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Which drive motors?


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Bundyrumandcoke



Joined: 01 Dec 2016
Posts: 31
Location: Gladstone Qld


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Which drive motors?

I am in the initial stages of the build of my first bot. Planning on sportsman class, probably open due to my planned weapon speed.

Reading back through the forums, it seems Kmart cordless drills are, or were, the best for drive motors. Is this still the case? There seems to be a much greater availability of 18V drills than 12V. Is the 12 V more preferable, or can you get 18V RC battery packs? If I go 18V, then it will have to be 3, one for weapon drive.

Price wise between the 3 brands I have found in town seems fairly compatable, around the $35 to $39 each, for Kmart, Ozito, or another brand from Bunnings, something like 101. Yet to check places like Supercheap. Also the local tip shop isn't much use. I also have to go the whole hog with all the RC gear.

Bot is based on a push hand mower, rotating drum, 2 wheel drive, bearing castors, will run max weight, so hopefully some decent armour.

Cheers for the advice and help.

Bundyrumandcoke

Post Mon Dec 12, 2016 8:58 pm 
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Windhammer



Joined: 19 Jun 2004
Posts: 338
Location: Roleystone WA


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http://www.kmart.com.au/product/12v-cordless-drill/748147

G'day Bundy,

The above link shows a cheap 12v option available in most Kmarts.

I wouldn't both with the battery they come with as it's crap quality. You can swap it out for a lithium battery up to about 18v.

I run these 12v drill on 18v and they seem OK so far Smile

Post Mon Dec 12, 2016 9:04 pm 
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Bundyrumandcoke



Joined: 01 Dec 2016
Posts: 31
Location: Gladstone Qld


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Yeah, not chasing the batteries, just the drive motors. Plan on running RC batteries.

Post Mon Dec 12, 2016 9:23 pm 
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miles&Jules
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Joined: 19 May 2010
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We run pickasso and flipper on 18v kmart drills running on zippy 2000mah 4s lipo- we have used these at quite a few events now without them burning out- so running 18v drills on a 16v battery seems to stop them from blowing up💥

https://hobbyking.com/en_us/zippy-flightmax-2000mah-2s1p-45c.html
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Post Mon Dec 12, 2016 9:23 pm 
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Bundyrumandcoke



Joined: 01 Dec 2016
Posts: 31
Location: Gladstone Qld


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How do automotive electric motors go on 18v? Planning on a fan blower or wiper motor for weapon drive. Possibly chain drive rather than V belt, due to confined space within the wheel hubs, if I can make it all fit.

Post Mon Dec 12, 2016 9:28 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Back in the day, we mostly used fan motors - the larger the better. Wiper motors could work in theory but adapting the output shaft is usually too difficult. Chain drive is not that great for weapon drive; it is heavy and can stretch and fall off unless you are careful. It can work but belts are less trouble and less weight.
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Post Mon Dec 12, 2016 9:39 pm 
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miles&Jules
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Chains always fall off stuff especially if they are little scooter chains- usually the chassis gets bent in the fights so chains usually fall off - they look cool before thst happens though- belts or gearboxes are the go 😎
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Post Mon Dec 12, 2016 10:07 pm 
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Bundyrumandcoke



Joined: 01 Dec 2016
Posts: 31
Location: Gladstone Qld


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The distance between drive and weapon shafts will only be about 4 inches. Trouble is, I cant go gear drive because the wheel axles are between the two. And I doubt I will get a V belt that short, unless I go for something like one of those emergency belts that you can make any length you want. I am also going to attempt to modify the original drive system to make an internal peripheral drive inside the wheels themselves. This means all drive, to both wheels and weapon will be outside the chassis, but inside the wheel circumference. A bit hard to explain, but if you have seen the internal working of these wheels, you might understand it. Wheels will have to also be armoured. Wheels are about 8 inches in diameter.

Post Tue Dec 13, 2016 12:34 pm 
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miles&Jules
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Sounds cool- but drills wont work on wheels that big without some mega gear reduction on them-jules tried with wanda originaly and they exploded 18v drills every fight using trolly sized wheels - now wanda uses hacked truck winches on trolly wheels which have been reliable for 5 years or so😎
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Post Tue Dec 13, 2016 3:34 pm 
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Nick
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For wheels that large, wiper motors might be worth a try. If you can find some with a longer axle and all metal gears, they should be fast enough on 18 volts.
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Post Tue Dec 13, 2016 4:24 pm 
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Bundyrumandcoke



Joined: 01 Dec 2016
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Location: Gladstone Qld


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Actually, the wheel drive gear reduction will occur as there is a tooth drive inside the wheel, and a much smaller gear to go onto the motor. Its the reverse of what happens with normal use with these mowers, pushing the mower makes the wheels turn, which inturn spins the cutting blade via a gear, at a guess around an 8 or 10 to 1 ratio. I want to reverse this, drive the cutting blade seperately, and using the drive gear for robot motion.

Post Tue Dec 13, 2016 5:03 pm 
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maddox



Joined: 21 Dec 2006
Posts: 753
Location: Belgium


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8 or 10 to one is way to low for a normal RPM featherweight motors.

Most Batterydrill drives vary between 16-1 and 36-1 with 16-1 for the bigger 775 motors, and that's for wheels of 80-125mm size.

Post Tue Dec 13, 2016 6:24 pm 
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