impeller as it is the power driving the impeller. As he stated - you can throw a lot more snow with 50 PTO hp and the impeller rotating at 300 rpm than 25 PTO hp and the impeller rotating at 600 rpm.

Idea being - - its brute force over rotational speed that will move the most snow.

I can't agree with this. The impeller running at 600 rpm has a lot more kinetic energy than one running at 300 rpm independent of the power of the engine that runs it. Now, if the snow was heavy enough to bog down the engine, this would make some sense but that doesn't happen. I've got 18 hp at the PTO and the engine rpms never vary when snow blowing. 100 hp would not put more energy into the snow that's being moved.

 

[atitus74]

I can't agree with this. The impeller running at 600 rpm has a lot more kinetic energy than one running at 300 rpm independent of the power of the engine that runs it. Now, if the snow was heavy enough to bog down the engine, this would make some sense but that doesn't happen. I've got 18 hp at the PTO and the engine rpms never vary when snow blowing. 100 hp would not put more energy into the snow that's being moved.

It depends on what you are disagreeing with. If you are talking about VOLUME of snow, then yes. The chute has a specific diameter, like a water pipe. There is a limit on how much snow will be able to pass through, aka flow rate. Once this flow rate is reached, it won't matter how much pressure/force you put behind it, the flow rate will not increase. Assuming that 18 hp will have sufficient pressure to max it out, then doubling the HP would have no effect.

If an engineer is building a snow blower designed for a 50 hp PTO, chances are they are going to add a bigger auger, wider chute, etc versus one designed for 18 hp. The impeller may run at a slower RPM however it will move more snow volume not because of its power but because of the flow rate of it being larger. It will need more power to move the larger amount of snow at once.

Don't believe it? Here would be the proof. If you set up an experiment where you took a snow blower designed for an 18 hp tractor and hooked it up to a 50 hp tractor, the volume of snow moved would not increase by much. That is of course assuming that the manufacturer who built it made sure that 18 hp was enough to maximize the flow rate.

 

[CobyRupert]

There's a lot of apples and oranges here.

 

[DK35vince]

It depends on what you are disagreeing with. If you are talking about VOLUME of snow, then yes. The chute has a specific diameter, like a water pipe. There is a limit on how much snow will be able to pass through, aka flow rate. Once this flow rate is reached, it won't matter how much pressure/force you put behind it, the flow rate will not increase. Assuming that 18 hp will have sufficient pressure to max it out, then doubling the HP would have no effect.

If an engineer is building a snow blower designed for a 50 hp PTO, chances are they are going to add a bigger auger, wider chute, etc versus one designed for 18 hp. The impeller may run at a slower RPM however it will move more snow volume not because of its power but because of the flow rate of it being larger. It will need more power to move the larger amount of snow at once.

Don't believe it? Here would be the proof. If you set up an experiment where you took a snow blower designed for an 18 hp tractor and hooked it up to a 50 hp tractor, the volume of snow moved would not increase by much. That is of course assuming that the manufacturer who built it made sure that 18 hp was enough to maximize the flow rate.

Your talking about 2 different sized blowers.
I never saw that mentioned.

 

[atitus74]

Your talking about 2 different sized blowers.
I never saw that mentioned.

Pretty sure I applied this theory to a single blower. Last 3 sentences of my post?

 

[Reb954]

It depends on what you are disagreeing with. If you are talking about VOLUME of snow, then yes. The chute has a specific diameter, like a water pipe. There is a limit on how much snow will be able to pass through, aka flow rate. Once this flow rate is reached, it won't matter how much pressure/force you put behind it, the flow rate will not increase. Assuming that 18 hp will have sufficient pressure to max it out, then doubling the HP would have no effect.

If an engineer is building a snow blower designed for a 50 hp PTO, chances are they are going to add a bigger auger, wider chute, etc versus one designed for 18 hp. The impeller may run at a slower RPM however it will move more snow volume not because of its power but because of the flow rate of it being larger. It will need more power to move the larger amount of snow at once.

Don't believe it? Here would be the proof. If you set up an experiment where you took a snow blower designed for an 18 hp tractor and hooked it up to a 50 hp tractor, the volume of snow moved would not increase by much. That is of course assuming that the manufacturer who built it made sure that 18 hp was enough to maximize the flow rate.

Like a water pipe? The way I take what you are saying is, if we take a 1" water pipe it will only let so much water through, regardless of how much water pressure there is?

 

[oosik]

WoW - mellow out guys. I didn't intend to start a flame war. I would love to discuss this knowledgeably but since I'm not a mechanical engineer - no joy.

 

[atitus74]

Like a water pipe? The way I take what you are saying is, if we take a 1" water pipe it will only let so much water through, regardless of how much water pressure there is?

Yeah you got it. Crazy isn't it? Increasing pressure can increase the flow velocity (how fast does it flow) but not the total amount of flow passing through at any one time.

 

[KennyG]

Not to beat a dead horse but...

You can move more snow at 300 rpm and more horsepower than 600 rpm and lower horsepower... but not with the same snowblower. The amount of snow is based on the volume displaced by the impeller and the distance thrown is based on the tip speed of the impeller, so to take advantage of the high horsepower at low speed you would need a much larger diameter impeller.

If you look at an 8 foot wide blower compared to a 5 foot wide blower you will see a much larger impeller. As impellers get bigger, eventually you would have to slow them down because of high tip speeds but I think most of the commercially available 3 point blowers are designed for 540 rpm. The bottom line is that if you can run at rated speed without bogging down the engine with a given snowblower, more horsepower would not make a difference.

As a Mechanical Engineer who did his masters work in fluid dynamics and design of rotating machinery, I'm sure the engineer at the implement company was correct that a blower could be designed to deliver more flow at lower speeds but it seems to not be a practical point.

If you want to move snow and already have a snowblower, run it as fast as you can.

 

[KennyG]

Like a water pipe? The way I take what you are saying is, if we take a 1" water pipe it will only let so much water through, regardless of how much water pressure there is?

Not true. As pressure increases flow increases until you reach sonic velocity and the flow chokes. I don't think choked flow is in any way possible with a snowblower.