Bigger Motor To Oset 12.5

[redline2097]

ok 45kv is ok but as I said the slower the wind the less torque it can make depending on gearing.. if its geared to high then it will get hot, for that diameter motor (120mm)@ 45-50kv you should still looking at around 3-4kw with 8kw bursts.

 the golden motors are very heavy :-)   thats all im going to say about them and also dont bother with the WC version its not worth the extra cash. 

I'll been watching this motor from Revolt: http://www.revolt.org.il/rv-120/rv-120pro-short/ it would fit very nicely to our bike. Just need to add 3cm to swingarm. 

 

Operation voltage: 24V-96V

Continuous power/ Peak power: 2.5KW/ 6KW

Standard KV: 49

Shaft diameter: 15mm

Weight: 2.7Kg

Price:

With hall sensors: 260USD

Economy Shipping price: 37USD

 

Do you think this is enough for 15kg kid and is there huge difference to stock motor @40v 50amps?

 

Stock motor is XYD-13

3.No load: No=2600rpm±10%  Io=2.5 A REF

4.Load:T=2.2N.m  Nn=2600rpm±10%  In=34.0 A REF

So running 2000w is the stock motor 7nm torque? Max we can output with revolt is something between 20-25nm. If I read this chart right, there is absolute no idea to run this stock motor over 2000watts. Effiency at 2000w is only 55%, so if switching to revolt we get almost 60% more mpg at top watts. 

 

This is Revolt 120 REGULAR (no pro, no-short)

 

This is efficiency at 60volts:

 

This is torque at 60volts:

So with 6000 watts (100amps, 60 volts) we get 20nm of torque @ 95% effiency.

 

Edited June 6, 2016 by redline2097

[gwhy]

in short yes it will be enough for a light kid.. the revolt generates more torque because its a bigger diameter motor .. brushless motors are nearly always more efficient and lighter than brushed motors, remember that the graphs shows the revolt with 60v input and that is appox 1.5x more voltage than the brushed motor is showing so both the graphs are not like for like i.e if the brushed motor was run @ 48v then it will generate more torque and because the speed will double then if you gear down to match the 24v speed then this also increases the torque. there are also a lot more other factors that come into play but more to do with heat and losses. but in general a brushless motor of the same kv and diameter or bigger will always be better than a brushed motor as long as the controller can handle the current for a kelly controller to be able to get max torque out of the revolt in that graph it would need to be able to handle around 2.5x the max battery current and this is where things start to get a little more complicated as the brushless kellys are advertised with max phase current ratings. 

 

edit:  a 100a brushless kelly contoller would be more or less the same spec as a 40A brushed controller

Edited June 6, 2016 by gwhy

[redline2097]

This is the graps at 36volt. Even then the torque at 100 amps is 20nm.

 

Would this Kelly Controller power the RV-120 short: http://kellycontroller.com/kls7240s24v-72v350asinusoidal-brushless-motor-controller-p-1344.html

Motor Current Limit, 10 seconds boost: 350A ,depending on the model.
Motor Current Limit, continuous: 150A ,depending on the model. 

 

These are the phase current readings, but you think this can reach the 100 battery amps? 10 seconds is DEFINITELY more than enough for this type of riding. We are not trying to drive speed over 100kmh...lol . Max speeds we use are something like 40-45kmh.

 

This is stock motor running 40 volts, comparing 40amps and 55amps. I think we will try to push this more (gwhy, can I try 100amps what is the max power of our kelly? ), but not in tarmac.

Edited June 7, 2016 by redline2097

[gwhy]

yes but its reaching that torque using only halve the power and halve the speed so achive the same torque if put on a bike geared higher to achive the same speed as if run at 60v but this will then halve the torque at the wheel .. you also need to look at the speed when working stuff out as regards torque.

 yes a 350A burst will be ok and will prob be way to much for a light rider and bike if geared for only 40-45kmh but you can always turn the the current down :-)

 

if you look at the raffe bike that is running a phase current of around 200A and battery current of around 100A and geared for around 60k and it will bite a light rider 

 

if its a 100A brushed kelly then you can run upto 100A and this is what you will get .. but a brushed motor will burn up very quickly if it gets bogged down or over geared.. may be fine if geared for only 40k but watch the temp of the motor.

