Belting Pulley Hubs & Discussion

[ttldomination]

Hello Everyone,

I know there are a multitude of posts on this topic, and I've tried to go through as many as possible, but I still have a few questions.

(1) Through the gates website, it appears that if we want to purchase a pulley for a belt (Let's assume PowerGrip GT2?) then there are two primary attachment types. Type 1 seems to be pressing the pulley onto the shaft and type 2 is using pulleys with set screw hubs.

Now my question is that are these set screw hubs reliable? I know that since they're sold in this application, they must "work", but I wanted some team input on this.

(2) Looking through McMaster, I learned that we can also buy pulleys which take in bushings, and then we can purchase bushings which have key bores. Anyone have any comments on this? Is there a way to purchase pulleys with a key hub already on them?

(3) Is there a place where I can get timing belt pulleys with a Hex Bore? All of my searching has proved fruitless.

(4) I would finally appreciate some advice on our situation. Our team has used #25 chain in the past with little success. I'm not blaming the chain; I'm blaming our building methods. So is stepping into belting a step in the right direction?

I am of the opinion that belting takes more effort/precision than #25 chain, and if we couldn't handle #25 chain, then perhaps timing belts are a bit out of our reach.

All comments are much appreciated,
Sunny G.

[ebarker]

My strong suggestion for FRC usage is to get the pulleys with set screws, preferably two set screws 90 degrees apart.

The using a good arbor press and keyway cutter, cut a keyway inside the bore and put the keyway directly under one of the set screws.

Then you can put it on a shaft with a key.

Some caveats. You will need a keyed shaft.

For example for doing 1/8 keys on 1/2 shaft we use the following parts from McMaster. The reamer is to size the bore. You may not need that. The broach and bushing match each other and is used to make the keyway. You will have to mill a keyway on a shaft or buy keyed shaft from McMaster. If you want a hex bore, you mill it yourself.

3106A42 High-Speed Steel Chucking Reamer, 1/2" Diameter,.4355" Shank Diameter, 2" Flute Length McMaster 1 $27.06

3153A16 Keyway Broach, Uncoated High-Speed-Steel, 1/8" Keyway, Broach Style A McMaster 1 $42.06

3151A115 Keyway Bushing for Broaches, for Broach Style A, Collared, 1/2" Diameter McMaster 1 $9.85

We are going to be having some workshops on this side of town and if you are interested we can demonstrate.

BTW - those tools above I keep locked up to keep untrained monkeys from making it as useful as a banana peel.

In general purpose usage, pulleys are bored much smaller than the final usage. Typically machinists bore the pulley to nearly proper size, then ream it with a precision reamer (above) and then make the keyways.

Pressed on bushings/pulleys/hubs when done properly are done with high pressure hydraulic presses Some stuff I've done in the past (not FRC) have used 60 and 100 ton presses to remove the hub.

In the past in FRC we have gone without keys but filed a flat spot on the shaft for the set screws to land. Really ghetto and only is useful for FRC robots with minimal loads or stresses. It requires constant maintenance is and a pain.

Ed

[Teched3]

we use a broach to cut the ketway in our wheel and pulley hubs, and either mill our own keyways in shaft material, or buy keyed shafting. We NEVER depend on set screws, but retain the keyway/wheel assembly using larger bushings outside the heel hub between the axle block or frame. if you do use set screws, it is advisable to double set them (one on top of the other) to lock them in place. Just another opinion for you to consider.

[sdcantrell56]

Hey sunny...sorry it's taken so long to get back to you. I would buy plain bore pulleys and then invest in a hex broach and use hex shaft. Once you go hex you'll never go back. We refuse to use keyed shaft unless it's the only option.

Your comment about having issues with 25 chain is not a good sign for belts though. If anything belts require more precision than 25 chain. We need to sit down and look at your drivetrain sometime and see where the issues are coming from. Until you can run 25 without breaking it or having it come off the sprocket stay far far away from belt. Honestly there's nothing wrong with sticking with 25. I am still debating what we will do in the future. I love belt but I like a lot of aspects of chain as well.

[Clem1640]

I love keyed shafts & pulleys. They turn together. Set screws will limit axial movement, but only is you and your team were born very lucky, otherwise they loosen and shift.

[Justin Montois]

I filled out the donation form for some Gates products. Has anyone else done this? I haven't gotten an email saying they received my request.

Does anyone have experience with this? Should I have received notification that they received it or it was shipped?

[ayeckley]

Originally Posted by Justin Montois

Has anyone else done this? I haven't gotten an email saying they received my request. Does anyone have experience with this? Should I have received notification that they received it or it was shipped?

In our case there was no direct acknowledgement that the emailed request was received until roughly a week later, and it came in the form of a shipping notice. The parts showed up last week (a total of about 2-3 weeks after the initial request) via FedEx Ground. Sorry I don't have the exact dates accessible at the moment. The sender's information on the shipping label offered no clue that it was from Gates; it wasn't until I opened it that I realized what it was.

Edit: Are you sure that you sent the request with the exact subject line that they instructed us to use? I'm assuming that determines how things get routed within the Gates offices.

[roystur44]

Team 971 made good use of GT2 timing belt the past year.

A 20 tooth GT2 5mm pitch (15 mm wide belt) is rated to 93 in-lbs

We used GT2 belt on our 2 stage elevator. I must say that our elevator is one of the best I've seen. We were fast, accurate, light weigtht and easy to manufacture and maintain.

We accidently caught our roller claw on the peg and the elevator picked up our 120 lbs robot no problem. The belting did not skip.

We use belting on our roller claw and that worked out pretty good.

We hex broached the pulleys and used nylon spacers to align the pulleys.

You can take a look at the use of the timing belt here:

https://picasaweb.google.com/1177698...anismCloseups#

http://www.youtube.com/user/roystur4.../9/3jm_yPl83gs

[Justin Montois]

Originally Posted by ayeckley

In our case there was no direct acknowledgement that the emailed request was received until roughly a week later, and it came in the form of a shipping notice. The parts showed up last week (a total of about 2-3 weeks after the initial request) via FedEx Ground. Sorry I don't have the exact dates accessible at the moment. The sender's information on the shipping label offered no clue that it was from Gates; it wasn't until I opened it that I realized what it was.

Edit: Are you sure that you sent the request with the exact subject line that they instructed us to use? I'm assuming that determines how things get routed within the Gates offices.

Thanks for the info. I did use the subject line as directed. I guess i'll just be patient. Thanks again!