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K9 Build - VIC.
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Jeeves Melchington

Joined: 06 Jun 2006
Posts: 16
Location: Melbourne

quote:
Originally posted by Spockie-Tech:
Just incase you dont already know, I *think* (confirm anyone ?) Wiper motors are advance-timed, so when using them opposite to each other like that, you might find K9 has a tendency to chase his tail (or at least drive in circles).

Yeah Spockie I was concerned about that as well. I have done a (mind you very rough!) test with the motors in both forwards and reverse and they do the same amount of revolutions both ways (116 rpm).

These motors are wiper motors but they are from a company called AMEquipment (resold through robot marketplace). They only have a negative and a positive terminal. I did go with a mate to check out motors at a wreckers yard but all the ones we looked at had VERY short shafts and also most of them had multiple terminals (eg most wipers have a "park" facility for when you turn them off).

BTW thanks for fixing up my login Smile

Wed Jul 12, 2006 7:50 am

Jeeves Melchington

Joined: 06 Jun 2006
Posts: 16
Location: Melbourne

Tonight I've tested the ESC's and hooked it all up (though looks a mess at the moment, will be better once the body is on as all the wires are far to long at the moment).

Something I'm not sure of... noise suppression capacitors. On my Mtroniks ESC's, it says you need two... one from the + terminal on the motor to the "can" and one from the - terminal to the "can". Dumb, dumb question... what's the "can"? I have bought the 0.1uF capacitors which is what Mtroniks Specifies.

Anyway here's some pics for the fun of it Smile

[/img]

Wed Jul 12, 2006 10:30 pm

ffej
Experienced Roboteer

Joined: 22 Jun 2004
Posts: 595
Location: Kurrajong, NSW

The can they refer to is the WW motor casing. Just the one across the motor terminals will do pretty much the same job.
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Wed Jul 12, 2006 10:38 pm

Philip
Experienced Roboteer

Joined: 18 Jun 2004
Posts: 3842
Location: Queensland near Brisbane

There are many opinions on noise suppression. Here is one of them. http://homepages.which.net/~paul.hills/Emc/Emc.html The bottom line is do what works for you.
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Thu Jul 13, 2006 4:08 am

Totaly_Recycled
Experienced Roboteer

Joined: 15 Jun 2004
Posts: 1346

Some brands of windscreen wiper motors already have good suspresion caps instaled internaly you would have to take one apart to find out though they are usualy on the brush holder circute board .

Thu Jul 13, 2006 10:52 am

Jeeves Melchington

Joined: 06 Jun 2006
Posts: 16
Location: Melbourne

Ah, thanks for the links to all the EMI stuff, very interesting. Looks like there are a couple of different schools of thought on it! Quite possibly my motors do have capacitors built in, I might send a mail to the supplier and see if they know for sure. I guess it can't hurt to install another one.

Re Spockie's post on the motors having different speeds and K9 driving in circles. Well it looks like this is the case to some extent, though I'm not sure if it's to do with the way my ESC's are set up or the motors or even my radio. The good thing is that it's all very adjustable, by setting the Travel limits on my radio different for each wheel I should be able to have them as identical or pretty close to it. My Radio is the T6XA Futaba and has a bunch of facilities. I am also using the VTAL mixer facility to allow driving with one stick.

BTW If someone wants to move this thread into the Builders Reports forum as it's probably more suited there than here Wink

Thu Jul 13, 2006 11:45 am

Jeeves Melchington

Joined: 06 Jun 2006
Posts: 16
Location: Melbourne

quote:
Originally posted by Giant Robo:
I`ll stick a pic of my K9 in the photo gallery.

Hey Jeff, just checked out your pic! He's cool! What did you make the body shell out of, and was he full size or a scale model?

As I mentioned previously mine is .75 size, though now I'm kind of wishing I'd made it .8 just to give me a bit more room internally, things are kind of tight, though sure it'll all come out in the wash.

Fri Jul 14, 2006 10:45 am

Valen
Experienced Roboteer

Joined: 07 Jul 2004
Posts: 4436
Location: Sydney

i wouldnt worry too much about the EMI stuff unless you are actually having problems.

K9 comes with a very handy antenna/tail that isnt likley to get ripped off by an opponent ;->

and WW motors are generally pretty benign in terms of RF anyway.
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Fri Jul 14, 2006 11:04 am

Jeeves Melchington

Joined: 06 Jun 2006
Posts: 16
Location: Melbourne

quote:
Originally posted by Valen:
K9 comes with a very handy antenna/tail that isnt likley to get ripped off by an opponent ;->

LOL, well funny you should mention that Valen. K9's tail is one half of a pair of rabbit ears which I extended to the appropriate length and then wrapped in insulation tape to stop it moving. It has a ring on the end (I just used a curtain ring and wrapped that in insulation tape as well.

