whats a better ride High KV or Low kv

[saming]

i was wondering about motor gearing would it be a better smother ride. a 300 Kv motor with 12/40 or a 170 Kv with at 15/32. i see so many options but im not sure the difference
Thanks

 

[onloop]

Hi Saming,

Depends what you mean by the words "better" and "smoother"

"better" could mean anything to anyone. So the answer is YES & NO

"smoother" I think i can make an assumption what you mean...

so here goes:

Smoother ride/acceleration/braking? : Yes the KV & Gearing ratio will make a difference, but so will the ESC software, the duro of the wheels, the diameter of the wheels, whether you have two motors or just one.....the list goes on.....

With 12-40 you might have cogging/slipping issues when accelerating & braking, therefore not a smooth ride!!

However this ultimately will depend on the center distancing.... I would avoid 12 teeth motor pulleys. When using HTD 5 pulleys & timing belts you need a minimum of 6 teeth in the mesh (6 teeth of the pulley - meshed with 6 teeth on the belt). Therefore the minimum would generally be 13 teeth for a motor pulley..... but this number goes up the bigger/closer the wheel pulley gets to the motor pulley.

The wheel pulley has other limitations also, on an 83mm wheel anything bigger than 36 teeth pulley may be a problem in terms of clearance with the ground.

So therefore that leaves you with MIN 13 TEETH -to- MAX 36 TEETH (if using an 83mm wheel)

I believe A 300kv motor would work in this gearing setup.... however maybe you will have limited hill climbing ability due to lower torque output...

170KV with 15/32 will also work... However after doing some testing using different KV motors, see my video: KV Comparison Video I now think you need to be careful when you design your system, You actually do not want to have too much torque, oddly enough it can actually diminish the ride quality.... When you have this much torque the board can easily wheel spin under hard acceleration, or if (read 'when') it does get traction the power may be to much to handle, if your not careful with the trigger finger you might end up on your ass... Torque is great but you only need so much of it.... I think the best rule for torque would be the answer to this Question: Can I get up the largest/steepest hill in my area carrying the max load I will ever carry?

Also, more torque normally means less top speed.... Torque and speed in a DC motor are generally inversely proportional...unless you have high tech electronics.

So how to choose what to use???... there really is only one way.... well depending how much spare cash you have there are several ways....

BUT, The most affordable way is to buy a motor, any motor, say something between 150kv & 300kv.... Then setup your gearing ratio with what you think might be good, then go to the biggest hill and see if you can get to the top. If you make it to the top really easily, without really slowing down much & without stressing (heat) the motors... this means you have ample torque available, so you can now reduce the ratio of teeth in your drive train to increase top speed.... You then go up the hill again.... if the motors are now not handling the job (over heating, squealing, on fire, etc) you now don't have enough torque... so increase the ratio between drive & driven pulleys.

hope this helps

 

[torqueboards]

For a 300kv motor if you aren't going dual motors. I would probably recommend a gearing ratio of 1:3. I'm running (2) 50mm SK3 motors with 280kv and run a 1:2 setup 20T/40T which works really well but the second motor helps a ton for going uphills which is what I wanted - reaches my 20mph top speed. If 1:3 doesn't work, you can always change your motor pulley to switch it to 1:2.

It's also very simple to change your gearing ratio. I originally started with 14T/40T which ended up being to low of a top speed so I made it 1:2 for less drag when pulling.

 

[saming]

thanks guys wonderful answer.

 

[Hummina Shadeeba]

you can fit a 44 tooth pulley on an 83mm wheel

 

[onloop]

you can fit a 52 tooth pulley on there as well..... but you wouldnt

with a 44T you have approx 6.5mm clearance not much is it? even less clearance when your wheels start to wear out!

 

[Hummina Shadeeba]

Maybe so but a lot of people seem to be using them. 44. There's the imaterialse.com print for the abec11

 

[onloop]

Maybe so but a lot of people seem to be using them. 44. There's the imaterialse.com print for the abec11

my design philosophy is to think about what a lot of people are not doing then ask yourself why.... this is the true path to innovation.