You will experience less “punch” and also higher current draw to get the same amount of watts
1 Like
buy it now, you won’t regret it. 
2 Likes
Hi, I ma doing something similar with bergmeister wheels for a short AT commute board and believe me that with 75Kv you won’t like the torque. I am using strong hubs 75Kv (by the performace compare to those or a big stronger I would say) that I converted to DD and at 12s they are crazy strong but I wouls use them up to 100, max 107mm wheels. Above too much speed and lower torque. For that I will get a custom 60Kv from the same motor. Just my two cents
3 Likes
You’re going to have not too much torque with a top speed of 75kmh… Good luck getting there 
1 Like
important note: I’m starting with 12S4P or 12S5P on TorqueBoard 110s, however, anyone following my plan should know that my gut tells me my endgame will be the 97 mm LazyRoller Halo wheels (if I can get an ABEC adapter for the eLofty).
I want the TB 110 mm due to the wider eLofty hanger, because it will keep the sick / proportionate look of 100 mm Boas on factory Evolve SuperCarves
I have a feeling, however, that I will wind up at ABEC 97mm or Boa 100s, max. Hope this helps!
how very interesting:
http://www.elofty-skateboard.com/index.php?route=product/product&manufacturer_id=11&product_id=55
3 Likes
looks like that means the ebay selling window might be closing <:(
heck I want these but im worried about the axles and I dont think I would pay 4xx for them 
hopefully the ebay link stays up for the summer 
1 Like
EDIT: I had mixed up Kv(with unit rpm/volt) and Ke(back emf constant with unit volt/rpm) and so all the analysis here is wrong. Ignore this post
Your 2 cents are absolutely correct. A little bit of analysis shows that I’ll have push about 8 times as much current through the new motors to generate the same amount of torque. The max per motor I consume of my geared pneumatic setup is 25Amps per motor, now to get the same amount of torque it has to be 200Amps per motor. OMG. I wish I had done the calculations before 
So here’s the analysis assuming both motors are identical in terms of stator size and magnets.
Case1: 16:50 geared setup with 190KV
Case2: DD with 75KV
KV_1/KV2 = n1/n2 = 190/75 = 2.5333 where n is number of turns in the stator
torque on wheel1 = 50/16 T1 where T1 is the torque produced by the motor1
torque on wheel2 = T2 where T2 is the torque produced by the motor2
T1 = K*n1*A1 & T2 = K*n2*A2 where K is some constant and A is current
T1/T2 = (n1/n2)*(A1/A2)=2.533*A1/A2
torque on wheel1 = torque on wheel2 This is what we want
(50/16) * T1 = T2
(50/16) * 2.533*A1=**A2= 7.91A1**
The advantage of lower KV is that the motors lets you push higher amps without having to connect to a higher volt battery. Also the resistive losses will be less in a low KV motor(given same copper weight)
@Pedrodemio, @rey8801, @bevilacqua. Does, what I said, seem right? What I am little doubtful is the torque equation( T1 = K*n1*A1). I should double check.
yes, low kv = big torque low speed
high kv = little torque high speed
im doing a 1:4 ratio with 170kv 6374 maytechs and getting a top speed of 30mph with 165mm wheels. Its going to be so much torque i can probably pull me and another fully equipped rider.
Using the esk8 calculators is also a good idea to ballpark your build against “regular” builds
2 Likes
Yes correct. High Kv compare to wheels will decrease the efficiency. Same motor, same wheels I have tried 130Kv and 75Kv and the difference in energy consumption is huge. High Kv for the wheels size will make the drive really inefficient. Too much amp to generate same torque.
2 Likes
(Basic Torque equation for Permag. Syn, Machines)
Psi is the permanent magnet magnetic flux, i the current and p the pole pair. Im not a fan of DD for pneumatic systems, the big downside is the immense current you have to generate for the equal torque as a geared system. How much? well, it depends on the PM-flux, but roughly you multiply the current by the gearing to get to a basic number.
You will need an immense stator, and high amps to counteract the gearing effect on torque.
But on the other hand, I get why there is so much interest. If you want to trade some torque and range in benefit of a smoother ride, and also have a simpler (more reliable in many cases) driving solution then go for it 
5 Likes
@bevilacqua, I am surprised that number of turns doesn’t contribute to torque. I thought it would be proportional to current*number of turns. I am very surprised. Time to read some motor theory.
Can you point me to the article or book, where you got that equation?
I think @Pedrodemio explained it over on his small DD thread, the KV-number does not affect torque but rather how fast it can turn.
yeah, let me check my uni books and I’ll post the literature
1 Like
The kv, which tells the kt, is torque per amp and integral in the equation.
@mishrasubhransu the only non-german literature I found referenced on my uni stuff was this one: Kwang Hee Nam: AC Motor Control and Electric Vehicle Applications. CRC Press, 2010.
hope it helps
seems your equation is missing the inductance calculation:
The psi in the equation is not magnetic flux, but flux linkage. Flux linkage encapsulates the number of turns without explicitly adding it into the equation.
its correct for a PMSM, that part falls out of the equation if I remember it correctly
It is possible, I’m not sure. However both equations use the same psi, which accounts for the number of turns. Kv is directly dependent on the number of turns, so it would be a bit confusing the say kv has no affect on torque.
1 Like
are you sure that the PM_mag flux is related to the no. of turns?
I’m almost certain. The amount of electromotive force should scale to the flux present at the coils in the stator. More windings means a larger surface to capture flux.
1 Like