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dual motor gear box ?

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snokol

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Can someone tell me what the main advantages would be in using adual motor setup within the same gearbox like this , as opposed to having one on both wheels ? ( Aside from cost / weight )

Would it be possible for example to use it to achieve more torque at lower speeds ?

thanks

snok
 
Presumably you want to build a small robotic carriage.
2 motors of the same type on one 'box isnt going to gain a lot compared to one larger motor, even if you had 2 diffo motors with diffo rev ranges you'd have to mechanically disconnect one to run the other adding complex mechanisms.
The major benefit of having 2 motors and 'boxes, one per wheel is that you can have differential steering, running the motors in diffo directions to make your machine turn on the spot, also you dont need an additional servo motor for steering.
 
In some situations where space is at a premium it might be more convenient to have two small motors rather than one large one. I assume their combined torque would be similar to that of the single larger motor.
 
Presumably you want to build a small robotic carriage.
2 motors of the same type on one 'box isnt going to gain a lot compared to one larger motor, even if you had 2 diffo motors with diffo rev ranges you'd have to mechanically disconnect one to run the other adding complex mechanisms.
The major benefit of having 2 motors and 'boxes, one per wheel is that you can have differential steering, running the motors in diffo directions to make your machine turn on the spot, also you dont need an additional servo motor for steering.

Not really, Ive been trying to look at ways I could build a mobility device ( motorised kneewalker ) that be used in the following ways:

slow enough to be used in public places , as a legit mobility device ( 1- 4 mph )
use more torque to go offroad and up hills
can go higher speeds in an emergency ( say 4 - 8 mph )
allow me to go manual / freewheel if Im low on battery or want exercise
be used to assist when walking so I perhaps get boost or short bursts at intervals without having to have the motor on full assist so the wheel is moving all the time .
low noise

snok
 
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I assume their combined torque would be similar to that of the single larger motor.

Yes, I think that is the main reason to use two motors (if you can't find suitable single motor). Just don't wire them in parallel. Wire them in series or use separate motor controllers for each motor. And don't connect them mechanically "in series" making one long motor. Couple them side by side.
 
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Why not connect them one behind the other, isnt that the same as side by side.
The advantages in your case would be size as in longer and thinner meaning you can have a lower c of g, and cost, you might be able to get 2 smaller motors cheaper than a one larger one.
That said if you want a wide range of torque and speed then look at brushless motors, one single ought to do what you need and then some, and you can get various shapes and styles, the only drawback is that you have to have a controller.
 
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What I was planning to do was use Cim with one of these toughboxes , as it saves me the hassle of machining or finding someone to machine parts given my own inability to handle most physical things.

I was planning to use that with one of these **broken link removed**

If i was to go with a more powerful motor like this ampflow motor **broken link removed** then Id obviously need to spend $$$ as Im not even sure the above controller would be ok for its 93 amps ( Im assuming Id need something closer to 150 at least ? )

And then theres the gearbox too which from what I can see here **broken link removed** not cheap either, and uses roller chains - which Im assuming would be better for motor use , but not so good if I need to push the wheel in manual .

So In hindsight the idea of cheaper setup ( esp as Im a novice ) that I could use as 12 or 24 volt motor seems a better idea , unless there are other better 24 v options available for single motors / gearboxes at cheaper price ?

snok
 
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This is starting to get out of my field, however what you say makes sense.

2.5hp on a vehicle carrying a single person would be decidedly energetic depending on the gear ratios.

Wheelchair or electric scooter type motors have the advantage of being cheap being quite common and are probably made to last a long time.
 
This is starting to get out of my field, however what you say makes sense.

2.5hp on a vehicle carrying a single person would be decidedly energetic depending on the gear ratios.

Wheelchair or electric scooter type motors have the advantage of being cheap being quite common and are probably made to last a long time.

Most of them have a gear that disengages the motor like a freewheel too , which is one other thing about motors primarily designed for robotics that bothers me , as I dont know if the CIM could be used in that way or not .

Would it be possible for example to set the controller so the motor disengages the drive shaft if the wheel spins or moves faster beyond a certain point i.e. if Im going down a hill or slope , but restarts again once the wheels slowed down ?

Or would it be a case of having to turn the motor off altogether if I needed to use it in manual without the motor ?

I was hoping there might be some way I could use the motor like an assist rather than having it direct drive all the time , or having to turn it off , but I think I would need some sort of sensor to do that so it could react to my own input ( walking pace ) rather than just having it set a low speed which is always going to be too fast or slow to be in sync with my own pace.

The guy who was helping me that stole all my parts was using a**broken link removed**with 36v 250w brushless hub motor to see if he could gear it down but I never heard what happened , so I have no idea if it worked.

I do know its possible to use Kelly ok with CIM ( I think ) because I saw this guy do it , though unlike me he didnt need to go crawling pace, so i have no idea how well it would work in that regard in terms of reducing overall speed.

He also used a toughbox or rather modified 2 into 1 for the 3 motors.

I built a new gearbox out of the two Toughbox's I scavenged. I removed one stage from each gearbox, so that the input:eek:utput ratio was 14:50, rather than (14:50)^2. I chopped up the gearboxes and aluminum-zinc brazed the pieces back together, to get a 3 motor 1 stage gearbox:

snok
 
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Why not connect them one behind the other, isnt that the same as side by side.

Yes, but the torque "builds up" to the pinion of the first motor. You must be sure that the torque is not too much for the pinion to handle. If you couple the motors side by side, you share the load to more than one pinion.
 
Yep thats a valid point esp on larger motors where the pinions will be working harder, good thinking.
The same applies to whatever the motors drive, if a chain then it must take twice the load of one motor.
 
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The scooter clutch centre looks very much like a modded bicycle freewheel.
You might be able to arrange something with the small sprocket, the freewheel however would be bigger than the sprocket, you can get clickless needle roller type one way clutches which take a fair amount of torque for the size, but if you talking 2.5hp then you'll still need something chunky.
Maybe if you really want a clutch you could take the drive away from the motor, through a clutch assy and then back.
 
The scooter clutch centre looks very much like a modded bicycle freewheel.
You might be able to arrange something with the small sprocket, the freewheel however would be bigger than the sprocket, you can get clickless needle roller type one way clutches which take a fair amount of torque for the size, but if you talking 2.5hp then you'll still need something chunky.
Maybe if you really want a clutch you could take the drive away from the motor, through a clutch assy and then back.

No, I think Im going to start small and use this as much as lesson as anything else , 2.5hp kneeling sounds a bad idea unless I redesign the whole frame / get a new one built ( which Im hoping to do )

Something else thats been bothering me broken link removed ( 4th down ) regarding the use of a freewheel with a sensorless motor ( in this case an RC )

Is something that would also apply to a brushed motor like the CIM too then ( given its sensorless ) if I added a freewheel , and if so would adding hall or some other sort of sensor overcome it ?

snok
 
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