Tip speed on snowblower Part II

Wardner asked what the tip speed should be on a 60" snowblower with an 18" blower wheel and I started out by saying typical snowblowers a little larger run the fan at standard PTO speed of 540 RPM's so the smaller one would need to run a bit faster.

Some others guessed as high as 1000, or, I believe even 1200 RPM's.

I emailed the sales guys at Quick Attach Attachments, Inc. asking what the fan speed was on their UTV model, which is 60" wide and has only a 16" fan.

Their reply...

"HI BOB,

THE FAN SPEED IS BETWEEN 700 AND 800 RPM. GIVE ME A CALL IF YOU HAVE FURTHER QUESTIONS.

THANKS FOR CHECKING US OUT."

So, using a average speed of 750 RPM's and a fan diameter of 16" tip speed would be about 3140 feet per minute.

(16" X 3.14 = 50.24" = 4.18667' X 750RPM = 3140 feet per minute.)

Working that out for the 18" fan:

3140'per minute/4.71' = 666.67 RPM's

(18" X 3.14 = 56.52" = 4.71' X 666.67 RPM's = 3140 feet per minute tip speed.)

(Link to Quick Attach Attachments, Inc. unit I used for comparison... http://www.quick-attach.com/attachments/utvsnowblower/)
Previous thread

A tip speed of 3140 feet per minute is equal to 35.68 mph and that seems reasonable to me.

Thanks Bob for following up.

There is, of course, a minimum speed otherwise the chute will plug up if the snow is heavy.

On the other hand, there is no limit on the maximum speed except for some higher RPM that would precipitate the snowblower's destruction. More speed just needs more power which results in a longer throw.

One source that I found on the internet suggests a 4.8 cubic inch motor for a 20" fan. That displacement was close to what my friend had but it did not work. I had a 2.8" motor. We put it on and the revs were quicker but still not adequate. Even if it did work, I am not sure it would hold up due to a continuous high pressure operation. It's possible that a relief valve would open as well under difficult conditions.

At this point, we need more GPM and a switch back to my friend's motor. That will require a higher capacity pump. Not sure what he wants to do at the moment. He likes to do everything on the cheap and I can't blame him for that.

There are two 540 PTO shafts on this tractor that run off the flywheel through a planetary reducer. I am suggesting that we overdrive a small pump by four times or go with a huge pump with 1" - 1.25" ports like the larger Prince PTO units. I think $500 for a new one is out of the question.

This tractor is hydraulically driven but not hydrostatic. He would prefer to operate at a slow ground speed around doors and other obstacles. That will reduce the pump's GPM and fan speed. He has a snowplow for the open areas.