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Discussion Starter · #1 ·
ok i have fantom brushes model standup, full face F321-M...first brushes i have bought for my fireball 15T motor...got myESC on the 24th janand the stock brushes died exactly 1 week later, 2 march...


soi bought new brushes 2 daysago...


on the first day the brushes wornout 1mm...


next dayanother 1-2mm...and had like another 2mm of brush spring left...


today 1 brush is all worn out....so er what do i do with that brush spring???



so thats like4 battery runs (maybe 5 if that spring was fixed?)with the brushes and they are gone, and only drove the car like 3 minutes today...reading the fantom website... or this http://www.minicar-racing.no/fantom/brush.htm


what does 'cut-comm 3-4 runs' mean?


well i've justput thestocklong brushin place of the worn out one...
but don't think i'll be driving for more than 2 batteries


whats the longest a pair of brushes has lasted?? should ibuysome brushless motor cause its starting to look like i'll be spending $10 on a pair of brushes every week...
 

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Something's wrong.


Brushes should last 5-10 runs as a minimum... usually a lot lot more. 50-100 would not be uncommon.


I usually change brushes only when I want to try something different... can't remember actually having worn any out. Toasted them blue yes, broke them sometimes but never worn to uselessness.


You haven't set your motor timing to be "reverse advanced" (= retarded), have you?
 

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migoreng said:
reading the fantom website... or this http://www.minicar-racing.no/fantom/brush.htm


what does 'cut-comm 3-4 runs' mean?

Means they're recommending you get your comm cut every 3-4 runs.


But some would say, if cutting your comm you should also renew the brushes.





btw, who told you to buy the F321M brushes?? From that website it suggests that this brush compound is best for ultra-mod motors <9T.


For general use maybe you should be looking at a F308 or F320.


But I don't know much about Fantom stuff.
 

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Discussion Starter · #4 ·
i've set the timing pointingto the 4thlinefrom the left, exactly how it was before i opened up the motor...well it was abit to the left of the 4th line i think...soo yeah


there are 12 lines...the 1st,5th and last are longer...


what is this reverse advanced?


i showed the guy my motor..i said i wanted brushes that last the longest...


is there something wrong by using brushes for more powerful motors than my 15T?


yeah i'll try ringing up hobbyco about the model numbers...and get some...


well howoften do people cut the comms?


what about brushless motors? how much are they?


edit: what other brand brushes are good? you told me brushes would cost like $5 in another thread...Edited by: migoreng
 

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migoreng said:
i've set the timing pointingto the 4thlinefrom the left, exactly how it was before i opened up the motor...well it was abit to the left of the 4th line i think...soo yeah


there are 12 lines...the 1st,5th and last are longer...


what is this reverse advanced?

Ok... rule #1: the lines usually mean nothing.



Look headon at the can... there's 2 pairs of screw holes right?? OK, find the midpoint between the 2 pairs of screwholes = the middle of the gap between the 2 magnets = call this the "zero" line.


Now draw a (imaginary) line between your brushhoods... the brushes should be at 90 degrees to the line above. If so, your brushes are "zero timed".


You know which way your motor goes... it'll be running anti-clockwise when seen headon.


To ADVANCE the timing, turn the endbell "into" the direction of rotation - get me? Turn it 'forwards' like running into the wind... ie clockwise.


Never run the motor at less than 'zero' timing. It is really bad for the motor.





is there something wrong by using brushes for more powerful motors than my 15T?

Permanent harm - no.


Life... possibly, yes.


Super-hot mod motors like to use soft brushes with lots of silver, to have the best current conduction. Silver is a great conductor but its pretty harsh on the comm. Its also soft so it'll wear out quicker.


well howoften do people cut the comms?

Its like how often you like to change your oil in your family car... varies between 'every run' to 'never'.
As said before - they manufacturer can recommend whatever they like, but there's no hard & fast rule.


Yes it needs a cut if its not perfectly round, or has bad scorch marks on it, or it has grooves on it bad enough to feel when you run your fingernail across it.


Racers who own lathes might cut them more often than bashers who don't... as the usual indicator when you need a cut is "fall off in performance".


what about brushless motors? how much are they?

At the moment, its still an infantile industry. Only Novak has brought BL motors out specifically for cars... about $400. The other brands (eg Hacker, Schultz etc) are all ex-airplane motors, they aren't very smooth at low speeds and cost even more $600-800+. Many also have a bad habit of blowing up their *special* very-expensive ESCs when they get too stressed.


what other brand brushes are good? you told me brushes would cost like $5 in another thread...

Yeah. go to a shop that is willing to sell you "loose" unpackaged brushes. They might have a box behind the counter, it won't be on the shelf. (Might also be the same shop that can help you cut a comm... which sounds like Hobbyco wouldn't.)


Or... you can sometimes find some retail bulk packs eg 5 pairs for $30 etc.


If you're in it for the long haul, might as well stock up!!






btw... there's a couple of alternatives to comm cutting, from the "old" days.



