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Comment by gabcoh | Hacker News Reader

This seems really awesome, but my God is it expensive. Maybe I am not reading correctly but it seems like just the nuts and bolts from McMaster cost $230 and that's still excluding the electronics and additional hardware! I guess I'll have to save up a bit before I can play with my own minituare rover.

edit: the motors also are going to cost around $500

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Regarding the motors, they wouldn't be suitable for this particular project but you can buy broken hoverboards really cheaply. Where I live you can get stripped ones (no battery, no logic board, but you can get hoverboard logic boards on AliExpress for under 20€) for 10€ and returned ones (99% of the time it's a dead battery) for 35€. The motors are fantastic and powerful (~350W each), and you can build lots of stuff with them. There's a great talk on how to use these things to build all kinds of moving objects (armchairs, bobbycars, motorised cargo carriers: https://twitter.com/JanHenrikH/status/1023218344282021888, ...) at https://www.youtube.com/watch?v=qnQSL9DBPaE. You can motorise anything this way for around 100€. The only thing that's hard to come by cheaply is the battery.

> The only thing that's hard to come by cheaply is the battery.

Dead laptop and power tool battery packs usually have at least some useable 18650 cells in them. A friend has built more than one battery pack for electric scooter out of harvested cells.

You do have to know what you're doing when working with unprotected cells though.

Yes it's easy enough to get unprotected cells, but the hoverboard batteries usually have short circuit and undervoltage protection, both of which are very nice to have as a beginner. If you know what you are doing you can also get RC hobby batteries for not too much money.

Hmmm... so I can see you haven't tried to build a practical robot lately. $2500 is approximately nothing for a robot that has the specs of this one. Sure, I've built $10 robots and $80 robots. But they don't do what this one does.

Yeah they list the cost as < $2,500.

That's a little pricey for most. But I'd imagine a school class would be able to afford that if it was going to be worked on by 30 - 40 students?

You can source nearly all of this for about half the price if you look around a bit and substitute some of the parts for cheaper equivalents. The wheels are a great example. You can pick up the same things from China for half the price or even use a different style. The motor drivers are pricey for what they are and could be replaced with many other, cheaper drivers.

It's really not too bad. To buy a 4WD all-terrain kit from somewhere like SuperDroid Robots costs around $1500-2000 without any kind of automated control system. That will get you four motors with encoders, batteries chassis, wheels, a good (Roboteq) motor controller and an RC kit.

The one we had at work could easily drive with a large adult (i.e. 80+ kg) sitting on it.

I mention SuperDroid because their chassis are high quality welded aluminium, chain driven wheels etc. They sell to hobbyists (robot wars) and industrial markets including law enforcement.

Most of the markup is on the frame. If you have acess to a welder and something to cut aluminium you could do it a lot more cheaply. And yes, high quality motors with encoders cost $150 each. As always, you can go cheap as a hobbyist and pay with your time.

If you want something semi autonomous you can buy a Clearpath Husky for about $20k.

Consider cost per number of hours of your time this project this will occupy. It's probably around that of other common pass-times.

McMaster is extremely overpriced. Good for just ordering stuff for quick prototypes where you don't need to shop on price, but otherwise, it's easy to end up paying multiple times as much for some item as you would if you found a good OEM supplier for each component (and this isn't even considering Chinese OEM suppliers).

I just recently learned about McMaster and noticed it's overpriced, but I don't know where else one would get all this variety of equipment. Where can I find such OEM suppliers?

Plus they have CAD models of nearly all their products. It's saved me hundreds of hours over the years.

This was my reaction as well, however I do appreciate the reasons for the expense. I'm curious if a "lite" version of this could be made for home hobbyist tinkering.

I agree a "lite" version for home hobbyist tinkering would be fun, here's my effort to make one: https://github.com/Roger-random/Sawppy_Rover

I'm sure there are many other versions, created by rover-loving hobbyists around the world.

you think $2500 for a bot is a lot?

https://www.robomaster.com/ , Chinese national robot competition with almost 200 teams competing each year, runs ~$10K bot teams, and those are build mainly from off the shelf DJI components.

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