Worm gear discussion

[killjoyken]

Finally got my high speed worm gears today and I'm a little puzzled. Everything I've read states that a worm drive's ratio is the number of teeth on the worm drive (big, round gear) to the number of teeth on the worm (basically 1). The stock worm gear has 30 teeth, giving it a ratio of 30:1. The high speed worm gear has.......30 teeth. The only difference between the two is that the high speed gears have more of an angle to them.

I've been trying to research worm drives, but most of the sites I find start getting into equations that are waaaaay over my head. And since my company is shut down for 2 weeks I don't have access to the mechanical engineers.

So, any mechanical engineers out there that can clue me in on how a 15:1 ratio is achieved with a 30 tooth worm gear?

[Brandon]

Its all in the angle. Imagine pushing an object 10mph but its only allowed to travel 10% of the speed you pushed in that direction. How fast will it be moving? 1mph correct?

Now imagine its allowed to travel at 20% of that speed you pushed. Therefore 2mph. Double the angle, you double the speed translated to the direction you pushed.

Same goes for the angle of the cut on the upper gear. The RPM of the top gear is being translated into rotational motion of the lower gear by a factor of 2, therefore the angle was probably doubled.

Or its really late and I am super tired and that made no sense?

So to directly relate to the worm drive gears on the RF: I am guessing that with one rotation of the original upper gear you move 1 tooth on the lower. Now with the increased angle you are moving 2 teeth on the lower gear.

[dkingston]

Originally Posted by Nluvwithxlr8ing

Its all in the angle.

BINGO!

Did you get those things installed yet????


- David

[dezmoon]

Originally Posted by Nluvwithxlr8ing

Its all in the angle. Imagine pushing an object 10mph but its only allowed to travel 10% of the speed you pushed in that direction. How fast will it be moving? 1mph correct?

Now imagine its allowed to travel at 20% of that speed you pushed. Therefore 2mph. Double the angle, you double the speed translated to the direction you pushed.

Same goes for the angle of the cut on the upper gear. The RPM of the top gear is being translated into rotational motion of the lower gear by a factor of 2, therefore the angle was probably doubled.

Or its really late and I am super tired and that made no sense?

So to directly relate to the worm drive gears on the RF: I am guessing that with one rotation of the original upper gear you move 1 tooth on the lower. Now with the increased angle you are moving 2 teeth on the lower gear.

what ever you did there,,i completely understand for some odd reason

[BILLYGOAT]

wow. i guess m still tired cause that makes perfect sence to me . thanks n-luv thats great info.

[Dewmerz]

Great explanation Nluv. I was wondering how the ratio could change but the overall gear size didn't.

[HiloDB1]

Worm gear ratio has nothing to do with pitch. If you look at the worm portion of the HS set I bet you can clearly see two "threads" on it. That is what makes the ratio different. The stock single "thread" worm is considered a 1 tooth gear. So stock worm is 1 and stock worm gear is 30 and you get 30:1. HS gear set worm has 2 "threads" on it so its considered a 2 tooth gear. And now you have 2 and 30 witch gives you 30:2 or 15:1 ratio.

[killjoyken]

Sorry Hilo, but I think Nluv's right. The HS worm still only has 1 tooth.

Makes sense now. Thanks Nluv. It was late and I just watched the entire 7th season of Family Guy and the last three episodes of South Park. I guess it's true that TV rots your brain.

Yeah, they're installed now along with the dig. Just need to program the dig servo and figure out what pinion/spur combo to run and I'll be set. Unfortunately, it's freakin raining again and doesn't look like it's going to clear up until Friday. At least I'll have time to work on my JK scaler.

Now I'm really curious to see the worm gears in the Losi.

[mike_d]

Now that you have the HS gears installed what motor do you plan on using?

[killjoyken]

Originally Posted by mike_d

Now that you have the HS gears installed what motor do you plan on using?

I just tested my rig in my garage with a 30t Holmes, Sidewinder/CCBEC, 3s lipo and 72/21 combo for a 51.4:1 ratio and it's about the same wheel speed as my GC-1. My GC-1 is running a 48:1 ratio with a 35t Holmes and it's perfect for me. I think I'm going to stick with this setup but I won't know til Friday when I can get it on the rocks. I just wish the RF came with the high speed gears from the start. Could have saved me a lot of headaches. At least it's quieter...not as quiet as my GC-1, but better.

The dig works great but it's sticking in the lock position. I'm not running springs or fuel tubing and my EPAs are set perfectly. (had a lot of practice with my DNA) Works perfectly on the bench, but on the floor with forward load applied the servo can't pull it out of lock. Good news is that a quick blip on reverse releases it without moving the rig backwards so it shouldn't count as a reverse. Again, more testing on Friday.

[EeePee]

Originally Posted by killjoyken

Good news is that a quick blip on reverse releases it without moving the rig backwards so it shouldn't count as a reverse.

Wiggle the steering tires first. That usually gets them things to let go.

[dkingston]

Originally Posted by EeePee

Wiggle the steering tires first. That usually gets them things to let go.

I watched EeePee do that with mine and it worked nearly every time there was a catch.


- David

[Rc_Cam]

i figured i would post this up here...

i finally got my rock force on the rocks today, and guess what... ran into the same problem everyone else is having, i coocked motors. the first was with stock gearing and a reedy stockstar 27t motor. fried. so, i put in 73t spur, 33t pinion and a novak 55t motor. it had alot less wheel speed with this set up but it was ok, still a lower gear than a stock axial. fried it too.


now, everyone is switching to hs gears, except for dezmoon, who put high grade marine grease in his diff cases, and is having no problems.

a discussion on the way home with ppl that work with worm gears a bit say that in order for them to work properly you need a thrust bearing on the input gear. with a standard bearing the inner race is pushed one way, and the outer race to push the other causing alot of stress on the bearing and jamming the driveshaft causing the motor to overheat.

when you install the high speed gears you cut the stress level on the bearing in half. what i plan on frying to do is get some brass bushings, lube them up good and install a pair of them on each worm gear to see if that helps and i will let you guys know if it works.

i hope this makes sence to you guys, and please comment.

[dezmoon]

i was just talking about this today,,i dont think the bearings are what caused you to burn up 2 motors,,i think people have made mistakes with gearing selection,,im running a 81t spur with a 23t pinion,,,the only thing i might change would be going to a 25t pinion,,,i do have hs gears on order,,i do want to try em,,my running gear is the way i like it,,i have good wheel speed,,with awesome low end control,,the goat has gobs of torque and plenty of speed with my gear selection,,what grease are you running in your gears?? i run a high end grease because i dont want it to break down quick,,plus its like glue,it stays in contact with what ever it touches.

[Rc_Cam]

im just using a white grease that i usually use for all my stuff. i know what that marine grease is like, it takes about a week to wash it off your hands:-P. i do want to try your gearing too and see where that gets me as well, but if i can find the right size im going to try the bushings as well.

[dezmoon]

yeah i use that sticky shit in my 1.1 rig,,and beat the hell out of it,,i think the pinion your choosing is to much,,try 78 spur and 26 pinion,,keep us updated on the race set up when youve figured it out

[Rc_Cam]

will do dez, i was just trying out a couple of extreems. so far im the only one that has one of these things up here.

[dave56bug]

quick search found this:

http://www3.towerhobbies.com/cgi-bin...?&I=LXPC40&P=7

might be something to try, would fit fine with some additional spacers i'd think.

[Dewmerz]

I'm pretty sure the diameter of the output is 6mm not 5mm.

[dave56bug]

Ah, my bad, well another quick search I found Hirobo makes a 6x12x4.5mm thrust bearing that should work.