unnamed drum spinner

Hi,
i've decided to start this build diary as i have finnaly got together all my parts for my drum spinner. Here are the specs.
drive motors: 2 argos 12v drill motors
weapon motor: 1 speed 900 on 24v
weapon: 1.2kg stainless steel spinning drum
ESC: sabertooth 2x25
wheels: 100mm blue wheels
armour: 20mm hdpe armour and bulkheads (i know nylon would have been better) and an ali base plate and lid
batteries 2 12v nicads in series to give me 24v

i think thats everything pictures will follow very soon !

some pics!
[attachment=2:1m1ros8k]robot_stufff_and_hampton_court_035.JPG[/attachment:1m1ros8k]
[attachment=1:1m1ros8k]robot_stufff_and_hampton_court_036.JPG[/attachment:1m1ros8k]
[attachment=0:1m1ros8k]robot_stufff_and_hampton_court_037.JPG[/attachment:1m1ros8k]

more pics!
[attachment=2:15oqhp17]robot_stufff_and_hampton_court_038.JPG[/attachment:15oqhp17]
[attachment=1:15oqhp17]robot_stufff_and_hampton_court_041.JPG[/attachment:15oqhp17]

Very nice. Are you just using o-rings for weapon belts though? You'd probably be better off with timing belts & pulleys, o-rings are almost definitely going to jump on pulleys with flanges that small (and lose traction)

At the moment I will just use 2 o-ring belts and will see how it goes and it is supposed to slip a bit to protect the motor but may upgrade to 1 timing belt if it proves ineffective

Looks good, I'll have to build one eventually :)

forgot to mention, everything in the first picture together ways 12kg but that doesn't include motor mounts, screws and bolts for holding everything together or the large bolts for holding the bearings in place so weight might be tight!

It's very disheartening when you weigh your components and they alone are near the limit!

Got a decent set of components there for a drum bot. How is the drum constructed? Trying to work it out but it's difficult from the pictures. Have you taken a sheet of stainless and bent it around?

You could potentially save a lot of weight with li-po. And can't quite see from the picture but you mightn't need that much HDPE?

The drum is just a piece of 2mm thick stainless steel tube with ends welded up and axels put on. The 'teeth' are made by cuttings arks out of a larger tube which are then bolted on.
To save weight I could invest in some lipos and some of the Ali is getting cut away for the wheels and to make space for the drum. If worst comes to worst I could drill large holes in some of the bits of hdpe which are just there for support and don't act as armour. Finally I could downgrade to 2mm Ali baseplate and lid (would help with ground clearance) or see if i can find some cheap titanium. Or I could get a brushless motor to power it

looking great! :)

some more pics!
[attachment=1:1jym2jk5]robot_stage_2_001.JPG[/attachment:1jym2jk5]
[attachment=0:1jym2jk5]robot_stage_2_004.JPG[/attachment:1jym2jk5]
i've now finished making the motor mounts and i've melted in some nuts to use to bolt on the bearings. unfortunaty i've put the nuts in the wrong place :angry: so now it is more cramped and i'll have to replace the two bit of hdpe at the front with either 3mm ali or 2mm steel (prefferably) depending on weight. apart from that everything is going well :D
and don't worry about it all looking wonky thats just my photo taking skills :lol:

Hi, I am going to buy timing pulleys from tecnobots, what gear ratio should I get for a 1.2 kg drum from a speed 900?

Also, is the name invictus taken?

What do most people use to power their battle switches?

Battle switches are usually powered by the 5/6V line that comes from the receiver - if you've got another speed controller with a BC in the machine (or even a separate Battery Eliminator Circuit) then this will regulate the main power voltage (24V you seem to be using?) to the 5 or 6V needed for the controller boards, including battle switch, so no seperate battery is required.

As for belt reduction with a Speed 900, is it this model http://www.cornwallmodelboats.co.uk/aca ... _6373.html ? and is it 24V you're running at?

Yes I am using that motor at 24v ,
Sorry I meant what battery do people use to control a larger relay from the battle switch?
Also I have just wired up everything in my robot and set the travel adjusts on my dx6i spectrum transmitter to 10% so I could check the adjusts were working but what I found was that when I tried to reverse the motor it used only 10% of the power but when I made it go forwards it used all the power and no limiting took place? It was the same with left and right (left 10% power right all the power) what have I done wrong?

I'd go for around 2.5-3 to 1 ratio (e.g. one of these http://www.technobotsonline.com/timing-pulley-12t.html plus one of these http://www.technobotsonline.com/timing-pulley-30t.html), you're basically trying to find a sweet spot between torque for spin-up and continued motion during impact (especially with smaller drum teeth) and energy stored through inertia, I reckon that'd be about right given 12000+rpm motor speed.

