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TimJr

snowblower RPM

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TimJr
Just wondered if anyone has an accurate way to check snowblower rotor/auger RPM. A photo tach is the best way. I have been working on a 4208 with a 36" blower. Engine RPM is just over 3400 RPM, auger speed is a bit under 1600 RPM. The blower was just installed to this tractor. Tractor and blower were both original - not messed with before being joined together now. It doesn't blow snow as well as I would thought it should. Engine RPM could be bumped up to 3600, but that's only going to be around 100 RPM at the auger. My 18hp Sovereign also has a 36" blower, which came off a 4000 series(changed hitch obviously). The engine is running about 3600 RPM, and the auger on mine is turning just under 2200 RPM. My Sovereign blows snow quite well. That's quite a difference in RPM. I did not measure the 4208 tractor PTO pulley and my Sovereign PTO pulley. By looks, the Sovereign may be a little bigger OD. The 4208 engine PTO pulley is quite worn into/cupped, so the belt is riding way down in the "V", which now looks like a "U". I am loosing some effective diameter there, but do you think I have lost that much to be such a difference? I can't find any literature that says how many RPM a single stage Simplicity blower turns. Can anyone verify theirs? Thanks, Tim

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RickS
I have blown snow with a 7012 (old and rebuilt motor), a 7118, and a Legacy (23 horse); for all three there is only one engine speed -- full throttle. The snow-blowers take a lot to spin so I run the engines wide open and never had a problem. The Legacy has a tach and it reads about 3,600 RPMs. Rick........

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CarlH
Agree on full throttle. And make sure full throttle is 3600 RPM. I've seen more than one at 3000 or less. Then some of us put a smaller sprocket on the auger for a little bit more RPM. If you do something to increase auger RPM, make sure you have plenty of power. I believe the power requirement goes up as the square of RPM.

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Brettw
I believe almost every garden tractor engine is designed to be working under full throttle, as are the attached implements. That is one reason why they are governed and at 3600 RPM. I think. Maybe. Or I could be completely wrong. But I'll never admit it.

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Al
Hi, I think you will find that the 4200 has a lower ratio of the pulleys due to lower hp. The tractor should be running 3600. You may be seeing some slippage due to the u in the pulley. V belts are so efficient at transferring power due to the way they function. When the belt starts to go around the pulley, as it bends the sides are squished out, so the belt contacts the pulley and as it bends the sides press very hard against the sides of the pulley. As the belt comes off the pulley it straightens out the side pull back in and release the grip on the pulley. This why the pulley wears in a U. With the U the belt is unable grip the pulley and will slip when a load is applied. New pulley might make a lot of difference. This is a common problem with the front drive pulley on 7000 and 7100 tractors on the ground drive. Shows up a lot on shuttles when the tractors won't spin the wheels under load. Al Eden

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Steve72
Great question. I just installed a 36" blower on my HB212 and was a bit disappointed in the short (maybe 8') distance it threw the snow. I have a hand held tach that I can check engine vs auger speed and I will tomorrow...now that you got me curious I might take my pajama butt outside and check it now!

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Al
Hi, On a 10 hp Wards Squire 10, (Landlord) I made a drive and put a 36" blower for a Broadmore on it. I drove from the large pulley of the mid PTO and I would think it ran about 2000 rpm or maybe slightly more. In a wet snow I could go down the sidewalk and plaster the snow about 10 feet up on the trees across the street. It would throw probably throw 3 to 4 times as far as my friends 3 belt blower. You can calculate the speeds by using the pulley diameters. Al Eden

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TimJr
The 4208 engine PTO pulley is about 4 7/8" total OD - the belt does not ride anywhere near the edge of the pulley, let alone the wear allowing to sit in even further. Tim

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Steve72
Checked the RPM of my HB212 when cranked up to what has always felt like a good working speed to me. It was 2,800. Much below the 3,600 that a couple have said you like to run. I couldn't get a reading on the auger as it was not center drilled. Regardless, I am either babying this or there are some incorrect calculations. Also---I removed the snowblower after about 15 min of using it and went back to my blade. Faster, cleaner, no constant white-out and just more fun rolling that snow over!

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