New Featherweights

Something to tickle your fancy.

Moderators: BeligerAnt, petec, administrator

Post Reply
alasdair
Posts: 563
Joined: Sat Jan 03, 2009 3:52 pm
Location: Marlow, Bucks

Post by alasdair »

Speedo ?43.13 Sabretooth 10A Dual Motor Controller

Motor ?9.99 Motor from 12v Cordless Drill Driver
Motor ?9.99 Motor from 12v Cordless Drill Driver
Battery ?0.00 Battery from 12v Cordless Drill Driver
RX ?35.00 Ar6100 Spektrum 2.4Ghz
Total: ?98.11

If those motors are under or are 5 Amps each i will get four not two increasing the total by ?20
Andrew_Hibberd
Posts: 1134
Joined: Tue Jan 20, 2004 12:00 am
Location: London
Contact:

Post by Andrew_Hibberd »

I would be careful. When you reverse the drive motors you get a huge spike in current drawn. I have read a couple of times that the 10Amp controller can fail with one motor if over volted. If you use a 25Amp controller you should have less chance of breaking it.
TEAM GEEK!
alasdair
Posts: 563
Joined: Sat Jan 03, 2009 3:52 pm
Location: Marlow, Bucks

Post by alasdair »

Andrew_Hibberd wrote:I would be careful. When you reverse the drive motors you get a huge spike in current drawn. I have read a couple of times that the 10Amp controller can fail with one motor if over volted. If you use a 25Amp controller you should have less chance of breaking it.
Okay, thanks andy. Here is my revised list: slightly over budget, but i will work on it.

Speedo ?95.00 Sabretooth 25A 2x Motor Driver Universal
Motor ?9.99 Motor from 12v Cordless Drill Driver
Motor ?9.99 Motor from 12v Cordless Drill Driver
Motor ?9.99 Motor from 12v Cordless Drill Driver
Motor ?9.99 Motor from 12v Cordless Drill Driver
Battery ?- Battery from 12v Cordless Drill Driver
RX ?35.00 Ar6100 Spektrum 2.4Ghz

Total: ?170 :o
alasdair
Posts: 563
Joined: Sat Jan 03, 2009 3:52 pm
Location: Marlow, Bucks

Post by alasdair »

I would like to know one thing:

If i have 4 motors going all going at 550rpm, with wheels 15cm in diameter, how many mph can the robot go??? I dont know how to do that calculation!
razerdave
Posts: 1562
Joined: Mon Jan 02, 2006 9:40 pm
Location: Carterton, Oxfordshire
Contact:

Post by razerdave »

There is a calculator for speed on Technobots
User avatar
BeligerAnt
Posts: 1872
Joined: Wed May 15, 2002 12:00 am
Location: Brighton
Contact:

Post by BeligerAnt »

Speed calculation:

Wheel diameter = D = 15cm or 0.15m
pi = 3.14
RPM = 550 or 9.17 revolutions per second

1 revolution = pi x D = 3.14 x 0.15 = 0.47m

Distance travelled in 1 second (i.e. speed)
= 0.47m x 9.17 revs/second = 4.3 meters per second
or 4.3 x 60 x 60 / 1000 = 15.48 kph

Speed (kph) = pi x D x RPM x 0.06
Gary, Team BeligerAnt
alasdair
Posts: 563
Joined: Sat Jan 03, 2009 3:52 pm
Location: Marlow, Bucks

Post by alasdair »

Thanks guys!

I have finished my design, with four driven wheels powered by argos value drill motors, all on the sbertooth 25a, powered by two drill batteries running in parallel. Very thin with hinged skirts on all sides.

:D
User avatar
terminaldamage
Posts: 180
Joined: Wed Jan 20, 2010 9:54 pm
Location: Aberdeen, Scotland
Contact:

Post by terminaldamage »

Total: ?170 :o
That may seem a lot, but for a featherweight that's not a bad price for your speedo, motors, battery and RX (basically all the components you need to make it move) Be prepared to spend up to ?250 though by the time you've finished as that would take into account chassis/armour materials, wires/connectors, fixings (nuts, bolts, screws) and perhaps the most unexpected cost, tooling. Breaking a drill bit or two results in a trip to the diy store and up to ?10 for a replacement pair of bits. May not sound a lot but have that happen a few times and it starts to add up, especially if you've been saving hard for robot funds.

This isn't to try and put you off though, just a heads-up as to what to possibly expect with respect to FW costs.
Jamie McHarg
RogueTwo Robots
www.rogue-two-robots.vze.com

With great power, comes great reliability.
alasdair
Posts: 563
Joined: Sat Jan 03, 2009 3:52 pm
Location: Marlow, Bucks

Post by alasdair »

terminaldamage wrote:
Total: ?170 :o
That may seem a lot, but for a featherweight that's not a bad price for your speedo, motors, battery and RX (basically all the components you need to make it move) Be prepared to spend up to ?250 though by the time you've finished as that would take into account chassis/armour materials, wires/connectors, fixings (nuts, bolts, screws) and perhaps the most unexpected cost, tooling. Breaking a drill bit or two results in a trip to the diy store and up to ?10 for a replacement pair of bits. May not sound a lot but have that happen a few times and it starts to add up, especially if you've been saving hard for robot funds.

This isn't to try and put you off though, just a heads-up as to what to possibly expect with respect to FW costs.
I know that it is not too much in comparison to other feathers, and it is not as if i do not have enough, but i am very paranoid about spending money, and i have been saving ages for something like this. Another good thing is that i will not have to spend too much money on body materials, as i have asked if i could put a club together in yr8 to build a combat robot, as we have something similar for micromouse, and it was turned down due to safety issues. But, i have been granted the use of school machinery (bandsaw will be useful) and materials (HDPE! Yay!) in compensation, so i can make some parts at school.

My budget max was ?200, so i am not doing that bad.

One thing i would like to know, is do you guys think that those drill motors will stand up to being thrown around by flippers, as they are only ?10 for a drill and battery...
User avatar
Jonny
Posts: 532
Joined: Mon Aug 30, 2010 8:18 pm
Location: Reigate
Contact:

Post by Jonny »

you can build your own speed controller for ?15 which will save a considerable amount of money. me and haz might try and start a robot club at our school aswell :D
Image
Post Reply