Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

what size pulley should iput on 305cc engine there is a 51/2'' pulley on blower .it is a 36' cut blower for a lawn mower but i am modifying to go on atv .its a single stage so i want to get most power i can out of it.any help would be appreciated thanks..

I do not know what you are trying to achieve. Do you want to spin faster or slower.  if you want to spin faster you need a bigger engine pulley. if you do that your engine will work harder and may bog down. When folk play with pulley sizes the mount a bigger engine to carry the load. this will allow you to change pulleys to make your auger spin faster with out bogging down. You can then throw snow with greater distance. If you get a smaller pulley you will have more power digging through snow. Your engine will work easyer, you will in turn will not through snow as far because your auger will not spin as fast. I do not know what your engine is doing rpm wise. Todays blower impellers spin 1130 rpm and engine speed around 3600. that is about 3 to 1 ratio. If your engine pulley is 5.5" your auger pulley must be 16.5". You can try a 6" engine pulley on your engine. It may work a little better. I will not go any bigger. You engine may bog through heavy snow

thanks for info so far i tried a 51/2 pulley on both engine and auger would only throw snow a few feet and bogged down stall engine easily this is a stage one blower no fan any help would be appreciated

Don't know whether this will be of any help without knowing more about what size engine you are driving your blower with. But standard sizes for pulleys on a lot of walk behind blowers are.
2 1/2 to 2 3/4" engine pulley and around a 9" pulley mounted on the impeller shaft.  But with a single stage it is probably different because you are just driving augers no impeller.  But having said that
the augers on tractor type single stage blowers spin much faster than the augers on a 2 stage blower.  The 5 1/2" pulley on the auger shaft may be about right???. But a 5 1/2" engine drive pulley sounds
a bit to large.  What type of setup are you using to drive the blower off the ATV?

If you are bogging down you need a smaller engine pulley. 305 cc should give you good power. Try not feeding it to fast

tried a 4 inch pulley on engine today seemed better than 6 inch it seemed to blow snow not too bad but not throwing it very far maybe 4 or 5 feet.should i try a 3 inch or smaller pulley will this help throw snow farther....thanks for info so far.

josjay wrote: Stepping down from a 4" drive pulley to a 3" will slow down the auger RPM.  So, no the 3" pulley will not "help throw the snow farther"
In your first post you said that The engine is a 305cc.  Is that the size of the ATV engine? And is that engine driving the blower using some type of PTO shaft or belt?  Or do you have a separate 305cc engine mounted somewhere driving the blower?  Is the auger shaft on the blower being driven or spun by a chain and sprocket?
Does the blower have a right angle gear box on the back of it? With a shaft that has a gear on the end which drives a chain,
which drives another sprocket that is mounted on the end of the auger shaft?
It's rather hard to give any advice without knowing what type of setup you have. What brand or make and model is the blower you're trying to use.
It's also very important to have some idea what RPM the engine drive shaft is spinning at.  It's normally around 3600 on most walk behind blowers at full throttle.

you are right on with what i got.  I have a 305 CC BnS engine and a 5 1/2 inch pulley with a sprocket running the chain for auger on bottom.  On top I have a 4 inch pulley on engine separate from ATV.  Throws snow only 4 to 5 feet.  Any more help would be appreciated thanks...

sorry i forgot to say auger is driven by chain and sprockt would it make any difference to change that part of it.thanks

Yes, changing any of the sprockets or pulley diameters will effect how the blower performs.  And how the engine responds when you fill the blower with snow.

I'm trying to figure out how many pulley's and or chain sprockets you have (I'm thinking probably 4).  Does the engine crankshaft have a belt pulley on it, or a chain sprocket?  Does that belt or chain go around another pulley or sprocket that is on a shaft that goes into a right angle gear box?  Is there then another longer shaft that comes out of the gear box that has a chain sprocket on the end of  it. And a chain that goes around another sprocket that is mounted on the end of the auger shaft?  Need to know the diameter of all the sprockets and or pulley's. What's coming off the engine shaft a belt or chain?  The is no way to figure out anything without knowing how the auger is being driven.

If it's any help, my single stage runs at 900 RPM when engine is at 3600. So a stepdown of 4:1 at 10 ft lbs of torque for each 1' of auger. If you have more torque per ft you can go faster thus throwing further.

ok this is what i got a 31/2' pulley on engine with a belt to a 51/2' pulley on shaft. at end of shaft there is a 2' sprocket and a 6' sprocket on auger driven by chain there is no gear box  . it seems to throw not bad but only about 4 feet would like to throw farther.any help is appreciated thanks.

josjay,

Do you have some pictures of your setup so we can get better understanding of your equipment?