1) we used to put the arms into the chuck of a cordless powerdrill, spin them and touchup the comm with some very-very-fine sandpaper or an ink eraser. Then complete the job by spinning with some metal polish on a soft cloth until its nice & shiny.


2) can sometimes find "comm sticks", these are like an ink eraser but its shaped like a long brush. Stick that down the brush hole and turn the arm in the can.


These were common practices before RCers invented pit lathes.
Better than nothing!
 

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Discussion Starter · #6 ·
ok...the hoods line is perpendicular to the magnet gaps midpointline...what does advanced retarded mean?...also can i turn the endbell around 180degrees asi want the motor hole to face upwards..?


hmm...i lost a washer after opening my motor for the first time beofre...i only have the plastic and metal washeron the comm end butno washer on the pinion end...
doh....so is that why my motor is hot?


but i've found another washer..it is slightly bigger...the armature doesn't move up and down now...and the motor seems to spin okay...



my 2nd pair of brushes worn out now...i'll get the longer lasting brushes...
 

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migoreng said:
ok...the hoods line is perpendicular to the magnet gaps midpointline...what does advanced retarded mean?...also can i turn the endbell around 180degrees asi want the motor hole to face upwards..?

Perpendicular = 90:90, good. That's "zero timing".


To ADVANCE the timing, you make it more than Zero.


Looking at it from the Brush end, turn the endbell ANTI-CLOCKWISE. Your angle becomes 80:100 or 85:95 etc.





hmm...i lost a washer after opening my motor for the first time beofre...i only have the plastic and metal washeron the comm end butno washer on the pinion end...
doh....so is that why my motor is hot?


but i've found another washer..it is slightly bigger...the armature doesn't move up and down now...and the motor seems to spin okay...

The 'correct' amt of washers on your armature between the bearings is found by Trial & Error.


1) open up the motor, take all washers out. Reassemble without washers, without brushes etc.


2) now give the arm a little spin by hand... the armature will centre itself in the magnetic field. It will find its own sweetspot between the 2 bearings.


3) now you know where the sweetspot is, put washers on both sides to keep the arm centred at its sweetspot. Repeat #2 as many times as necessary after adding washers. (Don't add so many that the arm is jammed when you screwdown the can.)


Any good LHS should be able to sell you a pack of motor washers of different thicknesses to help you do this job.
 

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migoreng said:
....so is that why my motor is hot?

Electric motors are very efficient devices at changing electricity to movement, but still they are only 70-75% efficient.


The remainder 25-30% is lost as heat & noise.


Some of it is caused by friction (bushes/bearings & brushes).


Rest of it is due to resistance in any wire; copper wire is not a superconductor. Pass high currents thru any wire it will get hot - that's just physics.





"Hot" is a relative term. How hot is hot?


I usually don't worry about brushed motors getting as hot as 70-80 degC straight after a race - that's normal. The batteries are usually about 65-75 degC too. (The whole car gets plonked onto a cooling station immediately.)


As for the human hand... 50 degC would be felt as uncomfortably hot already. Touch anything 70 degC and you'd be taking your hand away pretty quickly.
 

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Discussion Starter · #9 ·
wellthe timinglooks 90:90 to my eyes but maybe it could be 1 or 2 degrees off?



does 1 degree make a difference?


so what does amt mean?


alright i have let the armature spin to the sweetspot and it stays at the bottom of the can, as it doesn't move when i push it down...so i have put all 3 washers at the comm...hmmm...


brushes...i have been told to order from overseas...looking at tower hobbies and speedtechrc.combrushes are like US$3-4. i haven't checked the exhange rate for sometime...but guessing its around AU$5 a pair...


theres a 10 pairs pack for US$29.90..which is 2.99 a pair...


hmmm itscheap than compared to here which is around $8 a pair, the cheapest at hobbyco



what are seratted brushes? i see they have difference patterns...and what is silver percentage about?


well i'm looking for long lasting brushes...>10 runs a pair and i'll be happy...how much power is my motor losingif i use the longest lasting brushes than using those 1-3 runs racing brushes?


and my springs...my motor has been through 2 pairs of brushes, and one is always shorter...how can i fix this?
 
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weird...the first time i ran my TL01 with a esc and 16t motor and 21t pinion...the motor didnt get warm..it was still coolish.

and the esc didnt evn break a sweat....did i hit the sweet spot aswell???



Nismo
 

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Discussion Starter · #11 ·
yeah this afternoon while holding my car after a run...my fingers touched the motor and yeah it was freakin hot! owww...hmm it was a hot day too, around 28c...



i thought you should be able to touch a motor after a run...or is it normal to be hot that your fingers cannot touch it...?


the battery get warm but i can still touch it...i always take the battery out after its empty
 

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migoreng said:
wellthe timinglooks 90:90 to my eyes but maybe it could be 1 or 2 degrees off?

Hope you've realised: the endbell's screws should be exactly 90deg to the brushes... so just line the screws up with the gap between the magnets. There's probably even a little nick/arrow just where the screws are...



does 1 degree make a difference?

Just a tiny insignificant difference.


