2WD with mahoosive motors or 4WD with say drill motors?

[daveimi]

As above really, which do you think would give the best pushing result? 2WD with say speed 900's, or 4WD with say four drill motors?

Looking to get robot 3 and 4 together

[craig_colliass]

Tron is a very good pushing robot boring but good at pushing. the drive is supplied by 4 drill motors. The key is not so much the power of the motors as they are only 12v standard motors not over volted. It is all about grip, the tyres you use and the surface they run on.

[daveimi]

ohhh ok so traction. Would four 12V ish drills give enough shove?

[Ellis]

edit: christ I didn't know I wrote this much! Sorry! Overall tl:dr is wedge design and traction + desired display of power = more important than theoretically more powerful drives.

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It depends on lots of things, grunt of the motor(s), reduction from that motor, wheel size, tyre material, floor surface, what you actually want from the robot, etc.

Mathematically, a pair of speed 900s or similar have double or even triple the power of four drills, at least in theory. But then if you gear the drills to run a robot at 7mph, and the speed 900 drive means you have a theoretical top speed of 27mph, then the drills will likely defeat the other robot in pushing power (assuming no losses in traction, so still only in theory).

So, assuming perfect grip (no wheel spin at all, which is very very unrealistic), then if geared for the same top speed, a tug of war between a pair of s900s or similar and 4 drills will result in the s900 bot winning every time. But if both robots are powerful enough (and even 2 drills are) to spin the wheels when trying to push something, which is how it is in real life, then if the machines have the same wheel size/tyre compound then neither with push/pull the other significantly or impressively in a tug of war.

tl;dr listen to Craig he's right.

It depends also on what you want from the robot. A machine like Jarvis' Ricochet pushes everything but is quite slow, and whilst Satanix might not out-push Ricochet on paper, if it gets under it, the speeds that Satanix can reach will result in what appears to be a much more powerful pushbot.

If you just want to push others then drills will do the job. If you want to have an impressive rambot then you need speed, and you don't see very speedy and also pushy drill powered robots because drills aren't generally powerful/reliable enough beyond about 10-12mph.

All theories and shoulds become irrelevant if you can't get under the opponent. Design of the robot, and its wedge/scoop abilities, are possibly most important of all. Two drills in a shallow wedge robot will control a robot powered by 50 speed 900s if the s900 bot is badly designed!

[daveimi]

Craig and Ellis huge thanks as ever.

We're looking to build a hammer and a chequered plate rammer, the rammer being my brothers robot as he's driving me nuts pinching mine all the time. We can't really afford to build a s900 /torpedo 800 type thing with all the gearboxes etc so took the other tack and wanted to build a 4wd indestructible brick. I didn't want to set to if it would be a waste of time, and it's like you say it comes down to superior traction. Whether you have superior traction from lifting an opponent's drive off the floor, or literally out-pushing them with stickier wheels it's given us something to go on.

We wanted to move away from a wedge and just make a really fast brick that was fun to drive. Not really out to win anything, just wanted to have a load of fun with something reliable and solid that we can keep coming back with. This is opposed to rebuilding for every event lol. Because we are planning to put a bit more cash than usual into this we wondered whether it was worth the investment of a big drive set-up, or whether it was a moot point. We're looking to build something fast so I suppose torque isn't really the answer it's more down to grip than anything, assuming you have a half decent drive. We don't have the accuracy to make our own drives so will stick with the drills. I'm making my own wheels this time around so can make them quite large and grippy.

We just want to have some fun with it and try out ideas, we know we have no chance against some of the scary stuff out there but it's the most excellent hobby, and it's getting our kids interested which counts for something.

[Ellis]

Well, Tormenta 2 used to run 12v drills on 18v with 36:1 gearboxes, and 100mm wheels. We eventually swapped that around to 18v motors and 24:1 gearboxes, to put less stress on the system and claw back some reliability. Both styles result in roughly the same result, 10ish mph. You can see what that drives/looks like in various videos on my channel.

You will, without doubt, run into gearbox reliability issues, if you overvolt significantly or use big wheels for more speed (or drive like an idiot, like me). The extra load, even with all metal gears, will eventually make mincemeat of the innards. This is fine for a while and perfectly acceptable for a "first" competition machine but will get old quickly.

In the next few months parts might become available by several members of the community which will make drills more reliable but for the timebeing they're touch and go for a speedy rambot.

Also I'd definitely use a scoop if possible, any robot with any drive that you face, that has a scoop, will push you around regardless of your drive.

[daveimi]

Four drills would cost around £60 but I can get a pair of Torpedo 800's etc with mounts for £50. Bit of a no-brainer really lol. I just need some mod one's and some wheels from somewhere and I could have a go at making a basic gearbox.

[Ellis]

You need a bit more than that I'm afraid. Raw materials, bearings/bushings, gearbox plates, accurate drilling to make the gears mesh correctly, some method of firmly joining the pinion and the motor shaft, etc. All of the additional tools to cut pieces and drill the right size holes and the right grubscrews, etc etc. It will end up more expensive. It's very ambitious, but then you'll learn bucketloads and grow your stock of tooling in trying. I'm only now beginning to get into fully custom drive, 2+ years after getting into this.

Drills are a good starting point, they just won't last very long if you push them like we do in T2.

[daveimi]

Do you know if there are people around that would put gearboxes together for me for some cash if I supplied the motors, wheels and so on?

[maddox10]

Yes.

[Ellis]

Yes, one of them just posted :P

[daveimi]

Haha awesome just seen the PM B)

[maddox10]

No comment.

[shakesc]

Budget is going to play a part in any decision you make. You can get nice ready made gearboxes and 775 motors from Banebots but piece price and import costs will add up. Andymark makes nice 2 speed boxes that take sizeable motors. All at a cost

[daveimi]

which user is Andy Mark?