There are a lot of factors and number calculations that go into getting things like this correct.  Finding out what brand blower you have and what it was made to go on would be a big help to you.  Knowing what speed the auger was designed to spin at is an important number. If you know what brand blower you have and or what the model is. It would be to hard to get some information on it.

If you use the 900 RPM speed that Bill H posted and the pulley and sprocket size you posted.  It could go something like this
2700 RPM shaft speed X 2 (sprocket size) = 5400 / 6 (auger pulley size) = 900 RPM
(Engine crank speed) 3600 RPM X 3.5 (engine pulley size) = 12600 / 5.5 ( pulley size) = 2290 RPM
That 2290 RPM speed is to slow you need 2700 to have an auger speed of 900 RPM
So if you decrease the "driven" pulley size from 5.5" down to 4.5" you get.
12600 / 4.5 = 2800RPM
If you then recalculate that would work out to an auger speed of 933 RPM.
But all this depends on the 900 RPM auger speed being what you need.

What you're trying to do, is do able. But you have to know where you're trying to get to, before you can figure out how to get there.

I think you may need more information to get things right.

Don't know what make of blower it is, I think it was for a lawnmower but not sure, I want to increase throwing distance the engine pulley is easy to change but auger pulley is welded on shaft and would have to change shaft and all... I am goin to continue to import some pics I took.... Thanks.

Not havin much luck uploading pics can't understand the directions... will keep trying..

To BillH , what size of pulleys do you have on your engine and auger, and does it throw snow far? Thanks

http://www.facebook.com/photo.php?pid=17742599&l=7a643f213d&id=821330296

You may be able to view the photos on this site... let me know... Tks..

The photo does help. To make things a little easier. The pulley on the engine crankshaft is usually called the "drive" pulley.  The belt goes around that pulley then around the other larger pulley.  Called the "driven" pulley.  Same thing with the sprockets.  "Drive" sprocket (the 2"one) "Driven" sprocket (the 6" one)
Messing with the chain sprockets size probably isn't needed. At least the 6" one
Can you somewhat easily remove the (5.5") "driven" pulley from the shaft that it is mounted on?
For every 1/4" change that you make in the diameter of the "drive" pulley up or down.  You get a + or - change of 900 RPM.  That is with an engine RPM of 3600. 
By my calculation if you use a 4 1/4" "drive Pulley on the engine you should end up with an auger speed right around 900 RPM.
4.25" drive pulley 5.5" driven pulley  2" drive sprocket 6" driven sprocket. Auger shaft RPM around 900

Maybe someone else could check these numbers.  I'm not exactly sure about the sprockets.  I'm making an assumption that you can use the same formulas as are used for pulley's but not sure about that.
We don't know for sure if the 900 RPM auger speed is what it was designed to be run at.
 You are I believe using a 10HP engine.  Which may or may not be large enough.  If the tractor that the blower was meant to be used on was running a 12, 14 or 16hp engine then you may have a problem.
There is a point where the engine drive pulley that is needed to reach a certain RPM will be to large for the engine to maintain it's RPM when put under a snow load. When you get to that point or have that problem all you can do is bolt on a larger engine.
The blower should, for sure be able to throw snow further than 4 to 5'.  Single stage blowers don't usually throw as far as 2 stages.  But you should be able to get at least 12 to 15' or more if things work out.

Sorry josjay, but that info won't help you, since my driven pulley is on a shaft with a sprocket and the auger is chain driven from that sprocket. I'd have to do some disassembly to get all the numbers.

ok thanks for your info ,mine is the same driven pulley on shaft with sprocket auger ischain driven.

josjay, just thought of something else. On this type of blower, the distance between the auger and the housing is critical for distance. Make sure your auger is in close. If you can adjust it, great, if not, then make up something similar to a Clarence kit for the two throwing paddles. Also, they throw a lot better when the auger is kept full, so keep up your forward speed in light snow. Now that I can see your pic, it's not a lot different than mine except for length. My driven pulley is centered on the housing (longer shaft) because it comes off of the front PTO. This pic (if you can see it) shows a 20HP driving a single stage 48" blower. http://www.mytractorforum.com/attachment.php?attachmentid=145587&d=1298832440

got a 4'' pulley today could not find a 4 1/4 will try this one soon as i get time will let know how it works. thanks alot for info i understand how a pulley system works alot better now.bill h i seen your pic it throws snow good what is a clarence kit.

Just search here for 'clarence impeller kit'. You'll only need two pieces for your paddles. If you can adjust your auger within 1/8" or 3/16" of the housing you may not have to.

ok i tried the 4' pulley today it did not work very well it would stall engine very easily.then tried a 3 1/4' but not work as good as a3 1/2. so i guess the 31/2 is the best im going to get work not bad throw snow 10 feet  would like to get further but dont know what else to do also was very wet snow chute plugging up.

