Has anybody had any issues with the square holes in the worm wheels. I remember seeing that the standard gears have a rating of 33 in lbs before the square holes strip out. With the crazy reduction of the worm gears i could easily see putting over 33 in lbs on the worm wheel even with them doubled up.
I have been messing around in CAD and it looks like i could possibly get a cut down lock plate bolted to the worm wheel if i drilled some holes in it but i would be very tight.
Adding more worm wheels is an option but it would mean getting more brackets which is a lot of weight that i don’t need.
Has anybody found a way to reinforce the worm wheels that i am just not seeing? I feel like there used to be a picture of a reinforced worm wheel in the gallery but after searching for quite a while i couldn’t find it.
We tried using worm gears to hold onto the goal in Quad Quandry. We could latch onto the goal and not need power to hold it. But if a robot hit us, the impact would shatter the worm gear when the arm tried to drive it backwards. We never had any issue with them actually stripping. We had to come up with an alternate design.
This may be the one it does look very familiar. And with a little bit of trimming it looks like you could possibly get that to look pretty nice. Good find.
You may want to have a few layers of those, we tried using the diamond-shaped holes in the plates once as a lock plate (we had ran out of them) and they were easily twisted and stripped.
Yeah i had a way to make that idea work but with lock bars instead and i had finished the CAD but when i went into my room and looked at the parts i realized it was a case of me looking at something very small in the CAD and doing way to much with it.
The first think i did was test out the strength of the diamond hole in the plate i think two layers of plate on each side of the gear (total of 4 layers) will work perfectly, and maybe be a bit overkill.
One question, when you reinforced your worm wheels with the plate as shown above did you trim the corners so they do not hang over as they do in the picture or did they clear everything?
Here are some pics of my finished part. You can see I also used 4 layers (two on each side).
I did not trim the metal because I was just using the worm for a about 75° of rotation. The geometry I used would not work well for a continuous-rotation worm drive because the screw holes are just too close to the gear teeth.
Hopefully Vex will come out with a high-strength worm gear at some point, since this seems to be a recurring theme.
I agree. It seems like the worm gears are kind of too strong for themselves. 24 times 3.25 inch pounds (preferred torque) is about double what the worm gear is able to handle without stripping the square hole out. If you stall it out you have over 4 times the amount of torque it takes to strip out the square hole. I feel like a metal worm gears and worm wheels would be great.
I was able to modify your idea for reinforcing the square holes and i can cut them down a bit so i can get a full 360 out of it. However this involves cutting out the parts fairly precisely and then drilling some holes fairly precisely. It is probably worth doing it on the Bridgeport.
Does doubling the worm gear (seen in green) double the speed of the worm wheel (seen in grey) or does this not affect the worm wheels (grey gear) speed?
No, it wouldn’t affect the speed or torque. The calculation for the worm gear gear ratio is number of teeth on worm wheel : number of teeth on worm gear. As the worm gear (in green) has only one tooth, and the worm wheel has 24 teeth, the ratio is 24:1, even when you double the length of the worm gear.
Yup, a single-thread worm gear like the vex one will always be 1:number of teeth on output gear.
Alternate ratios could be obtained if the worm had 2, 3, or more “threads” on it, which would create a 1:12, 1:8, etc, ratio. Of course, this would probably require different output gears as well, with steeper angles on their teeth