[redline2097]

It's now geared 90:11 sprockets and max speed is around 32kmh (GPS checked) at 40 volts. With 40 volts and 55A it does not get even warm after 10km (average speed 22kmh) trail run which has big hills. So do you think I can safely ad 20 more amps for trail runs? 

 

I think I will buy Jitsie 68T rear sprocket, so top speed will hit around 42kmh which is good for trails. It will eat the torque 30% for Trial training but with 16 volts that we use on Trials (Kelly set 40% speed)  we can raise the amps to 70 (I think) which will help with obstacles and steep hills. 

[redline2097]

Actually I ordered 219 chains and sprockets. and now instead of 90:11 we will use 62:9 so top speed increases 18% and we do not have to tighten chains after every time we drive.

[gwhy]

you need to find the sweet spot for power, speed and motor temp.. motor temps can get very hot very quickly , the only thing I can say is if the motor is  warm to the touch then it will be roasting inside ( brushed motors more so ) its good that your motor do not get warm but its prob not hitting the current limit very often as your lad is light , the best way to test is if you ride it up a hill from a dead stop maybe 30-50 yards @ WOT then see how warm/hot the motor is. by gearing it faster it will increase the time it will be at the current limit so this will generate more heat, and this will also be the same if you increased the current limit of the controller. Also if the speed is only set to (e.g) 50% @ 40v @ 40A setup (800w) then that is halve of the max power that can be put into the motor i.e equivalent 100% speed  @ 40v @40A  (1.6kw) 

Edited June 8, 2016 by gwhy

[redline2097]

Is there any easy method/meter to measure motors temp while driving? 

[redline2097]

And how does the gear ratio effect batteries? 

[gwhy]

you would need to fit a temperature probe to the motor and ideally inside the motor where it will get the hotest need to be careful that the probe can not get caught on anything that is rotating.. some people use a bbq thermometers to monitor motor temps as these can read quite high temps.

 

the faster it is geared for then the more capacity will be used from the batterys , even if you are not getting upto the geared speed on a regular basis this will be because the motor will be bogged down for longer whilst getting upto speed,, if that makes sense.

[redline2097]

So 18% increase to speed is 18% decrease to batteries on same distance? 

[gwhy]

the loss will not be linear ,so loss in battery capacity may not be as much just because of the fact that the controller is limiting the current. but the motor will get warmer due to increased gearing but again this may not be a issue because you are running at reduced potential.

 

You may not need a different motor if its possible to gear it the final speed you desire ( rather than using the speed pot to reduce the speed ) as you are not making the most of what you have atm .

 

 

[redline2097]

I have geared it now to 42kmh what is my desired max speed on trails. On trial use I have to reduce it to around 15kmh. Trial use is so light to battery that it is not relevant to be better. My boy can drive up to 6 x 1,5h trial sessions on our batteries if needed. 

 

So now with 100% voltage from controller (40v) and 55A max amps it runs 42kmh which I want. Anything else to optimize? 

 

If I would like to upgrade to Revolt RV-120 I would not up the speed. I would just want the ultimate acceleration on dirt/trails, possibility to wheelie easily and maximize battery effiency. 

[gwhy]

I have geared it now to 42kmh what is my desired max speed on trails. On trial use I have to reduce it to around 15kmh. Trial use is so light to battery that it is not relevant to be better. My boy can drive up to 6 x 1,5h trial sessions on our batteries if needed. 

 

So now with 100% voltage from controller (40v) and 55A max amps it runs 42kmh which I want. Anything else to optimize? 

 

If I would like to upgrade to Revolt RV-120 I would not up the speed. I would just want the ultimate acceleration on dirt/trails, possibility to wheelie easily and maximize battery effiency. 

no nothing more to do 40v x 55A = 2200w peak.. keep a eye on heat of the motor, if not getting hot then up the current at 5a ago.

[redline2097]

We changed bearings to 6001 2RS from 6001 ZZ and added 219 Karting chains, and now motor braking is almost gone and wheels turn like a butter. Original bearings must be very very bad quality. Because "motor braking" was pretty rough.