Go Back  R/C Tech Forums > General Forums > Chat Lounge
Can 4 Motors shift 250kg? >

Can 4 Motors shift 250kg?

Can 4 Motors shift 250kg?

Old 11-01-2017, 09:21 PM
  #1  
Tech Initiate
Thread Starter
 
Join Date: Feb 2012
Posts: 24
Default Can 4 Motors shift 250kg?

Hi all,

It's been a long 5 years since I've been active on the forum. That was back in high school when I built from scratch a 1/12 scale RC car.

Now in University I'm working on an interesting project. To save the details, we're basically designing and building "mini" rovers - particularly 3 "mini" rovers - to prove a concept. This concept being multiple smaller rovers can be more effective and efficient than one larger rover.

The theoretical weight of these things would be ~300kg in reality but our prototypes may be slightly less. We intend to power just 4 of the 6 wheels to save money on motors (6 motors saved over all 3 rovers). Now, I know we could move this large mass with the use of some gear reduction, but technically we could move anything with enough gear reduction - we'd just have to wait a while.

I've searched around trying to find the heaviest RC vehicles about. I have come across some guys pulling weighted sleds with their 4x4 vehicles but no details of what's inside. Anyway, long story short. I'm looking for some ideas and examples to help me get the gear reductions at an aprox ball park figure. I've seen gear reductions of 500:1 and I'm sure that's overkill. I'm thinking something like 10:1 - 100:1 but not sure where to start. I have my RC car which I will probably run some tests to see what it can pull with it's current gear ratios.

Also, what do I look for when searching for a high torque motor? I heard higher "T" and lower "kv". Does that really matter if I'm going to play with the gear ratios anyway, or are there actually motors which produce more torque regardless. If someone has an RC vehicle they pull trailers with, load that up with 100kg, try climbing an incline of 30 deg and let me know how that goes!

ANY inputs is greatly appreciated!
BradD is offline  
Old 11-01-2017, 10:46 PM
  #2  
Tech Elite
iTrader: (2)
 
Join Date: Sep 2010
Location: Chicagoland
Posts: 2,196
Trader Rating: 2 (100%+)
Default

Work backwards. Figure out how fast you need to move, figure out how much energy that takes, and order motors based on that.

Most of what you'll see around here, are 540ish motors. They're only good for around 100w continuous. Depending on cooling. Even 400w isn't going to move 600lbs very quickly.

I should keep going. The "really hot" motors are up to 8-900w. But those can't do it for long. And in space, you don't get cooling gasses, so you need motors that can handle whatever heat they generate internally.
Nerobro is offline  
Old 11-01-2017, 11:05 PM
  #3  
Tech Elite
iTrader: (29)
 
R3VoLuTiOn's Avatar
 
Join Date: Jan 2004
Location: Vancouver, Canada
Posts: 2,702
Trader Rating: 29 (100%+)
Default

the question should be, how fast do you want it to go? if the weight is on wheels, you can gear accordingly, or you just need enough force to break the static friction if its a sled.
R3VoLuTiOn is offline  
Old 11-01-2017, 11:49 PM
  #4  
Tech Regular
iTrader: (1)
 
TB03Racer09's Avatar
 
Join Date: Mar 2011
Location: Sydney Australia
Posts: 427
Trader Rating: 1 (100%+)
Default

I will have to agree with the previous two comments, you need to decide what is an acceptable speed in order for you two select the correct motor and gear reduction. Otherwise, you wont be able to achieve an optimal solution.

Having said that, I'd suggest going for a brushless motor that can take high voltage, preferably more poles as well.
TB03Racer09 is offline  
Old 11-02-2017, 01:14 AM
  #5  
Tech Elite
iTrader: (37)
 
Join Date: Oct 2005
Location: St. Louis
Posts: 2,620
Trader Rating: 37 (100%+)
Default

A lot of the RC truck pulls you see use the gearboxes from kid ride on toys. I have seen a dual 540 rig pull a soda machine.
chensleyrc1 is offline  
Old 11-02-2017, 01:50 AM
  #6  
Tech Lord
 
Roelof's Avatar
 
Join Date: Aug 2007
Location: Holland
Posts: 10,026
Default

Car window wiper motors are strong motors with their reduction inside.

Search on Ebay to 550 size or even 775 size geared motors and you will find low rpm with huge torque motors.
Roelof is offline  
Old 11-02-2017, 08:14 AM
  #7  
Tech Initiate
Thread Starter
 
Join Date: Feb 2012
Posts: 24
Default

Thanks for all the helpful replies.

