Chain size and gear ratio

[pekabu]

Been thinking about a snowblower project I need to do. Anyway, I need to speed up the PTO output, so I though I would use a set of gears and chain. What size chain should I run? I was looking at Surplus Center and they have quite a selection. Also, if I run a 20 tooth gear off the pto, and 10 tooth gear shaft on the blower the shaft on the blower would be twice that of the PTO, right? I don't want to go that fast but I need a point to start figuring out what I need.

Should have also stated I currently have a 24hp tractor, but this blower could potentially be on a tractor up to 35HP
Thanks

 

[SPYDERLK]

You have the right idea on the gear ratio computation. Whatever size chain u use make it a good quality one. Keep the small sprocket at 15 teeth or more because the hi kink per link on a smaller sprocket will be bad on chain life. Small good quality chain lets you get enuf teeth in the size constraints. A #40 seems good to me. A high performance chain such as is used on motorcycles will transmit much more power safer and longer than std chain. Dont be fooled by a "heavy duty" designation either. Look for HorsePower rating. I see Hperf #40s transmitting 50 horses on mototcycles
larry

 

[diyDave]

The equation you are looking for is D1xN1=D2xN2, where D is #of teeth on the sprocket in question, and N is the speed of the shaft in question. For example: 20x540= 10(X) solved, X=1080 Get the idea here? Its just high school algebra, but when I lose that equation, I have to go hunting through machinists manuals to find it! Good luck on your project.

 

[vallyfarm]

Just curious, but why do you need to speed up the pto? Almost all tractors have used the standard 540 speed for decades. 1000 speed is for cat 2+ tractors. Are you trying to mount a belt driven blower from a lawnmower to the tractor? Most of them turn at 3600 rpm. You would need to have some quality machinework to keep parts from shaking loose. Mike P.S. Ask me how I know!

 

[jimgerken]

When I built my snowblower, I used #50 implement chain. I was tapping off the mid PTO, which is 2000 rpm. I wanted 1000 rpm on my single-stage impeller (some call this type of snowblower a "Snow thrower" if it is a single high speed auger with paddles, no seperate blower). Anyway, I reduced the speed from 2000 to about 1050 with chain and sprockets on the final drive. BTW, don't use an exact even reduction number, use an off number. Example, don't use a 20 tooth and a 40 tooth, instead choose 19 and 40 , or 20 and 41, etc. Less harmonic vibration that way. My tractor has 19 PTO HP. The toughest snow I blow with the blower (59 inches wide) is the stuff the road grader pushes into my drive when he goes by. Twice this winter when blowing this stuff I stretched my chain. Could tell right away cause I can clearly hear the slack. My tensioner is manual, so I stopped each time and retightened it and then the noise got lower agian. Next winter I will swap the chain for motorcycle 520, which I believe is the same pitch and will fit where #50 fits, but is a lot stronger and is pre stretched. Also motorcycle chain would be "o"ring equipped so would last forever on this application.