When advancing your motor, its usually a range of between 1-35 degrees... so you've got plenty of leeway for experimentation.


alright i have let the armature spin to the sweetspot and it stays at the bottom of the can, as it doesn't move when i push it down...so i have put all 3 washers at the comm...hmmm...

yeah, not much you can do about that then. Some motors come like that from the factory - not 'ideal' but not a deadly defect either. (motor is *horizontal* when you're doing it, right? Not standing up...)


Does your motor have bearings or bushes?


brushes...i have been told to order from overseas...looking at tower hobbies and speedtechrc.combrushes are like US$3-4. i haven't checked the exhange rate for sometime...but guessing its around AU$5 a pair...


theres a 10 pairs pack for US$29.90..which is 2.99 a pair...


hmmm itscheap than compared to here which is around $8 a pair, the cheapest at hobbyco

Don't forget the postage & packing/handling fees ...



O/S shopping is good if you've got a bunch of stuff to buy and you know someone reliable you can deal with o/s, but for small bits it'll usually be a lot of hassle for not much savings.


Try calling around different NSW hobbyshops though... just ask for the CHEAPEST BRUSHES they've got. Ask if they come cheaper in the bulk packs. (Don't worry about the brand.)


what are seratted brushes? i see they have difference patterns...and what is silver percentage about?

Serrated brushes have cuttings at the face, to help them wear in to the shape of the comm faster than a plain unserrated brush. They are a much of a muchness; most brushes have serrations now anyway.


Brush is made out of carbon, copper & silver. Like said before, Silver is a better conductor but a brush made from more silver is softer (wears faster) and chews the comm more (need comm cutting more often). Generally high-silver brushes are only good for racing with hot mods.





well i'm looking for long lasting brushes...>10 runs a pair and i'll be happy...how much power is my motor losingif i use the longest lasting brushes than using those 1-3 runs racing brushes?

5%?


I doubt you'll even notice it!!!



Honestly... I'd want to get that motor professionally looked at if I were you. Must be some reason why its chewing up the brush so quickly.


and my springs...my motor has been through 2 pairs of brushes, and one is always shorter...how can i fix this?

Are the springs the same tension? That's the most important bit.


Next is: how much tension is it? - impossible to tell without a guage, but a rough guide is the angle between the two legs.


If its 150-180deg its usually normal, over 180 is pretty strong. You can bend the legs too to adjust spring tension.
 

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migoreng said:
i thought you should be able to touch a motor after a run...or is it normal to be hot that your fingers cannot touch it...? the battery get warm but i can still touch it...

Said who??
Already said earlier, your fingers would not normally let you 'touch' anything hotter than 50degC without a jerk autoreaction.... but its pretty normal to run our motors to about 70-80degC. We run 540 motors even harder, 75-90degC is not uncommon.


Dumping a 3300mAh pack into a mod motor in 5 mins also heats them up quite a bit, they are often 55-60degC when they come back. Yes that is also untouchably hot. (Heat is bad for batteries, so as soon as it comes off the track, the whole car is plonked on a cooling stand with many fans blowing at it.)


As for comparision... the hot water from your household Hot Tap is usually not more than 50degC - and that's already uncomfortably hot for your skin.





All temps are checked using an InfraRed non-Contact Thermometer, btw. Don't use your skin.
 

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Discussion Starter · #14 ·
yeh i know the endbellscrews are exactly 90 to the brush hoods



i was finding the motor sweetspot with the motor horizontal...and my motor has bearings..


why does my motor wear out the brushes so quickly? i dunno...i got my ESC on the 24 Feb...on a tuesday... but couldn't drive my car till thursday...drove it on fri sat(got my pvc wheels)...and the brushes died on monday night...so thats only 7 runs...with the stock brushes


but i remembered where the lines were on the can and i put the endbell back in the stock position...so is that the factory set timing?...but nowit seems that 4th line from the left was some kind of advanced retard timing? its on the 5th line now as i've set the timingto 90:90


what happens if you set a motor to reverse advanced?
 

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migoreng said:
what happens if you set a motor to reverse advanced?

Generally agreed as 'bad' for the motor.


Running a motor with Negative timing usually makes it very inEfficient.


Inefficient = less power for the energy put in = more heat.
 
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well rebuilt my motor, cleaned comm(With nitro fuel)...and changed
brushes...advanced the timing a few notches...and boy...hold the motor
in hand, connect it all up, fresh batt, pull trigger full throttle and
the motor nearly jump out off hand....



Nismo
 

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After you change brushes and/or touch the comm... the brushes no longer wrap the comm properly, only at a tiny point.


You should have Run In your motor eg run it for 30 mins using 2.4V (2 cells) to give the brushes half a chance to bed in before giving it full 7.2V.
 
G

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yawn yawn yawn....you onestly dont think i did that....not for that
long long anyway...30mins..geez.....try like 5mins.....same thing went
for MIG...when he got new brushes..first thing i told him was to run
them in...



Nismo
 
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do i have to mention every detail in it..ffs...

man i went to the crapper a few times in between too, had so
food....went to town to get brushes...RAN IN BRUSHES ON 2 AA BATTS FOR
5 MINS....

geez man!!



Nismo
 
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