Speed Calculator

[BrianG]

I was thinking about adding all the motors I could find (Hacker included), but figured I would limit it to just what Mike has listed in his store. I know I don't technically "need" to, but it's a professional courtesy.

[jhautz]

Brian... Where did the KV numbers for the Lehner 19xx series motors come from. The numbers in your calculator dont match the kv numbers on the Lehner website.

Are these possibly unloaded numbers vs the loaded kv numbers that Lehner uses? If so where did you get them?

[neweuser]

I think one is loaded and the other is unloaded, I would assume Brian used loaded kv ratings.

[BrianG]

I don't remember where I found the values, but the "U" and "L" after the motor kv in the drop-down lists says whether the kv listed is loaded or unloaded. I tried to use unloaded wherever possible because the loaded value depends on current draw and that is too variable for my liking.

[lutach]

I think Lehner's spec is somewhat loaded. I think I saw some one in another forum saying this.

[jhautz]

All I know is I was looking up the 1950/7 on the Lehner site and its different than in the speed calc. I thought maybe there was a reason for it, but if not it looks like many of them are incorrect. Just pointing it out so you can update it if its not correct.

I do know that Lehner uses a loaded kv value.... but they dont publish what the load is so who knows what that actually means.

I will say this though. In my own calculations I use the Lehner loaded values and the nominal cell voltages (for example 14.8v for 4s) without any voltage drop and the speeds that are calulated are dang close to the real world speeds I get. When using the unloaded values from other motor you have to account for the voltage drop for the calculated speed numbers to match real world.

[Gee]

Brian, I didn't see novak hv 4.5 or 6.5 listed in the motors for your calculations. Do you think 4800 (4.5) and 3100 (6.5) are an accurate kv to use for calculations? Thanks.

[BrianG]

Yeah, that's because Mike doesn't stock those systems in his store. But, yeah, you can just plug in the kv values of any motor you want. The motor dropdown is just for convenience really. If those kv values are correct, then yes, you can use those...

[lincpimp]

Originally Posted by BrianG

If those kv values are correct, then yes, you can use those...

Man, what a smart a$$!

You crack me up Brian

Brian, If I'm running Trakpower packs in a 3 X 2s config. with a Neu 1512 2d. What nominal cell voltage should I choose from the drop down menu? I have been choosing 3.3v.

[BrianG]

Originally Posted by lincpimp

Man, what a smart a$$!

You crack me up Brian

LOL. Sorry, I didn't mean to come across that way.

@Countryhick: It depends on what you are looking for.

If you are looking for a good max speed estimate, use 3.7v and lower amperage (around 20A or so). At max speed, there isn't as much electrical load as at startup.

If you are looking for a decent max torque estimate, use higher amperage and ~3.3v. The most torque will be generated at low rpm. Also, since the highest amperage happens at low rpm at startup, that's where the biggest V drop will happen as well.

[BrianG]

Update to the calc:

- Fixed weight value for the Neu 1512 motors. Was at 360g and should've been 290g. Thanks CountryHick!

- Added differential ratio and spur gear options for the Ofna Ultra GTP.

A planned future addition will include a new page to calculate the proper gear selection when using two speed setups. Probably next week sometime.

[BrianG]

Added the Two-Speed Gear Mesh Calculator.

[BrianG]

Added TrakPower Lipos to the balancer wiring section of the Lipo Wiring page (scroll to the bottom).

Regarding the Two-Speed Gear Mesh Calculator: If anyone knows the formula for calculating the amount of shaft-to-shaft distance you lose by where the teeth meet, let me know. I have most of the code done to calculate shaft-to-shaft distance, but left it commented out until I know this.

[BrianG]

Something I've been toying with is the addition of code to estimate how much speed you lose due to wind resistance/drag. I know calculating this exactly is very difficult due to so many variables, but there's gotta be a rough estimate of speed loss.

Right now, I have a warning box that comes up if the final speed exceeds 45mph. What I was thinking is adding a reduction constant above 45mph. Basically use a formula something like:

mph_reduction = ( calc_speed - 45 ) X 0.4

So, for a top theoretical calculated speed of 60mph, the estimated actual speed would be closer to 54mph: ( 60 - 45 ) X 0.4 = 6mph loss. 60mph - 6mph = 54mph. It's just a matter of finding a constant (currently using 0.4) that is fairly close...

Whaddya think?