Snowblower Snowblower impeller/auger speed question

[massey driver]

hey there red dirt did some measuring for you.I have a older 48 ariens blower that I'am using on the front of my MF gc2300 it used to be on my old MF 1655so I measured pulleys etc; for you.I also had to put in a parellel shaft drive as the motor in the 1655 faces different then the g2300 so had to reverse direction as well,Hub city makes these things I live in Canada so had a place get me one.Anyway heres the facts.Main gear box inpeller and augers are running at 10.5-1 ratio now from the parellel shaft drive the first pulley is 6" running to a double pully so the 6" first pulley runs to a 9"part of the double pulley and the second part of the double pulley is 6" and run to a 10" pulley which drives the shaft into the main gear box this set up works just fine however can't tell you the tip speeds but it blows snow just fine.

 

[RedDirt]

this set up works just fine however can't tell you the tip speeds but it blows snow just fine.

massey driver,
That looks like a fine unit. Thanks for the measurements. I think I get your pulley assembly and ratios but not quite sure where the 10.5:1 ratio comes into play. Is that the Hub City gear box ratio? Are you slowing down your mid pto rpm at the Hub City gearbox and then increasing back up to the impeller (or blower "main" box?)? If this is the case what rpm is the pto running at (and blower "main" box? Main box speeding up or down?)?

Or is is the 10.5 from pto rpm to impeller rpm including the belt increases?

The easier answer for me would be: Do you happen to know your calculated rpm at the impeller and the diameter of the impeller?

BTW tip velocity is calculated at impeller diameter inches / 12 = impeller dia ft X 3.14 = impeller circumference ft X impeller rpm = tip velocity ft/min.

Is that a Model 22 Hub City gear box? I am looking at their Mod 22, 2:1, 17hp, service factor 1.5 model. I'm checking to ensure it can be used as a speed increaser. Some reducers and be run backwards, others cannot.

Isn't it ironic as we do these clever modifications that the costs keep going up? I bought the blower for 250 figuring I could adapt it for an additional 200 300. At each decision the price goes up. Chain drive, ok, cheep, easy, but need that added shaft, sprocket and bearings to get reversing and gears are "only" a bit more. Ok, gears...but a gear box is "only" a bit more than the gear parts. Pretty soon we end up putting as much into a backyard contraption as a used purpose built machine cost. The one the wife said I should get in the first place but I said no, I'm clever and handy, I can do it for less...

I sometimes wonder if being "clever and handy" isn't just a curse in disguise. Ah, we love doing...but I do seem to work to make more money so I can buy more work...

massey, mind you, I'm calling my project a contraption, not yours. If mine comes out looking as nice as your and it works well I'll be as proud of it as you should be of yours .

 

[Willl]

For these velocities my 12" dia impeller should be run between 955 and 1273 rmp.

How do u calculate that ?,

 

[RedDirt]

How do u calculate that ?,

Unless I am mistaken, tip velocity is calculated as above post: impeller diameter inches / 12 = impeller dia ft X 3.14 = impeller circumference ft X impeller rpm = tip velocity ft/min.

If you are calculating the other way for needed rpm for a desired velocity with a known impeller diameter then first find the circumference of the impeller in feet:

diameter inch/12 = diameter ft (d below)
pi x d = circumference in feet
velocity/circumference = rpm

Say you have a 20" dia impeller you want to run at 4200ft/min

20"/12 = 1.67' x 3.14 = 5.24' circumference, then:
4200/5.24 = 801.5 rpm needed

Some may now see that their 20" impeller (a fairly common size impeller) straight driven from a 540 pto will be running at 2824ft/min tip velocity...somewhat shy of what others recommend (4000 - 5000ft/min) to throw snow REALLY far.


BTW Willl, the post you quote is sometime back in the development of this project. I have since discovered I have a 14" impeller not the 12". I'm now looking at a 2:1 540 rpm pto increaser to get impeller to 1080 rpm to get 3956ft/min.

14/12 = 1.167 x 3.14 = 3.66 x 1080 = 3956ft/min

 

[massey driver]

Red Dirt I did some more measuring for you and a better picture of the pulley system.The 10.5-1 ratio I was talking about is the one built into the blower.The blower fan turns 10.5 full turns to 1 complete turn of the auger bringing the snow to the middle of the blower.The fan [blower dia = 14"with 6 blades on the fan] and the auger[dia.= 16"] Your also right about the gear box from hub city its a Model 22 -single reduction style A and its ratio is 1:1.Thats what I needed for my application.My pto input is from the mid mount pto so its speed is 1750 rpms. also 17.5 hp pto. your right about costs adding up on projects. I had this snowblower from off the other tractor so I wasn't about to buy anything else. again pulley on gear box 6" driving double pulley 9" which then turns into a 6" that runs to a 10" pulley.What it used to be was a pulley on the stub shaft sticking out of the 10" pulley there was a 4" there that then drove the 9" pulley it was direct to the pto.However because of the different rotation I needed to put in that parellel shat drive.I also had to speed things up a bit due to the other tractor having a almost direct drive to the blower so it was probably running at 2500rpms anyway this is what I have done with mine to get it to do the job that I need.The only other thing is that I'll say is we had a bit of snow here last night so winter is knocking on our door step.good luck with getting yours working.Hopefully this picture will give you a better idea of how the pulleys are set up.And of course the 10.5-1 ratio is pre determined in the blower [fan] auger gear box.As always Larry

 

[RedDirt]

Thank you Larry. That is a very clean installation you did especially considering the contortions that the power drive needed to take. It also looks like you built your own front mount. Very professional looking, both the blower and mount.

I decided to keep my drive as simple as possible yet still flexible for further modification if all my speed calculations and assumptions come up lacking.

I ordered the main parts, gears and bearings, this morning and went with a straight two gear drive that will give me reversing as well as speed increase. Even with the needed jackshafts, bearings and mounts this approach will be less expensive than the Hub City gear box and I have more option to refine the design than with the gearbox.

Now the wait for the parts. I know better than to start much actual construction without first having the parts in hand.

 

[Redneck in training]

If I am not mistaken power requirements to impeller speed has cubic relationship. In other words to double the speed of impeller will require increase of power eight times. Mass flow of snow will double while throwing distance will quadruple. The basic formula is power=constant*mass flow * throwing distance. The "constant" is a number that converts the result to HP or kW. It will be different for different impellers. What I want to say is that there is a penalty for to high impellers speed. It might throw far but smaller amount of snow. There is a sweet spot between the throwing distance and volume of snow cleared assuming constant available power.