Folding the plan... need recommendation for a motor - quick!

[Desertprep]

I am "folding" the plan to add a motor to my 16" dahon to get it to 30 mph. I took my bike down a steep hill last week. It rode well, but I could see, given the road conditions, that control could easily be an issue under less than ideal situations. I still plan to add a motor to it..but it will come later, and be a much less powerful match.

So...off to plan B. I saw an e-scooter 2 nights ago with 60v battery and 500 watt motor. The scooter body and parts were average to not bad. The motor and battery were pieces of junk...the scooter was practically begging me to rid it of the embarrassment of the trash that was within it and let its spirit fly....anyway, scooter is designed for the speed I want to go and even to carry 2 people, though I don't think the 500 watt motor will carry 2 people at such a high speed. The scooter, as it sits now, weighs 120 pounds. 50 pounds of that, per the salesman, is the sla battery pack. 15 is the motor. I can probably get the shell - scooter less motor and batteries for under US$100 and have a fun toy to operate on, that looks really cool. Cool looking is important when you are teaching uni students I think the scooter had 10" wheels but I have seen similar with 12".

I am still looking for 30 mph, but if a motor will give more without blowing up, I will take it.

Question 1: I have seen a few motors rated at 130-170 kv that were used by people in this forum doing projects - Turnigy and HTX, just to name 2 of them. They all seem to weigh 2-3 pounds and are rated to use 20-48 volts. Which motor/esc combo would you recommend? would you de-recommend any?

Question 2: Why do the mfg limit these motors to no more than 48v? I am not complaing...36-48 volt battery packs are becoming somewhat cheap here.

Is bigger always better? I know it is more expensive...but I usually like to exceed the requirements of a tool or machine by at least 50% to try to give it a longer life and make it more dependable.

Thanks in advance for any help you can provide. Quick would be good - I will be going to HK this weekend If I buy all of the parts in Asia I can get almost anything sent to me in 2 days, if not overnight.

 

[Carsten]

ok, i will have a try.
to 1. an answer u dont want to hear, it depends...
the lower the kV, the less reduction u need. so low kV helps to keep the drivetrain simple and the efficency loss low. the budget motors are all doin fine but some loose their magnets because of bad glueing. so reinforce the glue and they will last for a while.
for the controller u have mainly 2 options. a castle creations HV rc controller, small form factor, very efficient, advanced logging features, highly programmable. sensorless, limited to 50V, needs throttle translation, high price.
add hall sensors to the motor and use an ebike controller. sensored, up to 100V, throttle, ebrake connection included. maybe regen, much cheaper. huge and ugly.

to 2. because they dont have to. in rc business there arent higher voltages than 48V. the only limiting factor for rc motors is the heat they can take. the max power is more reliable than the max voltage. lets say a motor is rated for up to 3kW at 85% efficency, that means it can take 3kW*0.15=450W heat without overheating. it doesnt matter if u r running it on 100V 30A or 50V 60A. with active cooling u can push this limit but with outrunner motors harder than with inrunners.

but I usually like to exceed the requirements of a tool or machine by at least 50% to try to give it a longer life and make it more dependable.

there are only 3 parts that may fail in a brushless motor. insulation or magnets due to heat. see above. the bearings by wearout. easy to replace. so when ur stayin with the power limits there is no need for overrating it. controllers are different, they are known to blow up through power spikes. overrating is recommended.

i hope that helps

 

[Desertprep]

Hmmmm a good answer...i think :lol: What would you say are the 4 or 5 most reliable brands of r/c outrunner? And when you say "add some hall sensors" are you talking about something that mortal man can do? Is there a post or sticky somewhere that details it?

 

[Carsten]

there is nothing wrong with the turnigys. as mentioned before, apply some additional glue and they will be fine. quality differences to non-budget brands are mainly bearings (u can easily change them to higher quality) and glueing of the magnets. and of course they are wound with "love", e.g. patiently handwound stators compared to "quick and dirty" wound by tired chinese assembly line workers under time pressure, to get the maximum of copper inside. more copper = more power.
according to that, check out this thread http://endless-sphere.com/forums/viewtopic.php?f=28&t=20640

adding sensors is no magic, have a look at this http://endless-sphere.com/forums/viewtopic.php?f=30&t=15686&start=0&hilit=adding+hall+sensor+rc

 

[pankaj_india]

i also intend to convert my two wheelie ,have placed an order at hobbycity...
1)being a noob i don't want to add hall sensors and all,just esc and motor .....castle creations was very costly so i ordered turnigy...
2)are DEEP CYCLE LEAD ACID BATTERIES good enough for the task .
3)any other suggestions...

this is my first post ..so forgive for any mistakes...kindly help

 

[Carsten]

rc controllers are known in general to blew up when used in e-bikes. the castle creations seems to last longer and they have a flat replacement fee. afaik almost every turnigy esc used in this forum is blown quite quick. a slipper clutch may help to prevent it from blewing too fast. also u should pedal first before starting the engine and try to fit the gears in a way that ur able to drive most of the time on full throttle, partial throttle will kill it.

after u have blown ur first esc and still cant afford a castle creations one, i recommend adding sensors and try an infinion ebike esc. its not a big task, some simple solutions can be found here on es.

rc setups are able to draw a lot of amps, the voltage sag of leadacid batteries will let u run into lvc very soon, i guess u will not be able to pull more than the half of nominal capacity out of them and they wont last long. if u already have them i suggest ride them to the death and replace with other chemistry.

 

[AussieJester]

i also intend to convert my two wheelie ,have placed an order at hobbycity...
1)being a noob i don't want to add hall sensors and all,just esc and motor .....castle creations was very costly so i ordered turnigy...
2)are DEEP CYCLE LEAD ACID BATTERIES good enough for the task .
3)any other suggestions...

this is my first post ..so forgive for any mistakes...kindly help

You might as well fluch the 150 bucks you just wasted on that ESC down the drain sorry to say... many here have tried them all have ended in fried escs, they simply don't work, if you want to use a rc esc you will have to cough up the $$$ for a hv160 nothing smaller in the Castle Creations range will stand up to that motor...even the hv160 needs limiting to survive.. Lead acid are THE worst choice for ebike use, flick through a few more pages on HobbyCity for the 5s or 6s Turnigy or Zippy battery packs. Pays...or should i say 'saves' (money) to do some research and ask questiones before spending the $$$ ... :wink:

KiM