Team Shakesc : Build Diary

[shakesc]

So I realised that I have various build threads and I've reused some for multiple robots so confusing myself :S
After Gloucester I realised that a few things need to get done

1) Spur II - it eats Gimsons for breakfast. I'm not a sympathetic driver so need to update the drive chain especially as Gimson are looking as rare as Speed 900's. The weapon is a bit limited and combine that with its weight needs a rethink

2) Otis - its drive is Speed 900's , see note on Gimsons.... I have been toying with brushless for a while and following the various threads. I bought some Alien Power motors (I have a habit of buying things that are 'intersting')

http://alienpowersystem.com/shop/42m...r-300kv-1500w/

In testing the lifter for Gloucester it managed to rip itself apart. So this is going to take more weight to sort it out so will need to save some

[shakesc]

So Otis is a bit packaged inside (fresh air is a waste inside!)



I built some spacers so that I can fit an Alien Power in place of the Speed 900's



These are sensored motors on a single stage reduction so will be interested if they suffer cogging. Need to sort out a good ESC for these

[Rapidrory]

I'll be very interested to see how 4 horsepower of brushless motors mixes with a featherweight... :P

[shakesc]

I agree. They are dinky motors with a high advertised output. Its not as though Speed 900's can't put out decent power

[Rapidrory]

These are almost twice the power of S900s if the ratings are to be believed (which, being brushless, I'm inclined to), so you may have a little more 'fun' with it :L If it works out though, I'll be very interested in it as it is quite a bit cheaper than equivalent brushed motors..

[overkill]

The 1,500 watt rating is probably the short-term peak output but the motors are likely going to spin the wheels long before they hit that level of power. What gear ratio do you have - when I was testing the AP motors, I had 7.8:1 and the cogging wasn't too bad.

[maddox10]

Z12 on the motor, Z72 on the wheel. 6-1

If this setup works, I have lasercut adaptorplates with mounting holes for several sizes of motors.

[Rapidrory]

Running the numbers through with that motor, gear train, and what looks like ~80mm wheels (at 24v.. I'm not sure what it actually is) gives it a theoretical maximum of ~10mph with ~30kg of pushing power if grip was ideal.... aka, more than enough torque and speed :P

[shakesc]

Ordered my sensored ESC (only have unsensored at present)

Maddox - if this works I may well take you up on those laser cut items

[shakesc]

Well some more brushless testing. Using the HobbyKingâ„¢ 120A Sensored/Sensorless Car ESC (1:8/1:5)
Its ok and have a programming card now for it. It certainly wants the pause time between forward and reverse. Some other ESC are much better at this. So might look at these later.

The motor and ESC combo is about 200g lighter than the Speed 900 so thats a handy saving. Working on reassembling now

[shakesc]

Oh and played around a little with my NTM 50-60 270KV motor - that is a beast

[shakesc]

I've got the motors mounted onto the brackets with the wheels. Played around to get a good engage. Gives a neat tidy package



Mounted them into the chassis of Otis - yeh, looks like a box of wires just for testing



Need to put proper spacers under the brackets. For now spaced with nuts off the bolt heads.

The other thing I have done is used some of the weight to reinforce the flipper arm. The torque of the DeWut broke the welds a couple of times so have a bar bolted to the sprocket that connects to the arm. This should be alot stronger. My concern now is the strength of the chain.



I will weld the front forks onto the arm once I am happy with the clearance of the wheels.

The biggest learning from all of this is that the motor and ESC have to be viewed as a system along with the transmitter.
With brushed motors its pretty much plug it in, trim it up and away you go. With brushless for drive the 3 have to be viewed as a combination and at least 2 of them are programmable.
e.g. changing the trim significantly means reprogramming the limits on the ESC

Its driven (badly - left and right were reversed at the time) around the garage and on the basis of the things I knocked over looks promising
Time to get tuning, no turning back as I sold the speed 900s

[Eventorizon]

Let us know how she drives. It will be very interesting to see if the ESC and Motor combo works as well as a regular brushed system. I am worried that new brushless systems will have the same kind of delay that old relay based systems had, and all because they are dealing with more power rather than less.

[overkill]

Why would more power lead to delays? Did you mean reversing delays or just slow response in general?

[Eventorizon]

Yes I meant reversing delays. I was thinking something along the lines that brushless ESCs don't generally like suddenly reversing as they get out of sync and they have to deal with current running the wrong way but I am probably wrong.