Yep, those are the ones. Manufacturing tolerances are sometimes making the hole smaller at times than other times. So measuring and boring to what you want is a perfectly legal method to use.
Things like lithium grease are Lubricants in an emulsion of oil that gets squished out when pressed together making a nice slippery surface when you need it.
The friction is necessary for some parts but you want the pushing forces, not the forces sliding along the surface of the gear as it rolls through. The line of contact slides along at certain parts of the rotation. A wider gear means more surface sliding for friction.
You have to look at all the contact types as the gear rolls through.
The pictures in here show what I am talking about.
http://www.scielo.br/img/revistas/jbsmse/v34n2/a05fig02.jpg
See the frictional arrows in here…
http://www.scielo.br/img/revistas/jbsmse/v34n2/a05fig03.jpg
Now why would I ever use high strength gears you might ask? Well they are more rigid and won’t pop out of place as easily under load is the main reason. But once again trade offs of engineering come into play!!!
Reference on the low levels of gear nomenclature:
Some bearings come pretty high friction as well as some used bearings. I find sometimes it helps to drill out the beating. As said before, a clean build always helps. Leave one washer of leeway on both sides of your flywheel to reduce friction. Try to support axles on both sides of any gears. Don’t run your encoder on the same axle as the flywheel. Try to not have large gaps between the flywheel and the point where it’s supported to reduce vibration. If your running high rpms, it may help to balance your flywheel. Non high strength gears allow for a less clean or precise build to still work and the strength isn’t essential at such high speeds. Not that this was mentioned but i thought I’d also mention that chain seems to also have more friction than gears imo.
I’ve thought about using lubricant on my flywheel, but keep on avoiding it because it doesn’t seem like it would help that much and you would have to keep it maintained. I have only ever used grease on linear slides. Has anyone seen increased performance by adding lubricant? Does adding it in the bearing of the flywheel seem to help or is better used in the teeth of the gears?
I’ve been thinking about lubricating my thrower over winter break.
That is a great idea. I will suggest that to my team.
Thanks @Team80_Giraffes for the detailed explanation! It makes a lot of sense.
How substantial do you think the difference in friction is between high strength gears and normal gears? I think I will play around with this a little to compare gains in friction to loss in durability (it’s a trade-off like you said).
You’ll find the information you seek in @Team80_Giraffes’s two posts above.
(P.S. that semicolon seems to be a bug ^)
We have been using silicone spray on our shooter gearbox and it works really well.
Does it increase fire rate?
Make sure it is non aerosol though to be legal.
You’re welcome!
Most of our teams are using the wider gears of 60:12 and 36:12 for their flywheels (15:1) with two motors minimum per flywheel.
One team is trying 84:12 and 60:12 gear train (35:1 overall) and that seems to be more susceptible to the friction effects. I am not sure if the added torque needs is causing the issues to come through or if it is just the ridiculous torque. Three motors per flywheel on that one.
The sandwiched regular 84 tooth gears (the solution before high strength version) seems to work better than singles or newer high strength variety. Single 84 tooth had skips, new version just did not seem to work as well as the sandwich variety.
But narrow 60 tooth gears seem to work just as well if not better than the high strength ones on the second stage. Friction seems to be more than anticipated. Not sure why on that one.
I really don’t like the 12 tooth plastic gears as they seem fairly flimsy but they seem to have less friction. It’s metal 12 tooth gears everywhere. Two 12 tooth metal gears together and you can feel the friction effects in your fingers rolling them together. Maybe as they wear as they break in you can get less friction.
Have not tried the lithium grease in these gear trains to see if it becomes adequate, but lesser friction is always better to start and then improve with grease. Start with something that works and then improve it.
Does spray work better than putting grease directly on the gear?
Spray is very hard to control to not be in violation of R7.e
Making sure it does not drip on the field is the hard part when using sprays.
If I remember correctly, after applying the silicone spray to the gearbox over the summer, we ran it for a while for testing and most of the excess silicone spray came off.
So as long as the gears do not touch the field, I won’t be violating a rule, or if I just have an excess of grease, I will get disqualified?
What you have to avoid is the grease getting on any field objects. This could either be the result of having too much grease on your gears and the grease dripping on the field, or the gears as you say, touching the playing field walls, foam field surface, game objects, or other robots. As having a location (the gears) that does this is in violation of the second part of the rule.
Is there any type of grease that won’t drip?
From what I have heard, white lithium grease is good, as well as easy to apply and use without too much hassle.
Basically, if you are dripping any type of grease, you have too much grease applied.
Don’t get it on the garage floor! It’s hell to clean up.
What year was this? If it was 2014-2015 Skyrise, we had a very strange situation during a match where there was so much grease on our scissor lift, that when we bumped our opponent, a whole blob of grease dropped on their base. =3