What are some high level building tips that you want to share?
Quick list of important stuff I think everyone should know about
Screw joint anything that rotates, besides things that need axles such as motors. Screw joints are stronger and have less friction compared to axles (really nice for drive bases)
Triangle bracing is very important. On my first couple of robots I always tried to make things stronger by reinforcing the connection point, but using a standoff or something similar to create a triangle brace is so much more effective, and easier to do in most cases.
Most importantly keep things simple. Especially with gear ratios, more gears = more friction so make things such as drive bases as simple as possible. Also when designing new mechanisms for your robot, the more complex it is, the more failure points it will have, and the more time you will spend creating something that probably has an easier solution
Random resources that are cool:
Gear ratio spreadsheet
Drive base gearing examples
contrary to popular belief, there’s a lot of potential for custom parts on vex with the right hardware.
if you have access to a laser cutter, (with a fume extractor) 1/16" delrin is your best friend. it’s one of the best plastics for laser cutting. unlike polycarbonate, which i do not recommend lasering since it melts and burns, with the right settings we’ve gotten our cut widths down to under 0.2mm.
you can’t make rigid custom drives with only one layer of 1/16", but it’s the strongest, toughest plastic you can legally use on vex. it also has an extremely low coefficient of friction. alone, it works very nicely for small components. a compact odometry module for example, or if you stack two layers a ball bearing adapter that you can shape to fit nearly anywhere.
if you were to use two layers of delrin and some rigid spacing between the two sides, however, i think you could probably get some great results. i’d love to see that but i can’t guarantee it would work well. maybe i’ll make that an offseason project before i graduate.
with laser cut parts, you can also create things such as press fits, where a hole is very slightly smaller than whatever’s going in it. great way to secure bearings into holes, or align parts perfectly to screw shoulders. if you press fit a circular insert, you may need to lightly drill it with an 11/64" bit, as the insert can deform.
gonna take the time to restate the fume extractor part though. no matter what material you’re using, plastic fumes are very dangerous. never burn, melt, or laser cut plastics unless you’re sure you’re equipped with the necessary fume extraction.
if you have access to a cnc router/mill, you can make custom sized gears by milling high strength/low strength gears down to size cleanly. (v1 high strengths work best, if you use v2 high strength gears be careful of the steel insert that could destroy your endmill.) or maybe some really nice slip gears, there’s a lot you can do.
although this was made under vexu build rules, this post on vexforum could serve as inspiration for some of the above.
If you have a hacksaw, bandsaw, etc, don’t sleep on the power of half-cut c-channel for a weight and space-efficient solution to your problems.
We use it basically everywhere we would use normal c-channel but need to save space and don’t care about the structural strength lost. I’ve found it especially useful for mounting two parts at a 90° angle from each other.
Use keps nuts so building go fast
- Only use Half Lock Nuts
- Attach standoffs to collars for more complex mechanisms
- Practice building, just like how you practice driving
(my b for reviving an old thread)
I’ve seen mixed opinions on this. Some like to use only nylocs while others only use a mix between nylocs and keps for more efficiency. I’m curious what the community thinks of this and what people use on their robots.
How many nylocs do you use on your bot?
- All nylocs
- Half nylocs, half keps
- No nylocs (screw build quality!)
I don’t know what you mean by a half locknut, and i think by locknuts we are talking about nylocs which are nuts with a nylon collar. I would also argue that kepts nuts are locknuts as well.
I believe he means use half nylock and half keps. I’ll change the terminology in the poll real quick sorry.
He could have meant only using the thin nylocks (they’re about half the size of the normal one), this would save some weight.
if you can make anything out of standoffs, then make it out of standoffs (op)
I think using nylocs everywhere is objectively best option, you simply cannot rattle them loose. Worth the weight by far
I actually weighed some nuts this past year as part of the notebook. Steel nylocs and kepts nuts weighed about the same. Ig you could use nylon nuts, but i found that aluminum nylocs weigh about half as much as to steel.
Contrary to popular belief, it is actually not in your best interest to spam nylock nuts everywhere on your bot!
First off, I agree that using thin nylocks instead of the regular VEX ones is pretty much a must when you are using nylocks. The thing is though, you should be aware of the context in which each nut is being used.
Nylock nuts, and for that matter any steel nut, are quite heavy. I have found that nylon hex nuts are sufficient in many cases where something I am building will receive relatively low load and is not a critical piece of structure. Using nylon nuts for bearings is a good example.
Keps nuts have their own merit too. With some thread locker and a tight grip, you can easily get a keps nut to be as secure as a lock nut. One great thing about keps nuts is that the teeth help ‘clamp’ onto the metal and prevent it from rotating, which makes it a good suit for screw joints or any situation in which you don’t want the screw to rotate.
This is all to say, do not discount one type of nut over another. Each have their own merits and use cases. To answer OP’s question further, make sure to use proper spacing in all scenarios, and use a square and flat surface when building, it helps a lot.
If you have a stand-off on a shaft that will be spinning fast or rattling or anything, it goes a long way to put a small amount of loctite on the set screw, makes the robot quite alot more sturdy
idk i build my robot on the 2nd floor thats not a very high level
Square your robot it will help so much you will not regret it
is it possible to square robot with no shoulder screws
yup it is, harder but still possible. i would suggest using shoulder screw if you can find them
A speed square really helps too