Speed Calculator

[BrianG]

I just made a few more changes... :)

[BrianG]

Another update. Added the Neu motors, added Castle Creations Motors, fixed issues with the gear diameter calculator, added other minor features.

R/C Calculations

[MetalMan]

Hmm... 1.5" is too much extra ballooning for 4.5" tires? You should see the size of Geolanders when the Rustler is going! As for exceeding the RPM of 40,000, it isn't a problem when doing speed runs (or general running with the MM 4600 :005: )

EDIT: Just realized that the tire ballooning thing isn't working like I expected. I typed in 1.5" of tire ballooning for 4.5" tires, and it's saying the tires are 23in. in circumference. I assume that for the tire ballooning part we add the extra diameter of the tire causing by the excessive RPMs, or is it something else? I get the tire circumference at 6" total diameter to be 18in.

[BrianG]

Yeah, that's why they are warnings. Some motors have a 40krpm efficiency range, so that's why that is there. I could add a parameter for each individual motors ideal max range, but I have no idea what that would be. I know for the Wanderers it's generally accepted to be ~40kprm. What about the Castle Creations, Neu, LMT, Lehner?

As far as the balooning goes, the value you enter is the extra radius created by high rpm. The formula I used:

var tireC=Math.PI*(tireD+(tireB*2));

It's taking the tire diameter (tireD), adding the balooning value (tireB) multiplied by two because that's how much it affects the diameter, and then multiplies all that by PI to get total circumference (tireC). I did this so the user doesn't have to remember to multiply by two themselves. Can you think of a way to phrase the question so that people know what to put there? As to the max value, I figured 15% of the tire's diameter as a generic value. Should it be increased to say, 20% or something? And again, it's only a warning.

Despite the warnings, the calculator will still figure everything out - it just prompts the user to make sure they didn't accidentally enter an incorrect value. There are a bunch of other potential warnings that people may never see just for that reason (like making sure the pinion and spur tooth counts aren't reversed).

Thanks for the feedback though! That's the only way it will get better. I try to make it as user-friendly as possible, buit I look at things from a programming point of view while other people might not, so it is nice to get others perspective.

[MetalMan]

When I went to put in the tire ballooning, I put in the increase in diameter. It's easier for me to think of it that way. Maybe you could add that the tire ballooning is done by the increase in the radius, so people don't put in the tire ballooning as the increase in diameter.
As for how much tires can balloon, I would say 50%. The Geolandars I'm running:
http://www2.towerhobbies.com/cgi-bin...&I=LXEXA3&P=ML
can easily balloon to 6" without any sort of tape on the inside, which is a 50% increase in overall diameter.

Do you think you could add another vehicle's gear ratio? The Rustler/Stampede have 2.72.

[BrianG]

OK, I'll add a note about using radius instead of a diameter for the balooning and make it warn at 50% (wow, that's a lot!).

What exactly is 2.72 on the Stampede/Rustler? The tranny, the diffs?

[MetalMan]

It's the tranny ratio, and the only other gear ratio is the spur/pinion, so I didn't list tranny/diff ratio. I think it might be better put under the diff ratio, and then you could put a note to select "Direct spur/pinion drive" under tranny ratio.

[BrianG]

Originally Posted by MetalMan

It's the tranny ratio, and the only other gear ratio is the spur/pinion, so I didn't list tranny/diff ratio. I think it might be better put under the diff ratio, and then you could put a note to select "Direct spur/pinion drive" under tranny ratio.

I just took a look at the Stampede blow-up diagram and see what you are talking about now. I'll put the ratio under the tranny with a note. It's kinda built like the Jato tranny in that way except there isn't an extra ratio; just an input gear, and idler, and an output gear (diff).

One last question; my program actually requires me to use the actual gear tooth counts, not just a ratio. This lets me keep the precision as high as possible to avoid rounding errors. So, from buytraxxas.com, it lists the top gear as 22T. Does that mean the diff gear is 60T? I just want to verify because those tooth counts create a 2.727272:1 ratio. I can ignore the idler gear since it isn't doing any reduction.

[MetalMan]

If you were to use the 60t as the input, it shouldn't cause any problems. From your calculation it's definitely close enough.

[BrianG]

OK, the updated version is up...

[Edit]: Hey, it's my 1,000th post! :dft003:

[MetalMan]

MUCH better :). IMO I think this is the final version. The only problem now is that the theoretical speed of my Rustler is 73mph even though when running it it's only going about 50mph.

[BrianG]

Originally Posted by MetalMan

MUCH better :). IMO I think this is the final version. The only problem now is that the theoretical speed of my Rustler is 73mph even though when running it it's only going about 50mph.

Yeah, I forgot to add a note that after around 50ish mph that the top speed will probably be less than the calculated value. I'm sure wind resistance becomes a major factor. I also think terrian is more of a factor at higher speeds as well. Gentle terrain at 30mph becomes rough terrain at 50+ and the resulting jarring affects speed I'm sure.

As to the motor kv values. For the Wanderers, I list the loaded values found in the store. For any Feigao that does not have a Wanderer equivalent, I list the advertised kv from the manufacturer, which is unloaded. I actually would probably prefer to list unloaded values because the loaded values seem like a generic fudge factor to account for weight, gearing, terrain, wind resistance, and/or losses in kv from the amperage draw. This would explain why some people report faster speeds than calculated (Squee). I would like to keep the unloaded or loaded kv consistent across all the motors, but I don't know how the Lehner Basic/XLs, LMTs, Mambas, etc motors are rated. If anyone knows how everything is rated, I will be more than happy to change things to be consistent.

I don't think there will ever be a "final" version. :)

[Mike.L]

this is good for the noobies, great job brian:) really thoughtfull.:)

[nieles]

i found a little mistake a BK wanderer 9L is not 2212 but 2418
look at this

[neweuser]

Are you sure they are not listing the kv "without load"?