How to figure out belt lengths?

[RonnieS]

I know WCproducts has a calculator but I am getting really confused with it. How do I figure out the size belt I need? We are using 36 tooth pulleys and from center point to center point the distance is 9.843 inches.

[jee7s]

Well, plug in your numbers for pulley size and desired wheel spacing, and the calculator gives you the possible belt lengths. You are unlikely to get exactly what you desire for a spacing, but you'll have two options that are close.

In your case, your options are to use a 130 tooth belt at a spacing of 9.2529 or a 140 tooth belt at a spacing of 10.2372.

When you lay that out, you need to be fairly accurate, so I'd strongly recommend calipers, layout die, and a machinist's scale.

[Jibri Wright]

To calculate the belt length you would add both circumferences of the pulleys together then divide by 2. You would then add this to twice the distance between the centers. Basically you have this equation:

((C1+C2)/2)+(2*d)

Once you have this length, divide it by the length of one of the teeth. This gives you how many teeth you need on the belt. If its a decimal, just round up.

[yash101]

You can try the datasheet, or you could try some basic arithmetic.

If it is on two sprockets:

PHP Code:

Here it is:
   /\--------/\
   \/--------\/
        \     \
         \    +sprocket
          +belt 


as per that ascii art, basically find:
the circumference of ONE sprocket (because you have 2)
Add that to the distance between the center points of the sprockets, times 2.

subtotal those and you should be off in flames!

[Jeffy]

Originally Posted by Jibri Wright

To calculate the belt length you would add both circumferences of the pulleys together then divide by 2. You would then add this to twice the distance between the centers. Basically you have this equation:

((C1+C2)/2)+(2*d)

To make it even more clear:
You would want to use the pitch diameter here.

[jee7s]

Originally Posted by Jibri Wright

To calculate the belt length you would add both circumferences of the pulleys together then divide by 2. You would then add this to twice the distance between the centers. Basically you have this equation:

((C1+C2)/2)+(2*d)

Once you have this length, divide it by the length of one of the teeth. This gives you how many teeth you need on the belt. If its a decimal, just round up.

I'm not speaking to the correctness of this formula, but if you are going to use a manual calculation, make sure you use the pitch diameter of the pulley. Also, you'll need to round up by 10 for the HTD timing belt. Other belts may have other size selections. But it's not like every tooth count is available.

[AlecS]

If you are using our Belt Calc, the calculator will run any time a value changes or when you press enter. Entry boxes that are white are user edited material. Greyed out boxes are what the calculator returns. The calculator runs in default 5mm HTD pitch.

To use, first select the two pulley sizes. The dropdown features all VEXpro pulley sizes, and by selecting other, you can manually enter your own size. In your case, you would need to enter 36 for each pulley, which is a standard VEXpro pulley.

Next, enter your desired center distance. In your case this would be 9.843". The calculator will try to find the nearest VEXpro belt sizes above and below this number.

Next, you can choose to edit the center distance tolerance with the Center Add box. This manually adds distance to the center distance to adjust belt tightness. The default +.001 works well in most cases. YMMV

The calculator then outputs numbers for the two nearest belt sizes, Smaller and Larger, than the desired center distance.

# of Teeth is the number of the teeth in the belt.

Center Distance is the exact center distance for the pulley+belt combo, plus the center tolerance.

P1 Teeth in Mesh is the number of teeth on Pulley 1 that are in the belt mesh. This number is useful when you have a very large and very small pulley on the same belt. Too few teeth in the mesh can result in belt slippage. For your case, this number can be usually be ignored.

P2 Teeth is the same thing as above but for the second pulley.

The calc says that you could use either a 130 or 140 tooth belt, which would have a center distance of 9.2529 or 10.2372 respectively.

Let me know if you have any more questions

[Chris Fultz]

http://www.gates.com/first/resources.html

I would use this design tool from Gates.

If you put in your data, it says you need a 136 tooth (680 mm) belt and that will give you your desired center distance.

[RonnieS]

Thank you, all of you. This really helps!

[magnets]

Originally Posted by yash101

You can try the datasheet, or you could try some basic arithmetic.
basically find:
the circumference of ONE sprocket (because you have 2)
Add that to the distance between the center points of the sprockets, times 2.

subtotal those and you should be off in flames!

Make sure you use the pitch diameter to find the circumference, and don't multiply the whole thing by 2. If you're using the same size pulleys, then its
C+2d.
It's not 2(c+d)