Will these parts zoom, crawl, or go bang!

[sl33py]

How does this whole kv thing work? If I use the spreadsheet to increase the kv, the speed increases, yet everyone says lower kv is best.

Found a batch of turnigy motors on eBay cheap, kv:
149
236
275

Now if I use a 236 and current gearing, it goes slower. Confused :?

ah - kv fun... kv is revolutions per volt. so a 200kv motor (what i have) * 8s battery (33.6v fully charged) = 6720 rpms.

Why kv matters... higher kv is faster, but less torque. You want torque for starting/hills/heavier weight rider.

Usually you want the lowest kv you can find/afford and then set your gearing to give you a decent top speed. I target a max of 20-25mph, but really anything over 15-18mph i feel is gravy and i'm not likely to use it mutch. Being gargantuan, i wanted hill/torque setup for hauling my heavy butt around.

so... If you are worried about going too slow... I would look at your battery voltage/# in series. Your 6s battery, 83mm wheel, 16/60 = 11.9mph - same setup on 8s = 15.9. Same on 10s = 19.9mph

BUT your ESC likely is limited to 6s or less... Looking for the redbrick 125a ESC specs now... and it's 2-7s lipo. Hmm... This is the challenge if you can't swap your gearing because of belt fitment!

So - adjustable tension on your motor mount?

 

[Easy-pd]

I cannot get the gear off the old motor, so I need new. As I am ordering new, what is a good match to the motor?

If I go to 25-30 teeth, the speed increases, but my logic says I will sacrifice elsewhere? 20mph top speed would be cool if the acceleration etc is not too affected?

 

[Easy-pd]

5065 236kv ordered! Think it comes from overseas, so I'll have to wait.

Give me time to research gears. Thinking 25-30 teeth and making the mount adjustable, as long as the bigger gearing won't decrease acceleration much.

Thanks for your help and advice. Could've been a disaster up to now!

 

[2wayspeaker]

Why kv matters... higher kv is faster, but less torque. You want torque for starting/hills/heavier weight rider.

Usually you want the lowest kv you can find/afford and then set your gearing to give you a decent top speed. I target a max of 20-25mph, but really anything over 15-18mph i feel is gravy and i'm not likely to use it mutch. Being gargantuan, i wanted hill/torque setup for hauling my heavy butt around.

And this is the tradeoff you make with your gearing.
You can look at it like this *very roughly simplified*.
Gearing at 18mph gets you all of the motors power in that range (0-18)
Gearing for 25mph get you only 70% of the motors power in the (0-18) range.
So you'll accelerate slower, but if you have long flats instead of a hilly area, and are confident in your ability/helmet, you can reach the higher speeds.

Maybe get a friend with a bicycle and speedometer to pull you on your board to get a feel for the speed you want to aim for.

 

[Easy-pd]

So about 25-26 teeth will keep it useable for daily fun. Just need to find them with the correct bore. Can only find 7mm at the moment. Off to bed, searching tomorrow. Thanks for your help again. Will keep you updated as I go...

 

[sl33py]

i've heard that folks like to shoot for 3:1 ratio for good torque... I've aimed for 2.5-3:1 for my build (i have a couple different motor gears).

Someone more experienced maybe can illuminate the gearing ratio you should target?

 

[Easy-pd]

26 tooth ordered, motor on its way, esc on its way. Found a price of aluminium at work perfect to cut an adjustable mount.

Will update as I go (or run into problems )

 

[Easy-pd]

Reading up, waiting for the rest of the bits. Just wondered a couple things from reading:

The arduino should not be powered from the escs 5v transmitter power source as it will fry it.

Don't use the board from standing stop, as it will kill the motor.

Just what I've read and wondered if that's correct.

Also, just wanted to say I used the beltingonline website and got the order wrong. I contacted them nearly 2 days later when I noticed and they cancelled the order without any prob so I could reorder correctly. Thumbs up

 

[sl33py]

Not sure about the Arduino... how are you going to use it? You have the Wii and Wiichuck adapter already as your receiver correct?

Standing stop - it will "cog" or stutter starting, but i don't think that's a sure way to kill your motor. It just isn't much use stuttering to start - a good kick or two and you should be fine. Or get a sensored motor/ESC, or VESC...

 

[Easy-pd]

To be honest, I don't know! Arduino arrived, waiting on wiichuck adaptor.

I just saw its possible and thought it would look like a fun side project

I guess stuttering will put strain on the gearing, so push start it is. Can't wait now. Just waiting on wiichuck, motor, and pulley, then I can start playing.

 

[2wayspeaker]

The arduino should not be powered from the escs 5v transmitter power source as it will fry it.

Can somebody confirm this?

 

[Easy-pd]

Trying to find a link to where I saw it. There seems to be a 80/50 split regarding true and untrue statements re electric boards on the net though. I see quite a few do it with no probs