Initially I didn't want to choose a speed and work backwards because I thought that wouldn't bring about the most optimal performance - like we might get way more than enough torque and lose out on rpm's for no reason. Basically, we want to have these things move as quick as possible (highest rpm feasible) but still with just enough torque to move.

If speed had to be chosen we would consider covering 1 meter in 5-10 seconds appropriate. Using wheels of diameter 15-20cm that is approx 1 full rotation/10s so about 5-6rpm.

We have considered the atmosphere in space and it's ability to cool etc. But these motors are just for our earth prototype to prove the concept. So cooling would be considered at earths atm pressures and temps. The rover prototypes would not really have to move for lengthy periods of time. Just enough to get in position and work together so I suppose the motors won't be running for very long at any one moment. (I can't see us moving these things more than 10m max in one go)

Roelof - we have considered these type of high torque motor/gear combination but they are too bulky for our packaging requirements. The most compact torque motors seem to be the RC car can motors. There's also a large amount of gear reduction transmissions available for these.

Also, when looking at motors, what do I look for when trying to find the most powerful motors? Is it simply constant current rating?

Last edited by BradD; 11-02-2017 at 08:42 AM.
BradD is offline  
Old 11-02-2017, 08:42 AM
  #8  
Tech Elite
iTrader: (2)
 
Join Date: Sep 2010
Location: Chicagoland
Posts: 2,196
Trader Rating: 2 (100%+)
Default

Yaknow... the place to look is drills. Specifically, drills that are designed for mixing grout/cement. They have high duty cycles, and very, very powerful motors. "just one" would move this quite quickly, at a very reasonable price.

https://www.homedepot.com/p/RIDGID-1...FVAtaQod7IoFZg

Most of those will happily run on DC too. And are easily controlled with a pretty standard r/c speed controller, as long as the voltages are compatible.
Nerobro is offline  
Old 11-02-2017, 09:22 AM
  #9  
Tech Lord
 
Roelof's Avatar
 
Join Date: Aug 2007
Location: Holland
Posts: 10,026
Default

https://www.ebay.com/itm/High-Power-...s7INGO2pKITQvw
Roelof is offline  
Old 11-03-2017, 10:55 AM
  #10  
Tech Apprentice
iTrader: (1)
 
Join Date: Dec 2015
Posts: 74
Trader Rating: 1 (100%+)
Default

I believe the 775 size motors are also used in a lot of power tool applications.

https://www.ebay.com/sch/i.html?_fro...motor&_sacat=0
jkaetz is offline  
Old 11-03-2017, 04:15 PM
  #11  
Tech Fanatic
iTrader: (7)
 
gubbs3's Avatar
 
Join Date: Aug 2006
Location: MN
Posts: 763
Trader Rating: 7 (100%+)
Default

Hobby level motors might be the most cost effective for a university project but considering the application there are a lot of industrial motors that would be better suited. The coordinate measuring machines built at my workplace run via sensored brushless motors and move bridges which weigh around 500kg at around 700mm/s. Motors for that application are sized around 40mm x 100mm and put off very little heat at 24v.
gubbs3 is offline  
Old 11-05-2017, 07:58 PM
  #12  
Tech Initiate
Thread Starter
 
Join Date: Feb 2012
Posts: 24
Default

Originally Posted by Nerobro View Post
Yaknow... the place to look is drills. Specifically, drills that are designed for mixing grout/cement. They have high duty cycles, and very, very powerful motors. "just one" would move this quite quickly, at a very reasonable price.

Most of those will happily run on DC too. And are easily controlled with a pretty standard r/c speed controller, as long as the voltages are compatible.
I was trying to stick to the RC car motors because of their size. We're looking at using wheels of about 15-20cm diameter so the relatively compact 5cm motors works well.

I've seen many of those generic motors with various gear reductions all over ebay, Toaboa, alibaba etc etc. But they just look to be high torque through gearing whilst using the cheapest generic motors they can manufacture... I don't know for sure, but I'm sure if they were then you guys would be using them instead.

Originally Posted by gubbs3 View Post
Hobby level motors might be the most cost effective for a university project but considering the application there are a lot of industrial motors that would be better suited. The coordinate measuring machines built at my workplace run via sensored brushless motors and move bridges which weigh around 500kg at around 700mm/s. Motors for that application are sized around 40mm x 100mm and put off very little heat at 24v.
Same as above with packaging. 100mm is a little too large for us.