All was going beautifully... until my cat decided to have a bit of a play, and actually SNAPPED his tail in half! Smile

I didn't actually see her do it!

Thankfully I have bought a supply of elcheapo TV antennas from the Reject Shop and will cannabilise those as spares (I have a feeling that wasn't the first antenna to be broken, and probably won't be the last)!

Never fear though, once K9 is operational I'm sure he'll get his revenge by chasing the cat around the house. When I do I'll film it and post somewhere.

Fri Jul 14, 2006 11:40 am

Valen
Experienced Roboteer

Joined: 07 Jul 2004
Posts: 4436
Location: Sydney

stick a lazer pointer in his nose see how the cat feels then.
make it servo controlled for the win.
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Fri Jul 14, 2006 1:46 pm

Giant Robo
Experienced Roboteer

Joined: 17 Jun 2004
Posts: 583
Location: Marayong NSW

Thanks for those plans guys, they`re great. Though I do agree, the head in the first set is quite a bit wonky.

Mine appears to have come in a bit undersized, 10cm off the base length.
It`s made from thick project card on a ply base.

It would be nice to build a new one, full size.
What colour did you use? I just settled on a few cans of cheap machinery gray. For a long time I couldn`t decide on the right shade of gun metal as there were a few resprays over there series.

Sat Jul 15, 2006 12:55 am

Glen
Experienced Roboteer

Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect

you might want to move that big 7ah battery closer to the wheels so it drives alot better, and maybe knock it up to 24v, ive never seen k9 in the series but two wiper motors on 12v will be slooooww

we should have a k9 fight xD
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Sat Jul 15, 2006 9:31 am

Jeeves Melchington

Joined: 06 Jun 2006
Posts: 16
Location: Melbourne

quote:
Originally posted by Giant Robo:
It would be nice to build a new one, full size.
What colour did you use? I just settled on a few cans of cheap machinery gray. For a long time I couldn`t decide on the right shade of gun metal as there were a few resprays over there series.

Hey Jeff, well I actually used a metallic grey just bought from bunnings. (the White Knight Brand). I got some special primer for the MDF, did a couple of coats, sanded it back so it was relativelyl smooth, and then sprayed with the metallic grey.

At first, it was REALLY dark... I wasn't to sure about it, but now I'm quite liking it, even though it's not the exact proper colour. you are right, there were a number of resprays of K9 throughout the series. If you check out the Doctor Who Prop Builders club on MSN, there is a guy called Ahmed who actually got hold of one of the original K9 fibreglass shells and has rebuilt it exactly as seen in the series. Looks totally amazing, but he's done it in a blue colour that I dont' think was ever seen in the series at all.

quote:
Originally posted by Glen:
you might want to move that big 7ah battery closer to the wheels so it drives alot better, and maybe knock it up to 24v, ive never seen k9 in the series but two wiper motors on 12v will be slooooww

Yep Glen, my plan is to mount various flashing light circuits etc on that "wheel arch" where the battery is in that shot. The battery will be up closer to the motors to provide better balance. I'm not really to worried about the speed, and i think once the wheels are on and everything's up and running that it'll all move along pretty nicely (touch wood!). I'm planning on doing some videos of him once that happens.

And yep, K9 in the series was actually pretty slow. You'd see him chasing along after the Doctor, miles behind, and then in the next shot K9 has miraculously caught up with the Doctor Smile

One of the most often uttered lines was "Come on K9!" (not far behind "Shut up K9!") Very Happy

Sat Jul 15, 2006 11:07 pm

Jeeves Melchington

Joined: 06 Jun 2006
Posts: 16
Location: Melbourne

K9 Moves! :)

Update, K9 now moves Smile My friend with a lathe helped do up some hubs for the wheels using the things I bought at Metfasteners. The wheels are a bit wonky (for $6 wheels at bunnings) but otherwise it all works pretty well. He spins 360 degrees in his own length, and the speed controllers allow movement in any direction. I'll hopefully post a video in the next few days of him in action.

Sat Jul 22, 2006 6:51 pm

Philip
Experienced Roboteer

Joined: 18 Jun 2004
Posts: 3842
Location: Queensland near Brisbane

It is a great moment when you see your creation move the way you want it to move.
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Sun Jul 23, 2006 5:47 am

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