Help with Purchasing Correct Pulley
 

My team and I are connecting a miniCIM to a 100:1 versaplanetary gearbox, to a 10 tooth pulley to a 60 tooth pulley to give us an overall ratio of 600:1 for our arm mechanism.

We've went to SDP/SI for our pulleys but we are new to this type of mechanism and are unsure of what exact components we will need to make sure everything connects correctly.

Here are the two pulleys (10 and 60 tooth, both with double flange)
http://sdp-si.com/ss/pdf/81002029.pdf

What components do we need to purchase with our versaplanetary gearbox kit so that it will connect to the 10 tooth pulley and what do we need to buy to mount the 60 tooth pulley to our 1/2" hex rod?

Thank you for the help!

Re: Help with Purchasing Correct Pulley
 

You would need a 1/2" hex broach or turn down the 1/2" hex to the bore of the pulleys.
I would recommend using #25 chain and sprockets instead, or even #35, as it is readily available at Vex and Andymark, is much more forgiving in terms of strength and precision, and comes in 1/2" hex bore sizes.

EDIT: Those are MXL pulleys, which are not commonly used due to their lower working load. GT2 or HTD pulleys are generally better for our purposes.

Re: Help with Purchasing Correct Pulley
 

If we were to switch to chain on VEX, could you recommend a setup with approximately 600:1 using vex components? Using a 12t to a 60t would work for our purposes, but I don't think we can spare the 7 inches for the 60t sprocket.

Would it be ridiculous to connect 3 versaplanetary gearboxes and avoid large sprockets altogether?

Thanks for the help!

Re: Help with Purchasing Correct Pulley
 

At 100:1, you are already exceeding the maximum rated load of the Versaplanetary. See the load rating guide here: http://content.vexrobotics.com/vexpr...s-20151221.pdf

Geared this far down, you're looking at some pretty large amounts of torque. I'd definitely prefer to go chain over belt, and might even want to step up to #35 chain.

Re: Help with Purchasing Correct Pulley
 

I didn't see where the load of the arm was posted. a 600:1 reduction doesn't necessarily exceed the load rating.

Re: Help with Purchasing Correct Pulley
 

It doesn't look like you can attatch a 10 tooth pulley to a half inch hex rod. The 10Tooth Pulley (A 6A16-010DF2504) has a OD of .235 inches.

Re: Help with Purchasing Correct Pulley
 

Ideally, yes. But as soon as the arm attempts to drive itself into a hard stop due to a bug in the code, tries to rotate against a field element or another robot on the field, etc, you'll see much higher than the intended load. Cracking the carrier plate inside a VP isn't my cup of tea when it comes to failure modes.

Re: Help with Purchasing Correct Pulley
 

You are exceeding the load only if you stall out the motor. Placing a current limit or voltage limit on the motor will stop that from occurring. Theoretically at hose ratios one could use a BAG motor or something smaller, but the greater mass of a minicim or CIM makes it a bit safer.

Re: Help with Purchasing Correct Pulley
 

If you want to go with a belt, you can try the Gates calculator.
http://ww2.gates.com/first/resources.html

I like Gates belts for the drive train and I've found belts to also work well for low force applications like an intake roller.

In 2014 we used chain to transfer motor torque on our shooting arm. Chain is more tolerant of lateral mis-alignment and the tension variation than belts.

Dave

Re: Help with Purchasing Correct Pulley
 

600:1 is huge. Are you sure you need that much torque? If you want to stay with belts, you definitely need to use the wider 18mm belts and pulleys.

To stay close to your original design (333:1 instead of 600:1) Vex has some great pulleys already broached for the 1/2 hex - smallest is 18T. http://www.vexrobotics.com/vexpro/mo...tdpulleys.html Also they have light weight 60T http://www.vexrobotics.com/vexpro/mo...rsapulley.html Most importantly, they have a calculator that is set up for these stock parts to help you pick the correct belt for you pulley pitch http://www.wcproducts.net/how-to-belts/