Speed Calculator - Page 7 - RC-Monster Forums

BrianG · 09.07.2006, 03:52 PM

Quote:

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. :)

MetalMan · 09.07.2006, 05:47 PM

Part of my problem with achieving the theoretical speed is my range and GPS that I use. My range is limited due to glitching, and the GPS updates itself only so often, so it might not record the actual highest speed. Maybe another note you could put might say that after 50mph you need more space to hit the top speed than anything lower (for those who aren't familiar with kinetic energy [KE=V^2 x m).

coolhandcountry · 09.07.2006, 06:07 PM

The kv of a lmt is rated at it's most efficent rpm and under load.

tallyram · 08:38 PM

this calc. is getting pretty close to the real world. i shot my bl-revo with a radar gun and it hit 49mph. i then entered my data into the calc. and it read 48.7mph! pretty damn close, huh? thanks for all the work!

BrianG · 10.07.2006, 09:07 PM

You're welcome!

Any ideas of things to add (and not only to the speed calc) is welcome...

MetalMan · 10.07.2006, 10:23 PM

My thoughts are that you only need to load in more cars' diff/tranny ratios. If anyone has any to add, that would be great. In the meantime, I'll see if I can pull some up.

BrianG · 10.07.2006, 11:29 PM

Great! By all means, let me know...

Serum · 10.08.2006, 04:09 AM

What setup do you use tallyram?

tallyram · 10.08.2006, 03:50 PM

i'm using a g2r running with stock diffs and a flm half case tranny with gmaxx single speed and steel idler with strobe setup and 18t pinion. setup is lmt 1950/8t non high amp with quark 125b on 5s and 6s lipos. 49mph was on asphalt with wabash/crimes and probably about 3.9-4.0v/cell. i know i can break into the 50's with my road rages and a little work on the driveline, which is very fatigued! the quark is really screwy as well. hard to get going on 6s, but once moving it works great as long as i dont come to a complete stop! this thing hauls!

Serum · 10.08.2006, 03:56 PM

what lipo's are you using, and this was with 6S?

I just took out my mugen and reached 44.4 mph on a first charge of a set of GP3300's (14 cells, 7XL and a 9920) that buggy is heavy!

a weird thing;

if i based my calculations on 14V (relative fair for 14 cells under load) and a kv of 2145 for the motor, it should do a 39.2 mph.

I think i might change the pinion a bit. The batteries felt rather cool.

tallyram · 10.08.2006, 04:04 PM

my batts were barely warm to the touch, yeah 6s. the quark doesn't like that much voltage, but i force feed it anyway! i'm a little pissed that $280.00 for an esc that is rated for 6s, but can't handle it. looks like i'll have to send in my 12020 and they can maybe fix the mid range throttle problem.

Serum · 10.08.2006, 04:08 PM

I didn't quite understand what the problem is with the quark on 6S?

tallyram · 10.08.2006, 10:30 PM

its the same problem most people run into trying to run 6s, the car stutters really bad. its like really bad cogging! coolhand will confirm this aswell. if you can get it running the condition gradually gets better as the voltage drops. 5s is usually decent, but i've run into problems with it also!

coolhandcountry · 10.10.2006, 02:05 PM

After I get mine going on 6s it seems to go ahead and run. Just trying to get it to go is the problem. It works great on 4s though. It is almost like a phase is out. It heats the motor up some to. I think when I fried the first one it took out my motor to. That sucks taking out a 19 series motor. ARG

tallyram · 10.10.2006, 03:37 PM

Quote:

Originally Posted by coolhandcountry

After I get mine going on 6s it seems to go ahead and run. Just trying to get it to go is the problem. It works great on 4s though. It is almost like a phase is out. It heats the motor up some to. I think when I fried the first one it took out my motor to. That sucks taking out a 19 series motor. ARG

that really sucks! i'm thinking of getting a 1950/6 and running it with the quark on 4s, how does that sound?