belt size

[diycnc]

what size and type of belt should i use for belt reduction using kelling 226oz servo (1125 oz-in Peak) would 3/4" wide L belt be sufficient?

[harryn]

Hi, I will take a stab at your question, but for more detailed info, refer to brecoflex.com - a really good belt company.

Most belts are rated based on tooth strength (when it will break a tooth). That is ok, but it seems like you need at least 10 X this to have low stretch, at least by my thinking.

I cannot really see going less than 1 inch / 25mm wide belt for much of anything. The nice thing, is that 1 inch wide belt is pretty standard stuff. Probably a bit overkill, but imagine the effect of your belt stretching or not - becomes significant real fast.

[diycnc]

once past 3/4" wide the price seems to increase dramatily. who is a good vendor of affordable 1" timing pulleys?

[harryn]

Hi, I have only received quotes so far from brecoflex for AT-5 and AT-10 pitch belt. You just go to their web site, use the drop down menus to pick a belt or pulley spec, and they will send you a quote. Personally, I prefer published prices but it worked.

Just to give you some rough pricing (older quote prices), here is a link to my build thread which has some examples starting around post 14.

http://cnczone.com/forums/showthread.php?t=38940

Belt was about $ 1 / inch for AT-10 / 25mm wide. (1 inch) Pulleys were approx $ 30 - 50 each, depending. (not exactly cheap, so let me know what you find) After doing some more reading, I was not convinced that AT-5 would be strong enough (from a tooth deflection viewpoint), which was sort of confirmed by their application examples and suggestions.

For me, the nice thing about going with metric belt / metric bores is that I could more easily match up a 12mm hole with a 12 mm shaft and a 12mm dia inner race bearing. I am sure it works with the inch system, I just was having a harder time figuring it out, especially how the tolerances stacked up.

You should know that I am still accumulating parts and have not yet built my router. If you decide to go for some AT-10 parts, let me know - maybe we can group our order and get to the qty discount point.

[ger21]

If you're just going pulley to pulley, from the servo to a screw or pinion, You can probably get away with 1/2" or even less. Go to www.sdp-si.com and do some research.

[diycnc]

yes its just 4:1 belt reduction using very short belt. its going from the servo to a ball screw. i think i will go with the .75" L belt as it seems to be the most economical solution out there.

[Kipper]

HTD5 15mm width is what you want.

[diycnc]

please explain how you figured this out.

[Kipper]

Originally Posted by diycnc please explain how you figured this out.

1, It's a short span...no need for 25mm belts to minimise stretching.
2, High speed high torque capability.
3, You're looking for low backlash so HTD is shouting to be used.
4, They are a doddle to make.

[diycnc]

having a hard time finding a vendor that has the sizes i need in htd for a reasonable price. my motor is 1/2 and the screws are 12mm. i need a ~20 on the motor and ~80 on the screw.

[harryn]

Originally Posted by diycnc having a hard time finding a vendor that has the sizes i need in htd for a reasonable price. my motor is 1/2 and the screws are 12mm. i need a ~20 on the motor and ~80 on the screw.

4:1 - That is a big range to find in one step and roughly the same diameter shaft. You might end up having to bore out the lower tooth count pully to fit the motor, and use a pulley with a larger bore for the 80 tooth.

There are some pulley mounting setups that use a sort of collet to tighten the shaft and pulley that can adapt to that difference in hole size. They are kind of expensive, so I have so far avoided them, but they are well thought of as they apply very even pressure on the gear and shaft.

I don't personnally have the equipment or skill to precision bore a timing pulley, but you can also buy "blanks" with the teeth cut and no holes if you like.