Tue Feb 09, 2010 7:13 pm
Tue Feb 09, 2010 8:21 pm
I just had a very nice conversation with Roger who has just come home from having his staples taken out. He had an full open field Gall Bladder surgery (not a laproscopy) on the 18th, and although he is recovering, he will be off of work for 4 - 6 weeks and then for the next 10-12 weeks is not able to lift anything. I was surprised he called back, but happy as well since he is sounding better than I expected.
He is quite familiar with what I am trying to do, and he tries to help me solve my puzzles. So.. Here is the gist of our conversation as it pertains to snow blowers and rpms.
Engines produce anywhere between 3,000 and 4,000 rpm at the shaft. Optimum rpms should be 3,200 to 3,400 rpm.
Typical pulley sizes on the shaft will be 3" to 3-1/2"
Typical pulley sizes on the cage will be 8" to 10-1/2"
Typically the reduction ratio will be on the order of 3 to 1 again depending on the size of the pulleys that manufacturers chose for each unit.
Discussing auger rpms.. Roger said that the auger rpms will be determined by shaft size, auger size and primarily gear reduction. Gear reduction can be nomially 2 to 1 for newer models and up to 4 to 1 for older models. This means that on average one should look for maximum auger rpms to be 500 rpm but more likely between 350 and 475 on the whole, again depending on which units are paired up.
I do not understand it all, but I got this much figured out. The 10 hp Tecumseh Sno King I have with a 3-1/2" pulley on the shaft mated to the 8-1/4" pulley on my cage with 16" augers, the older heavier 4 to 1 reduction should provide approximately 250 rpms at the auger. With the larger augers, he says I can actually reduce the size of the pulley at the cage to around 6" to increase the rpms without problem. No danger of blowing up the blower or the reduction unit.
Does that help?
Best I can do.. been trying for a long time to understand this and get answers. Most techs have no clue as to any of this, you really have to talk to the old timers.. so that is why it takes a while. I ain't no mechanic, I just have a clue as to what I want to be able to do.. getting there however, it the real adventure So far it has been at least a 2 year project with me, I want to be able to understand it and get it right. I don't want to blow anything up.
I sort of thought that the ratios between impeller and auger was more on the lines of 10 to 1, and mentioned it to Roger. He shot that one down real fast. That would make the the auger way too slow and could not provide enough snow to the impellers to actually move. On the older machines with the heavier gear reduction units, the ratios were 3 or 4 to 1 and the newer ones are closer to 2 to 1. Combine the smaller 12" auger size with the lower gear reduction ratios's and you can throw snow farther, in smaller volumes but farther.
I sure hope this is explained well enough.
Sat Feb 13, 2010 7:15 pm
Sat Feb 13, 2010 8:06 pm
Sat Feb 13, 2010 8:27 pm
Sat Feb 13, 2010 9:24 pm
Sat Feb 13, 2010 11:03 pm