For a larger relay (e.g. http://www.jaycarelectronics.co.uk/prod ... BCATID=754 ) you can use either the RC/BEC power or main battery power for the control side - many relays are rated for a range of switching voltages (3-32V in the linked example) so will operate on either. I'd use the BEC circuit if possible to avoid main power shorts.

Not sure about the transmitter, took me ages to refine my settings myself though so just look through the manual/rc forums and I'm sure you'l crack it.

I've solved the transmitter issues (you had to push the channel stick in the direction you want to adjust the travel on)
I've ordered a 40 tooth pulley and a 20 tooth pulley and will see how it goes, if I have problems spinning it up I will change the 20 tooth to something small and then tension the belt with another pulley.
At the moment I have the battle switch running off two double a batteries, how do I use the bec from a sabertooth?

you won't have issues spinning it with a 2:1 ratio. Boner has used speed 900s with a 2.4:1 ratio with a 4kg drum. Spun up no issue. You could probably have gotten away with a 1:1 ratio on a kilo drum.

Gary's probably right, I've honestly not run a 900 or a drum before!

Been a while since last update because I've just been doing small jobs like the wiring and melting in nuts to hold the bearings. Progress has been halted as I am waiting to get the axels on the drum enlarged (Misread the bearings website) and also need to get the new timming pulley put on it.

Drum has been altered so tomorrow I can Mark out and cut the Ali lid and base plate and then start securing everything
I am however very annoyed that tecnobots have closed for a couple of days I need my fuses,deans and LEDs NOW!!!!!

Hi all,
Just wondering if most people cover the cooling air holes on their speed 900s or if they need the cooling, I am using it to power the drum so it will be on most the time.

yeh i cover them on any motor i use in robotics

Can I ask why that is?

shrapnel and other rubbish can get inside

I covered mine as well (although the current one is uncovered). Never had a problem with them overheating. They got warm/mildly hot but never anything extreme.

Ideally, some form of fine mesh would be a good compromise. Fine enough to cover the holes to prevent any crud from getting in, but holey enough to keep drawing in some air.

i just dont bother covering them, seems to work

http://www.ebay.co.uk/itm/Stainless-...-/130569785908
http://www.ebay.co.uk/itm/Stainless-...-/130569786129

If your concerned about your motors, that's the kind of stuff you need. The open area of the larger one is 43% and the super fine about 32% so it will reduce cooling by that percentage but its better than blocking them off altogether. Also it's stainless steel so it's non-magnetic and won't rust like other steel and iron woven mesh.

I was thinking more along the lines of old sock, but OK! :)

Today I cut the aluminium base plate and nearly finished the last few jobs before I screw the hole thing together! Also watched Thor and ripper and their teams on epic win on BBC 1 trying to smash their way out of a caravan but it was an epic fail!!

Been trying to make removable link today but it doesn't want to work , nothing sticks to a deans connector!!!!

some pics,
my cut aluminium base plate:
[attachment=2:1rmo5dd3]robot pics stage 3 005.JPG[/attachment:1rmo5dd3]
My general layout:
[attachment=1:1rmo5dd3]robot pics stage 3 004.JPG[/attachment:1rmo5dd3]
my timming pulley on the drum:
[attachment=0:1rmo5dd3]robot pics stage 3 003.JPG[/attachment:1rmo5dd3]

more pics,
hinge covering my removable link:
[attachment=1:3qgk3zjb]robot pics stage 3 002.JPG[/attachment:3qgk3zjb]
My electronics mounted on a piece of hdpe
[attachment=0:3qgk3zjb]robot pics stage 3 001.JPG[/attachment:3qgk3zjb]

Looking good!

They're some hefty bearings!! With the cast iron housings they weigh almost half a kilo each do they not? Suppose it's fine if weight's not a problem, but if your robot's too heavy they'll be a prime candidate for weight reduction.

Overall it's looking rather fine though. Always nice to see another drum :)

have started screwing everything together and hooked up electronics inside the robot. have just had first spin up test of the drum and it worked great! it has a fast spin up time and seems to be well ballanced. also retested the drill motors but found that one at least was flashing inside when i changed directions! i have never noticed it before so thought it was worth asking if this was normal?

Sounds like it's going well! If you're able to get a video online of the spin-up, that would be pretty awesome :)
The flashing inside the drill motors tends to occur more when you change from one direction to the other at high speeds (it also occurs at low speeds, but can be less noticeable). It's just the sudden change of current that causes an electric arc. It's not an ideal life-cycle for the motor, but considering we're using them in robotics and put them through a helluva lot of abuse, they still last for quite a long time.