Speed Calculator

[squeeforever]

coolhand, i was wondering the same thing but i just thought of it. think of it this way, the front tires are gonna balloon more than the rear because all the weight is gonna be transfered to the rear when accelerating.

[BrianG]

Originally Posted by squeeforever

coolhand, i was wondering the same thing but i just thought of it. think of it this way, the front tires are gonna balloon more than the rear because all the weight is gonna be transfered to the rear when accelerating.

I think I see what you're saying. It's hard to guage, but when I saw my tires balloon on a straight run, they looked like they were all ballooning by the same amount. Of course, if the truck is turning or there's a change in the ground traction (loose dirt etc), that will cause the left or right tire to balloon more because of the front/rear diff. Unless there is some "give" somewhere; like a center diff, a clutch of some sort, or there is some tire slip in the front or rear, they will all balloon the same since the tranny is driving both sets of wheels at the same time.

[BrianG]

OK, new version. Changed the battery voltage selector so you can select cell count and the voltage-per-cell seperately. This should allow you to calculate "best case" speed with a fully charged battery, "worst case" with a almost discharged battery, and various spots in between. This was mainly done for Squee (I hope you're happy ;)).

Also added a motor selector that lists the BK Wanderer, LMT, and Lehner Basic motors and puts the kv value in for you. I didn't realize how big Mike's list was, and I didn't even put all his motors on there!!!

Same link as before: http://www.scriptasylum.com/rc_speed.html

Oh, can a mod change the title of the thread so it can be found easier next time? Something like "Speed Calculator" or something?

[tallyram]

i tried it and it seems right on the money for my truck. 44mph is close for my gearing, 15/51.

thanks brianG, this is a really useful tool for everyone at this forum!

[squeeforever]

Great Brian...Make me feel bad.... lol. It still only says about 39 MPH but its close than it was. I guess my packs were charging very high voltage like 1.5 volts per cell +.

[Gustav]

It always worked for me and i test my speeds with GPS and it's usually very close to the calculated speed.I never had a tested speed turn out to be higher than a calculated speed.I just put in the nominal voltage and 6" for a 5.75" tyre.

[BrianG]

Thanks guys (and thanks for changing the title). Suggestions for future "releases" are welcome! :)

Squee: lol. I have no idea why yours is so far off. I don't think the packs charged quite that high, but there has to be something to account for the discrepency...

what a nice tool you put online!!! all thanks guy! :)
What could be nice is a warning signal for overgearing i.e...
I don't know if it's possible to do, but I would like to be prevented of thermalings or overgearings... i think the type of motor and the tires diameter should be enough to prevent this??? I realy don't know, just suggest...

And you could also add Feigao motors on your list...

You can be proud of your work BrianG!!!

[BrianG]

Thanks!

I could add an overspeed warning for the motors, although I only know the ideal rpm range for the Wanderers to be about 40k rpm. The LMTs says 65k. Is this the ideal limit, or the physical limit? What about the Feigao's (I assume they are like the Wanderers)? And, what is the limit for the Lehner basics?

As far as adding an overgearing (or undergearing) warning, that is dependent on weight, drivetrain drag, and other hard-to-quantify variables. It is really up to the user to monitor temperature to make sure gearing is OK. If anyone has an idea on how to implement this, I can do it as long as it is fairly accurate and not simply a "fudge factor".

Also, you can save the page and add whatever options you want. If you view the source, you'll see there are sections where you can easily add options to present lists.

[squeeforever]

Brian, some of the motors are rated for more RPM's but there ideal range is almost always in the 35 to 40,000 RPM's.

very nice software... i don't understand anything to these calculations, for me it's just a hobby, but i like to learn and i've another idea...
- Why to not add an optional field for the weight of the truck?
- You could write some alert message, or recommendations, about what to do to make your motor cooler in the case of thermaling, or what do do in case of under/overgearing... you could preconise some solutions (i.e:"reduce pinion gear teeth number to prevent early warming") ??? I think you don't need more that 10 messages to help everyone to set their car correctly...

I really enjoy your work guy!

[BrianG]

Squee: Cool, that makes things a little easier. I actually figured the LMTs to have a higher ideal rpm since they have better bearings and magnet structures.

fagzz: I'll have to think on the idea about using vehicle weight as a factor for speed. I still think there are a lot more variables that affect speed like; tire size (width), bearing drag, drivetrain drag, wind resistance, terrain, drive angle (uphill/downhill), and so on.

The calculator is really not that hard. The actual "work" is only about 10 lines of code. The rest is error trapping, input varification, visual appearance, and other "bells and whistles". The same thing could be done (and has) been done in Excel.

Thanks!

[squeeforever]

Brian, don't get me wrong, the LMT's can handle more RPM's but its safe to say that it will be better on the motor for the 35 to 40k range as well as its were its gonna run cool AND efficient.

[neweuser]

fagzz: I'll have to think on the idea about using vehicle weight as a factor for speed. I still think there are a lot more variables that affect speed like; tire size (width), bearing drag, drivetrain drag, wind resistance, terrain, drive angle (uphill/downhill), and so on.


Wouldn't weight be a factor IN all of the above too?

[squeeforever]

That it would...