Max rpm for auger??? - Snowblower Forum : Snow Blower Forums
 
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post #1 of 10 Old 02-28-2017, 12:52 PM Thread Starter
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Max rpm for auger???

Realistically, what kind of rpm's can a worm drive handle? I know most small engines will spin @ 3200-3500. Could a older, heavy duty auger tranny handle say, 1.5X?
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post #2 of 10 Old 02-28-2017, 01:25 PM
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Well, single stage blowers spin their augers pretty fast. Are the gearboxes on those designed differently?
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post #3 of 10 Old 02-28-2017, 01:31 PM
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The RPM of the crankshaft is reduced by the belt and size of the two pulleys. Most small engines run at 3600rpm and can't be adjusted to overcome impeller/auger speed significantly. You can take the sheave diameter and the auger pulley diameter, basic distance between the two centers and come up with an output speed for your worm set, typically they reduce at a 10:1 ratio from the impeller pulley to the augers themselves .
The speed of augers is not fast, the impeller is relatively fast when compared, but far less than engine. You can play around with numbers and sizes to see what you get.
Pulley Calculator. RPM, Belt Length, Speed, Animated Diagrams

I think most gear sets can take the slight increase we can obtain by modifying the sheave size (easiest is the crank sheave). Impeller speed increase will translate into better throwing distance, but you need some level of torque to complete/support the process. Ariens does this on their SHO versions. The engine is no more powerful than if on a non SHO machine. They change the impeller speed with sheave sizes. I don't know the cutoff that overpowers or overspeeds the auger gear set intake. Most impellers run around 1100rpm , and bumping them to 1400rpm shows significant improvement of throwing distance. I don't think any gear set is going to see excessive stress going from 110rpm to 140rpm.
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post #4 of 10 Old 02-28-2017, 01:33 PM
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Quote:
Originally Posted by guyl View Post
Well, single stage blowers spin their augers pretty fast. Are the gearboxes on those designed differently?
Single stage don't have gearboxes, the auger paddles are also the impeller and are usually belt driven, in a 2 stage the gearbox works like a differential on a car, Spinning shaft goes to gearbox and turns the auger shaft that's at a 90 deg. As for how much speed and abuse it could take. I have no idea lol

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post #5 of 10 Old 02-28-2017, 02:18 PM Thread Starter
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Quote:
Originally Posted by jtclays View Post
The RPM of the crankshaft is reduced by the belt and size of the two pulleys. Most small engines run at 3600rpm and can't be adjusted to overcome impeller/auger speed significantly. You can take the sheave diameter and the auger pulley diameter, basic distance between the two centers and come up with an output speed for your worm set, typically they reduce at a 10:1 ratio from the impeller pulley to the augers themselves .
The speed of augers is not fast, the impeller is relatively fast when compared, but far less than engine. You can play around with numbers and sizes to see what you get.
Pulley Calculator. RPM, Belt Length, Speed, Animated Diagrams

I think most gear sets can take the slight increase we can obtain by modifying the sheave size (easiest is the crank sheave). Impeller speed increase will translate into better throwing distance, but you need some level of torque to complete/support the process. Ariens does this on their SHO versions. The engine is no more powerful than if on a non SHO machine. They change the impeller speed with sheave sizes. I don't know the cutoff that overpowers or overspeeds the auger gear set intake. Most impellers run around 1100rpm , and bumping them to 1400rpm shows significant improvement of throwing distance. I don't think any gear set is going to see excessive stress going from 110rpm to 140rpm.
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post #6 of 10 Old 02-28-2017, 04:46 PM
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Originally Posted by guyl View Post
Well, single stage blowers spin their augers pretty fast. Are the gearboxes on those designed differently?
There's no "gearbox". Just a belt and some pulleys.
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post #7 of 10 Old 02-28-2017, 04:48 PM
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Originally Posted by Dauntae View Post
Single stage don't have gearboxes, the auger paddles are also the impeller and are usually belt driven
There's no impeller in a single stage. Auger only. The impeller is what makes a two stage machine two stage.
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post #8 of 10 Old 02-28-2017, 05:22 PM
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Originally Posted by buffettck View Post
There's no impeller in a single stage. Auger only. The impeller is what makes a two stage machine two stage.
LOL yes I know, was just trying to break it down for someone who doesn't know, that's why I said "IS ALSO" implying there is just one item throwing the snow.

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post #9 of 10 Old 02-28-2017, 06:55 PM
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When I did the math for the Gilson impellers they rotated at about 1000 RPM with the engine at 36000 RPM depending on the model. The worm drives are 21 tooth, double helix for a 10.5:1 ratio and yield an auger speed around 95 RPM.

Can they go faster? I think it certainly depends on the worm drive in question. An oil bath case running the worm in tapered needle bearings probably has a lot of headroom. A grease packed case relying on Oilite all around, not so much.

The raw speed, heat and wear are one thing. A bigger concern is probably the higher force/shock loads it will be exposed to when you spin it up. The lesser cases have a hard time staying together as it is.

Pete
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post #10 of 10 Old 02-28-2017, 06:56 PM
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Quote:
Originally Posted by buffettck View Post
There's no impeller in a single stage. Auger only. The impeller is what makes a two stage machine two stage.
Some will call it a rotor for the sake of differentiating.
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