Speed Calculator

[BrianG]

Yeah, I forgot that one... :dft001: It just proves there are so many factors that an approximation is the closest you'll get.

[squeeforever]

I think instead of factoring in all of those...just factor in weight.

[neweuser]

that was kinda my point...LOL

[MetalMan]

But what will factoring in the weight do for you? It would be almost near impossible to factor in the friction due to weight and air resistance as well.

[neweuser]

For me, personally? Not a thing, my speed gauge is basically how much it hurts when i hit my shins on high speed passes! OUCH, yeah, that was about 40 mph!!!!LOL

[MetalMan]

Ah, well in that case you could factor in weight - momentum is equal to the product of velocity and mass :005:

[BrianG]

Unfortunately, the problem seems to be that our trucks go faster than the calculator would suggest (which I still think is related to the actual kv rating of the motor vs the published values). Any adjustments would only cause the top speed result to be slower.

[coolhandcountry]

Well you figure if you put a lower gear on a truck the amp draw is less the voltage stays higher for the truck will run faster. Not only that but the motor has less of a load so the kv is little higher as well. It should not be for a exact figure but a rough one. The only true way is to get the motors at test them with a speed device. Every body and truck will have a different drag to it for how high the body sits or low as well as the type.

[skellyo]

Originally Posted by BrianG

Unfortunately, the problem seems to be that our trucks go faster than the calculator would suggest (which I still think is related to the actual kv rating of the motor vs the published values). Any adjustments would only cause the top speed result to be slower.

I'd have to believe that either the battery voltage is staying higher than the input value or the motor constant is a bit higher than spec'd. That's the only thing that can account for higher speed than calculated. The thing is, going faster than the theoretical calculated value just isn't possible unless the user is incorrect in one of their input variables. I'd really like to know all the details of someone going faster than the calculated speed, especially if it's GPS verified.

[squeeforever]

Well, I know for a fact that mine was at least 50 mph simply because my truck does 40 now and it was WAY faster with the XL3100 on 12 cells. A little speed comparo for ya. My truck right now has a 10XL on 14 cells. Its calculated at around 40 mph. My Revo, stock would run right with it. Almost exact same top speed. With the mods I've done, its around 45 mph and slightly faster than the E-Revo. Now, with the XL3100, it went FLYING by my highly modified nitro Revo (which came 40+ stock). It was doing 50 I know. It was almost impossible to control it in a straight line. Since it only says 39 mph, I know for a fact, it IS possible for it to go faster than the calculatos projected speed.

[BrianG]

Originally Posted by skellyo

I'd have to believe that either the battery voltage is staying higher than the input value or the motor constant is a bit higher than spec'd. That's the only thing that can account for higher speed than calculated. The thing is, going faster than the theoretical calculated value just isn't possible unless the user is incorrect in one of their input variables. I'd really like to know all the details of someone going faster than the calculated speed, especially if it's GPS verified.

Well, AFAIK, Squee the one that seems the most inaccurate so far. This was what he was using.

EDIT: Squee posted his response before I got mine in...

[BrianG]

Version 1.3, not much new, just added a few warnings; one of which is for the 40krpm motor limit.

[SpEEdyBL]

Tire balooning is the most difficult factor to calculate that could easily increase your speed beyond the calculated value. This is especially true with small tires, which can get pretty tall!

[BrianG]

Originally Posted by SpEEdyBL

Tire balooning is the most difficult factor to calculate that could easily increase your speed beyond the calculated value. This is especially true with small tires, which can get pretty tall!

It is pretty amazing how much just 1/4" will adjust speed. I have a warning set for ballooning values greater than 1/2", but thinking that maybe a percentage of the tire diameter may be a better choice. What do you think?

[neweuser]

i run 40 series and there is little ballooning, so for me, that would be better. But others? Not sure.