Team Bitza

[PJ-27]

I've shy'd away from the car fan motors because they are so big and heavy, plus didn't seem to offer a huge power advantage over the drill motors and gearboxes.
We have a couple of spare all metal Dewalt motor/gearboxes, so hoping to put them to good use. I think they have 700 size cans.

[Ellis]

They sound good. Ours is an 885-size can. Also, unless I'm missing something, surely the torque figures for a 550 are dwarfed by those of a good fan motor? Are you sure you weren't looking at motor figures for the fan motor and after gearbox figures for drills? Of course if the power to weight of a fan motor+gear reduction vs a drill motor is in favour of the drill then that makes sense. Either way, I look forward to what you build!

[joey_picus]

Spawn Of Scutter had what I think was a low/full pressure (I can't remember but I know they tried to run a low pressure ram at full pressure in series 7 and blew the end cap off the ram when they fired it unloaded) spike pointing upwards in series 4 - it was very good at flipping opponents over, but not very good at all at putting holes in them even with the extra gravitational assistance...

The only other robots I can think of that had *serious* spike weapons were 101 and Pain - 101 kept running into the problem of pushing its opponents away instead of doing damage even on full pressure CO2, and Pain's weapon was banned due to the fact it involved barely controlled explosions and the robot didn't work!

Apologies for hijacking thread, I'll go back to lurking ^^;;

[PJ-27]

@Joey no worries! Spear weapons are an interesting area.

@Ellis, Oh yeh the fan motors are way more torque-y. In terms of stall toque though, drill motors after the gearbox should be sufficient.
My main consideration is the weight (1.6kgs each) and size (110mm Dia, about 60mm deep) for fan motors, and that's without any sort of gearing. They'll also stall at 200a each at 24v, drill motors shouldn't get above 100a (which is the rating SSRs I have).

What reduction did you say you were running? 5:1? It seems pretty quick and can obviously lift other robots fine.

[Ellis]

We're running 4:1 after the drill, but of course the drill is pretty big. Size isn't everything (shh! Lol), but it's quite punchy. If you have a smaller motor (885 can or less) you may want to gear higher. That said if you're powering the rear "leg" in a four-bar there's a ratio so you may be fine.

I don't actually know what ratio our drill has in low speed, only that it is about 400rpm at nom. voltage. We're overvolting to where that rpm is theoretically around 580rpm. Take 4:1 from there and the weapon would do about 145rpm. We just kind of round that down, allowing for load and losses, to about 120rpm on the weapon. If you aim for something along those lines you should topple other machines over nicely.

One thing I'll say, though, is that make sure the transfer from the drill to the weapon business is up to it. You may remember we had a real struggle to contain the torque when T2 came into being. Keep the torque limiter if those dewalt gearboxes have one, on its near-max it shouldn't slip when lifting but should when the weapon can't move. It's awful to hear and look at when it kicks in but I think it has saved us more than once!

[PJ-27]

Using the torque limiter is a good idea! I think Mike who built a lifter on here bought a dedicated one for his system.
Using 2 drills should help me share the load hopefully.

[PJ-27]

Having a bit of trouble deciding lengths for the 4 bar arms. Simulating the movement is proving tricky so thought I'd look at other 4 bar bots to see what they used.
At which point it occurred to me that I had never considered looking at Storm 2, d'oh!

So has anyone got any decent side on pictures of some 4bars with the arms up so I can deduct ratios, or better yet the actual measurements!

Cheers!

[Gaseraki]

I know its a little tricky to simulate in 3d but if you have any measurments I can quickly do a few mockup animation tests in maya. Sorry I havnt read the past 12 pages but is it electric of pneumatic?

[Ellis]

There's this, if it helps:

http://i1088.photobucket.com/albums/...2032012327.jpg

You can see the lower pivot point for the rear "leg" of the lifter glinting towards the back of the machine, at top panel height. That's the very top of an m10 bolt. You should be able to fairly accurately deduce the dimensions from that.

We designed the weapon as we did because it gave us the greatest lift height achievable in the space we had inside the machine.

[RogueTwoRobots]

four_bar_linkage_sizes.jpg

Found this online years back (I think it was the Aussie forum). The sizes are specific to that robot but I seem to remember the user saying that this was the optimum ratio he'd deduced and it would be easy enough to transplant your sizes in keeping the same ratios. Although obviously you can vary it if you want more power or travel.

[daliad100]

http://www.totalinsanity.net/tut/mec...arfrontbar.php - Finds the torque to hold a load at each point in the travel of your lifter, find the maximum and spec a bigger motor so it will actually lift things.

[plargen]

isnt there somthing on storm 2 in the real robots books with pics of the arm

[Eventorizon]

An alternative use for our 50x100mm cylinder is a 4 bar lifter. I have been examining Ziggy, the US Superheavy weight. That makes things fly! Though the whole thing is built from Titanium and has 2 massive buffer tanks to insure a constant thrust which you cant really do in a feather but its worth a look!

[PJ-27]

Thanks for the responses everyone, a great help!

@Marco, that would be a great help thanks!
I found Biohazard to have:
Top Bar is twice the length of Front Bar
Front Bar is twice that of Rear Bar
Where they attach is a differebt matter.

It's electric. The tricky parts are designing so that the thing will lay flat (at at least ear flat) when retracted, and have decent reach when fully extended. I figured to be decent at this scale the tip of the arm should be at least 30cm from the floor and from the robot.

@Ellis, cheers! Deciding height over reach is a tricky one.

@Jamie, that's a great help. Ignoring the right angle in the front bar it's length is 210mm, so;

Top Bar 360mm
Front Bar 210mm
Rear Bar 135mm
Lower Pivot Distance 235mm
Upper Pivot Distance 160mm

@Marco, could you possible animate this?

@Daliad, that's a great tool I used a bit to calculate how much torque I would need, but it's quite buggy and difficult to set up.

@Plargen, I believe Jamie has them all online, I'll have to trawl through.

[PJ-27]

@Alex, Ziggy is something else! Have you seen it self right?