RC Car General Discussions This forum is for all general discussions related to radio control cars. Check forums below for more specific categories if applicable.

Adapting 1/8 sensored motor to 1/5 scale truck

Reply
Old 07-16-2017, 06:35 AM
  #1
Digigumball
Thread Starter
 
Join Date: Jul 2017
Posts: 3
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Adapting 1/8 sensored motor to 1/5 scale truck

Hi All,
Relatively new to RC and due to it's size, I got a RedCat Rampage XTE Electric 1/5 scale Monster truck (specs below my signature), that I hope to turn into a professional video platform, for the purpose of making video walking tours.

So the video RC truck needs to have the ability to carry 10 lbs. camera rig weight and drive as quietly as possible at a walking pace all at the same time.

Now the RC Truck I have is designed for speed and bashing, but I need to tame it down and want to replace the 980 kv electric brushless motor with a sensored brushless motor, for much better smooth forward control at very low speeds (walking), however 2 problems: 1. I can not find a 1/5 scale sensored replacement / ESC combo, so considering stepping down to the 1/8 scale sensored brushless motors - but how would I adapt the physical size differences of the body and shaft?

And 2, does anyone know of a Sensored, brushless motor for 1/5 scale? (My current motor is a 980kv brushless 44mm Diameter, 84mm Length, Shaft size: 5mm and Connector: 4mm male bullet)

Any thoughts are welcome
Digigumball is offline  
Reply With Quote
Old 07-16-2017, 03:30 PM
  #2
EXT2Rob
 
EXT2Rob's Avatar
 
Join Date: Dec 2010
Location: Placerville, CA
Posts: 3,013
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

You might consider just changing the gearing. To achieve a crawling pace, you'll probably have to change the spur and pinion both. With 980kv, you should have gobs of torque. But in order to get the lower speed, you'll need a smaller pinion and larger spur. Once you get the brushless motor into its run mode it should be quite smooth. Sensorless motor ESC software uses a start up routine and the back voltage from the motor to determine rotor position, and get it spinning. Then the run mode kicks in. All in milliseconds. Just a few rotor revolutions. If you're geared really low, you're gonna move what, an inch or less? With the big tires probably less.
EXT2Rob is offline  
Reply With Quote
Old 07-16-2017, 11:44 PM
  #3
Digigumball
Thread Starter
 
Join Date: Jul 2017
Posts: 3
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

@Ext2Rob Thank you for your response! However, I need to clarify that due to an upgrade to the Spektrum DX4C transmitter /controller replacing the factory version, I'm able to pull the trigger a move at a walking speed, however not without some serious cogging the first few seconds every time I move forward, which is not at all what I need for smooth video.

Additionally the clanking sound the drive train and diff makes along with hte cogging motion is bad for recording audio as well, which is wrong for a video platform...this is what I need to eliminate! So I have the speed but need to eliminate hte cogging, the reason why I was looking into a sensored motor. I'm not sure a smaller pinion and larger spur would eliminate this issue?
Digigumball is offline  
Reply With Quote
Old 07-17-2017, 01:47 PM
  #4
EXT2Rob
 
EXT2Rob's Avatar
 
Join Date: Dec 2010
Location: Placerville, CA
Posts: 3,013
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

So you've modified the DX4C to give you more trigger movement to throttle response? Effectively just dialing back the throttle rate, right? But you still have the same gearing. So of course a sensorless motor is going to cog. I hear ya, not good for a video platform. The ESC and motor are getting even less throttle input from the radio and not getting out of the start-up routine range. A sensored system may indeed solve that. Using a eighth scale motor in a fifth scale is still going to require you to gear down. For heat reasons. You'll probably also need a fan-sink on the motor. Another noise source.

The point I was trying to make, was that if you have to gear down anyways, why not first try gearing your sensorless system down low enough to where it shouldn't cog at start up, because the gear ratio allows the motor to turn more easily and quickly, minimizing the time the system needs to get going. The motor will be working in a happier rev range, and you get your slower speed.
EXT2Rob is offline  
Reply With Quote
Reply


Thread Tools
Search this Thread
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -8. The time now is 09:29 AM.