Worm Gear Upgrades

Jeeman,
In response to your thread:
https://vexforum.com/t/double-puncher/32071/1

As a kluge, you could drill a circular pattern of holes through the worm wheel and another gear, mount them on the same axis, and use bolts through the pair of gears to distribute the task of transferring torque to the shaft.

From the “what do you have left to lose?” department: You could file out the stripped hole in the worm wheel you damaged to a square barely large enough to hold a metallic hub from the high strength gear kit, then force-fit the hub into the worm wheel. (I haven’t done this yet, but I’ve been planning to do it the first time I strip a worm wheel.)

Good Luck,
Eric

Check out the brass worm gear and DC motor that I purchased from ALL Electronics and adapted it to work with VEX:

https://vexforum.com/gallery/showimage.php?i=3566&catid=member&imageuser=392

tswift1,

My understanding is that Jeeman’s problem is with the worm wheel, not the worm itself. In that case, your brass worm isn’t likely to help much. :frowning:

As the worm is the high speed/low torque member of the pair, it makes sense that the stripping would occur in the worm wheel, the low speed/high torque member. Furthermore, the square hole through the worm is much longer than the one through the worm wheel, so the torque it can transfer (assuming the materials are the same) should be much higher.

Eric

I had this problem using a worm to open and close a claw. I drilled a pair of holes in the worm wheel and added some plate metal to either side to grip the axle.

Thread here; pictures here.

Cheers,

  • Dean

Dean,

May I attribute this to my intracranial flatulence? :wink: I had forgotten that the smaller holes on the plates fit snugly enough on the shafts to fix the angles. For at least three reasons, metal plates are preferable to gears as means of improving the torque couple.

On a minor note, I was able to follow your link to the thread, but your link to the pictures leads me to a page that shows only text. (FWIW, I’m running Firefox 3.5.4 under LuzXPpro.

Eric

I’m not sure why the site isn’t working for you. It is a MobileMe website (Apple) which has been viewed correctly for Windows systems and from Macs running FireFox. Regardless, I’ve directly linked three of the more relevant photos here:

http://web.mac.com/dean.reece/Vex/Improved_GRIPPER_files/Media/Modified_Parts/web.jpg

http://web.mac.com/dean.reece/Vex/Improved_GRIPPER_files/Media/Worm%20Gear%20Side/web.jpg

http://web.mac.com/dean.reece/Vex/Improved_GRIPPER_files/Media/Worm%20Gear%20Back/web.jpg

Cheers,

  • Dean

Here’s a simple reinforcement we have used.
Drill inside dia of a pair of locking collars to .250".
Press these collars onto worm gear hubs.

What is the exact failure mode people are experiencing? Is the center square hole “stripping out”, or is it something else?

I actually broke the center portion of one of my not-the-worm-gear gears of the pair. It didn’t exactly strip the square hole, it just cracked enough that under load it expands just enough to let the metal bar click around.

In the gears favor, I put way to much load on it.

Got a picture of the failure? Email support@vexrobotics.com “Attention John”.

-John

It’ll be a couple weeks before I am back home with my Vex collection and even then I’m not sure if I kept the gear or not. I’d bet I kept it, because I’m a pack rat and hate throwing anything away… but I’m not sure.

Close, but not quite stripping out. In my case, it was wallowing out so that the worm wheel had something like 20° of play. I was using it to direct-drive a claw, so that movable finger wobbled way too much. Also, every time I gripped anything moderately tightly the play would get worse.

Personally, I’d love to see a high-strength worm-wheel with the following features:
[LIST=1]
*]Four screw holes around the hub so torque can be transferred directly via attachment rather than through the hub&axle
*]1/4" square hub for use with high-strength gear inserts
*]Possibly larger diameter to accommodate the above and to make mounting geometry easier.
[/LIST]

BTW, I’ve never had any problems with the worm gear itself. It has an excellent hub and it is always on the low-torque side of the gear set. I don’t think a high-strength version of it is needed.

Cheers,

  • Dean

We sure should have a larger selection of worm wheels with different amounts of teeth to make it easier to change the gear ratio.

Several Times I broke this gear when it was under a high load from the worm gear. A Crack led from the center hole to the Teeth and made it unusable. The worm gear kit would be benifited if this peice was metal.

http://web.mac.com/dean.reece/Vex/Improved_GRIPPER_files/Media/Modified_Parts/web.jpg