Extreme measures to lose weight

Given that hanging will be better achieved with a light robot, please contribute if you have any (good) ideas as to how to obtain the ultimate feather-weight robot.

Here are a couple:

  1. Do not use any non-functional decorations.
  2. Use omni wheels instead of mecanum wheels.

Cheers, Paul

Take a close look at the 7682 Sack Attack robot, it’s full of weight reduction techniques to the point of actually being able to hang without any modification.

Replace all screws with zip ties. Might work… as long as no one is crashing onto you :stuck_out_tongue:

We’re actually doing this. Not for hanging, for acceleration. But it’s the same idea.

Cut everything. Every bit of metal that you don’t need slows you down. If it isn’t structural or functional, it goes. The same goes for extra lengths of screws. Everything you cut, put it in a bin to weigh later. You’ll be amazed how much comes off.

Use the minimal amount of screws. Those things are heavy. The same goes for Nylocks and Nuts.

Use collars instead of spacers whenever possible. Use a pair to sandwich whatever you don’t want moving.

Lexan>Aluminum>Steel. Use Lexan creatively to reduce weight.

Loose the bits of tank tread that aren’t necessary. Put chain between the flaps on your intake, put sprockets near the wheels to reduce the amount of chain needed.

Loose the power expander if you can. The extra battery hurts.

Use as few motors as possible. If you can do everything with 8, leave the other two in the box. Those things are heavy. Similarly, if you can use a 269 for the same purpose with no change in function, do it.

Limit sensors. Eventually, they add up.

Finally, get a grinding wheel. Everything that IS structurally necessary should be ground down to be as thin as possible while retaining function. If you mess it up, you’re too fragile and break. Do it right, and you can take half a pound off.

Your mileage may vary, but we’re under 9 lbs. right now and I’m not finished shedding weight.

You could use one of the 2000mAh batteries insted of the standard 3000mAh battery

You can use the 1/4" Pitch Metal Kit-it has more holes meaning less weight

On the note of using lexan creatively, use ALL of your lexan. Hold on - that sounds dumb in a weight saving thread. Let me elaborate:

Use your lexan intelligently. Never ever use a big, flat sheet. I’d like to use my own team as an example. Every piece was either in strips, or bent in a L or C. The Super Stacker also used nearly all of the 12x24" sheet, but managed to get 3 18" intake shutes out of it. Our first Gateway robot had the entire intake structure made out of lexan C channels, L pieces and mounted on the arm. Lexan was made a structural piece, which is lighter than metal.

Remember, if you’ve got a lot of holes in it, you’re doing it right.

Also, Protip: use small pieces of lexan as really thin/cheap bearings if you don’t need a whole lot of structure. Also, if you need to cheap out on double-supporting an axle, stack some bearing blocks.

all aluminium, no - non functional decoration, use lexan in as many places as possible, use all lexan this year, one 3000mah battery and no power expander …

these are the general things that we are going with … and my robot is pretty light and can hang easily :cool:

Does anyone know if it is legal to cut off the threads on the tanks. They weigh a considerable amount and I am pretty sure they add no structural capacity or functionality for vex.

Well if saving weight is a concern (and it should be), there are a few options but most of these are pretty obvious.

Less framing == less weight

Forget aluminum (well actually don’t forget aluminum), point being even with aluminum framing, less is still better. Do you really really need 1x5x1 all over your robot? Probably not, yet I see this all the time. For that matter do you even need C-chan? Really can L-chan do the job just as well? If so, use it and don’t be afraid to cut it up either!

H4 took some pretty good measures to keep weight down, but with H5 we are really having to address this issue. We’ve even done something with framing that has never been seen or done before (I’m 99.5% sure of this) and this technique is high-school legal so when the robot is unveiled take a good look at the framing.

My last framing point is simple, polycarbonate is very very strong. Done right you most certainly can use it for framing needs (alongside good old aluminum of course). Andrew Remmers build an entire gearbox out of lexan sheet and from what I heard it stood up really well.

Pneumatics are heavy!

And yes you might be able to get away with cutting down the tank (please Q&A that) but I have safety concerns, and personally wouldn’t do it. Use pneumatics wisely, they are “free” in the sense that they are not motors which are limited, but there is a mass and volume associated with using them. Put the tank somewhere where the weight is going to help you (like as low as possible and close to the wheels) and keep your tubing runs as short as you can.

Wire is heavy!

Wire does add up, good wiring will save you a little weight done right but more importantly good cable management will make your robot more reliable so do a good job with wires and enjoy the perks.

Don’t be a hoarder!

If you don’t need it, get rid of it! Cut that framing out, remove that extra part and ditch the flag spinner.

Collars are the devil!

If you try really hard to remove as many shaft collars as possible, you will save a stunning amount of weight. Those things are really freaking dense and they tend to find ways into your robot all the time, four here another eight over there, six here, there and everywhere. Kill the collars and you’ll save a bunch.