Put a big Vangard V-twin on it.  The additional power will allow a lot of pulley size flexibility.

Not surprised the engine didn't have enough to drive a 4" pulley and turn a 36" blower.  That's asking a lot of a 10hp engine.  Your probably going to need something like a 16hp to really get things going.
Or as borat suggested the Vangard V-twin would certainly give you what you need.

would bigger pulley on bottom make any difference or would i be wasting my time.

A bigger pulley on the bottom (driven pulley) would help some with the engine bogging down problem.  But using a larger "driven" pulley is going to drop the RPM of the shaft.  So the auger
RPM will be dropping as well.  Your throwing distance will suffer.  The Blower width, auger RPM, pulley/sprocket combination and engine size are all engineered to work together. If you drop the HP
that the system was designed to be used with.  There really is nothing you can do to get around the lack of power.  You can always increase the power/HP driving a designed system and improve the
blower performance.  But you can't go the other way and offset a lack of engine power by changing the gearing so to speak. 

Bill H has a 48" blower on his tractor which I know is 12" wider than yours.   But he also has a 20hp engine.  That's twice the size of yours, roughly.  I'm afraid you only real option is to get a larger engine.
A 16hp would probably do it.  And as was suggested reducing the clearance between the throwing portion of the auger and the housing is also important. 
If you want to get the maximum performance out of the blower.

As a single stage blower owner and being extremely jealous of all of you knowledgeable 2 stage owners I read all of these threads with great interest. I was thinking about the issue of impeller and auger housing clearance and thought about the possibility of using something like a roll-on truck bed liner like dupli-color bed armor or something similar. Enough coats would probably help with the auger clearance while protecting the housing at the same time. Good idea or bad?

I wouldn't think that the bed liner material would be a good idea.  Although it would be durable.  You need a smooth surface for the snow to travel over. The smoother and slicker the better.  Most bed liner material is textured. It's designed to produce somewhat of an anti skid surface. 

Just to clarify, it isn't really about auger clearance.  On a single stage tractor type blower.  The clearance issue is limited to the two or so blades in the center of the augers. That actually catch and throw the snow up the chute. The augers to the left and right of the center blades/paddles simply move the snow to the center for discharge.

On a two stage blower.  It's the impeller blade to housing clearance is the important issue. 

thanks for all the info iguess ineed more hp.just wonderin would a 2 stage blower work better or would it be the same as a single stage.

A two stage would work. But you'd have the same sort of problem.  A 10hp engine would not be big enough to run a 36" 2 stage blower.

ralphfr wrote:

Is your auger adjustable? Some large single stage blowers have a means of adjusting the auger clearance. Check your manual if you can't tell by looking, or even the parts manual. It makes a HUGE difference.

JRTREBOR - Makes sense. I had a feeling the texture might be an issue. Initially I thought this was just an impeller issue until I read a post earlier in this thread alluding to auger clearance as an issue. Thanks.

BILL_H - Not an issue for my Toro SS as the housing is plastic and the auger is rubber and wears with use but thanks for the suggestion.

checked my rpm on engine today it is at 3640 rpm.would it be safe to turn it up,iread on here someone had turned up to 4500 with no problem.

Most OPE four stroke engines are designed to run at 3600 rpm.  You could spin it at 4500 but who knows what effects it will have?   I have no reservations spinning up two cycle engines.  Not sure I'd want to be spinning an OPE four stroke engine too high.   Go-cart racers do it all the time but they also rebuild their engines every so often. 

I had 4 stroke Honda 160cc engine running above 4000 RPM and it didn't feel right.  The noise was quite loud with the existing muffler.  The vibration was unbearable without some kind of isolation engine mounts from the chassis.

Increasing the RPM isn't really going to accomplish much.  On OPE engines an increase in RPM at the high end won't do anything to increase the torque. It fact it will probably drop, the higher you rev the
engine.  So the auger may spin faster, until you put a snow load on them. There is no short cut to take if your you don't have enough HP to run a blower.  And that is the problem you have. 
A 10HP engine simply isn't large enough to power a 36" blower. 

If there was a way around that problem with gearing someone would already be doing it.  Blower augers (single stage) and blower impellers
(2 stage)  need the right mixture of power and RPM to operate well.

There is no replacement for displacement when it comes to torque.

borat wrote:

Reminds me of an old hot rodder's saying "There's no substitute for cubic horsepower" :)

ok good to know for sure  tks for all the info you guys were a great help.