Snowblower Snowblower impeller/auger speed question

[RedDirt]

Thanks rbargeron, your reply and especially your linked post was quite helpful. I think I am going to up my target velocity a bit and try for at least 4000, maybe 4200ft/min. This would put my impeller rpm around 1000, 1200. If my mod works I think the unit can handle the increased rpm's.

My buddy's coming by tomorrow and I am anxious for his input. He was my equipment fabrication instructor in college thirty + years ago so I value his opinion. If he steers my to hydraulics I'm likely to have to ask a bunch more questions. Not only do I need to increase speed I need to reverse direction and this is a challenge mechanically (on a budget!) which is why hydraulic may be easier.

Will keep you posted.

 

[rbargeron]

.............. I need to reverse direction and this is a challenge mechanically.......

Yes - I noticed the chute was on the opposite side from most machines. In past years Bervac made an interesting adapter for putting a rear-mount up front - they used an extra sprocket to change pto direction. There would be some opportunity to change speed with sprocket sizes. pics below. Erskine's chain box is enclosed running in oil. But for homeowner use an exposed setup might hold up well enough.

 

[RedDirt]

they used an extra sprocket to change pto direction.

Boy, would that be a handy item for me to have right now. Anyone got one to let go?

I have searched for a suitable gear box on the web and come up empty. Lots of boxes available, especially right angle ones, but parallel shaft in the 2:1 range are not to be found. Anyone know a source?

I had a better reply written then accidentally closed the page before sending. Hate it when that happens. Here's the condensed version.

Buddy came and we brainstormed a pulley/belt solution. Seemed better than my chain/sprocket. Hours of struggling to get it developed on CAD just led to the conclusion it would not work. Too many twists in confined spaces. Belt would have jumped the sprockets. I'm now reviving a previously dicarded concept using spur gears. The design came out well and the plan is off to Owen for look-see-comment.

I had to sacrifice 200 rpm from the belt design to keep cost comparable and keep the conversion package within the confines of the blower body. If I use the bigger gears material cost goes up 40% and the gears need more complicated support. I should get 1080 rpm, 4000ft/min impeller tip velocity. Hope that is enough. I don't need to throw but about 10' -15', 20' - 25' would be a bonus. Too bad wet snow is what we normally get.

I'm also having trouble finding a web source for American gears. Found a great metric gear place, Quality Transmission Components, qtcgears.com compleate with detailed measurements and cad drawings of thousands of gears. But no one like it for fractional gears. Owen is a quality machinist so we will bore out metric gears if we need to but finding the right bores in the first place could save that step. Anyone know a source?

 

[RedDirt]

Here is my current plan if anyone is interested. I value all comments and advice.

My main concern with this design is if the 3" impeller gear is too small. I had larger pulley and a larger sprocket on those designs but I think a solid gear can be smaller. A 1" bigger gear here means a 2" bigger gear above, etc, and the whole assembly gets much larger and likely cost prohibitive.

View attachment Snowblower Gear Drive_112009.pdf

This is a 24x36 drawing so it is only viewable onscreen unless you have a plotter. Also it is is a see-through drawing. You may need to compare the two views to see what overlaps what. For me This type of drawing works to find conflicts. If it was a published drawing I'd hide appropriate lines/layers and add additional sections so there was no overlap of details in depth.

 

[PILOON]

Reddirt:
I sent you a PM

 

[RedDirt]

Reddirt:
I sent you a PM

Thanks PILOON, I've replied.

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BTW the reason I'm using 1 1/4" shafting in the pdf drawing is that 1 1/4" is the existing shaft from the blower (with a 7/8" dia spline tooth end that goes into the back of the impeller fan). This shaft went into a gear reducer box that I am discarding except for the shaft. The big gear jack shaft is 1 1/4" because Surplus Center has a neat and reasonable 15hp pto shaft that ends with a 1 1/4" bore where I can connect with a shear pin.

 

[ChuckinNH]

I picked up a brochure on the Frontier 3pt hitch snow blowers today, and it has this information about impeller / auger speed.

Tractor PTO speed: 540 rpm
Auger speed : 170 rpm
Impeller Speed : 540 rpm

This information is for the smaller ( up to 74" blowers)

 

[RedDirt]

Tractor PTO speed: 540 rpm
Auger speed : 170 rpm
Impeller Speed : 540 rpm

Nice to see another slow impeller speed. Most of the specs I found give higher auger speeds. As far as impeller speeds I think tip velocity seems to be the critical issue and that depends on both the rpm and impeller diameter.

I did find a web source for American gears but I cannot yet comment on pricing as I have to wait for a quote. But their website has a good online catalog and dwg drawings and also a pdf downloadable catalog. What I really liked was their online HP formula calculator. Once I figured out gear terminology I could change variables and compare one gear choice to the next. Gear material, Dia, pitch angle, tooth count, gear thickness, rpm, service factors, etc are the variables and the tool instantly calculates the HP, velocity, torque, pitch loading, etc. It was easy to see which gear would perform better. I was lucky with my uninformed gut reaction choice and had happened to pick very suitable gears for my project. The calculator answered comparative questions like more teeth better or not but more importantly confirmed my gears aren't going to fly apart on the first trial run after putting in a lot of fabrication hours. I can rest a bit easier. The site is rushgears.com.

 

[JohninCT]

This place has parellel shaft gear drives similar to what you're building. I don't know how much they cost, but it may save you time/effort buying vs fabricating.

Hub City Inc - Standard Products

 

[RedDirt]

This place has parellel shaft gear drives similar to what you're building. I don't know how much they cost, but it may save you time/effort buying vs fabricating.

Hub City Inc - Standard Products

Whoopie! I had searched for parallel shaft gearboxes but could not find any the fir my purpose. Thank you. First glance at Hub City's catalog and specs indicate they may have a suitable reduction box. I got a quote for a "think it may work" gearbox from my local distributor and it is $600...almost triple my homemade reduction assembly. But the distributor just happened to have four new "surplus" boxes exactly the same that he would sell for $400ea. So now that's got me thinking again and back to deciphering specifications. By the time I add supporting steel to my gear, jackshaft and bearing assembly the $400 may be about a wash.

In the meantime I received the gear quote from Rush Gears. You can go to their site for the good design tools and drawings but buying there is out of the question for a single gear. The 6" gear I need was $1600 for one or $350 for 10! I found a similar gear at McMaster & Carr for $136. Unfortunately Mc does not carry the heavier duty 20 degree pitch angle gear, only the 14.5PA type. A trip to rushgear.com HP tool calculator says the 14.5 gear just meets my HP needs.