Belt drive clutch?

[smooth90]

What are typical tension ratings on v belts?

This website seems to give very large values that I don't really understand.

http://www.gizmology.net/pulleysbelts.htm


My engine is rated at 20hp at 3600rpm (29 ft lbs of torque).

I used the formula Horsepower = (Torque*RPM) / 5252 to adjust the horsepower/rpm of the engine.

Lets say I had 2 x 6in pulleys 18 inches apart pushing 5.5hp at 1000rpm.

According to the site I would need

30lbs Minimum tension
146lbs Max tension
122lbs Initial tension

Can a typical 1/2in A belt take 120lbs in tension? That seems like a lot of weight to put on a little v belt but I don't know.

 

[Doc Sprocket]

I can't help you on actual tension values- I do that stuff by feel. But there's no way a simple "A" section belt is going to tolerate that kind of power. The tension or weight on the belt is one problem, but IMO the bigger problem is expecting too much of it.

 

[smooth90]

Well after crunching the numbers for a little bit I ordered some parts that created a system with much more reasonable values.

First off I realized that this is WAY too much power to be pushing through a single A belt as toystory_4wd said there's no way a simple "A" section belt is going to tolerate that kind of power.

Second the bigger the pulley the more surface area there is for the belt to grip and thus less tension although bigger bearing loads.

So I ordered a 6.4in pitch pulley and an 8.4in pitch pulley. They are both double groove and can accept B belts which are are a substantial amount stronger than the A belts. I also got some flat idler pulleys that I will mount to act as the tensioner.

So now I will have dual B belts which cut the tension in half on the spot running on larger pulleys. It basically means that I need about 50 - 70lbs of tension on each belt which really isn't that much. That is at maximum speed too 4000rpm at minimum speed 1000rpm I only need about 25lbs.

I'm super excited about this......this clutch mathematically works unlike the centrifugal clutch lets hope this pans out correctly!

 

[Doc Sprocket]

Can you give us some detail on the application?

 

[smooth90]

I am going to use this pulley system as a belt tension clutch for my go cart.

Basically I am putting an Onon p220g 782cc 20hp engine into an off road dune buggy made for 150cc.

The cart frame is a 150cc SunL frame with 22in rear tires.

I have posted before about this and my hunt for a clutch system. I blew off the belt idea in the beginning only to revisit it and figure out that its perfect.....lol that's $150 wasted on that burnt centrifugal clutch (may be fixable). I can't begin to go into all the projects I've ordered something for then figured out I needed a totally different part. Guess some day all the crap I collect will go to use.

http://www.diygokarts.com/vb/showthread.php?t=14360

 

[qtband]

I'd sure like to see pics of your belt set up.....

 

[smooth90]

I'd sure like to see pics of your belt set up.....

I will post pictures next weekend once I have everything installed.