What RC car motor would you guys go straight to for the most power whilst still considering cost. I want to pick out the best motor now and see what we can justify price wise, then see what gearing we need to make it work.
BradD is offline  
Old 11-05-2017, 08:26 PM
  #13  
Tech Adept
 
Join Date: Jan 2009
Location: colorado
Posts: 237
Default

Look at out runner motors for electric aircraft if you want to avoid gear boxes. They will have far more torque and less rpm than 540 style motors. Hobbyking offers quite a few options.
slotracer577 is offline  
Old 11-05-2017, 08:41 PM
  #14  
Tech Fanatic
iTrader: (81)
 
SuperFastSnail's Avatar
 
Join Date: Feb 2012
Posts: 929
Trader Rating: 81 (100%+)
Default Help the boy out!

I would suggest you look into brushless rc boat or rc helicopter motors. They produce more torque and power then rc car motors. The new motors are 6 poles and at low rpm, around 1650kv. If you go to horizonhobby.com and look under rc boat such as the Varocity, you should be able to get an idea for the project. Another place you can go is hobbyking.com they have super cheap deals on all sorts of electrical motors to batteries.

If you are planning on sticking with pure rc car motors then you should look into castlecreations.com 4 pole motors with the lowest KV rating. You could also try holmeshobbies.com used for rc rock crawling where torque and power is more emphasized.

Good luck on the search and you can always pm me if you need more specific findings.
SuperFastSnail is offline  
Old 11-06-2017, 06:10 PM
  #15  
Tech Initiate
Thread Starter
 
Join Date: Feb 2012
Posts: 24
Default

Originally Posted by slotracer577 View Post
Look at out runner motors for electric aircraft if you want to avoid gear boxes. They will have far more torque and less rpm than 540 style motors. Hobbyking offers quite a few options.
Avoiding gearboxes would be great but I still can't see one motor driving ~50-75kg all by itself (300kg between 4 motors) up an incline.

Just from a few calculations looking at a max weight of 350kg, a 45 degree incline would require about 2500N to climb negating frictional drag. So that is 625N/driven wheel and with a radius of 0.1m, 62.5Nm of torque required to overcome that. Unless I'm missing something vital, that should be our max required torque - thus the reason for needing a gearbox. I just had a look at the outrunner motors and they look good, I imagine they get more torque from the larger diameter motors. I like the pancake shape because it means they could fit basically inside the wheel. This is better than using a 2/3 inch tall motor vertically which would need a transmission that has the output shaft at a right angle.

But still, we would need some form of gear reduction, maybe 100:1? I have seen the planetary gearboxes used in drills and other can motors which basically attach inline with the motor/output shaft. Do they make these which could work on the front of these outrunner motors? (Similar to attached image).





Originally Posted by SuperFastSnail View Post
I would suggest you look into brushless rc boat or rc helicopter motors. They produce more torque and power then rc car motors. The new motors are 6 poles and at low rpm, around 1650kv. If you go to horizonhobby.com and look under rc boat such as the Varocity, you should be able to get an idea for the project. Another place you can go is hobbyking.com they have super cheap deals on all sorts of electrical motors to batteries.

If you are planning on sticking with pure rc car motors then you should look into castlecreations.com 4 pole motors with the lowest KV rating. You could also try holmeshobbies.com used for rc rock crawling where torque and power is more emphasized.

Good luck on the search and you can always pm me if you need more specific findings.
I was only looking at RC car motors because of their size, but I'll definitely check out the boat/helicopter ones too. The drill motors was the first "go-to" but the can size was sort of too large.

I really like the design of the outrunner motors and I think they could work perfect if I can find a gear reduction transmission that'll work with it. Has anyone seen the "tidnab" motor conversion? That sort of idea - with gear reduction - would work well for us which is similar to the larger outrunner motors. Are there any other motors that are similar to the outrunners? That being, larger in diameter and smaller in length, because those characteristics are preferable for our design. With the wheel being about 10cm wide, we can fit the motor in there with pretty large diameters. Then all we need is a stubby gear reduction system that'll mate with the output shaft of the motor!


Thank you guys for all the input!!

Last edited by BradD; 11-06-2017 at 08:44 PM.
BradD is offline  

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.