Same goes for lock nuts and hardware. Try to avoid them where you can, but don’t skimp out too badly here, your robot still has to stay in one piece after all.

So as usual, good design tends to lead to a lighter robot. It all involves the creative thinking process of designing a robot, and CAD helps this processes take place. CAD can also help you measure those weight savings.

I know for some of us measuring things is a foreign concept, but try it out. I’m sure you’ll find the results to be interesting. I mean some results HAS to be more interesting than none.


Use pop rivets instead of screws+nuts for bearing flats. And on that note, use nylon fasteners (available from McMaster-Carr fairly inexpensively). It’s already been mentioned, but definitely use aluminum, and 1x5x1 c-channels are much stronger than 1x2x1 c-channels for non-torsional applications, but you rarely, if ever, need the larger c-channels in VEX (they’re just too strong). For torsional applications (linking the two sides of the drive base), make a tube out of two 1x2x1 c-channels.

Most importantly, look for big things! Small things do add up, but big things add up faster.

Subtle things that add weight:

Keps nuts are lighter. Bearings do not need nylocks if you tighten the keps nuts well. This is true of almost every application that has plastic in between.

No one needs an encoder on every wheel.
Pots are lighter than encoders (lift).
Speakers are unnecessary.
You can re-download your code instead of using jumpers or pots for autonomous selection.
If it is a low-strength application, consider using a 269 instead of a 393.

Many times you can get by with putting a few chain links between every flap, using smaller flaps, etc.
Low strength chain has its uses.

Zip ties
Replace heavy things with zip ties!
They are light and versatile, and can sometimes be used instead of bolts/nuts, bearings, chain flaps, metal, etc.

The Rack Gearbox Bracket as a battery holder is heavy. So are brackets like it.
The Winch and Pulley Kit bracket is ridiculously heavy!

The 2.75" double roller omni is over double the weight of the 2.75" single roller omni which is also lighter than the high traction 2.75" wheel.
Four 4" mecanum wheels weigh the same as five 4" omnis.

Non functional decoration.
Universal joints.
Hinges. (Can be replaced with pillow blocks, chain or zip ties.)

I think charged batteries will affect robot performance. :smiley:

Other ways to save more weight:
Drill lexan bearings, don’t use the heavy delrin ones.
File down all metal and lexan pieces.
Take all rubber bands off your lift.*
Wipe off fingerprints, or wear gloves to avoid them.
Stop using shaft collars; heat up the axle and hammer the end so it mushrooms out.
Strip all the bolt heads, or better yet, sand the heads down (after they’re tight).
While you’re at it, calculate how many threads you need, and sand down threads on the bolt that you don’t need.
Make all your wires go straight to their destination. Don’t run wire up your lift.
Use spacers instead of standoffs.
Run your pneumatic system in reverse: pull as much air OUT of the tanks as you can. Use outside pressure to activate pneumatics.*
Use chain/1x25 bars/zip ties/string instead of C channel when you have only tensile forces acting on it (no torsion or compression forces).
Cut down your flag. (Weight and air resistance.)
Use the small black spacers instead of the large white ones.
Sand down your cortex. Don’t go too far, as it is more susceptible to heat, thus more likely to get fried.
Keep your 393’s internal gears in high-torque mode; the high speed mode gears are heavier.
Not using either set of gears is lighter. Not using a motor is even lighter. In fact, not making a robot will keep it the lightest!*
Don’t use loctite.
Use as short of bolts that work.
Use 2.75 inch single-roller omnis at 45 degree angles instead of those weighty mecanum wheels.

  • Signifies a change that will likely make your robot perform less effectively in some ways. Decide for yourself if it is worth it.

Try using all aluminum pieces instead of steel.

Hello All,
We split some off-topic posts out of this thread into the Chit-Chat forum. This way it will be easier on future forum users when they come here searching for actual tips to reduce robot weight.

Please keep it on topic. :slight_smile:

it is always a good idea to think about weight management and logically taking out weight that is unnecessary, but I think an even more important task is power management. if you can reduce friction you have more total power and can do things at a higher rpm and with less worries.

This is true, but you are a little late to this thread, …

A year late…

I’m typically not one for necro-bumping but this is a really good thread and is applicable to this year’s game. I recommend that everyone gives it a read. Also, in the current stage of VEX, what can we do about the omni-wheels being so heavy? I’d love to see some high tech single rollers come out soon.

Product Suggestion maybe? :stuck_out_tongue: Wheels are one area where I continually wonder whether they were internationally designed to perform at a lower level in order to balance the components (the big obvious example being the mecanum wheels).

For anyone who wants some rather amusing ways to remove weight (even to a negative degree), thekingofjuice has you covered.

Make a chassis that is only 10" long (or shorter), don’t use 2 battery’s, all aluminium, standoff nation.

Guess this is another grey area.
What you have just quoted is R7c… but right before this rule (i.e. R7b), it says all non-Vex products must be identically in all ways (except colours).

I would presume “all ways” include the material as well.