Heavyweight Drive System

[pikaprince1345]

Hi. I am new to robot building. What are possible setups for the drive system? What motors and gearboxes do people use and roughly what works together?

[Ocracoke]

For a relatively simple system, I known 800W scooter motors with sprockets and chains to be used to good effect which is relatively affordable. Beyond that, you could go with big CIM motors, NPC or Ampflow motors with gearboxes on them or even go brushless though they can be quite fiddly. In theory, wheelchair motors also work but they tend to be underpowered for this level I feel. Speed controllers, in terms of brushed motors, usually go along the lines of VEX BBs, RobotEqs and the like though I've known Cytrons to be used as well with a bit of modification.

I do advocate reading the build diaries here, they are a wealth of information of what works and, perhaps more importantly, what doesn't.

However, it is worth bearing in mind that to get a system that works and works well (that includes the motors, the gearing and the speed controllers and the batteries), it can get quite expensive and if you've never built a fighting robot of any description before, it's worth starting in a lighter weight class like Featherweights or Beetleweights simply because they are far cheaper to build and maintain plus, in my experience, they are easier to learn the basics with.

For example, my Beetleweight I put together for about £75 I want to say (albeit with some components reused from other projects) but the axe motor and speed controller in my Middleweight easily cost will in excess of twice that alone. One of my Featherweight robots cost me ~£300, my first Middleweight was in the £700 region all told and that is before the cost of keeping them running.

[pikaprince1345]

Cool. Atm I have made an ant weight and working on a featherweight. Wanted to start doing the research early for something heavier.
I have had a read on some of the stuff but I'm semi worried as something like ampflow one motor with gearbox people have said isn't powerful enough yet another is. Is there like a specific go to for roboteers?

[Ocracoke]

Without knowing which combination of motor and gearbox they are talking about, I can't say. I tend to make my own gear reductions for my Middleweights drive (and will have to for my next big project as I talked about in my build diary). Each motor has its own characteristics and quirks.

For example, the CIM motors I use seem to be fine being overvolted to quite a height with a 6.35:1 single stage reduction drive to the wheels using MOD 1.25 gears. That's fine for the weight it has to shift and for the application it is being used for but I wouldn't dream of using that same combination in a Heavyweight because of the extra weight. I am envisaging having double that reduction in my next project with A28-400 Ampflow motors though that does rather depend on which weight class it ends up being. ^^;

The off the shelf gearbox on Ampflows is 8.3:1 I think, which is relatively high and possibly where that comment comes from if it was paired up with something like a E30-150, which is the "smallest" motor Ampflow make as of writing I think. With the right gearing, that can be used I feel though I must confess, I can't think of any examples right at this moment.

[pikaprince1345]

I've managed to grab myself some Ampflow A28-150-F48-G motor and gearbox for a cheap ish price (https://www.rapidonline.com/ampflow-...earbox-37-0318).

They are 48v and I can't seem to find 12s lipos online, at least not a sensible price. I thought that I could run two 6s in series?

Also I was thinking about maybe looking at the cytron dual channel 60A ESC (https://www.robotshop.com/uk/cytron-...or-driver.html) for these but not sure itl be suitable.

Any thoughts are welcome.

[Ocracoke]

They are 48v and I can't seem to find 12s lipos online, at least not a sensible price. I thought that I could run two 6s in series?

So long as your wiring is of good gauge then sure, I use a pair of 4S LiFes in my Middleweight in series without issue.

Also I was thinking about maybe looking at the cytron dual channel 60A ESC (https://www.robotshop.com/uk/cytron-...or-driver.html) for these but not sure itl be suitable.

I've used these in my MWs before and whilst it is very plug and play, the exposed capacitors in that can easily be knocked out. The low amperage (comparatively) is also a problem. It'll drive the motors with no load without issue but its not a regularly used ESC in the MW and HW scenes so it is a bit of an unknown as to how robust they are with 12S LiPo. That being said, my MW was easily in a pulling match with another MW the last time it was used and didn't die on me then. The other issue as well is that it is actively cooled which whilst can be worked around, is yet another failure point.

[pikaprince1345]

Ok. So what you're saying is that the cytron would run it but may fail depending on circumstance?

I've read some of the other forums and saw some people suggesting the 4QD range.

[Ocracoke]

4QDs are tried and tested definitely. RobotEQs are more modern and I am sure robots like Thor use that exact motor and ESC combo.

Ok. So what you're saying is that the cytron would run it but may fail depending on circumstance?

I am saying that the draw from the motors in terms of overall amperage could cause the ESC to cut out. With a bit of preventative modifications (such as putting a vented box around the ESC for example), it should hold up but it is still a relatively untested piece of kit. That being said, I think Tango (HW pusher) uses a Cytron but with scooter motors.

[pikaprince1345]

I take it both the 4QDs and RobotEQs are not just plug and play?

[Ocracoke]

I can't speak about 4QDs as I've no hands on experience with them but I've heard that they require interface boards and such. RobotEQs you do need to read the documentation to get working.