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drive calculations


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Glen
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Joined: 16 Jun 2004
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drive calculations

hey george + tim ill continue that talk here..


quote:
I cant work out the calc it keeps giving me 1.2 amps max lol anyway can you work out 12v drill motors one per side at 18v on a 3600 pack with 5 inch wheels same width as the blue wheels.


probably because youve got the ratio on the motors wrong, it should be 1:1 for drills.

Torque (per motor) to spin wheels 540 oz-in
Amps (per motor) to spin wheels 16.640 Amps
Theoretical Top Speed 11.154 MPH
Total Peak Amps 33.281 Amps
Amp Hours Required - 3 Min 1.6640 AH
Amp Hours Required - 5 Min 2.7734 AH

youll probably only half use the pack in a 5 minute rumble so your set there... and acceleration is decent.


quote:
THanks for that, interesting
half stalled is about half max power and seems like will need to run batteries in parralel but thats cool.

Whats your opinion on the data Glen, any advice on the ideal gear ratio for the setup mentioned or does it sound like it shoud work ok, hard question I know.


btw i believe at half RPM (half stalled) you get maximum power from your motors so i guess thats optimum in that behalf, but 30amps per motor to spin the wheels is alot.

25:1 or 30:1 seems good, youll get for 25:1

Torque (per motor) to spin wheels 25.92 oz-in
Amps (per motor) to spin wheels 24.224 Amps
Theoretical Top Speed 7.5569 MPH
Total Peak Amps 48.448 Amps
Amp Hours Required - 3 Min 2.4224 AH
Amp Hours Required - 5 Min 4.0373 AH

and acceleration - Time to Top Speed: 1.2100 sec
Distance to Top Speed: 7.8686 feet
Top Speed, Side-to-side: 6.0544 mph
Time to Side: 3.2523 sec
Top Speed, Corner-to-Corner: 6.0544 mph
Time to corner: 4.4655 sec

which is fairly slow

and at 30:1

Torque (per motor) to spin wheels 21.6 oz-in
Amps (per motor) to spin wheels 20.186 Amps
Theoretical Top Speed 6.2974 MPH
Total Peak Amps 40.373 Amps
Amp Hours Required - 3 Min 2.0186 AH
Amp Hours Required - 5 Min 3.3644 AH

and acceleration - Time to Top Speed: 1.2100 sec
Distance to Top Speed: 7.8686 feet
Top Speed, Side-to-side: 6.0544 mph
Time to Side: 3.2523 sec
Top Speed, Corner-to-Corner: 6.0544 mph
Time to corner: 4.4655 sec

so there is what happens, not alot of difference really, id probably go the 30:1

interestingly though is that youd probably be better of changing to a 9.6v drill motor at about 35:1, acceleration would be faster youd use less batteries. and youd be faster at about 8mph or so.... thats about all i can really say. testing testing testing!
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Post Sat Apr 02, 2005 2:47 pm 
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timmeh
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Ok sweet thanks.
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Post Sat Apr 02, 2005 2:57 pm 
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Nexus
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THanks again Glen, have another one for u, this will be the last, I promise. Rolling Eyes Rolling Eyes

Tried to do it myself but didnt see scooter motors.

THought to aplly the calculations to the the fights where the hot glue melted out of the packs and see what the data is saying the batteries are doing.

2 x 250 watt scooter motors running 18 cells, gear ratio 3.33:1, 6 inch wheels at 20kg.
BTW what do u generally use as the CF setting
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Post Sun Apr 03, 2005 4:24 pm 
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Glen
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heh i like doing these, interesting results all the time

for CF i leave it at 0.9, that figures as good traction as you can get, i believe 1 is the absolute maximum.

really cant say about the scooter motors but if i figure EV warriors which are about the same i guess -

Torque (per motor) to spin wheels 285.40 oz-in
Amps (per motor) to spin wheels 43.243 Amps
Theoretical Top Speed 24.082 MPH
Total Peak Amps 86.486 Amps
Amp Hours Required - 3 Min 3.0270 AH
Amp Hours Required - 5 Min 5.0450 AH

really need the stall current and torque of the motor to know for sure.
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Post Sun Apr 03, 2005 4:39 pm 
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Spockie-Tech
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A really good place to find motor specs all in one place is either the Robot Market Place, (which takes a bit of browsing).

Or the Enigma Industries Link Page
http://www.enigmaindustries.com/links.htm
where you can click on a lot of the link and it will bring up detailed specifications for many of the motors.

Have you had a look at the Electronic Drive Train Simulator ? Its quite interesting, although requires to have a few paramters like ineteria figures and a few things that might stump some builders.

Nice that you actually get to "drive" your combination and watch the voltage and current in real time though.
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Post Sun Apr 03, 2005 4:43 pm 
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Glen
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i love that program,

scary thing is the robots actually drive fairly realistically too.

one thing i wish they had so badly was to be able to import a rhino render or some such and use that as the model,
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Post Sun Apr 03, 2005 4:47 pm 
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Nexus
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quote:
Originally posted by Glen:
really cant say about the scooter motors but if i figure EV warriors which are about the same i guess -

Amp Hours Required - 3 Min 3.0270 AH
Amp Hours Required - 5 Min 5.0450 AH



I would guess the EVs would draw about twice the current at the same voltage.
I was getting 5 to 6 minutes out of 2.4AH pack.

Wish there was data on those freaking scooter motors Confused
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Post Sun Apr 03, 2005 5:17 pm 
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Spockie-Tech
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make it too easy for people to build "Virtual" bots and they might not want to get their hands dirty doing the hard work of turning them into real steel though. Confused

I agree though, I often thought about something like Robot Arena 2 with its physics modelling and skin-able bots combined with some hardcore simulation of actual power consumption and torque etc like EDT sim. I think they're great tools to visualise and imagine ideas and test them a bit first.

But still, whats works on the computer screen can often be let down by something as simple as a nut or bolt coming loose that just doesnt happen in the virtual world of simulations where everything always works the way its supposed to.

Thats what makes building these things for real so much fun. Watching a physical combination of bolts, metal, and sweat and tears do your bidding in real life is far more satisfying than making virtual pixels dance about on a computer screen..

Kind of like the difference between looking at screen pixels that are coming from some adult web site on the net versus.. <ahem> well you know what I mean.. Razz
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Post Sun Apr 03, 2005 5:20 pm 
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