Brushed or brushless?

[Gordon TarlingParticipant @gordontarling37126]

I'm getting ever closer to pulling the trigger on a lathe and mill purchase. Those I have my eye on both have brushed motors. Now, being of electrical parentage, I'm very familiar with the pros and cons of most motors, but is there any real disadvantage to having brushed motors on these machines? I realise that brushes might need changing every now and then, but I can't see any other practical disadvantages.

[Gordon TarlingParticipant @gordontarling37126]

[frank brownParticipant @frankbrown22225]

For an "amateur" there is not a big problem. If you are a 24 /365 operator, the difference between maintenance periods of 2000 or 50,000 Hrs means a lot, Brushed motors can ultimately wear out (never seen it) due to the commutator just being eroded away. and need suppression.

Frank

[JasonBModerator @jasonb]

I think the main difference you will see on teh hobby machines is the brushless motors are higher torque so you won't stall the machine so easily and they will work better at lower speeds.

Therefore on the smaller brushlessmachines you don't need a belt or gears to give the full speed range like you find on the brushed ones which tend too have two speed ranges as the lower torque of the brushed motor has to be geared/belted down for lower speeds.

For example my X3 mill with brushed motor has a two speed gearbox which is a bit noisy and youi have to change between teh two speeds to suit teh job in hand. The latest brushless version goes straight from motor to spindle with a quiet belt and you get the full speed range just by twiddling teh knob

 

J

Edited By JasonB on 05/03/2015 17:27:33

[Neil WyattModerator @neilwyatt]

+1 to all that Jason says.

I have seen plenty of positive comment on brushless motors and no negative comment that I recall.

Neil

[Gordon TarlingParticipant @gordontarling37126]

Thanks for your helpful remarks chaps. Model engineering is not my main hobby and the machines will be mainly used to produce parts for model aircraft and maybe the occasional boat. I certainly won't be using the machines on a daily basis, so I think buying the brushed motor versions will serve me adequately and save me a few bob into the bargain. I guess I could always upgrade to brushless at a later date if I felt the need.

[Brendan CorcoranParticipant @brendancorcoran61081]

Surely Model Aircraft and Boats are part of the Model Engineering hobby

[JasonBModerator @jasonb]

And you only have to look how they have all gone over to brushless motors in RC models to see the advantages.

Edited By JasonB on 05/03/2015 18:35:12

[Neil WyattModerator @neilwyatt]

And a brushless motor lathe is one lever simpler, so less to worry about!

Neil

[Ian PParticipant @ianp]

Posted by JasonB on 05/03/2015 18:33:41:

And you only have to look how they have all gone over to brushless motors in RC models to see the advantages.

Edited By JasonB on 05/03/2015 18:35:12

Brushless motors (or more accurately electric flight) have changed R/C modelling out of all recognition in the last few years, the motors though are now very specialised and adapted for that purpose and only really work well within certain limitations. A motor used for powering a lathe or any machine tool is really only a distant relative of brushless model type motors.

Induction and brushless DC motors both have the advantage of minimal maintenance. A brushed motor will sooner or later need servicing. I think the main decision hinges around the control system. (Variable speed, soft start/stop, ease of reversing,) as well as noise and other physical factors. More important than the choice of motor is the choice of lathe as the two are usually sold as one.

Given a free choice I would opt for induction with VFD.

Ian P

Gordon, Do you remember Aveox?

[John Stevenson 1Participant @johnstevenson1]

My take on this is not so much the motor but the motor controller.

 

The machines that use these brushed motors are usually the cheaper end of the scale but saying cheap you certainly get a lot for your money. If they were made in this country for the price you would get a handful of bolts and maybe a bearing or two

 

However to keep to this cheaper end they cut corners, they need to do so because WE will only pay peanuts.

 

All too often the shout goes up why can't they make better, short answer is they can but WE won't pay for it.

 

So DC motors are DC motors at the end of the day. Two magnets, two bearings and a bit of wire wrapped round $5 worth of tin, not much there to skimp on – already been skimped on.

Where the cost saving is mainly is the board. Basically you can go from a light dimmer switch to some advanced circuitry with feedback etc. This is where they make a saving and this is the weak point of any DC drive.

 

How much protection is built in ? If it overloads will it trip or burn out ?

 

Now when you get onto brush less it's a different ball game. The motor is more expensive to make as they make less of them and TBH they are far, far better designed and built.

The boards are also better designed and built and because they have to protect a more expensive motor, more safeguards are built in.

 

So basically this is the answer when people say Why can't they make it better ? They can, they have done and now people are still bitching they are too expensive.

 

How can anyone win ?

 

Answers on the back of a £5 note sent direct please as I'm certain Neil kept the last few grand that was sent 'cause I didn't see any

 

[edit]

Ian P opted in a previous post to go for AC induction motor and VFD but in a lot of case there is not the room to fit one of these, especially to a mill that has to carry the extra weight on the head.

Edited By John Stevenson on 05/03/2015 21:37:14

[Bob Brown 1Participant @bobbrown1]

BLDC motors are becoming more popular and are now found in things like washing machines and vacuum cleaners, this will reduce the price as volume always brings the price down.

I have a BLDC geared 24v motor driving my power feed on my mill, did not cost a lot about £50.00 including the speed controller shown here.

must put some labels on the switches, left to right, brake, on off.

Bob

[Ian PParticipant @ianp]

Posted by Bob Brown 1 on 05/03/2015 21:42:21:

BLDC motors are becoming more popular and are now found in things like washing machines and vacuum cleaners, this will reduce the price as volume always brings the price down.

I have a BLDC geared 24v motor driving my power feed on my mill, did not cost a lot about £50.00 including the speed controller shown here.

must put some labels on the switches, left to right, brake, on off.

Bob

Bob

Well I can see the belt drive and the control panel, but it would be good if you could share details of the motor and controller.

Ian P

[Ian S CParticipant @iansc]

I see that a lot of the portable Electric tools, ie., battery drills are now powered with brushless motors.

Ian S C

[Capstan SpeakingParticipant @capstanspeaking95294]

Brushless motors are synchronous and brushed are not.

Frequency speed control is superior to pulse width modulation but as a hobbyist you'll get the job done either way.

I wouldn't base a purchasing decision on such a minor refinement alone.

[Gordon TarlingParticipant @gordontarling37126]

Thanks again chaps!

Yes, I suppose you could call my hobbies as part of the Model Engineering hobby. I have actually built a steam engine or two in the past and might well do so again.

As founder member of the (now defunct) British Electric Flight Association, I'm very well aware of the advantages of brushless motors. However, brushed motors served us very well until they came along and the extra motor weight on a lathe is really of little consequence. As for the controllers, I used to build my own, so repairs should be no problem should the need ever arise.

In view of the large price difference I'm seeing between approximately equal brushed and brushless lathes, I'm willing to take a chance with brushed motors. Should the need ever arise, I ought to be able to convert either machine to brushless without too much trouble.

[Bob Brown 1Participant @bobbrown1]

Ian P

I've added some more pictures of the motor etc in my albums ( 2-8-0 loco), the motor does have a gearbox on the end and then driven by timing belts to the x axis.

Bob

[Ian PParticipant @ianp]

Thanks for the info Bob, are the motor and controller you use still available? £50 or so seems a good price for that wattage.

Ian P

[Brian Rice 1Participant @brianrice1]

My mill is brushless got bags of torque where's the lathe whith is brushed struggles at low speed.

[Author]

Posts