Speed Calculator

[BrianG]

Originally Posted by Nick

I found a typo by the way, when I put 7XL motor and put it over RPM the Message says it's a 6XL. :)

Fixed in both the regular and beta versions... Actually, the recommended rpm displayed in the warning box was wrong as well. Was simply an issue with array indexing.

[BrianG]

I'm working on the motor selector and have some questions. I need to group all the 540 can motors by S, L, XL, and XXL size.

Would the Lehner Basics be considered S size?
Would the Lehner Basics XL be considered L size?
Would both the LMT 1940 and 1950 be considered XL size? Or is the 1940 more L size and the 1950 XL size?

Argg! LMT has too many sizes! Better question:
Where do the following motors fall in the S, L, XL (and maybe XXL) size rating?
1920 S?
1930 L?
1940 XL?
1950 XXL?

[BrianG]

OK, no one has responded to my questions, so I guess I'll have to make some assumptions.

Anyway, I did a little more work. It's not quite done yet as I still have to factor in the weight variable (tomorrow night's project) so it picks the motor can length (S, L, XL, XXL), but I think I have the layout done. So far, it picks the motor can type (540, 380, etc) from the weight entered and picks motors whose kv value are +/- 5% of the calculated value. Then the program divides the remaining motors by motor quality. Take a look and offer feedback. BETA VERSION.

BTW: The "hard coded" values in there are just to ease my testing. Those will be stripped in the final version. Just override as necessary.

[aqwut]

yeah... I would agree with your assumption

[coolhandcountry]

The 1950 is like a xl. It has almost the same deminsions. The 1930 is little shorter than l the 1940 is little longer. I think the 1920 is about an s can.

[BrianG]

Thanks. So, the 1920 is an "S", the 1930 is an "L", and the 1940/1950 are considered "XL"?

The only reason for this rating system is so that I can choose the appropriate motor for the weight of the vehicle. Heavier ones need more torque, which requires a longer can. I guess I could get away form the S, L, XL, thing and simply go with a number rating system.

[coolhandcountry]

The 1940 is kind of inbetween the l and xl. So you can kind of say either.

[BrianG]

OK, the final version is up. R/C Calculations

[Dafni]

Sweet tool! Very good job, Brian. Thank you.

DAF

[Nick]

Very good!

[sjcrss]

thanks brian...I like the final version....very easy to navigate thru

[BrianG]

Thanks all!

I still am not too sure on the motor selector. See if this sounds right to you:

For choosing the motor size (300 vs 540 can, and then S, L, XL) I am using the truck weight:

If weight < 1.5lbs, use the smaller 300/380 size can. (regular Mamba).
If weight between 1.5 and 5 lbs, use an S size
If weight between 5 and 8 lbs, use an L size
If weight between 8 and 16 lbs, use an XL size
If weight between 12 and 25 lbs, use an XXL size (LMT 1950)

I have some weight overlap for the XL and XXL size, but I wonder if there should be some overlap with the others? I know a smaller motor may work on a heavier truck, but this is for an "ideal" setup.

Then, I use the calculated requried kv value to determine the applicable motors which have a kv that falls near that value.

[aqwut]

I wonder if there's any way to figure out how many watt/lbs we need to go a certain speed?.. that would be Freakin' awesome..... I don't know if I'm sayin' it right, but you' know what I mean....

[BrianG]

Yeah, the trouble is getting that spec from all the different motor manufacturers. This is more generic and gained from experience and reading these forums, but probably not as accurate.

[Dafni]

Maybe I can have a word with Mr Lehner about this. When he's in the right mood, he's very helpful ;)

But the weight/size thing looks good, Brain. From my experience it makes sense.